blender-archive/intern/cycles/kernel/svm/svm_gradient.h

/*
 * 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.
 */

CCL_NAMESPACE_BEGIN

/* Gradient */

ccl_device float svm_gradient(float3 p, NodeGradientType type)
{
	float x, y, z;

	x = p.x;
	y = p.y;
	z = p.z;

	if(type == NODE_BLEND_LINEAR) {
		return x;
	}
	else if(type == NODE_BLEND_QUADRATIC) {
		float r = fmaxf(x, 0.0f);
		return r*r;
	}
	else if(type == NODE_BLEND_EASING) {
		float r = fminf(fmaxf(x, 0.0f), 1.0f);
		float t = r*r;
		
		return (3.0f*t - 2.0f*t*r);
	}
	else if(type == NODE_BLEND_DIAGONAL) {
		return (x + y) * 0.5f;
	}
	else if(type == NODE_BLEND_RADIAL) {
		return atan2f(y, x) / M_2PI_F + 0.5f;
	}
	else {
		/* Bias a little bit for the case where p is a unit length vector,
		 * to get exactly zero instead of a small random value depending
		 * on float precision. */
		float r = fmaxf(0.999999f - sqrtf(x*x + y*y + z*z), 0.0f);

		if(type == NODE_BLEND_QUADRATIC_SPHERE)
			return r*r;
		else if(type == NODE_BLEND_SPHERICAL)
			return r;
	}

	return 0.0f;
}

ccl_device void svm_node_tex_gradient(ShaderData *sd, float *stack, uint4 node)
{
	uint type, co_offset, color_offset, fac_offset;

	decode_node_uchar4(node.y, &type, &co_offset, &fac_offset, &color_offset);

	float3 co = stack_load_float3(stack, co_offset);

	float f = svm_gradient(co, (NodeGradientType)type);
	f = saturate(f);

	if(stack_valid(fac_offset))
		stack_store_float(stack, fac_offset, f);
	if(stack_valid(color_offset))
		stack_store_float3(stack, color_offset, make_float3(f, f, f));
}

CCL_NAMESPACE_END