#version 120
#extension GL_EXT_gpu_shader4: enable
#extension GL_EXT_geometry_shader4: enable

uniform float Shrink;
varying in vec3 Normal[3];
varying out float LightIntensity;

const vec3 LightPos = vec3( 0., 10., 0. );

vec3 V[3];
vec3 CG;

void
ProduceVertex( int v )
{
	LightIntensity  = dot( normalize(LightPos - V[v]), Normal[v] );
	LightIntensity = abs( LightIntensity );
	LightIntensity *= 1.5;

	gl_Position = gl_ProjectionMatrix * vec4( CG + Shrink * ( V[v] - CG ), 1. );
	EmitVertex();
}



void
main()
{
	V[0]  =   gl_PositionIn[0].xyz;
	V[1]  =   gl_PositionIn[1].xyz;
	V[2]  =   gl_PositionIn[2].xyz;

	CG = 0.33333 * ( V[0] + V[1] + V[2] );

	ProduceVertex( 0 );
	ProduceVertex( 1 );
	ProduceVertex( 2 );
}