Cycles: Add voxel texture sampler shader node

The idea of this node is to sampling of 3D voxels at a given coordinate
supporting different mapping strategies (world space mapping, object
local space etc).

Currently not in use, it's a preparation step for supporting point density
textures.

intern/cycles/kernel/svm/svm.h

@@ -179,6 +179,7 @@ CCL_NAMESPACE_END
 #include "svm_checker.h"
 #include "svm_brick.h"
 #include "svm_vector_transform.h"
+#include "svm_voxel.h"
 
 CCL_NAMESPACE_BEGIN
 
@@ -446,6 +447,11 @@ ccl_device_noinline void svm_eval_nodes(KernelGlobals *kg, ShaderData *sd, Shade
 				svm_node_blackbody(kg, sd, stack, node.y, node.z);
 				break;
 #  endif  /* __EXTRA_NODES__ */
+#  if NODES_FEATURE(NODE_FEATURE_VOLUME)
+			case NODE_TEX_VOXEL:
+				svm_node_tex_voxel(kg, sd, stack, node, &offset);
+				break;
+#  endif  /* NODES_FEATURE(NODE_FEATURE_VOLUME) */
 #endif  /* NODES_GROUP(NODE_GROUP_LEVEL_3) */
 			case NODE_END:
 				return;

intern/cycles/kernel/svm/svm_types.h

@@ -125,7 +125,8 @@ typedef enum NodeType {
 	NODE_TANGENT,
 	NODE_NORMAL_MAP,
 	NODE_HAIR_INFO,
-	NODE_UVMAP
+	NODE_UVMAP,
+	NODE_TEX_VOXEL,
 } NodeType;
 
 typedef enum NodeAttributeType {
@@ -349,6 +350,11 @@ typedef enum NodeBumpOffset {
 	NODE_BUMP_OFFSET_DY,
 } NodeBumpOffset;
 
+typedef enum NodeTexVoxelSpace {
+	NODE_TEX_VOXEL_SPACE_OBJECT = 0,
+	NODE_TEX_VOXEL_SPACE_WORLD  = 1,
+} NodeTexVoxelSpace;
+
 typedef enum ShaderType {
 	SHADER_TYPE_SURFACE,
 	SHADER_TYPE_VOLUME,

intern/cycles/kernel/svm/svm_voxel.h

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2011-2015 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
+
+/* TODO(sergey): Think of making it more generic volume-type attribute
+ * sampler.
+ */
+ccl_device void svm_node_tex_voxel(KernelGlobals *kg,
+                                   ShaderData *sd,
+                                   float *stack,
+                                   uint4 node,
+                                   int *offset)
+{
+	int id = node.y;
+	uint co_offset, density_out_offset, color_out_offset, space;
+	decode_node_uchar4(node.z, &co_offset, &density_out_offset, &color_out_offset, &space);
+	float3 co = stack_load_float3(stack, co_offset);
+	if(space == NODE_TEX_VOXEL_SPACE_OBJECT) {
+		co = volume_normalized_position(kg, sd, co);
+	}
+	else {
+		kernel_assert(space == NODE_TEX_VOXEL_SPACE_WORLD);
+		Transform tfm;
+		tfm.x = read_node_float(kg, offset);
+		tfm.y = read_node_float(kg, offset);
+		tfm.z = read_node_float(kg, offset);
+		tfm.w = read_node_float(kg, offset);
+		co = transform_point(&tfm, co);
+	}
+	if(co.x < 0.0f || co.y < 0.0f || co.z < 0.0f ||
+	   co.x > 1.0f || co.y > 1.0f || co.z > 1.0f)
+	{
+		if (stack_valid(density_out_offset))
+			stack_store_float(stack, density_out_offset, 0.0f);
+		if (stack_valid(color_out_offset))
+			stack_store_float3(stack, color_out_offset, make_float3(0.0f, 0.0f, 0.0f));
+		return;
+	}
+#ifdef __KERNEL_GPU__
+	float4 r = make_float4(0.0f, 0.0f, 0.0f, 0.0f);
+#else
+	float4 r = kernel_tex_image_interp_3d(id, co.x, co.y, co.z);
+#endif
+	if (stack_valid(density_out_offset))
+		stack_store_float(stack, density_out_offset, r.w);
+	if (stack_valid(color_out_offset))
+		stack_store_float3(stack, color_out_offset, make_float3(r.x, r.y, r.z));
+}
+
+CCL_NAMESPACE_END