#version 120
attribute vec2 in_vertex;
attribute vec2 in_position;
attribute vec2 in_velocity;

uniform float maxAge;
varying float decay;
varying vec2 velocity;
varying vec2 vertex;
uniform float time;
uniform float size;
void main()
{
  //decay = min(1.0, time+5.0*length(velocity)) / maxAge;
  //decay = max(decay*decay, sqrt(decay));
  decay = time / maxAge;

  vec2 base = in_vertex;
  vec2 p = size*base;
  p += log(1.0+time) * in_velocity;
  p += in_position;
  gl_Position = vec4(p, 0.0, 1.0);

  vertex   = base;
  velocity = in_velocity;
}