BLI: Adjust interpolation to support integers, other tweaks

In order to allow interpolation of integers with a float, add a separate
template parameter for the factor and multiplication types.
Also move some helper constexpr variables to the "base" header
(reversing the dependency to "base" -> "vector").

This also adds a distance function for scalar types, which is
helpful to allow sharing code between vectors and basic types.

Differential Revision: https://developer.blender.org/D14446

2 files changed, 25 insertions, 0 deletions

diff --git a/source/blender/blenlib/tests/BLI_math_base_test.cc b/source/blender/blenlib/tests/BLI_math_base_test.cc
index 62f2b2775d0..dd35deef4a8 100644
--- a/source/blender/blenlib/tests/BLI_math_base_test.cc
+++ b/source/blender/blenlib/tests/BLI_math_base_test.cc
@@ -151,4 +151,9 @@ TEST(math_base, Midpoint)
   EXPECT_NEAR(math::midpoint(100.0f, 200.0f), 150.0f, 1e-4f);
 }
 
+TEST(math_base, InterpolateInt)
+{
+  EXPECT_EQ(math::interpolate(100, 200, 0.4f), 140);
+}
+
 }  // namespace blender::tests
diff --git a/source/blender/blenlib/tests/BLI_math_vector_test.cc b/source/blender/blenlib/tests/BLI_math_vector_test.cc
index 8c310645d6d..282be5f1963 100644
--- a/source/blender/blenlib/tests/BLI_math_vector_test.cc
+++ b/source/blender/blenlib/tests/BLI_math_vector_test.cc
@@ -85,4 +85,24 @@ TEST(math_vector, Clamp)
   EXPECT_EQ(result_2.z, -50);
 }
 
+TEST(math_vector, InterpolateInt)
+{
+  const int3 a(0, -100, 50);
+  const int3 b(0, 100, 100);
+  const int3 result = math::interpolate(a, b, 0.75);
+  EXPECT_EQ(result.x, 0);
+  EXPECT_EQ(result.y, 50);
+  EXPECT_EQ(result.z, 87);
+}
+
+TEST(math_vector, InterpolateFloat)
+{
+  const float3 a(40.0f, -100.0f, 50.0f);
+  const float3 b(20.0f, 100.0f, 100.0f);
+  const float3 result = math::interpolate(a, b, 0.5);
+  EXPECT_FLOAT_EQ(result.x, 30.0f);
+  EXPECT_FLOAT_EQ(result.y, 0.0f);
+  EXPECT_FLOAT_EQ(result.z, 75.0f);
+}
+
 }  // namespace blender::tests