nuclear@0: #version 410 compatibility
nuclear@0: 
nuclear@1: layout(quads, ccw) in;
nuclear@0: 
nuclear@0: out vec3 normal;
nuclear@0: out vec3 vpos;
nuclear@2: out vec2 uv;
nuclear@0: 
nuclear@1: uniform vec3 norm_scale;
nuclear@1: 
nuclear@0: vec3 bezier_patch(float u, float v);
nuclear@0: vec3 bezier_patch_norm(float u, float v);
nuclear@0: float bernstein(int i, float x);
nuclear@0: 
nuclear@0: void main()
nuclear@0: {
nuclear@0: 	vec3 pos = bezier_patch(gl_TessCoord.x, gl_TessCoord.y);
nuclear@0: 	normal = gl_NormalMatrix * bezier_patch_norm(gl_TessCoord.x, gl_TessCoord.y);
nuclear@0: 
nuclear@2: 	uv = gl_TessCoord.xy;
nuclear@2: 
nuclear@0: 	gl_Position = gl_ModelViewProjectionMatrix * vec4(pos, 1.0);
nuclear@0: 	vpos = (gl_ModelViewMatrix * vec4(pos, 1.0)).xyz;
nuclear@0: }
nuclear@0: 
nuclear@0: vec3 bezier_patch(float u, float v)
nuclear@0: {
nuclear@0: 	int i, j;
nuclear@0: 	vec3 res = vec3(0.0, 0.0, 0.0);
nuclear@0: 
nuclear@0: 	for(j=0; j<4; j++) {
nuclear@0: 		for(i=0; i<4; i++) {
nuclear@0: 			float bu = bernstein(i, u);
nuclear@0: 			float bv = bernstein(j, v);
nuclear@0: 
nuclear@0: 			res += gl_in[j * 4 + i].gl_Position.xyz * bu * bv;
nuclear@0: 		}
nuclear@0: 	}
nuclear@0: 	return res;
nuclear@0: }
nuclear@0: 
nuclear@0: #define DT 0.0001
nuclear@0: vec3 bezier_patch_norm(float u, float v)
nuclear@0: {
nuclear@0: 	vec3 tang = bezier_patch(u + DT, v) - bezier_patch(u - DT, v);
nuclear@0: 	vec3 bitan = bezier_patch(u, v + DT) - bezier_patch(u, v - DT);
nuclear@1: 	return cross(tang, bitan) * norm_scale;
nuclear@0: }
nuclear@0: 
nuclear@0: float bernstein(int i, float x)
nuclear@0: {
nuclear@0: 	float invx = 1.0 - x;
nuclear@0: 
nuclear@0: 	if(i == 0) {
nuclear@0: 		return invx * invx * invx;
nuclear@0: 	}
nuclear@0: 	if(i == 1) {
nuclear@0: 		return 3 * x * invx * invx;
nuclear@0: 	}
nuclear@0: 	if(i == 2) {
nuclear@0: 		return 3 * x * x * invx;
nuclear@0: 	}
nuclear@0: 	return x * x * x;
nuclear@0: }