MAYA LIVE / MOTION TRACKING WORKFLOW

In a previous blog I mentioned the problems I was encountering when matchmoving some video in Maya Live. It turned out the CMOS technology within my camera produced a rolling shutter effect that made things very difficult when tracking as each frame slightly bent and warped with the movement of the camera. I sort of gave up for a while with the intention of coming back to this when I got my hands on a different camera. However I had got tired of waiting and believed that if the camera movement was kept to a mininal amount, some degree of successful may follow. I was right. Below is my step-by-step process to create a smooth track with little but some handheld real world camera movement.

1. Load Maya Live into the plug-in Manager and create a New Matchmove Scene

2. Browse for the Image Sequence of the video that needs tracking and click the green icon Ready To Track

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3. Change from Setup to Track in the drop-down box. Click the red arrow icon and Create to insert the first tracking point into the scene.

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4. Move the tracking point1 onto a spot or well defined area where there is a sharp contrast in tonal range. This data is important for the efficiency of the track and must be chosen carefully. Click Start Track.

5. Once point1 has tracked the full length of the clip the results will show in the graph window where the data is represented by the colour green if successful, yellow if moderate or red for a failed attempt. The image below shows tracking point2 only reaching frame 150 before losing its mark. If this happens, return the tracking marker to the point it’s following and press Start Track to continue.

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6. When the coloured bar at the bottom of the graph window is mainly green Maya is ready to Solve the scene. Around 10 tracking points are generally needed before this occurs.

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7. Change from Track to Solve in the drop-down box and chose the option Survey. It’s important now to create a plane that will line up with the ground in our video. After selecting all the tracking points on the floor change the Constraint Type to Plane and click create. Make sure that Registration Only is ticked.

8. Select 2 tracking points from the scene and change the constraint type to Distance. Enter a number that will represent the physical distance between each point and uncheck Registration Only for this.

9. The last constraint we need to create is a Point constraint that will snap the blue plane to one of the tracking markers in the center of our scene.

Picture 7(2)

10. Once these 3 constraints have been made click back onto the Solve icon where the tracking data will be solved and parented to the 3D camera.

11. If the solve is successful you will see the blue plane fixed to the ground when you playback the video. The 3D camera in Maya now accurately copies the movement of the video camera, allowing realistic integration of CGI over live-action.

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