Manual Tracking Motion Capture

Manual Motion capture using 2 cameras (One Month)

Introduction

This method is a replica of what is done in performance capture studio using Optical Motion capture. In this method 2 Cameras are used with frame rate of 60FPS to avoid motion blur, so that the markers are seen properly for tracking. No special suit used. Wore black cloths and some reflective tape to make reflective markers which gives perfect contrast and gets track very easily. Used Autodesk suit for the entire process and School’s photo studio to capture motion.

Equipment’s

2 cannon 550D cameras, 2 tripod, 2 Halogen lights, and several meters of reflective tape.

Stage
Media Design Photo Studio. Sufficient area to capture motion. There was sufficient distance between actor and camera. As the lens was 18-55 I was able to capture wide angle. Used black curtains behind to get contrast with markers

Pre-Capture

It took almost two weeks to search for reflective tape which can be used for markers. Wrapped around paper and attached it with glue. Made the markers round so that it can be visible from everywhere. Stage was set up with black cloth. For the light to reflect I used small torch which I kept it on top of the camera for same angle. But the power of the light was insufficient so used Halogens which was kept just above the camera for the light to get reflected.

Performance Capture

Capture session lasted for 4 days whit different angels and measurements. 4th day shoot was perfect where all the settings were matching and was able to calibrate both the videos. Both the cameras were same with same setting. As the measurement of the cameras were similar, calibration was done properly. A small tape was placed on ground which measures the Z and X coordinates.
This is how the software will understand the 3D world.

Post Processing

Once the shooting was done, footage was imported in Autodesk Match mover.
Match mover has technology of solving two cameras. Match mover measures the distance in units it also calculates the distance of cameras to center point. Both the cameras gets calibrate in this software. All the markers will have tracking points which will get track in this software. Once all the points are tracked, it can be exported as .trc file which is readable in Motion builder. Motion builder is another Autodesk software which reads motion data. The trc file will be readable in this software. The file will get imported as small blue cube markers in the software. These markers will then get attached to actor which is a default character in motion builder, this actor will drive the rigged character which is exported from Maya. And then thrown back to Maya with animation. The rig which is exported from Motion builder is in form of .fbx. This file contains all the format which is readable in Maya. Motion builder’s exports animation which is baked on all the key frames. This rig can be attached to any character which has same joint structure.
Retweeting is next step where all the unwanted movement and jerks are removed. We can put new animation on top of current animation. Downloaded a script which removes unwanted key frames and makes our work easy. Final step is to render.

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