Keyframes
Question
At the beginning of the video, there are three little foxes: one stays still at the entrance of the den, while the other two are running. From the perspective of the stationary fox, in which direction are the other two little foxes running? Select the best answer to the following multiple-choice question based on the video. Respond with only the letter (A, B, C, D, E, F, G, or H) of the correct option. A. Left. B. Directly behind. C. Front. D. 11 o'clock direction on the left side. E. Directly above. F. Right front. G. Circling around the stationary little fox. H. Left rear.
Ground truth A
SpatialClaw A
Agent wins

No-tool Baseline

✗ Incorrect

To determine the direction in which the running foxes are moving relative to the stationary fox, we examine the first frame of the video.

  1. Identify the stationary fox: In the first frame, one small fox is peeking out from a gap in the logs (the den entrance), looking directly toward the camera.
  2. Identify the running fox(es): To the right of the stationary fox, another fox is captured in motion, running from left to right across the scene.
  3. Determine the relative direction:
    • The stationary fox is facing the viewer (forward).
    • The running fox is positioned to the right of the stationary fox and is moving further to the right.
    • Because the running fox is in the open area in front of the den, it is in front of the stationary fox's position.
    • Therefore, from the perspective of the stationary fox, the running fox is moving toward the right front.

Comparing this to the given options: A. Left B. Directly behind C. Front D. 11 o'clock direction on the left side E. Directly above F. Right front G. Circling around the stationary little fox H. Left rear

The correct description is "Right front".

F

Single-pass code

✗ Incorrect
Purpose
Identify the positions and motion of the three fox pups at the beginning of the video to determine the direction of the running foxes relative to the stationary one.
Reasoning
1. I will first inspect the first few frames to identify the stationary fox at the den and the running foxes. 2. I'll use `vlm.locate` to get coordinates for the foxes in a frame where all are visible. 3. I'll use `tools.SAM3` to segment them and `tools.Reconstruct` to get their 3D positions. 4. I will determine the facing direction of the stationary fox. 5. I will compute the relative direction of the running foxes' motion from the stationary fox's perspective.
Next Goal
Locate and segment the foxes in the first few frames.
Code
import numpy as np

# 1. Inspect the first few frames to find the foxes
# Key frame #1 is InputImages[0]. Let's check frames around there.
show([InputImages[0], InputImages[1], InputImages[2]])

# 2. Use VLM to locate the foxes in the first frame
# Stationary fox is peeking out of the den.
# Running fox is moving to the right.
# The prompt mentions three foxes. Let's see if we can find them all.
stationary_fox_coords = vlm.locate(InputImages[0], "Give the (x, y) center coordinates in 0-1000 normalized scale for the little fox peeking out of the den. Reply with ONLY the numbers.")
running_fox_coords = vlm.locate(InputImages[0], "Give the (x, y) center coordinates in 0-1000 normalized scale for the little fox running to the right. Reply with ONLY the numbers.")

print(f"Stationary fox coords: {stationary_fox_coords}")
print(f"Running fox coords: {running_fox_coords}")

# Let's also check if there's a third fox in the first few frames.
# Key Frame #1 (InputImages[0]) shows one peeking and one running.
# Maybe the third one is less visible or appears slightly later.
# Let's try to find all fox pups in the first frame.
all_foxes = vlm.ask_with_thinking(InputImages[0], "How many fox pups are visible in this image? Describe their positions and actions.")
print(f"All foxes in frame 0: {all_foxes}")

# To be thorough, let's reconstruct the first few frames to track them.
# Use a small range for reconstruction to be fast and accurate.
recon = tools.Reconstruct.Reconstruct(InputImages[0:10])

# Segment the foxes across these frames.
# Since we have coordinates for the first frame, we can use them for tracking.
W, H = InputImages[0].width, InputImages[0].height
try:
    sx, sy = map(int, stationary_fox_coords.split(','))
    rx, ry = map(int, running_fox_coords.split(','))
    spx, spy = tools.Geometry.normalized_to_pixel((sx, sy), W, H)
    rpx, rpy = tools.Geometry.normalized_to_pixel((rx, ry), W, H)
    
    # Track stationary fox
    seg_stat = tools.SAM3.segment_video_by_points([[ [spx, spy] ]], [[ [1] ]], ["stationary_fox"], prompt_frame_idx=0, start_frame=0, end_frame=10)
    # Track running fox
    seg_run = tools.SAM3.segment_video_by_points([[ [rpx, rpy] ]], [[ [1] ]], ["running_fox"], prompt_frame_idx=0, start_frame=0, end_frame=10)
except Exception as e:
    print(f"Error in segmentation: {e}")
    seg_stat = None
    seg_run = None

if seg_stat and seg_run:
    # Get 3D positions over time
    fi = seg_stat.frame_indices[0]
    stat_3d = seg_stat.get_centroid_3d(recon, frame=fi)
    run_3d = seg_run.get_centroid_3d(recon, frame=fi)
    
    # Get positions in a later frame to see motion
    fi_late = seg_stat.frame_indices[-1]
    stat_3d_late = seg_stat.get_centroid_3d(recon, frame=fi_late)
    run_3d_late = seg_run.get_centroid_3d(recon, frame=fi_late)
    
    print(f"Stationary fox 3D: {stat_3d} -> {stat_3d_late}")
    print(f"Running fox 3D: {run_3d} -> {run_3d_late}")
    
    # The stationary fox is facing the camera.
    # Camera pose at frame fi:
    pose = recon.extrinsics[fi]
    cam_pos = pose[:3, 3]
    cam_fwd = pose[:3, 2] # Camera forward (into scene)
    
    # Stationary fox is facing roughly -cam_fwd (towards the camera)
    fox_facing = -cam_fwd
    
    # Motion vector of running fox
    motion_vec = run_3d_late - run_3d
    
    # Relative direction from stationary fox to running fox (at start)
    rel_vec = run_3d - stat_3d
    
    # Project rel_vec and motion_vec onto the stationary fox's coordinate system
    # Fox's Forward = fox_facing
    # Fox's Right = cross(fox_facing, world_up) where world_up is [0, 1, 0]
    world_up = np.array([0, 1, 0])
    fox_right = np.cross(fox_facing, world_up)
    fox_right /= np.linalg.norm(fox_right)
    
    dot_fwd = np.dot(rel_vec, fox_facing)
    dot_right = np.dot(rel_vec, fox_right)
    
    print(f"Relative position: fwd={dot_fwd}, right={dot_right}")
    
    # Also check the motion direction relative to the fox
    dot_motion_fwd = np.dot(motion_vec, fox_facing)
    dot_motion_right = np.dot(motion_vec, fox_right)
    print(f"Motion direction: fwd={dot_motion_fwd}, right={dot_motion_right}")

# Final conclusion based on the above:
# If dot_right is negative, it's to the fox's left.
# If dot_fwd is positive, it's in front of the fox.
# In the image, the running fox is to the right of the stationary fox.
# Since the stationary fox faces the camera, image-right is fox-left.
# So it should be "Left" or some variation.
# Let's check the options: A. Left, F. Right front, H. Left rear.
# If it's moving to the right of the image, it's moving to the fox's left.
# If it's also moving further away from the den, it's moving "Left" and "Front".
# Let's look at the options again. "Left" (A) is a strong candidate.
# "Right front" (F) would be image-left.
# Let's refine the answer after seeing the printed values.
Output
 [image: show_0001] 
[VLM Q | locate] Before answering, first check whether what the question describes is clearly visible in the provided image(s). If it is absent or ambiguous, reply EXACTLY `Not visible` on its own line (optionally followed by one short line explaining what you saw instead) — do NOT return coordinates in that case. Only if the requested target is clearly and unambiguously present, answer the request below.

Request: Give the (x, y) center coordinates in 0-1000 normalized scale for the little fox peeking out of the den. Reply with ONLY the numbers.
[VLM A | locate] 454 738
[VLM Q | locate] Before answering, first check whether what the question describes is clearly visible in the provided image(s). If it is absent or ambiguous, reply EXACTLY `Not visible` on its own line (optionally followed by one short line explaining what you saw instead) — do NOT return coordinates in that case. Only if the requested target is clearly and unambiguously present, answer the request below.

Request: Give the (x, y) center coordinates in 0-1000 normalized scale for the little fox running to the right. Reply with ONLY the numbers.
[VLM A | locate] 840 675
Stationary fox coords: 454 738
Running fox coords: 840 675
[VLM Q | thinking] How many fox pups are visible in this image? Describe their positions and actions.
[VLM A | thinking] There are 2 fox pups visible: one is peeking out from under the log wall in the center, and the other is running across the grass on the right.
All foxes in f
show_0001
Final answer
F

Structured tool-call

✗ Incorrect
Plan

Task Analysis

The goal is to determine the direction in which two running foxes are moving from the perspective of a third, stationary fox at the beginning of the video.

Target Variable: The relative direction of motion (velocity vector) of the running foxes relative to the stationary fox's heading. Objects Involved: Three little foxes (one stationary, two running). Answer Format: Multiple-choice (A-H).

Coordinate System Resolution: The question asks for the direction "from the perspective of the stationary fox." This is an object-perspective coordinate system.

  • Front: The direction the stationary fox is facing.
  • Back: The opposite direction of the stationary fox's facing.
  • Left/Right: Relative to the fox's own left and right sides.
  • Clock-face (e.g., 11 o'clock): A polar representation where 12 is front, 3 is right, 6 is back, and 9 is left.

To solve this, I must:

  1. Determine the world-space position and heading (facing direction) of the stationary fox.
  2. Determine the world-space velocity vectors of the two running foxes.
  3. Project the running foxes' velocity vectors onto the stationary fox's local coordinate system (Front/Right axes).

Information Needs

  1. Object Identification: Which fox is stationary and which two are running?
  2. Stationary Fox Heading: Which way is the stationary fox facing in the world? (Since it's at the den entrance, its heading is likely perpendicular to the den opening).
  3. 3D Trajectories: The 3D world positions of all three foxes over the first few frames to calculate the running foxes' velocity vectors.
  4. Spatial Layout: A top-down view (BEV) to sanity-check the relative positions and motion paths.

Computation Plan

  1. Initial Visual Grounding:

    • Use show(InputImages[0]) to identify the three foxes and the den.
    • Use vlm.ask_with_thinking on the first few frames to confirm which fox is stationary and which are running, and to describe the stationary fox's facing direction (e.g., "The stationary fox is facing away from the den, towards the [left/right/center] of the frame").
  2. Segmentation and Tracking:

    • Use tools.SAM3.segment_video_by_text(prompts=["little fox"], ...) on the first 16 frames to get masks for all foxes.
    • Verify masks using seg.visualize(fi) and show(). If text segmentation is ambiguous, use vlm.locate to get points for each fox and use tools.SAM3.segment_video_by_points.
  3. 3D Reconstruction:

    • Use tools.Reconstruct.Reconstruct(InputImages[:16]) to generate the 3D point cloud and camera poses for the initial sequence.
  4. Quantitative Motion Analysis:

    • For each fox, extract 3D centroids across the reconstructed frames using seg.get_centroid_3d(recon, frame=fi, object=i).
    • Calculate the world-space velocity vector $\vec{V}{run}$ for the running foxes by taking the difference in positions between the first and last frames of the sequence: $\vec{V} \approx (P{end} - P_{start}) / \Delta t$.
    • Identify the world-space position $P_{stat}$ of the stationary fox.
  5. Heading and Local Frame Construction:

    • Determine the stationary fox's heading vector $\vec{H}_{stat}$ in world space. I will combine the VLM's description of the fox's facing direction with the camera's pose (from recon.extrinsics) to define this vector.
    • Define the stationary fox's local "Right" vector: $\vec{R}{stat} = \vec{H}{stat} \times [0, 1, 0]$ (assuming Y is world-up).
  6. Relative Direction Computation:

    • Project the running foxes' velocity vector $\vec{V}_{run}$ onto the local frame:
      • $Forward_Component = \vec{V}{run} \cdot \vec{H}{stat}$
      • $Right_Component = \vec{V}{run} \cdot \vec{R}{stat}$
    • Determine the direction based on the signs and magnitudes of these components:
      • Both positive $\rightarrow$ Right Front.
      • Both negative $\rightarrow$ Left Rear.
      • Forward positive, Right negative $\rightarrow$ Left Front.
      • Forward negative, Right positive $\rightarrow$ Right Rear.
    • For clock-face directions (like 11 o'clock), calculate the angle $\theta = \operatorname{atan2}(Right_Component, Forward_Component)$.
  7. Visual Validation:

    • Render a BEV map using recon.render_bev(masks=seg) to visually confirm the trajectories of the running foxes relative to the stationary fox's position and orientation.

Verification Checklist

[
  {"priority": "HIGH", "description": "Correctly identify which fox is stationary and which are running"},
  {"priority": "HIGH", "description": "Accurately determine the stationary fox's heading vector in world space"},
  {"priority": "HIGH", "description": "Verify that the running foxes' masks are consistent and not swapping identities across frames"},
  {"priority": "MEDIUM", "description": "Cross-validate the calculated relative direction with the BEV trajectory plot"},
  {"priority": "LOW", "description": "Check if the 'stationary' fox is actu
Step 0
LLM · Tool Call
Purpose
Initial visual grounding to identify the three foxes and the den.
Reasoning
I need to see the first frame to identify the stationary fox, the running foxes, and the general layout of the scene (including the den) to establish a baseline for the spatial reasoning.
Next Goal
Use `vlm.ask_with_thinking` to confirm which fox is stationary, which ones are running, and the facing direction of the stationary fox.
Tool Call
{
  "tool": "show",
  "args": {
    "image": "InputImages[0]"
  }
}
Execute
Output
 [image: show_0001] 
show_0001
Step 1
LLM · Tool Call
Purpose
Confirm the identity and motion of the three foxes and determine the stationary fox's heading.
Reasoning
The first frame shows one fox peeking from the den (stationary) and at least one running to the right. I need to verify if there are indeed three foxes and confirm their trajectories and the stationary fox's facing direction to establish the object-perspective coordinate system.
Next Goal
Segment the foxes to track them in 3D.
Tool Call
{
  "tool": "vlm.ask_with_thinking",
  "args": {
    "visual_input": "InputImages[:16]",
    "question": "In the first few frames, there are three little foxes. Please identify which one is stationary at the den and describe the movement of the other two foxes. Also, specify the direction the stationary fox is facing (e.g., facing the camera, facing left, etc.)."
  }
}
Execute
Output
[VLM Q | thinking] In the first few frames, there are three little foxes. Please identify which one is stationary at the den and describe the movement of the other two foxes. Also, specify the direction the stationary fox is facing (e.g., facing the camera, facing left, etc.).
[VLM A | thinking] Based on the first few frames, only two foxes are clearly visible. The stationary fox is the one peeking out from the den, and it is facing the camera. The other fox is running quickly to the right (seen in frame 0).
Step 2
LLM · Tool Call
**Purpose**: Segment all little foxes in the first 16 frames to identify their trajectories and count. **Reasoning**: The VLM only identified two foxes, but the prompt states there are three. I will use `segment_video_by_text` to find all instances of "little fox" in the initial sequence. This will allow me to track them in 3D and confirm their number and motion. **Next Goal**: Visualize the masks to verify the segmentation and identify the three foxes. **Tool Call (translated)**: ```python result_2 = tools.SAM3.segment_video_by_text(prompts=["little fox"], prompt_frame_idx=0, start_frame=0, end_frame=16) ```
Step 3
LLM · Tool Call
Purpose
Segment all little foxes in the initial sequence to identify and track them.
Reasoning
The VLM only identified two foxes, but the prompt mentions three. By using `segment_video_by_text`, I can attempt to find all instances of "little fox" across the first 16 frames, which will allow me to track their 3D positions and verify the total count and their movements.
Next Goal
Reconstruct the 3D scene to compute the world-space positions and velocities.
Tool Call
{
  "tool": "tools.SAM3.segment_video_by_text",
  "args": {
    "prompts": [
      "little fox"
    ],
    "start_frame": 0,
    "end_frame": 16
  }
}
Step 4
LLM · Tool Call
Purpose
Verify the segmentation masks for the foxes.
Reasoning
I need to ensure that all three foxes were correctly segmented and tracked across the frames before proceeding to 3D reconstruction and motion analysis. I will visualize the masks for the first frame.
Next Goal
Reconstruct the 3D scene using the first 16 frames.
Tool Call
{
  "tool": "show",
  "args": {
    "image": "result_3.visualize(result_3.frame_indices[0])"
  }
}
Execute
Output
 [image: show_0002] 
show_0002
Step 5
LLM · Tool Call
**Purpose**: Ground the coordinates of all three foxes to improve segmentation. **Reasoning**: The text-based segmentation failed to identify the running foxes. I will use the VLM to provide precise normalized coordinates for all three foxes in the first frame, which I can then convert to pixels for point-based segmentation. **Next Goal**: Convert normalized coordinates to pixels and segment the video by points. **Tool Call (translated)**: ```python result_5 = vlm.locate(visual_input=InputImages[0], question='Give the (x, y) center coordinates in 0-1000 normalized scale for each of the three little foxes in this image. Reply with ONLY the numbers as a list of tuples, e.g., [(x1, y1), (x2, y2), (x3, y3)].') ```
Step 6
LLM · Tool Call
Tool Call
{
  "tool": "feedback.ask_vlm",
  "args": {
    "visual_input": "InputImages[0]",
    "question": "Give the bounding boxes (x1, y1, x2, y2) in 0-1000 normalized scale for all the little foxes visible in the image. Reply with ONLY the numbers for each box, separated by newlines."
  }
}
Step 7
LLM · Tool Call
Purpose
Accurately locate all three foxes in the first frame to provide precise prompts for segmentation.
Reasoning
The previous text-based segmentation only captured the stationary fox. To track all three foxes and compute their relative motion, I need precise coordinates for each of them. I will ask the VLM to provide bounding boxes for all foxes visible in the first frame.
Next Goal
Convert these normalized coordinates to pixels and use them for video segmentation.
Tool Call
{
  "tool": "vlm.locate",
  "args": {
    "visual_input": "InputImages[0]",
    "question": "Give the bounding boxes (x1, y1, x2, y2) in 0-1000 normalized scale for all the little foxes in the image. Reply with ONLY the numbers for each box, separated by newlines."
  }
}
Execute
Output
[VLM Q | locate] Before answering, first check whether what the question describes is clearly visible in the provided image(s). If it is absent or ambiguous, reply EXACTLY `Not visible` on its own line (optionally followed by one short line explaining what you saw instead) — do NOT return coordinates in that case. Only if the requested target is clearly and unambiguously present, answer the request below.

Request: Give the bounding boxes (x1, y1, x2, y2) in 0-1000 normalized scale for all the little foxes in the image. Reply with ONLY the numbers for each box, separated by newlines.
[VLM A | locate] 422, 685, 485, 785
680, 545, 998, 805
Step 8
LLM · Tool Call
Purpose
Locate all three foxes in a frame where they are more likely to be visible (Key frame #4 / `InputImages[49]`).
Reasoning
The VLM only found two foxes in the first frame, but the problem statement specifies three. Looking at the key frames, `InputImages[49]` shows more activity and likely all three foxes. I will get bounding boxes from this frame to ensure I track all of them.
Next Goal
Convert these boxes to pixels and perform video segmentation to track all three foxes.
Tool Call
{
  "tool": "vlm.locate",
  "args": {
    "visual_input": "InputImages[49]",
    "question": "Give the bounding boxes (x1, y1, x2, y2) in 0-1000 normalized scale for all the little foxes in the image. Reply with ONLY the numbers for each box, separated by newlines."
  }
}
Execute
Output
[VLM Q | locate] Before answering, first check whether what the question describes is clearly visible in the provided image(s). If it is absent or ambiguous, reply EXACTLY `Not visible` on its own line (optionally followed by one short line explaining what you saw instead) — do NOT return coordinates in that case. Only if the requested target is clearly and unambiguously present, answer the request below.

Request: Give the bounding boxes (x1, y1, x2, y2) in 0-1000 normalized scale for all the little foxes in the image. Reply with ONLY the numbers for each box, separated by newlines.
[VLM A | locate] 376 302 856 786
Step 9
LLM · Tool Call
Purpose
Segment all foxes in the first 32 frames to identify all three and track their motion.
Reasoning
Previous attempts to locate them in a single frame were inconsistent. By segmenting "fox" across a larger window of the initial sequence, I can capture all three individuals and their trajectories, which will be essential for the BEV analysis and velocity calculations.
Next Goal
Reconstruct the 3D scene for these frames.
Tool Call
{
  "tool": "tools.SAM3.segment_video_by_text",
  "args": {
    "prompts": [
      "fox"
    ],
    "start_frame": 0,
    "end_frame": 32
  }
}
Step 10
LLM · Tool Call
Purpose
Reconstruct the 3D scene for the first 32 frames to enable spatial analysis.
Reasoning
To determine the relative direction of motion, I need the 3D world positions of the foxes. `tools.Reconstruct.Reconstruct` will provide the depth maps and camera extrinsics necessary to map the 2D masks to 3D coordinates.
Next Goal
Render a BEV map to visually identify the stationary fox and the trajectories of the running foxes.
Tool Call
{
  "tool": "tools.Reconstruct.Reconstruct",
  "args": {
    "frames": "InputImages[:32]"
  }
}
Step 11
LLM · Tool Call
**Purpose**: Visualize the 3D trajectories of the foxes from a top-down perspective to identify the stationary fox and the direction of the running foxes. **Reasoning**: A BEV (Bird's Eye View) rendering will explicitly show which object is stationary (represented as a bounding box) and which are moving (represented as color-graded trajectory lines). This will allow me to visually determine the relative direction of motion. **Next Goal**: Based on the BEV, determine the stationary fox's position and the running foxes' direction, then cross-reference with the stationary fox's facing direction. **Tool Call (translated)**: ```json {"tool": "show", "args": {"image": "result_10.render_bev(masks=result_9)"}} ```
Step 12
LLM · Tool Call
Purpose
Use a Bird's Eye View (BEV) map to identify the stationary fox and the trajectories of the running foxes.
Reasoning
The `render_bev` tool automatically distinguishes between stationary and moving objects, drawing trajectories for the latter. This will provide a clear, top-down view of the relative positions and motion vectors of all segmented foxes, which is the most reliable way to determine the direction of movement.
Next Goal
Analyze the BEV map to identify the stationary fox's position and the running foxes' direction, then correlate this with the stationary fox's heading.
Tool Call
{
  "tool": "show",
  "args": {
    "image": "result_10.render_bev(masks=result_9)"
  }
}
Execute
Output
 [image: show_0003] 
show_0003
Step 13
LLM · Tool Call
Purpose
Determine the relative direction of the running foxes from the perspective of the stationary fox.
Reasoning
1. **Stationary Fox Heading**: From the visual evidence in `InputImages[0]` and the VLM's analysis, the stationary fox is peeking out of the den and facing the camera. Therefore, its "Front" is the direction towards the camera, and its "Back" is towards the den. 2. **Running Foxes Motion**: In the first frame and subsequent frames, the running foxes are moving from the left side of the image to the right side. 3. **Coordinate Transformation**: - Since the stationary fox is facing the camera, the "Right" side of the image corresponds to the stationary fox's **Left**. - The running foxes are moving across the grass, which is in front of the den. Since the fox is facing away from the den (towards the camera), this motion is in the fox's **Front**. 4. **Combining Vectors**: The motion is both to the fox's left and in its front. In a clock-face representation (where 12 is front and 9 is left), this corresponds to the **11 o'clock direction**. 5. **Verification**: - Right of image $\rightarrow$ Left of fox. - Towards camera $\rightarrow$ Front of fox. - Result $\rightarrow$ Left Front $\rightarrow$ 11 o'clock.
Next Goal
Return the final answer.
Tool Call
{
  "tool": "ReturnAnswer",
  "args": {
    "answer": "D"
  }
}
Execute
Output
[ReturnAnswer] Answer submitted: D
Answer
D

SpaceTools

✗ Incorrect
Reasoning

Based on the visual information provided (specifically image 5, which shows three young foxes), one fox is stationary near the entrance/platform, and the other two are running away from it. From the perspective of the stationary fox, the others are running forward and slightly to the right.

The correct option is F.

Final answer

Based on the visual information provided (specifically image 5, which shows three young foxes), one fox is stationary near the entrance/platform, and the other two are running away from it. From the perspective of the stationary fox, the others are running forward and slightly to the right.

The correct option is F.

Final response

Based on the visual information provided (specifically image 5, which shows three young foxes), one fox is stationary near the entrance/platform, and the other two are running away from it. From the perspective of the stationary fox, the others are running forward and slightly to the right.

The correct option is F.

SpatialClaw

✓ Correct
Plan

Task Analysis

The objective is to determine the direction in which two running foxes are moving relative to a stationary fox at the beginning of the video.

Implicit Coordinate System: The question specifies "From the perspective of the stationary fox." This requires an Object Perspective coordinate system. I must first determine the stationary fox's 3D position and its facing direction (heading). The "front" direction is defined by where the stationary fox is looking, and "left/right" are defined relative to that heading.

Target Variable: The relative direction of the motion vectors of the two running foxes with respect to the stationary fox's local coordinate system.

Answer Format: Multiple choice (A-H).

Information Needs

  1. Object Identification: Identify which fox is stationary and which two are running in the first few frames.
  2. Segmentation Masks: Precise masks for all three foxes over a temporal window to track their 3D centroids.
  3. 3D Geometry: A 3D reconstruction of the scene to obtain world-space coordinates and camera poses.
  4. Facing Direction: The orientation (heading vector) of the stationary fox, which can be determined via visual reasoning (VLM) and confirmed with show().
  5. Motion Vectors: The change in 3D position of the running foxes over time to calculate their velocity vectors.

Computation Plan

  1. Initial Visual Grounding:

    • Use show(InputImages[0], InputImages[1], InputImages[2]) to visually identify the three foxes and the den entrance.
    • Use vlm.ask_with_thinking on the first 5 frames to confirm which fox is stationary and describe the general direction the stationary fox is facing (e.g., "facing the camera," "facing the right side of the frame").
  2. Segmentation:

    • Use tools.SAM3.segment_video_by_text on the first 16 frames (start_frame=InputImages.frame_indices[0], end_frame=InputImages.frame_indices[15]) with the prompt ["fox"] to find all foxes.
    • If segment_video_by_text fails to distinguish the three individuals, I will use vlm.locate on the first frame to get bounding boxes for "the stationary fox", "running fox 1", and "running fox 2", then use tools.SAM3.segment_video_by_box.
    • Verify masks using seg.visualize(fi) and show() for a few frames.
  3. 3D Reconstruction:

    • Perform reconstruction on the first 16 frames: recon = tools.Reconstruct.Reconstruct(InputImages[:16]).
    • Render a BEV plot: recon.render_bev(masks=seg). This will provide a top-down view of the trajectories and the stationary fox's position.
  4. Quantitative Motion Analysis:

    • Extract 3D centroids for the stationary fox and the two running foxes across the first 16 frames using seg.get_centroid_3d(recon, frame=fi, object=i).
    • Calculate the motion vector $\vec{v}_{run}$ for the running foxes by taking the difference between centroids at the end and start of the sequence (or using a linear fit).
    • Verify the stationary fox's centroid remains constant (within a small noise threshold).
  5. Relative Direction Calculation:

    • Define Local Frame: Based on the VLM's description and visual inspection of InputImages[0], define the stationary fox's forward vector $\vec{f}$ in world space. (e.g., if the fox faces the camera, $\vec{f}$ is roughly opposite to the camera's forward vector recon.extrinsics[fi][:3, 2]).
    • Compute Right Vector: Calculate the right vector $\vec{r} = \vec{f} \times \text{world_up}$ (where world_up is $[0, 1, 0]$).
    • Project Motion: For each running fox's motion vector $\vec{v}_{run}$:
      • dot_fwd = np.dot(v_run, f) (Positive = Front, Negative = Rear)
      • dot_right = np.dot(v_run, r) (Positive = Right, Negative = Left)
    • Map these dot products to the multiple-choice options (e.g., dot_fwd > 0 and dot_right < 0 $\rightarrow$ Left Front).

Verification Checklist

[
  {"priority": "HIGH", "description": "Confirm segmentation masks correctly isolate the three foxes and maintain identity across frames"},
  {"priority": "HIGH", "description": "Accurately determine the facing direction (heading) of the stationary fox via VLM and visual check"},
  {"priority": "HIGH", "description": "Verify that the 'stationary' fox's 3D centroid does not show significant movement"},
  {"priority": "MEDIUM", "description": "Cross-reference the calculated relative direction with the BEV trajectory plot"},
  {"priority": "LOW", "description": "Check that 3D centroids are not NaN and are physically plausible (e.g., on the ground plane)"}
]

Fallbacks

  • Mask Failure: If SAM3 cannot distinguish the foxes, I will use vlm.locate to provide precise bounding boxes for each fox in the first frame and track them using segment_video_by_box.
  • Facing Direction Ambiguity: If the stationary fox's heading is unclear from a single frame, I will use vlm.ask_with_thinking across multiple frames to see if any slight head movements or
Step 0
LLM
Purpose
Initial visual grounding to identify the three foxes and determine the stationary fox's facing direction.
Reasoning
I need to visually confirm the positions and identities of the three foxes mentioned in the prompt. By inspecting the first few frames and using a VLM, I can identify which fox is stationary at the den entrance and determine its orientation, which is critical for establishing the "Object Perspective" coordinate system.
Next Goal
Segment the three foxes across a temporal window to track their 3D movements.
Execute
Code
# Show the first few frames to visually identify the foxes
show([InputImages[0], InputImages[1], InputImages[2]])

# Use VLM to identify the stationary fox and its facing direction
# We use the first 5 frames to provide temporal context for "stationary" vs "running"
question = (
    "In these frames, there are three little foxes. "
    "One is stationary at the entrance of the den, and two are running. "
    "1. Which fox is the stationary one? Describe its position. "
    "2. In which direction is the stationary fox facing? (e.g., facing the camera, facing right, etc.) "
    "3. In which general direction are the other two foxes running relative to the frame?"
)
vlm_answer = vlm.ask_with_thinking(InputImages[:5], question)
print(f"VLM Answer:\n{vlm_answer}")
Output
 [image: show_0001] 
[VLM Q | thinking] In these frames, there are three little foxes. One is stationary at the entrance of the den, and two are running. 1. Which fox is the stationary one? Describe its position. 2. In which direction is the stationary fox facing? (e.g., facing the camera, facing right, etc.) 3. In which general direction are the other two foxes running relative to the frame?
[VLM A | thinking] Based on the provided frames:

1. **The stationary fox** is the small pup located at the bottom center, peeking out from the entrance of the den (the gap under the logs).
2. The stationary fox is **facing the camera**.
3. The other foxes are running toward the **right** side of the frame (visible in frame 0).
VLM Answer:
Based on the provided frames:

1. **The stationary fox** is the small pup located at the bottom center, peeking out from the entrance of the den (the gap under the logs).
2. The stationary fox is **facing the camera**.
3. The other foxes are running toward the **right** side of the frame (visible in frame 0).
show_0001
Step 1
LLM
Purpose
Segment the three foxes across the first 16 frames to track their 3D positions.
Reasoning
To compute the relative motion, I need precise masks for each individual fox. I'll start with `segment_video_by_text` as it's the most straightforward method. If it fails to identify three distinct objects, I will fall back to VLM-guided bounding boxes for each fox.
Next Goal
Perform 3D reconstruction and render a BEV plot to visualize the trajectories.
Execute
Code
# Segment foxes in the first 16 frames
# start_frame and end_frame are absolute video frame indices
start_f = InputImages[0].frame_index
end_f = InputImages[15].frame_index

seg = tools.SAM3.segment_video_by_text(
    prompts=["fox"], 
    prompt_frame_idx=0, 
    start_frame=start_f, 
    end_frame=end_f
)

print(f"Number of objects detected: {seg.num_objects}")

# Verify the masks on the first frame
fi = seg.frame_indices[0]
vis = seg.visualize(fi)
show([InputImages[0], vis])

# Programmatic check for mask areas in the first frame
for i in range(seg.num_objects):
    mask = seg.get_mask(frame=fi, object=i)
    area = mask.sum()
    print(f"Object {i} area: {area} pixels")
Output
Number of objects detected: 1
 [image: show_0002] 
Object 0 area: 974 pixels
show_0002
Step 2
LLM
Purpose
Precisely segment the three foxes using VLM-guided bounding boxes.
Reasoning
The text-based segmentation failed to identify all three foxes. I will now use `vlm.locate` to find the bounding boxes for the stationary fox and the two running foxes in the first frame, and then use `segment_video_by_box` to track them across the video.
Next Goal
Perform 3D reconstruction and render a BEV plot to visualize the trajectories.
Execute
Code
# Locate the three foxes in the first frame
# 1. Stationary fox
# 2. Running fox 1
# 3. Running fox 2
img = InputImages[0]
W, H = img.width, img.height

box_stationary = vlm.locate(img, "Give the bounding box (x1, y1, x2, y2) in 0-1000 normalized scale for the stationary fox peeking from the den. Reply with ONLY the numbers.")
box_run1 = vlm.locate(img, "Give the bounding box (x1, y1, x2, y2) in 0-1000 normalized scale for the running fox on the right. Reply with ONLY the numbers.")
box_run2 = vlm.locate(img, "Give the bounding box (x1, y1, x2, y2) in 0-1000 normalized scale for the other running fox. Reply with ONLY the numbers.")

print(f"Stationary box: {box_stationary}")
print(f"Running 1 box: {box_run1}")
print(f"Running 2 box: {box_run2}")

def parse_box(box_str):
    # Remove any non-numeric characters except commas/spaces/dots
    import re
    nums = re.findall(r"[-+]?\d*\.\d+|\d+", box_str)
    return [float(n) for n in nums]

# Convert normalized to pixel coordinates
try:
    b_stat_norm = parse_box(box_stationary)
    b_run1_norm = parse_box(box_run1)
    b_run2_norm = parse_box(box_run2)
    
    b_stat = tools.Geometry.normalized_to_pixel(b_stat_norm, W, H)
    b_run1 = tools.Geometry.normalized_to_pixel(b_run1_norm, W, H)
    b_run2 = tools.Geometry.normalized_to_pixel(b_run2_norm, W, H)
    
    boxes = [b_stat, b_run1, b_run2]
    labels = ["stationary_fox", "running_fox_1", "running_fox_2"]
    
    # Segment and track the foxes
    seg = tools.SAM3.segment_video_by_box(
        boxes=boxes, 
        labels=labels, 
        prompt_frame_idx=0, 
        start_frame=start_f, 
        end_frame=end_f
    )
    
    # Verify masks on the first frame
    fi = seg.frame_indices[0]
    vis = seg.visualize(fi)
    show([img, vis])
    
    for i, label in enumerate(seg.labels):
        area = seg.get_mask(frame=fi, object=i).sum()
        print(f"{label} area: {area} pixels")

except Exception as e:
    print(f"Error during segmentation: {e}")
Output
[VLM Q | locate] Before answering, first check whether what the question describes is clearly visible in the provided image(s). If it is absent or ambiguous, reply EXACTLY `Not visible` on its own line (optionally followed by one short line explaining what you saw instead) — do NOT return coordinates in that case. Only if the requested target is clearly and unambiguously present, answer the request below.

Request: Give the bounding box (x1, y1, x2, y2) in 0-1000 normalized scale for the stationary fox peeking from the den. Reply with ONLY the numbers.
[VLM A | locate] 422 692 483 786
[VLM Q | locate] Before answering, first check whether what the question describes is clearly visible in the provided image(s). If it is absent or ambiguous, reply EXACTLY `Not visible` on its own line (optionally followed by one short line explaining what you saw instead) — do NOT return coordinates in that case. Only if the requested target is clearly and unambiguously present, answer the request below.

Request: Give the bounding box (x1, y1, x2, y2) in 0-1000 normalized scale for the running fox on the right. Reply with ONLY the numbers.
[VLM A | locate] 682, 546, 1000, 807
[VLM Q | locate] Before answering, first check whether what the question describes is clearly visible in the provided image(s). If it is absent or ambiguous, reply EXACTLY `Not visible` on its own line (optionally followed by one short line explaining what you saw instead) — do NOT return coordinates in that case. Only if the requested target is clearly and unambiguously present, answer the request below.

Request: Give the bounding box (x1, y1, x2, y2) in 0-1000 normalized scale for the other running fox. Reply with ONLY the numbers.
[VLM A | locate] Not visible
Only one running fox is present; the other fox is peeking from under the logs.
Stationary box: 422 692 483 786
Running 1 box: 682, 546, 1000, 807
Running 2 box: Not visible
Only one running fox is present; the other fox is peeking from under the logs.
E
Step 3
LLM
Purpose
Identify all three foxes and their locations across the first few frames.
Reasoning
The previous attempt to locate three foxes in a single frame failed because the VLM only saw two. The prompt explicitly mentions three foxes (one stationary, two running). I need to find where the third fox is. I'll use `vlm.ask_with_thinking` over a range of frames to pinpoint when all three are visible and where they are, then I'll use those frames to get bounding boxes.
Next Goal
Segment all three foxes and perform 3D reconstruction.
Execute
Code
# Use VLM to find all three foxes across the first 16 frames
question = (
    "In the first 16 frames, there are three little foxes: one stationary at the den and two running. "
    "Please identify the frames where all three are clearly visible. "
    "For those frames, describe the positions of the three foxes (stationary, running 1, running 2) "
    "relative to the frame (e.g., center, right, far right)."
)
vlm_fox_analysis = vlm.ask_with_thinking(InputImages[:16], question)
print(f"Fox Analysis:\n{vlm_fox_analysis}")

# Let's also just show a few more frames to see them ourselves
show([InputImages[0], InputImages[4], InputImages[8], InputImages[12]])
Output
[VLM Q | thinking] In the first 16 frames, there are three little foxes: one stationary at the den and two running. Please identify the frames where all three are clearly visible. For those frames, describe the positions of the three foxes (stationary, running 1, running 2) relative to the frame (e.g., center, right, far right).
[VLM A | thinking] Based on the provided frames, there are no frames where three little foxes are clearly visible. In frame 0, only two foxes are visible: one stationary in the den (center) and one running to the right (far right). In frames 1 and 2, only the stationary fox in the den is visible. Frames 3 through 5 show a close-up of a single fox, and the remaining frames feature different animals.
Fox Analysis:
Based on the provided frames, there are no frames where three little foxes are clearly visible. In frame 0, only two foxes are visible: one stationary in the den (center) and one running to the right (far right). In frames 1 and 2, only the stationary fox in the den is visible. Frames 3 through 5 show a close-up of a single fox, and the remaining frames feature different animals.
 [image: show_0003] 
show_0003
Step 4
LLM
Purpose
Determine the relative direction of the running foxes from the perspective of the stationary fox.
Reasoning
1. **Stationary Fox's Orientation**: From the VLM analysis and visual inspection of `InputImages[0]`, the stationary fox is peeking out of the den and is facing the camera. 2. **Running Foxes' Motion**: The VLM and visual inspection confirm that the running fox(es) are moving toward the right side of the image frame. 3. **Coordinate Transformation**: - The stationary fox's **forward (front)** direction is toward the camera. - From the perspective of someone facing the camera, the **right side of the image** corresponds to their **left side**. - Therefore, an object moving toward the right side of the image is moving to the **left** of the stationary fox. 4. **Conclusion**: Since the running foxes are moving toward the right of the frame and the stationary fox is facing the camera, they are running to the stationary fox's left. This matches option A.
Next Goal
Submit the final answer.
Execute
Code
ReturnAnswer("A")
Output
[ReturnAnswer] Answer submitted: A
Answer
A
Evaluation
Ground truth: A · Agent: A