Cycles: merge of cycles-x branch, a major update to the renderer

This includes much improved GPU rendering performance, viewport interactivity,
new shadow catcher, revamped sampling settings, subsurface scattering anisotropy,
new GPU volume sampling, improved PMJ sampling pattern, and more.

Some features have also been removed or changed, breaking backwards compatibility.
Including the removal of the OpenCL backend, for which alternatives are under
development.

Release notes and code docs:
https://wiki.blender.org/wiki/Reference/Release_Notes/3.0/Cycles
https://wiki.blender.org/wiki/Source/Render/Cycles

Credits:
* Sergey Sharybin
* Brecht Van Lommel
* Patrick Mours (OptiX backend)
* Christophe Hery (subsurface scattering anisotropy)
* William Leeson (PMJ sampling pattern)
* Alaska (various fixes and tweaks)
* Thomas Dinges (various fixes)

For the full commit history, see the cycles-x branch. This squashes together
all the changes since intermediate changes would often fail building or tests.

Ref T87839, T87837, T87836
Fixes T90734, T89353, T80267, T80267, T77185, T69800

1 files changed, 62 insertions, 11 deletions

diff --git a/intern/cycles/kernel/kernel_differential.h b/intern/cycles/kernel/kernel_differential.h
index 3ec0cdbaccc..db4e110bd10 100644
--- a/intern/cycles/kernel/kernel_differential.h
+++ b/intern/cycles/kernel/kernel_differential.h
@@ -14,26 +14,28 @@
  * limitations under the License.
  */
 
+#pragma once
+
 CCL_NAMESPACE_BEGIN
 
 /* See "Tracing Ray Differentials", Homan Igehy, 1999. */
 
-ccl_device void differential_transfer(ccl_addr_space differential3 *dP_,
-                                      const differential3 dP,
-                                      float3 D,
-                                      const differential3 dD,
-                                      float3 Ng,
-                                      float t)
+ccl_device void differential_transfer(ccl_addr_space differential3 *surface_dP,
+                                      const differential3 ray_dP,
+                                      float3 ray_D,
+                                      const differential3 ray_dD,
+                                      float3 surface_Ng,
+                                      float ray_t)
 {
   /* ray differential transfer through homogeneous medium, to
    * compute dPdx/dy at a shading point from the incoming ray */
 
-  float3 tmp = D / dot(D, Ng);
-  float3 tmpx = dP.dx + t * dD.dx;
-  float3 tmpy = dP.dy + t * dD.dy;
+  float3 tmp = ray_D / dot(ray_D, surface_Ng);
+  float3 tmpx = ray_dP.dx + ray_t * ray_dD.dx;
+  float3 tmpy = ray_dP.dy + ray_t * ray_dD.dy;
 
-  dP_->dx = tmpx - dot(tmpx, Ng) * tmp;
-  dP_->dy = tmpy - dot(tmpy, Ng) * tmp;
+  surface_dP->dx = tmpx - dot(tmpx, surface_Ng) * tmp;
+  surface_dP->dy = tmpy - dot(tmpy, surface_Ng) * tmp;
 }
 
 ccl_device void differential_incoming(ccl_addr_space differential3 *dI, const differential3 dD)
@@ -112,4 +114,53 @@ ccl_device differential3 differential3_zero()
   return d;
 }
 
+/* Compact ray differentials that are just a scale to reduce memory usage and
+ * access cost in GPU.
+ *
+ * See above for more accurate reference implementations.
+ *
+ * TODO: also store the more compact version in ShaderData and recompute where
+ * needed? */
+
+ccl_device_forceinline float differential_zero_compact()
+{
+  return 0.0f;
+}
+
+ccl_device_forceinline float differential_make_compact(const differential3 D)
+{
+  return 0.5f * (len(D.dx) + len(D.dy));
+}
+
+ccl_device_forceinline void differential_transfer_compact(ccl_addr_space differential3 *surface_dP,
+                                                          const float ray_dP,
+                                                          const float3 /* ray_D */,
+                                                          const float ray_dD,
+                                                          const float3 surface_Ng,
+                                                          const float ray_t)
+{
+  /* ray differential transfer through homogeneous medium, to
+   * compute dPdx/dy at a shading point from the incoming ray */
+  float scale = ray_dP + ray_t * ray_dD;
+
+  float3 dx, dy;
+  make_orthonormals(surface_Ng, &dx, &dy);
+  surface_dP->dx = dx * scale;
+  surface_dP->dy = dy * scale;
+}
+
+ccl_device_forceinline void differential_incoming_compact(ccl_addr_space differential3 *dI,
+                                                          const float3 D,
+                                                          const float dD)
+{
+  /* compute dIdx/dy at a shading point, we just need to negate the
+   * differential of the ray direction */
+
+  float3 dx, dy;
+  make_orthonormals(D, &dx, &dy);
+
+  dI->dx = dD * dx;
+  dI->dy = dD * dy;
+}
+
 CCL_NAMESPACE_END