Problem
Planar tracking fails when the target surface becomes partially occluded by a foreground object.
Solution
Root Cause / Diagnostic:
Planar tracking algorithms evaluate homography by analyzing optical flow and luminance patterns across an entire planar surface region. When a foreground subject (such as an actor's hand or walking pedestrian) passes across the tracking plane, the tracker incorporates the foreground object's motion vectors into the planar equation. This corrupts the transformation matrix, resulting in sudden jumps, severe rotation errors, or complete tracking failure.
Actionable Fix:
1. Draw a foreground exclusion matte (garbage mask) around the occluding subject and link it to an independent foreground track placed above the background tracking layer in the layer stack.
2. In Mocha AE, place the occlusion matte layer higher in the layer list so the planar solver excludes foreground pixels from the background plane calculation.
3. Inspect tracking point confidence scores across the occlusion frames to confirm that zero foreground drift influences the background planar solve.
Pro Tip:
Always order tracking layers in Mocha from closest to camera at the top to furthest from camera at the bottom; Mocha automatically clips out underlying planes using higher-level splines.
Planar tracking algorithms evaluate homography by analyzing optical flow and luminance patterns across an entire planar surface region. When a foreground subject (such as an actor's hand or walking pedestrian) passes across the tracking plane, the tracker incorporates the foreground object's motion vectors into the planar equation. This corrupts the transformation matrix, resulting in sudden jumps, severe rotation errors, or complete tracking failure.
Actionable Fix:
1. Draw a foreground exclusion matte (garbage mask) around the occluding subject and link it to an independent foreground track placed above the background tracking layer in the layer stack.
2. In Mocha AE, place the occlusion matte layer higher in the layer list so the planar solver excludes foreground pixels from the background plane calculation.
3. Inspect tracking point confidence scores across the occlusion frames to confirm that zero foreground drift influences the background planar solve.
Pro Tip:
Always order tracking layers in Mocha from closest to camera at the top to furthest from camera at the bottom; Mocha automatically clips out underlying planes using higher-level splines.