/*
 * Copyright 2011-2013 Blender Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "stdosl.h"

shader node_normal_map(
	normal NormalIn = N,
	float Strength = 1.0,
	color Color = color(0.5, 0.5, 1.0),
	string space = "tangent",
	string attr_name = "geom:tangent",
	string attr_sign_name = "geom:tangent_sign",
	output normal Normal = NormalIn)
{
	color mcolor = 2.0 * color(Color[0] - 0.5, Color[1] - 0.5, Color[2] - 0.5);
	int is_backfacing = backfacing();

	if (space == "tangent") {
		vector tangent;
		vector ninterp;
		float tangent_sign;
		float is_smooth;

		getattribute("geom:is_smooth", is_smooth);
		if (!is_smooth) {
			ninterp = normalize(transform("world", "object", Ng));

			/* the normal is already inverted, which is too soon for the math here */
			if (is_backfacing) {
				ninterp = -ninterp;
			}
		}

		// get _unnormalized_ interpolated normal and tangent
		if (getattribute(attr_name, tangent) &&
		    getattribute(attr_sign_name, tangent_sign) &&
		    (!is_smooth || getattribute("geom:N", ninterp)))
		{
			// apply normal map
			vector B = tangent_sign * cross(ninterp, tangent);
			Normal = normalize(mcolor[0] * tangent + mcolor[1] * B + mcolor[2] * ninterp);

			// transform to world space
			Normal = normalize(transform("object", "world", Normal));
		}
		else {
			Normal = normal(0, 0, 0);
		}
	}
	else if (space == "object") {
		Normal = normalize(transform("object", "world", vector(mcolor)));
	}
	else if (space == "world") {
		Normal = normalize(vector(mcolor));
	}
	else if (space == "blender_object") {
		/* strange blender convention */
		mcolor[1] = -mcolor[1];
		mcolor[2] = -mcolor[2];
	
		Normal = normalize(transform("object", "world", vector(mcolor)));
	}
	else if (space == "blender_world") {
		/* strange blender convention */
		mcolor[1] = -mcolor[1];
		mcolor[2] = -mcolor[2];
	
		Normal = normalize(vector(mcolor));
	}

	/* invert normal for backfacing polygons */
	if (is_backfacing) {
		Normal = -Normal;
	}

	if (Strength != 1.0)
		Normal = normalize(NormalIn + (Normal - NormalIn) * max(Strength, 0.0));
}