#version 330 core

uniform float particleSize;

layout(points) in;
layout(triangle_strip, max_vertices = 4) out;

in Vertex {
 vec2 texCoord;
 vec4 colour;
} IN [];
out Vertex {
 vec2 texCoord;
 vec4 colour;
} OUT; 

void main() {
 for (int i = 0; i < gl_in.length(); ++i) {
  OUT.colour = IN[i].colour;
  
 // Top Right 
  gl_Position = gl_in [i].gl_Position;
  gl_Position.x += particleSize;
  gl_Position.y += particleSize;
  OUT.texCoord = vec2(1,0);
  EmitVertex();
  
 // Top Left
  gl_Position =  gl_in[i].gl_Position;
  gl_Position.x -= particleSize;
  gl_Position.y += particleSize;
  OUT.texCoord = vec2(0,0);
  EmitVertex();
  
// Bottom Right
  gl_Position = gl_in[i].gl_Position;
  gl_Position.x += particleSize;
  gl_Position -= particleSize;
  OUT.texCoord = vec2(1,1);
  EmitVertex();
  
// Bottom Left
  gl_Position = gl_in[i].gl_Position;
  gl_Position.x -= particleSize;
  gl_Position.y -= particleSize;
  OUT.texCoord = vec2(0,1);
  EmitVertex();

  EndPrimitive();
   }
}