uniform int PrimitiveIdBase;
uniform int osd_active_uv_offset;

varying vec3 varnormal;
varying vec3 varposition;

in block {
	VertexData v;
} inpt[4];

uniform bool osd_flat_shading;
uniform int osd_fvar_count;

#define INTERP_FACE_VARYING_2(result, fvarOffset, tessCoord)  \
	{ \
		vec2 v[4]; \
		int primOffset = (gl_PrimitiveID + PrimitiveIdBase) * 4; \
		for (int i = 0; i < 4; ++i) { \
			int index = (primOffset + i) * osd_fvar_count + fvarOffset; \
			v[i] = vec2(texelFetch(FVarDataBuffer, index).s, \
			            texelFetch(FVarDataBuffer, index + 1).s); \
		} \
		result = mix(mix(v[0], v[1], tessCoord.s), \
		             mix(v[3], v[2], tessCoord.s), \
		             tessCoord.t); \
	}

uniform samplerBuffer FVarDataBuffer;

out block {
	VertexData v;
} outpt;

void set_mtface_vertex_attrs(vec2 st);

void emit_flat(int index, vec3 normal)
{
	outpt.v.position = inpt[index].v.position;
	outpt.v.normal = normal;

	/* Compatibility */
	varnormal = outpt.v.normal;
	varposition = outpt.v.position.xyz;

	/* TODO(sergey): Only uniform subdivisions atm. */
	vec2 quadst[4] = vec2[](vec2(0,0), vec2(1,0), vec2(1,1), vec2(0,1));
	vec2 st = quadst[index];

	INTERP_FACE_VARYING_2(outpt.v.uv, osd_active_uv_offset, st);

	set_mtface_vertex_attrs(st);

	gl_Position = gl_ProjectionMatrix * inpt[index].v.position;
	EmitVertex();
}

void emit_smooth(int index)
{
	outpt.v.position = inpt[index].v.position;
	outpt.v.normal = inpt[index].v.normal;

	/* Compatibility */
	varnormal = outpt.v.normal;
	varposition = outpt.v.position.xyz;

	/* TODO(sergey): Only uniform subdivisions atm. */
	vec2 quadst[4] = vec2[](vec2(0,0), vec2(1,0), vec2(1,1), vec2(0,1));
	vec2 st = quadst[index];

	INTERP_FACE_VARYING_2(outpt.v.uv, osd_active_uv_offset, st);

	set_mtface_vertex_attrs(st);

	gl_Position = gl_ProjectionMatrix * inpt[index].v.position;
	EmitVertex();
}

void main()
{
	gl_PrimitiveID = gl_PrimitiveIDIn;

	if (osd_flat_shading) {
		vec3 A = (inpt[0].v.position - inpt[1].v.position).xyz;
		vec3 B = (inpt[3].v.position - inpt[1].v.position).xyz;
		vec3 flat_normal = normalize(cross(B, A));
		emit_flat(0, flat_normal);
		emit_flat(1, flat_normal);
		emit_flat(3, flat_normal);
		emit_flat(2, flat_normal);
	}
	else {
		emit_smooth(0);
		emit_smooth(1);
		emit_smooth(3);
		emit_smooth(2);
	}
	EndPrimitive();
}

void set_mtface_vertex_attrs(vec2 st) {