Cycles: Expose volume voxel data interpolation to the interface

It is per-material setting which could be found under the Volume settings
in the material and world context buttons.

There could still be some code-wise improvements, like using variable-size
macro for interp3d instead of having interp3d_ex to which you can pass the
interpolation method.

3 files changed, 27 insertions, 9 deletions

diff --git a/intern/cycles/kernel/geom/geom_volume.h b/intern/cycles/kernel/geom/geom_volume.h
index 33a20494966..3cb6d168f80 100644
--- a/intern/cycles/kernel/geom/geom_volume.h
+++ b/intern/cycles/kernel/geom/geom_volume.h
@@ -52,7 +52,11 @@ ccl_device float volume_attribute_float(KernelGlobals *kg, const ShaderData *sd,
 #ifdef __KERNEL_GPU__
 	float4 r = make_float4(0.0f, 0.0f, 0.0f, 0.0f);
 #else
-	float4 r = kernel_tex_image_interp_3d(id, P.x, P.y, P.z);
+	float4 r;
+	if(sd->flag & SD_VOLUME_CUBIC)
+		r = kernel_tex_image_interp_3d_ex(id, P.x, P.y, P.z, INTERPOLATION_CUBIC);
+	else
+		r = kernel_tex_image_interp_3d(id, P.x, P.y, P.z);
 #endif
 
 	if(dx) *dx = 0.0f;
@@ -68,7 +72,11 @@ ccl_device float3 volume_attribute_float3(KernelGlobals *kg, const ShaderData *s
 #ifdef __KERNEL_GPU__
 	float4 r = make_float4(0.0f, 0.0f, 0.0f, 0.0f);
 #else
-	float4 r = kernel_tex_image_interp_3d(id, P.x, P.y, P.z);
+	float4 r;
+	if(sd->flag & SD_VOLUME_CUBIC)
+		r = kernel_tex_image_interp_3d_ex(id, P.x, P.y, P.z, INTERPOLATION_CUBIC);
+	else
+		r = kernel_tex_image_interp_3d(id, P.x, P.y, P.z);
 #endif
 
 	if(dx) *dx = make_float3(0.0f, 0.0f, 0.0f);
diff --git a/intern/cycles/kernel/kernel_compat_cpu.h b/intern/cycles/kernel/kernel_compat_cpu.h
index e00caf5a720..37cba03ff97 100644
--- a/intern/cycles/kernel/kernel_compat_cpu.h
+++ b/intern/cycles/kernel/kernel_compat_cpu.h
@@ -151,6 +151,13 @@ template<typename T> struct texture_image  {
 
 	ccl_always_inline float4 interp_3d(float x, float y, float z, bool periodic = false)
 	{
+		return interp_3d_ex(x, y, z, interpolation, periodic);
+	}
+
+	ccl_always_inline float4 interp_3d_ex(float x, float y, float z,
+	                                      int interpolation = INTERPOLATION_LINEAR,
+	                                      bool periodic = false)
+	{
 		if(UNLIKELY(!data))
 			return make_float4(0.0f, 0.0f, 0.0f, 0.0f);
 
@@ -331,6 +338,7 @@ typedef texture_image<uchar4> texture_image_uchar4;
 #define kernel_tex_lookup(tex, t, offset, size) (kg->tex.lookup(t, offset, size))
 #define kernel_tex_image_interp(tex, x, y) ((tex < MAX_FLOAT_IMAGES) ? kg->texture_float_images[tex].interp(x, y) : kg->texture_byte_images[tex - MAX_FLOAT_IMAGES].interp(x, y))
 #define kernel_tex_image_interp_3d(tex, x, y, z) ((tex < MAX_FLOAT_IMAGES) ? kg->texture_float_images[tex].interp_3d(x, y, z) : kg->texture_byte_images[tex - MAX_FLOAT_IMAGES].interp_3d(x, y, z))
+#define kernel_tex_image_interp_3d_ex(tex, x, y, z, interpolation) ((tex < MAX_FLOAT_IMAGES) ? kg->texture_float_images[tex].interp_3d_ex(x, y, z, interpolation) : kg->texture_byte_images[tex - MAX_FLOAT_IMAGES].interp_3d_ex(x, y, z, interpolation))
 
 #define kernel_data (kg->__data)
 
diff --git a/intern/cycles/kernel/kernel_types.h b/intern/cycles/kernel/kernel_types.h
index ca1210f2d80..e49a6c6669e 100644
--- a/intern/cycles/kernel/kernel_types.h
+++ b/intern/cycles/kernel/kernel_types.h
@@ -616,18 +616,20 @@ enum ShaderDataFlag {
 	SD_HAS_BSSRDF_BUMP = 65536,			/* bssrdf normal uses bump */
 	SD_VOLUME_EQUIANGULAR = 131072,		/* use equiangular sampling */
 	SD_VOLUME_MIS = 262144,				/* use multiple importance sampling */
+	SD_VOLUME_CUBIC = 524288,
 
 	SD_SHADER_FLAGS = (SD_USE_MIS|SD_HAS_TRANSPARENT_SHADOW|SD_HAS_VOLUME|
 	                   SD_HAS_ONLY_VOLUME|SD_HETEROGENEOUS_VOLUME|
-					   SD_HAS_BSSRDF_BUMP|SD_VOLUME_EQUIANGULAR|SD_VOLUME_MIS),
+	                   SD_HAS_BSSRDF_BUMP|SD_VOLUME_EQUIANGULAR|SD_VOLUME_MIS|
+	                   SD_VOLUME_CUBIC),
 
 	/* object flags */
-	SD_HOLDOUT_MASK = 524288,			/* holdout for camera rays */
-	SD_OBJECT_MOTION = 1048576,			/* has object motion blur */
-	SD_TRANSFORM_APPLIED = 2097152,		/* vertices have transform applied */
-	SD_NEGATIVE_SCALE_APPLIED = 4194304,	/* vertices have negative scale applied */
-	SD_OBJECT_HAS_VOLUME = 8388608,		/* object has a volume shader */
-	SD_OBJECT_INTERSECTS_VOLUME = 16777216, /* object intersects AABB of an object with volume shader */
+	SD_HOLDOUT_MASK = 1048576,			/* holdout for camera rays */
+	SD_OBJECT_MOTION = 2097152,			/* has object motion blur */
+	SD_TRANSFORM_APPLIED = 4194304,		/* vertices have transform applied */
+	SD_NEGATIVE_SCALE_APPLIED = 8388608,	/* vertices have negative scale applied */
+	SD_OBJECT_HAS_VOLUME = 16777216,		/* object has a volume shader */
+	SD_OBJECT_INTERSECTS_VOLUME = 33554432, /* object intersects AABB of an object with volume shader */
 
 	SD_OBJECT_FLAGS = (SD_HOLDOUT_MASK|SD_OBJECT_MOTION|SD_TRANSFORM_APPLIED|
 	                   SD_NEGATIVE_SCALE_APPLIED|SD_OBJECT_HAS_VOLUME|