/*
 * Copyright 2011-2016 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.
 */

/* Functions for retrieving attributes on triangles produced from subdivision meshes */

CCL_NAMESPACE_BEGIN

/* Patch index for triangle, -1 if not subdivision triangle */

ccl_device_inline uint subd_triangle_patch(KernelGlobals *kg, const ShaderData *sd)
{
	return (sd->prim != PRIM_NONE) ? kernel_tex_fetch(__tri_patch, sd->prim) : ~0;
}

/* UV coords of triangle within patch */

ccl_device_inline void subd_triangle_patch_uv(KernelGlobals *kg, const ShaderData *sd, float2 uv[3])
{
	uint4 tri_vindex = kernel_tex_fetch(__tri_vindex, sd->prim);

	uv[0] = kernel_tex_fetch(__tri_patch_uv, tri_vindex.x);
	uv[1] = kernel_tex_fetch(__tri_patch_uv, tri_vindex.y);
	uv[2] = kernel_tex_fetch(__tri_patch_uv, tri_vindex.z);
}

/* Vertex indices of patch */

ccl_device_inline uint4 subd_triangle_patch_indices(KernelGlobals *kg, int patch)
{
	uint4 indices;

	indices.x = kernel_tex_fetch(__patches, patch+0);
	indices.y = kernel_tex_fetch(__patches, patch+1);
	indices.z = kernel_tex_fetch(__patches, patch+2);
	indices.w = kernel_tex_fetch(__patches, patch+3);

	return indices;
}

/* Originating face for patch */

ccl_device_inline uint subd_triangle_patch_face(KernelGlobals *kg, int patch)
{
	return kernel_tex_fetch(__patches, patch+4);
}

/* Number of corners on originating face */

ccl_device_inline uint subd_triangle_patch_num_corners(KernelGlobals *kg, int patch)
{
	return kernel_tex_fetch(__patches, patch+5) & 0xffff;
}

/* Indices of the four corners that are used by the patch */

ccl_device_inline void subd_triangle_patch_corners(KernelGlobals *kg, int patch, int corners[4])
{
	uint4 data;

	data.x = kernel_tex_fetch(__patches, patch+4);
	data.y = kernel_tex_fetch(__patches, patch+5);
	data.z = kernel_tex_fetch(__patches, patch+6);
	data.w = kernel_tex_fetch(__patches, patch+7);

	int num_corners = data.y & 0xffff;

	if(num_corners == 4) {
		/* quad */
		corners[0] = data.z;
		corners[1] = data.z+1;
		corners[2] = data.z+2;
		corners[3] = data.z+3;
	}
	else {
		/* ngon */
		int c = data.y >> 16;

		corners[0] = data.z + c;
		corners[1] = data.z + mod(c+1, num_corners);
		corners[2] = data.w;
		corners[3] = data.z + mod(c-1, num_corners);
	}
}

/* Reading attributes on various subdivision triangle elements */

ccl_device_noinline float subd_triangle_attribute_float(KernelGlobals *kg, const ShaderData *sd, const AttributeDescriptor desc, float *dx, float *dy)
{
	int patch = subd_triangle_patch(kg, sd);

#ifdef __PATCH_EVAL__
	if(desc.flags & ATTR_SUBDIVIDED) {
		float2 uv[3];
		subd_triangle_patch_uv(kg, sd, uv);

		float2 dpdu = uv[0] - uv[2];
		float2 dpdv = uv[1] - uv[2];

		/* p is [s, t] */
		float2 p = dpdu * sd->u + dpdv * sd->v + uv[2];

		float a, dads, dadt;
		a = patch_eval_float(kg, sd, desc.offset, patch, p.x, p.y, 0, &dads, &dadt);

#ifdef __RAY_DIFFERENTIALS__
		if(dx || dy) {
			float dsdu = dpdu.x;
			float dtdu = dpdu.y;
			float dsdv = dpdv.x;
			float dtdv = dpdv.y;

			if(dx) {
				float dudx = sd->du.dx;
				float dvdx = sd->dv.dx;

				float dsdx = dsdu*dudx + dsdv*dvdx;
				float dtdx = dtdu*dudx + dtdv*dvdx;

				*dx = dads*dsdx + dadt*dtdx;
			}
			if(dy) {
				float dudy = sd->du.dy;
				float dvdy = sd->dv.dy;

				float dsdy = dsdu*dudy + dsdv*dvdy;
				float dtdy = dtdu*dudy + dtdv*dvdy;

				*dy = dads*dsdy + dadt*dtdy;
			}
		}
#endif

		return a;
	}
	else
#endif  /* __PATCH_EVAL__ */
	if(desc.element == ATTR_ELEMENT_FACE) {
		if(dx) *dx = 0.0f;
		if(dy) *dy = 0.0f;

		return kernel_tex_fetch(__attributes_float, desc.offset + subd_triangle_patch_face(kg, patch));
	}
	else if(desc.element == ATTR_ELEMENT_VERTEX || desc.element == ATTR_ELEMENT_VERTEX_MOTION) {
		float2 uv[3];
		subd_triangle_patch_uv(kg, sd, uv);

		uint4 v = subd_triangle_patch_indices(kg, patch);

		float f0 = kernel_tex_fetch(__attributes_float, desc.offset + v.x);
		float f1 = kernel_tex_fetch(__attributes_float, desc.offset + v.y);
		float f2 = kernel_tex_fetch(__attributes_float, desc.offset + v.z);
		float f3 = kernel_tex_fetch(__attributes_float, desc.offset + v.w);

		if(subd_triangle_patch_num_corners(kg, patch) != 4) {
			f1 = (f1+f0)*0.5f;
			f3 = (f3+f0)*0.5f;
		}

		float a = mix(mix(f0, f1, uv[0].x), mix(f3, f2, uv[0].x), uv[0].y);
		float b = mix(mix(f0, f1, uv[1].x), mix(f3, f2, uv[1].x), uv[1].y);
		float c = mix(mix(f0, f1, uv[2].x), mix(f3, f2, uv[2].x), uv[2].y);

#ifdef __RAY_DIFFERENTIALS__
		if(dx) *dx = sd->du.dx*a + sd->dv.dx*b - (sd->du.dx + sd->dv.dx)*c;
		if(dy) *dy = sd->du.dy*a + sd->dv.dy*b - (sd->du.dy + sd->dv.dy)*c;
#endif

		return sd->u*a + sd->v*b + (1.0f - sd->u - sd->v)*c;
	}
	else if(desc.element == ATTR_ELEMENT_CORNER) {
		float2 uv[3];
		subd_triangle_patch_uv(kg, sd, uv);

		int corners[4];
		subd_triangle_patch_corners(kg, patch, corners);

		float f0 = kernel_tex_fetch(__attributes_float, corners[0] + desc.offset);
		float f1 = kernel_tex_fetch(__attributes_float, corners[1] + desc.offset);
		float f2 = kernel_tex_fetch(__attributes_float, corners[2] + desc.offset);
		float f3 = kernel_tex_fetch(__attributes_float, corners[3] + desc.offset);

		if(subd_triangle_patch_num_corners(kg, patch) != 4) {
			f1 = (f1+f0)*0.5f;
			f3 = (f3+f0)*0.5f;
		}

		float a = mix(mix(f0, f1, uv[0].x), mix(f3, f2, uv[0].x), uv[0].y);
		float b = mix(mix(f0, f1, uv[1].x), mix(f3, f2, uv[1].x), uv[1].y);
		float c = mix(mix(f0, f1, uv[2].x), mix(f3, f2, uv[2].x), uv[2].y);

#ifdef __RAY_DIFFERENTIALS__
		if(dx) *dx = sd->du.dx*a + sd->dv.dx*b - (sd->du.dx + sd->dv.dx)*c;
		if(dy) *dy = sd->du.dy*a + sd->dv.dy*b - (sd->du.dy + sd->dv.dy)*c;
#endif

		return sd->u*a + sd->v*b + (1.0f - sd->u - sd->v)*c;
	}
	else {
		if(dx) *dx = 0.0f;
		if(dy) *dy = 0.0f;

		return 0.0f;
	}
}

ccl_device_noinline float3 subd_triangle_attribute_float3(KernelGlobals *kg, const ShaderData *sd, const AttributeDescriptor desc, float3 *dx, float3 *dy)
{
	int patch = subd_triangle_patch(kg, sd);

#ifdef __PATCH_EVAL__
	if(desc.flags & ATTR_SUBDIVIDED) {
		float2 uv[3];
		subd_triangle_patch_uv(kg, sd, uv);

		float2 dpdu = uv[0] - uv[2];
		float2 dpdv = uv[1] - uv[2];

		/* p is [s, t] */
		float2 p = dpdu * sd->u + dpdv * sd->v + uv[2];

		float3 a, dads, dadt;

		if(desc.element == ATTR_ELEMENT_CORNER_BYTE) {
			a = patch_eval_uchar4(kg, sd, desc.offset, patch, p.x, p.y, 0, &dads, &dadt);
		}
		else {
			a = patch_eval_float3(kg, sd, desc.offset, patch, p.x, p.y, 0, &dads, &dadt);
		}

#ifdef __RAY_DIFFERENTIALS__
		if(dx || dy) {
			float dsdu = dpdu.x;
			float dtdu = dpdu.y;
			float dsdv = dpdv.x;
			float dtdv = dpdv.y;

			if(dx) {
				float dudx = sd->du.dx;
				float dvdx = sd->dv.dx;

				float dsdx = dsdu*dudx + dsdv*dvdx;
				float dtdx = dtdu*dudx + dtdv*dvdx;

				*dx = dads*dsdx + dadt*dtdx;
			}
			if(dy) {
				float dudy = sd->du.dy;
				float dvdy = sd->dv.dy;

				float dsdy = dsdu*dudy + dsdv*dvdy;
				float dtdy = dtdu*dudy + dtdv*dvdy;

				*dy = dads*dsdy + dadt*dtdy;
			}
		}
#endif

		return a;
	}
	else
#endif  /* __PATCH_EVAL__ */
	if(desc.element == ATTR_ELEMENT_FACE) {
		if(dx) *dx = make_float3(0.0f, 0.0f, 0.0f);
		if(dy) *dy = make_float3(0.0f, 0.0f, 0.0f);

		return float4_to_float3(kernel_tex_fetch(__attributes_float3, desc.offset + subd_triangle_patch_face(kg, patch)));
	}
	else if(desc.element == ATTR_ELEMENT_VERTEX || desc.element == ATTR_ELEMENT_VERTEX_MOTION) {
		float2 uv[3];
		subd_triangle_patch_uv(kg, sd, uv);

		uint4 v = subd_triangle_patch_indices(kg, patch);

		float3 f0 = float4_to_float3(kernel_tex_fetch(__attributes_float3, desc.offset + v.x));
		float3 f1 = float4_to_float3(kernel_tex_fetch(__attributes_float3, desc.offset + v.y));
		float3 f2 = float4_to_float3(kernel_tex_fetch(__attributes_float3, desc.offset + v.z));
		float3 f3 = float4_to_float3(kernel_tex_fetch(__attributes_float3, desc.offset + v.w));

		if(subd_triangle_patch_num_corners(kg, patch) != 4) {
			f1 = (f1+f0)*0.5f;
			f3 = (f3+f0)*0.5f;
		}

		float3 a = mix(mix(f0, f1, uv[0].x), mix(f3, f2, uv[0].x), uv[0].y);
		float3 b = mix(mix(f0, f1, uv[1].x), mix(f3, f2, uv[1].x), uv[1].y);
		float3 c = mix(mix(f0, f1, uv[2].x), mix(f3, f2, uv[2].x), uv[2].y);

#ifdef __RAY_DIFFERENTIALS__
		if(dx) *dx = sd->du.dx*a + sd->dv.dx*b - (sd->du.dx + sd->dv.dx)*c;
		if(dy) *dy = sd->du.dy*a + sd->dv.dy*b - (sd->du.dy + sd->dv.dy)*c;
#endif

		return sd->u*a + sd->v*b + (1.0f - sd->u - sd->v)*c;
	}
	else if(desc.element == ATTR_ELEMENT_CORNER || desc.element == ATTR_ELEMENT_CORNER_BYTE) {
		float2 uv[3];
		subd_triangle_patch_uv(kg, sd, uv);

		int corners[4];
		subd_triangle_patch_corners(kg, patch, corners);

		float3 f0, f1, f2, f3;

		if(desc.element == ATTR_ELEMENT_CORNER) {
			f0 = float4_to_float3(kernel_tex_fetch(__attributes_float3, corners[0] + desc.offset));
			f1 = float4_to_float3(kernel_tex_fetch(__attributes_float3, corners[1] + desc.offset));
			f2 = float4_to_float3(kernel_tex_fetch(__attributes_float3, corners[2] + desc.offset));
			f3 = float4_to_float3(kernel_tex_fetch(__attributes_float3, corners[3] + desc.offset));
		}
		else {
			f0 = color_byte_to_float(kernel_tex_fetch(__attributes_uchar4, corners[0] + desc.offset));
			f1 = color_byte_to_float(kernel_tex_fetch(__attributes_uchar4, corners[1] + desc.offset));
			f2 = color_byte_to_float(kernel_tex_fetch(__attributes_uchar4, corners[2] + desc.offset));
			f3 = color_byte_to_float(kernel_tex_fetch(__attributes_uchar4, corners[3] + desc.offset));
		}

		if(subd_triangle_patch_num_corners(kg, patch) != 4) {
			f1 = (f1+f0)*0.5f;
			f3 = (f3+f0)*0.5f;
		}

		float3 a = mix(mix(f0, f1, uv[0].x), mix(f3, f2, uv[0].x), uv[0].y);
		float3 b = mix(mix(f0, f1, uv[1].x), mix(f3, f2, uv[1].x), uv[1].y);
		float3 c = mix(mix(f0, f1, uv[2].x), mix(f3, f2, uv[2].x), uv[2].y);

#ifdef __RAY_DIFFERENTIALS__
		if(dx) *dx = sd->du.dx*a + sd->dv.dx*b - (sd->du.dx + sd->dv.dx)*c;
		if(dy) *dy = sd->du.dy*a + sd->dv.dy*b - (sd->du.dy + sd->dv.dy)*c;
#endif

		return sd->u*a + sd->v*b + (1.0f - sd->u - sd->v)*c;
	}
	else {
		if(dx) *dx = make_float3(0.0f, 0.0f, 0.0f);
		if(dy) *dy = make_float3(0.0f, 0.0f, 0.0f);

		return make_float3(0.0f, 0.0f, 0.0f);
	}
}

CCL_NAMESPACE_END