blender-archive/source/blender/draw/modes/shaders/object_particle_prim_vert.glsl

uniform bool screen_space;
uniform float draw_size;
uniform vec3 color;
uniform sampler1D ramp;

/* ---- Instantiated Attrs ---- */
in vec3 inst_pos;
in int axis;

/* ---- Per instance Attrs ---- */
in vec3 pos;
in vec4 rot;
in float val;

flat out vec4 finalColor;

vec3 rotate(vec3 vec, vec4 quat)
{
  /* The quaternion representation here stores the w component in the first index */
  return vec + 2.0 * cross(quat.yzw, cross(quat.yzw, vec) + quat.x * vec);
}

void main()
{
  if (screen_space) {
    gl_Position = ViewMatrix * (ModelMatrix * vec4(pos, 1.0));
    gl_Position.xyz += inst_pos * draw_size;
    gl_Position = ProjectionMatrix * gl_Position;
  }
  else {
    float size = draw_size;

    if (axis > -1) {
      size *= 2;
    }

    vec3 pos_rot = pos + rotate(inst_pos * size, rot);
    gl_Position = point_object_to_ndc(pos_rot);
  }

#ifdef USE_AXIS
  if (axis == 0) {
    finalColor = vec4(1.0, 0.0, 0.0, 1.0);
  }
  else if (axis == 1) {
    finalColor = vec4(0.0, 1.0, 0.0, 1.0);
  }
  else {
    finalColor = vec4(0.0, 0.0, 1.0, 1.0);
  }
#else
  if (val < 0.0) {
    finalColor = vec4(color, 1.0);
  }
  else {
    finalColor = vec4(texture(ramp, val).rgb, 1.0);
  }
#endif
}