bounce ball shader

gistfile1.txt

// fragment shader
#version 150
 
uniform float time;
uniform vec2 mouse;
uniform vec2 startingPosition;
uniform float gravity;
uniform vec2 initialVelocity;
uniform float ballRadius;
uniform float rebound;
uniform int numBounces;
out vec4 outputColor;
 
void main()
{
  float x = startingPosition.x + initialVelocity.x * time;
  float y = startingPosition.y;

  float prevBounce = 0;
  for(int n = 0; n < numBounces; n++){
     float thisBounce = (initialVelocity.y * pow(rebound,n-1))/gravity + prevBounce;

    if(time > prevBounce && time < thisBounce){
      y = startingPosition.y + initialVelocity.y*pow(rebound,n-1) * (time - prevBounce) - gravity*pow(time-prevBounce,2);
    }
    prevBounce = thisBounce;
  }

  vec2 ball = vec2(x,y);

  vec2 pos = (gl_FragCoord.xy - ball);
  float dist_squared = dot(pos, pos);
  
  if (dist_squared < ballRadius){
    outputColor = vec4(1,1,1,1);
  } else {
    outputColor = vec4(0,0,0,1);
  }
}

gistfile2.txt

// vertex shader (passthrough)
#version 150
uniform mat4 modelViewProjectionMatrix;
in vec4 position;
 
void main(){
    gl_Position = modelViewProjectionMatrix * position;
}