Intial commit for volume motion blur.

3 files changed, 40 insertions, 4 deletions

diff --git a/intern/cycles/kernel/geom/geom_volume.h b/intern/cycles/kernel/geom/geom_volume.h
index 346f228e961..51a7efc1457 100644
--- a/intern/cycles/kernel/geom/geom_volume.h
+++ b/intern/cycles/kernel/geom/geom_volume.h
@@ -47,11 +47,40 @@ ccl_device_inline float3 volume_normalized_position(KernelGlobals *kg,
 	return P;
 }
 
-ccl_device float volume_attribute_float(KernelGlobals *kg, const ShaderData *sd, const AttributeDescriptor desc, float *dx, float *dy)
+/* Returns normalized P.
+ * If motion blur is enabled, returns normalized and advected P. */
+
+ccl_device_inline float3 volume_get_position(KernelGlobals *kg,
+                                             const ShaderData *sd)
 {
 	float3 P = volume_normalized_position(kg, sd, sd->P);
+
+	/* Eulerian motion blur. */
+	if(kernel_data.cam.shuttertime != -1.0f) {
+		AttributeDescriptor v_desc = find_attribute(kg, sd, ATTR_STD_VOLUME_VELOCITY);
+
+		if (v_desc.offset != ATTR_STD_NOT_FOUND) {
+			InterpolationType interp = (sd->flag & SD_VOLUME_CUBIC)? INTERPOLATION_CUBIC: INTERPOLATION_NONE;
+
+			/* Find velocity. */
+			float3 velocity = float4_to_float3(kernel_tex_image_interp_3d(kg, v_desc.offset, P.x, P.y, P.z, interp));
+
+			/* Find advected velocity. */
+			P = volume_normalized_position(kg, sd, sd->P + velocity * sd->time);
+			velocity = float4_to_float3(kernel_tex_image_interp_3d(kg, v_desc.offset, P.x, P.y, P.z, interp));
+
+			/* Find advected P. */
+			P = volume_normalized_position(kg, sd, sd->P + velocity * sd->time);
+		}
+	}
+
+	return P;
+}
+
+ccl_device float volume_attribute_float(KernelGlobals *kg, const ShaderData *sd, const AttributeDescriptor desc, float *dx, float *dy)
+{
 	InterpolationType interp = (sd->flag & SD_VOLUME_CUBIC)? INTERPOLATION_CUBIC: INTERPOLATION_NONE;
-	float4 r = kernel_tex_image_interp_3d(kg, desc.offset, P.x, P.y, P.z, interp);
+	float4 r = kernel_tex_image_interp_3d(kg, desc.offset, sd->P_v.x, sd->P_v.y, sd->P_v.z, interp);
 
 	if(dx) *dx = 0.0f;
 	if(dy) *dy = 0.0f;
@@ -61,9 +90,8 @@ ccl_device float volume_attribute_float(KernelGlobals *kg, const ShaderData *sd,
 
 ccl_device float3 volume_attribute_float3(KernelGlobals *kg, const ShaderData *sd, const AttributeDescriptor desc, float3 *dx, float3 *dy)
 {
-	float3 P = volume_normalized_position(kg, sd, sd->P);
 	InterpolationType interp = (sd->flag & SD_VOLUME_CUBIC)? INTERPOLATION_CUBIC: INTERPOLATION_NONE;
-	float4 r = kernel_tex_image_interp_3d(kg, desc.offset, P.x, P.y, P.z, interp);
+	float4 r = kernel_tex_image_interp_3d(kg, desc.offset, sd->P_v.x, sd->P_v.y, sd->P_v.z, interp);
 
 	if(dx) *dx = make_float3(0.0f, 0.0f, 0.0f);
 	if(dy) *dy = make_float3(0.0f, 0.0f, 0.0f);
diff --git a/intern/cycles/kernel/kernel_shader.h b/intern/cycles/kernel/kernel_shader.h
index 937a50cba8b..64b1e070982 100644
--- a/intern/cycles/kernel/kernel_shader.h
+++ b/intern/cycles/kernel/kernel_shader.h
@@ -1211,6 +1211,9 @@ ccl_device_inline void shader_eval_volume(KernelGlobals *kg,
 			/* todo: this is inefficient for motion blur, we should be
 			 * caching matrices instead of recomputing them each step */
 			shader_setup_object_transforms(kg, sd, sd->time);
+
+			/* Cache volume P. */
+			sd->P_v = volume_get_position(kg, sd);
 #endif
 		}
 
diff --git a/intern/cycles/kernel/kernel_types.h b/intern/cycles/kernel/kernel_types.h
index 72fbf7be557..63ff8f3ba6f 100644
--- a/intern/cycles/kernel/kernel_types.h
+++ b/intern/cycles/kernel/kernel_types.h
@@ -1058,6 +1058,11 @@ typedef ccl_addr_space struct ShaderData {
 
 	/* At the end so we can adjust size in ShaderDataTinyStorage. */
 	struct ShaderClosure closure[MAX_CLOSURE];
+
+#ifdef __VOLUME__
+	/* Normalized volume position. May be advected for motion blur. */
+	float3 P_v;
+#endif
 } ShaderData;
 
 typedef ccl_addr_space struct ShaderDataTinyStorage {