Fix size_t -> int -> size_t round trip in Cycles

There are two things achieved by this change:

- No possible downcast of size_t to int when calculating motion steps.
- Disambiguate call to `min()` which was for some reason considered
  ambiguous on 32bit platforms `min(int, unsigned int)`.
- Do the same for the `max()` call to keep them symmetrical.

On an implementation side the `min()` is defined for a fixed width
integer type to disambiguate uint from size_t on 32bit platforms,
and yet be able to use it for 32bit operands on 64bit platforms without
upcast.

This ended up in a bit bigger change as the conditional compile-in of
functions is easiest if the functions is templated. Making the functions
templated required to remove the other source of ambiguity which is
`algorithm.h` which was pulling min/max from std.

Now it is the `math.h` which is the source of truth for min/max.
It was only one place which was relying on `algorithm.h` for these
functions, hence the choice of `math.h` as the safest and least
intrusive.

Fixes 32bit platforms (such as i386) in Debian package build system.

Differential Revision: https://developer.blender.org/D14062

1 files changed, 2 insertions, 2 deletions

diff --git a/intern/cycles/device/optix/device_impl.cpp b/intern/cycles/device/optix/device_impl.cpp
index cb6c36d5ea6..e49c67c7f91 100644
--- a/intern/cycles/device/optix/device_impl.cpp
+++ b/intern/cycles/device/optix/device_impl.cpp
@@ -1586,7 +1586,7 @@ void OptiXDevice::build_bvh(BVH *bvh, Progress &progress, bool refit)
         if (ob->is_traceable() && ob->use_motion()) {
           total_motion_transform_size = align_up(total_motion_transform_size,
                                                  OPTIX_TRANSFORM_BYTE_ALIGNMENT);
-          const size_t motion_keys = max(ob->get_motion().size(), 2) - 2;
+          const size_t motion_keys = max(ob->get_motion().size(), (size_t)2) - 2;
           total_motion_transform_size = total_motion_transform_size +
                                         sizeof(OptixSRTMotionTransform) +
                                         motion_keys * sizeof(OptixSRTData);
@@ -1660,7 +1660,7 @@ void OptiXDevice::build_bvh(BVH *bvh, Progress &progress, bool refit)
 
       /* Insert motion traversable if object has motion. */
       if (motion_blur && ob->use_motion()) {
-        size_t motion_keys = max(ob->get_motion().size(), 2) - 2;
+        size_t motion_keys = max(ob->get_motion().size(), (size_t)2) - 2;
         size_t motion_transform_size = sizeof(OptixSRTMotionTransform) +
                                        motion_keys * sizeof(OptixSRTData);