// Copyright (C) 2011 by The Alexandra Institute Ltd.
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

#version 330
#extension GL_EXT_geometry_shader4 : enable

layout(triangles) in;
layout(triangle_strip, max_vertices = 3) out;

precision mediump float;

// Attributes
out vec3 kTexcoord;	// Texcoord

// Uniforms
uniform int iGridSize;	// Grid cell count

// Shader code
void main() 
{
	for(int i = 0; i < 3; i++)
	{
		// Find grid position
		vec4 kGridPos = gl_in[i].gl_Position;
		
		// Offset by half a gridcell size to center of grid cell
		kGridPos += 1.0 / iGridSize;
		
		// Use position as texcoord
		kTexcoord = (kGridPos.xyz + 1.0) * 0.5;
		
		// Set layer and emit vertex into LPV grid
		gl_Position = vec4(kGridPos.xy, 0.0, 1.0);
		gl_Layer = int(floor(kTexcoord.z * iGridSize));
		EmitVertex();
	}
	
	EndPrimitive();
}