extern number factor;
varying vec4 vpos;

#ifdef VERTEX
vec4 position( mat4 transform_projection, vec4 vertex_position ) {
  vpos = vertex_position;
  return transform_projection * vertex_position;
}
#endif

#ifdef PIXEL
vec4 effect( vec4 color, Image texture, vec2 texture_coords, vec2 screen_coords ) {
  texture_coords += vec2(factor * cos(0.1 * vpos.x), factor * sin(0.075 * vpos.y));
  vec4 texcolor = Texel(texture, texture_coords);
  return texcolor * color;
}
#endif