uniform mat4 ModelViewProjectionMatrix; uniform float size; uniform float outlineWidth; in vec2 pos; out vec4 radii; void main() { gl_Position = ModelViewProjectionMatrix * vec4(pos, 0.0, 1.0); gl_PointSize = size; // calculate concentric radii in pixels float radius = 0.5 * size; // start at the outside and progress toward the center radii[0] = radius; radii[1] = radius - 1.0; radii[2] = radius - outlineWidth; radii[3] = radius - outlineWidth - 1.0; // convert to PointCoord units radii /= size; }