Motion Capture - Week 1

Motion Capture Lab 1 - Documentation


This week's lab was learning how to calibrate the Optitrack system using IR reflector markers so that we could make our own rigid bodies that could then control objects in Unreal!


Step 1 - Calibration

First, we needed to make sure the cameras knew where they were in relation to each other and the space. We wanted to mask out objects that we did not want to track or any cameras that were seen by the other cameras. We made sure all 16 cameras were working (2 cameras had some issues so we ended up going with 14 cameras instead).


Next, came the wanding. We moved the wand in figure 8 movements around the space, make sure to capture all the points up and down. Each camera needed to have at least 10,000 points in order for the calibration score to be excellent.


To calibrate the floor, we placed the L shape wand on the floor with the Z axis pointing in the forward direction or where the director would be standing (with an offset of 55 from the floor).



Step 2 - Create Rigid Body


We then used a basketball and put some IR reflector markers to create our own rigid body. We needed at least a minimum of three reflective points, but put five to be safe from occlusion (someone obstructing one of the points from the camera). We moved the ball around and bounced it off of the floor, observing its movement as we tracked it. And then recorded a scene with its movement.





Step 3 - Unreal Engine:

Then we transferred our rigid bodies to objects in Unreal and experimented with live input, with one rigid body doubling as a camera within Unreal. Finding the right angel was hard and figuring out how to move the camera to find these bodies was also difficult. It took a while to finally get the hang of it. The other thing was figuring out how to navigate a larger space than the one we were in and adjusting to scale and controlling the space. Because of the placement of the centroid of the object that was the camera, it was very difficult to control and navigate the unreal environment.


Overall, this was a great first hands on lab to experiment with motion capture and unreal and i'm excited to learn more!