feat: add world origin triad and explicit render-space mapping to visualization

py_workspace/README.md

@@ -75,11 +75,12 @@ Use `--birdseye` for a top-down X-Z view (looking down Y axis).
 uv run visualize_extrinsics.py -i output/extrinsics.json --birdseye --show
 ```
 
-**Ground Plane Overlay:**
-Render a semi-transparent X-Z ground plane to anchor camera poses.
+**Ground Plane & Origin Overlay:**
+Render a semi-transparent X-Z ground plane and/or a world origin triad.
 - `--show-ground/--no-show-ground`: Toggle ground plane (default: show).
 - `--ground-y FLOAT`: Set the Y height of the plane (default: 0.0).
 - `--ground-size FLOAT`: Set the side length of the plane in meters (default: 8.0).
+- `--show-origin-axes/--no-show-origin-axes`: Toggle world origin triad (X:red, Y:green, Z:blue) (default: show).
 
 *Example: Ground plane at Y=-1.5 with 10m size*
 ```bash

py_workspace/visualize_extrinsics.py

@@ -474,6 +474,11 @@ def run_diagnostics(poses: Dict[str, np.ndarray], convention: str):
     default=8.0,
     help="Size of the ground plane (side length in meters).",
 )
+@click.option(
+    "--show-origin-axes/--no-show-origin-axes",
+    default=True,
+    help="Show a world-origin axis triad (X:red, Y:green, Z:blue).",
+)
 def main(
     input: str,
     output: Optional[str],
@@ -491,6 +496,7 @@ def main(
     show_ground: bool,
     ground_y: float,
     ground_size: float,
+    show_origin_axes: bool,
 ):
     """Visualize camera extrinsics from JSON using Plotly."""
     try:
@@ -546,6 +552,52 @@ def main(
             intrinsics=cam_intrinsics,
         )
 
+    if show_origin_axes:
+        origin = np.zeros(3)
+        axis_len = scale
+        fig.add_trace(
+            go.Scatter3d(
+                x=[origin[0], origin[0] + axis_len],
+                y=[origin[1], origin[1]],
+                z=[origin[2], origin[2]],
+                mode="lines",
+                line=dict(color="red", width=4),
+                name="World X",
+                legendgroup="Origin",
+                showlegend=True,
+                hoverinfo="text",
+                text="World X",
+            )
+        )
+        fig.add_trace(
+            go.Scatter3d(
+                x=[origin[0], origin[0]],
+                y=[origin[1], origin[1] + axis_len],
+                z=[origin[2], origin[2]],
+                mode="lines",
+                line=dict(color="green", width=4),
+                name="World Y",
+                legendgroup="Origin",
+                showlegend=True,
+                hoverinfo="text",
+                text="World Y",
+            )
+        )
+        fig.add_trace(
+            go.Scatter3d(
+                x=[origin[0], origin[0]],
+                y=[origin[1], origin[1]],
+                z=[origin[2], origin[2] + axis_len],
+                mode="lines",
+                line=dict(color="blue", width=4),
+                name="World Z",
+                legendgroup="Origin",
+                showlegend=True,
+                hoverinfo="text",
+                text="World Z",
+            )
+        )
+
     if show_ground:
         half_size = ground_size / 2.0
         x_grid = np.linspace(-half_size, half_size, 2)
@@ -583,10 +635,16 @@ def main(
             eye=dict(x=0, y=2.5, z=0),
         )
 
+    render_desc = (
+        "OpenCV: local +X,+Y,+Z (Y-down)"
+        if render_space == "opencv"
+        else "OpenGL: local +X,-Y,-Z (Y-up, Z-back) rel. to OpenCV"
+    )
+
     fig.update_layout(
-        title=f"Camera Extrinsics ({pose_convention}, {render_space})",
+        title=f"Camera Extrinsics ({pose_convention})<br><sup>{render_desc}</sup>",
         scene=scene_dict,
-        margin=dict(l=0, r=0, b=0, t=40),
+        margin=dict(l=0, r=0, b=0, t=60),
         legend=dict(x=0, y=1),
     )