spookonomics/shaders/firefly/vertex.glsl

attribute float aScale;

uniform float uPixelRatio;
uniform float uTime;

void main()
{
    vec4 modelPosition = modelMatrix * vec4(position, 1.0);
    modelPosition.y += sin(uTime + modelPosition.x * 100.0) * aScale * 0.1;
    vec4 viewPosition = viewMatrix * modelPosition;
    vec4 projectionPosition = projectionMatrix * viewPosition;

    gl_Position = projectionPosition;
    gl_PointSize = 100.0 * aScale * uPixelRatio;
    gl_PointSize *= (1.0  / -viewPosition.z);
}