Rollpie Motion Path Animation is a free trajectory and swept-area simulator that runs in your browser with no install. Roll a circle, sector, square, equilateral triangle, or rectangle along a line, a slope, or the inside of a box, and visualize the path a point on the shape traces and the region the shape sweeps. It helps with learning how shapes roll and rotate.
Pick a shape and an environment, click the point on the shape you want to trace, and press play to roll the shape while it draws the trajectory and swept region. Adjust the speed and playback position, and save your animation as a video or an image.