blender/intern/cycles/kernel/geom/geom_motion_curve.h

/*
 * 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

/* Motion Curve Primitive
 *
 * These are stored as regular curves, plus extra positions and radii at times
 * other than the frame center. Computing the curve keys at a given ray time is
 * a matter of interpolation of the two steps between which the ray time lies.
 *
 * The extra curve keys are stored as ATTR_STD_MOTION_VERTEX_POSITION.
 */

#ifdef __HAIR__

ccl_device_inline int find_attribute_curve_motion(KernelGlobals *kg, int object, uint id, AttributeElement *elem)
{
	/* todo: find a better (faster) solution for this, maybe store offset per object */
	uint attr_offset = object*kernel_data.bvh.attributes_map_stride + ATTR_PRIM_CURVE;
	uint4 attr_map = kernel_tex_fetch(__attributes_map, attr_offset);
	
	while(attr_map.x != id) {
		attr_offset += ATTR_PRIM_TYPES;
		attr_map = kernel_tex_fetch(__attributes_map, attr_offset);
	}

	*elem = (AttributeElement)attr_map.y;
	
	/* return result */
	return (attr_map.y == ATTR_ELEMENT_NONE) ? (int)ATTR_STD_NOT_FOUND : (int)attr_map.z;
}

ccl_device_inline void motion_curve_keys_for_step(KernelGlobals *kg, int offset, int numkeys, int numsteps, int step, int k0, int k1, float4 keys[2])
{
	if(step == numsteps) {
		/* center step: regular vertex location */
		keys[0] = kernel_tex_fetch(__curve_keys, k0);
		keys[1] = kernel_tex_fetch(__curve_keys, k1);
	}
	else {
		/* center step not stored in this array */
		if(step > numsteps)
			step--;

		offset += step*numkeys;

		keys[0] = kernel_tex_fetch(__attributes_float3, offset + k0);
		keys[1] = kernel_tex_fetch(__attributes_float3, offset + k1);
	}
}

/* return 2 curve key locations */
ccl_device_inline void motion_curve_keys(KernelGlobals *kg, int object, int prim, float time, int k0, int k1, float4 keys[2])
{
	/* get motion info */
	int numsteps, numkeys;
	object_motion_info(kg, object, &numsteps, NULL, &numkeys);

	/* figure out which steps we need to fetch and their interpolation factor */
	int maxstep = numsteps*2;
	int step = min((int)(time*maxstep), maxstep-1);
	float t = time*maxstep - step;

	/* find attribute */
	AttributeElement elem;
	int offset = find_attribute_curve_motion(kg, object, ATTR_STD_MOTION_VERTEX_POSITION, &elem);
	kernel_assert(offset != ATTR_STD_NOT_FOUND);

	/* fetch key coordinates */
	float4 next_keys[2];

	motion_curve_keys_for_step(kg, offset, numkeys, numsteps, step, k0, k1, keys);
	motion_curve_keys_for_step(kg, offset, numkeys, numsteps, step+1, k0, k1, next_keys);

	/* interpolate between steps */
	keys[0] = (1.0f - t)*keys[0] + t*next_keys[0];
	keys[1] = (1.0f - t)*keys[1] + t*next_keys[1];
}

ccl_device_inline void motion_cardinal_curve_keys_for_step(KernelGlobals *kg, int offset, int numkeys, int numsteps, int step, int k0, int k1, int k2, int k3, float4 keys[4])
{
	if(step == numsteps) {
		/* center step: regular vertex location */
		keys[0] = kernel_tex_fetch(__curve_keys, k0);
		keys[1] = kernel_tex_fetch(__curve_keys, k1);
		keys[2] = kernel_tex_fetch(__curve_keys, k2);
		keys[3] = kernel_tex_fetch(__curve_keys, k3);
	}
	else {
		/* center step not store in this array */
		if(step > numsteps)
			step--;

		offset += step*numkeys;

		keys[0] = kernel_tex_fetch(__attributes_float3, offset + k0);
		keys[1] = kernel_tex_fetch(__attributes_float3, offset + k1);
		keys[2] = kernel_tex_fetch(__attributes_float3, offset + k2);
		keys[3] = kernel_tex_fetch(__attributes_float3, offset + k3);
	}
}

/* return 2 curve key locations */
ccl_device_inline void motion_cardinal_curve_keys(KernelGlobals *kg, int object, int prim, float time, int k0, int k1, int k2, int k3, float4 keys[4])
{
	/* get motion info */
	int numsteps, numkeys;
	object_motion_info(kg, object, &numsteps, NULL, &numkeys);

	/* figure out which steps we need to fetch and their interpolation factor */
	int maxstep = numsteps*2;
	int step = min((int)(time*maxstep), maxstep-1);
	float t = time*maxstep - step;

	/* find attribute */
	AttributeElement elem;
	int offset = find_attribute_curve_motion(kg, object, ATTR_STD_MOTION_VERTEX_POSITION, &elem);
	kernel_assert(offset != ATTR_STD_NOT_FOUND);

	/* fetch key coordinates */
	float4 next_keys[4];

	motion_cardinal_curve_keys_for_step(kg, offset, numkeys, numsteps, step, k0, k1, k2, k3, keys);
	motion_cardinal_curve_keys_for_step(kg, offset, numkeys, numsteps, step+1, k0, k1, k2, k3, next_keys);

	/* interpolate between steps */
	keys[0] = (1.0f - t)*keys[0] + t*next_keys[0];
	keys[1] = (1.0f - t)*keys[1] + t*next_keys[1];
	keys[2] = (1.0f - t)*keys[2] + t*next_keys[2];
	keys[3] = (1.0f - t)*keys[3] + t*next_keys[3];
}

#endif

CCL_NAMESPACE_END