Cycles: Fix nan in decomposed transform for degenerated input

The decomposed transform would have consists of nan values if the input
transform had zero scale.

Now the decomposition will check for zero scale, and if it is detected
then the result will be ensured to be finite. Additionally, rotation
value will be copied from previous/next time step to help avoiding
obscure interpolation.

The latter step can become more comprehensive than the current simple
implementation.

Differential Revision: https://developer.blender.org/D8450

2 files changed, 54 insertions, 0 deletions

diff --git a/intern/cycles/test/CMakeLists.txt b/intern/cycles/test/CMakeLists.txt
index 6dcc7f7b3dd..07b345baff8 100644
--- a/intern/cycles/test/CMakeLists.txt
+++ b/intern/cycles/test/CMakeLists.txt
@@ -112,3 +112,4 @@ set_source_files_properties(util_avxf_avx_test.cpp PROPERTIES COMPILE_FLAGS "${C
 CYCLES_TEST(util_avxf_avx "cycles_util;bf_intern_numaapi;${OPENIMAGEIO_LIBRARIES};${BOOST_LIBRARIES}")
 set_source_files_properties(util_avxf_avx2_test.cpp PROPERTIES COMPILE_FLAGS "${CYCLES_AVX2_KERNEL_FLAGS}")
 CYCLES_TEST(util_avxf_avx2 "cycles_util;bf_intern_numaapi;${OPENIMAGEIO_LIBRARIES};${BOOST_LIBRARIES}")
+CYCLES_TEST(util_transform "cycles_util;${OPENIMAGEIO_LIBRARIES};${BOOST_LIBRARIES}")
diff --git a/intern/cycles/test/util_transform_test.cpp b/intern/cycles/test/util_transform_test.cpp
new file mode 100644
index 00000000000..58ce0fdfee4
--- /dev/null
+++ b/intern/cycles/test/util_transform_test.cpp
@@ -0,0 +1,53 @@
+/*
+ * Copyright 2011-2020 Blender Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "testing/testing.h"
+
+#include "util/util_transform.h"
+#include "util/util_vector.h"
+
+CCL_NAMESPACE_BEGIN
+
+TEST(transform_motion_decompose, Degenerated)
+{
+  // Simple case: single degenerated matrix.
+  {
+    vector<Transform> motion = {transform_scale(0.0f, 0.0f, 0.0f)};
+    vector<DecomposedTransform> decomp(motion.size());
+    transform_motion_decompose(decomp.data(), motion.data(), motion.size());
+    EXPECT_TRUE(transform_decomposed_isfinite_safe(&decomp[0]));
+  }
+
+  // Copy from previous to current.
+  {
+    vector<Transform> motion = {transform_rotate(M_PI_4_F, make_float3(1.0f, 1.0f, 1.0f)),
+                                transform_scale(0.0f, 0.0f, 0.0f)};
+    vector<DecomposedTransform> decomp(motion.size());
+    transform_motion_decompose(decomp.data(), motion.data(), motion.size());
+    EXPECT_NEAR(len(decomp[1].x - decomp[0].x), 0.0f, 1e-6f);
+  }
+
+  // Copy from next to current.
+  {
+    vector<Transform> motion = {transform_scale(0.0f, 0.0f, 0.0f),
+                                transform_rotate(M_PI_4_F, make_float3(1.0f, 1.0f, 1.0f))};
+    vector<DecomposedTransform> decomp(motion.size());
+    transform_motion_decompose(decomp.data(), motion.data(), motion.size());
+    EXPECT_NEAR(len(decomp[0].x - decomp[1].x), 0.0f, 1e-6f);
+  }
+}
+
+CCL_NAMESPACE_END