layout(triangles, invocations=2) in;
layout(triangle_strip, max_vertices=3) out;
out vec4 fcolor;
in vec4 fca[];
in int gl_InvocationID;
uniform mat4 mvp;

void main(){
	vec3 a = gl_in[2].gl_Position.xyz - gl_in[0].gl_Position.xyz;
	vec3 b = gl_in[1].gl_Position.xyz - gl_in[0].gl_Position.xyz;
	vec3 normal = normalize(cross(b,a));

	for(int i = 0; i < 3; i++){
		if(1 != gl_InvocationID)
			gl_Position = mvp * (gl_in[i].gl_Position + vec4(normal, 0) * 3);
		else 
			gl_Position = mvp * gl_in[i].gl_Position;

		fcolor = fca[i];
		EmitVertex();
	}	
	EndPrimitive();
}