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/* SPDX-License-Identifier: Apache-2.0
* Copyright 2011-2022 Blender Foundation */
/* Volume Primitive
*
* Volumes are just regions inside meshes with the mesh surface as boundaries.
* There isn't as much data to access as for surfaces, there is only a position
* to do lookups in 3D voxel or procedural textures.
*
* 3D voxel textures can be assigned as attributes per mesh, which means the
* same shader can be used for volume objects with different densities, etc. */
#pragma once
CCL_NAMESPACE_BEGIN
#ifdef __VOLUME__
/* Return position normalized to 0..1 in mesh bounds */
ccl_device_inline float3 volume_normalized_position(KernelGlobals kg,
ccl_private const ShaderData *sd,
float3 P)
{
/* todo: optimize this so it's just a single matrix multiplication when
* possible (not motion blur), or perhaps even just translation + scale */
const AttributeDescriptor desc = find_attribute(kg, sd, ATTR_STD_GENERATED_TRANSFORM);
object_inverse_position_transform(kg, sd, &P);
if (desc.offset != ATTR_STD_NOT_FOUND) {
Transform tfm = primitive_attribute_matrix(kg, sd, desc);
P = transform_point(&tfm, P);
}
return P;
}
ccl_device float volume_attribute_value_to_float(const float4 value)
{
return average(float4_to_float3(value));
}
ccl_device float volume_attribute_value_to_alpha(const float4 value)
{
return value.w;
}
ccl_device float3 volume_attribute_value_to_float3(const float4 value)
{
if (value.w > 1e-6f && value.w != 1.0f) {
/* For RGBA colors, unpremultiply after interpolation. */
return float4_to_float3(value) / value.w;
}
else {
return float4_to_float3(value);
}
}
ccl_device float4 volume_attribute_float4(KernelGlobals kg,
ccl_private const ShaderData *sd,
const AttributeDescriptor desc)
{
if (desc.element & (ATTR_ELEMENT_OBJECT | ATTR_ELEMENT_MESH)) {
return kernel_data_fetch(attributes_float4, desc.offset);
}
else if (desc.element == ATTR_ELEMENT_VOXEL) {
/* todo: optimize this so we don't have to transform both here and in
* kernel_tex_image_interp_3d when possible. Also could optimize for the
* common case where transform is translation/scale only. */
float3 P = sd->P;
object_inverse_position_transform(kg, sd, &P);
InterpolationType interp = (sd->flag & SD_VOLUME_CUBIC) ? INTERPOLATION_CUBIC :
INTERPOLATION_NONE;
return kernel_tex_image_interp_3d(kg, desc.offset, P, interp);
}
else {
return zero_float4();
}
}
#endif
CCL_NAMESPACE_END
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