Jan 9, 2015

For the radar visualization (top of the right panel) wanted to achieve the look of this graphic by Anton Repponen, sort of like a warped circular radar, bent at certain points. Previously, I’ve used sequences of bezier curves to create a b-spline (continuous at the second derivative, as described here), and animating it by only controlling the points along the control polygon/a-frame. For example, the four graphs on the left panel use this technique.

For the radar, we just added the third dimension. The control points were constrained to a sphere, so while the spline still retains somewhat of a circular shape, it still appears warped:

The spline was then just repeated, slightly smaller each time for the concentric rings look. Making the curves anything more than hairline thin was the main challenge behind this animation. From what I’ve found OpenGL 3 refuses to allow anything above 1.0 for glLineWidth, and the conventional solution is to make each line a quad. For a bezier curve, this meant subdividing it into sequences of lines and then making each line a quad with a geometry shader like so. This worked well in 2D, moving it to 3D has some problem with which way the quad is facing, but for my case it was subtle enough to ignore.

After that I made the spline fade away like a radar giving the final look:

Tomorrow I’ll upload the animation, and hopefully make some progress on the remaining components.