Geometry Nodes: better support for byte color attributes

Since {rBeae36be372a6b16ee3e76eff0485a47da4f3c230} the distinction
between float and byte colors is more explicit in the ui. So far, geometry
nodes couldn't really deal with byte colors in general. This patch fixes that.
There is still only one color socket, which contains float colors. Conversion
to and from byte colors is done when read from or writing to attributes.

* Support writing to byte color attributes in Store Named Attribute node.
* Support converting to/from byte color in attribute conversion operator.
* Support propagating byte color attributes.
* Add all the implicit conversions from byte colors to the other types.
* Display byte colors as integers in spreadsheet.

Differential Revision: https://developer.blender.org/D14705

1 files changed, 62 insertions, 18 deletions

diff --git a/source/blender/blenkernel/BKE_attribute_math.hh b/source/blender/blenkernel/BKE_attribute_math.hh
index 9efa64d1474..4482e13e1cf 100644
--- a/source/blender/blenkernel/BKE_attribute_math.hh
+++ b/source/blender/blenkernel/BKE_attribute_math.hh
@@ -5,6 +5,7 @@
 #include "BLI_array.hh"
 #include "BLI_color.hh"
 #include "BLI_cpp_type.hh"
+#include "BLI_math_color.hh"
 #include "BLI_math_vector.h"
 #include "BLI_math_vector.hh"
 
@@ -18,17 +19,23 @@ namespace blender::attribute_math {
 template<typename Func>
 inline void convert_to_static_type(const CPPType &cpp_type, const Func &func)
 {
-  cpp_type.to_static_type_tag<float, float2, float3, int, bool, int8_t, ColorGeometry4f>(
-      [&](auto type_tag) {
-        using T = typename decltype(type_tag)::type;
-        if constexpr (std::is_same_v<T, void>) {
-          /* It's expected that the given cpp type is one of the supported ones. */
-          BLI_assert_unreachable();
-        }
-        else {
-          func(T());
-        }
-      });
+  cpp_type.to_static_type_tag<float,
+                              float2,
+                              float3,
+                              int,
+                              bool,
+                              int8_t,
+                              ColorGeometry4f,
+                              ColorGeometry4b>([&](auto type_tag) {
+    using T = typename decltype(type_tag)::type;
+    if constexpr (std::is_same_v<T, void>) {
+      /* It's expected that the given cpp type is one of the supported ones. */
+      BLI_assert_unreachable();
+    }
+    else {
+      func(T());
+    }
+  });
 }
 
 template<typename Func>
@@ -91,6 +98,22 @@ inline ColorGeometry4f mix3(const float3 &weights,
   return result;
 }
 
+template<>
+inline ColorGeometry4b mix3(const float3 &weights,
+                            const ColorGeometry4b &v0,
+                            const ColorGeometry4b &v1,
+                            const ColorGeometry4b &v2)
+{
+  const float4 v0_f{&v0.r};
+  const float4 v1_f{&v1.r};
+  const float4 v2_f{&v2.r};
+  const float4 mixed = v0_f * weights[0] + v1_f * weights[1] + v2_f * weights[2];
+  return ColorGeometry4b{static_cast<uint8_t>(mixed[0]),
+                         static_cast<uint8_t>(mixed[1]),
+                         static_cast<uint8_t>(mixed[2]),
+                         static_cast<uint8_t>(mixed[3])};
+}
+
 /** \} */
 
 /* -------------------------------------------------------------------- */
@@ -134,9 +157,13 @@ template<> inline float3 mix2(const float factor, const float3 &a, const float3
 template<>
 inline ColorGeometry4f mix2(const float factor, const ColorGeometry4f &a, const ColorGeometry4f &b)
 {
-  ColorGeometry4f result;
-  interp_v4_v4v4(result, a, b, factor);
-  return result;
+  return math::interpolate(a, b, factor);
+}
+
+template<>
+inline ColorGeometry4b mix2(const float factor, const ColorGeometry4b &a, const ColorGeometry4b &b)
+{
+  return math::interpolate(a, b, factor);
 }
 
 /** \} */
@@ -278,19 +305,33 @@ class SimpleMixerWithAccumulationType {
   }
 };
 
-class ColorGeometryMixer {
+class ColorGeometry4fMixer {
  private:
   MutableSpan<ColorGeometry4f> buffer_;
   ColorGeometry4f default_color_;
   Array<float> total_weights_;
 
  public:
-  ColorGeometryMixer(MutableSpan<ColorGeometry4f> buffer,
-                     ColorGeometry4f default_color = ColorGeometry4f(0.0f, 0.0f, 0.0f, 1.0f));
+  ColorGeometry4fMixer(MutableSpan<ColorGeometry4f> buffer,
+                       ColorGeometry4f default_color = ColorGeometry4f(0.0f, 0.0f, 0.0f, 1.0f));
   void mix_in(int64_t index, const ColorGeometry4f &color, float weight = 1.0f);
   void finalize();
 };
 
+class ColorGeometry4bMixer {
+ private:
+  MutableSpan<ColorGeometry4b> buffer_;
+  ColorGeometry4b default_color_;
+  Array<float> total_weights_;
+  Array<float4> accumulation_buffer_;
+
+ public:
+  ColorGeometry4bMixer(MutableSpan<ColorGeometry4b> buffer,
+                       ColorGeometry4b default_color = ColorGeometry4b(0, 0, 0, 255));
+  void mix_in(int64_t index, const ColorGeometry4b &color, float weight = 1.0f);
+  void finalize();
+};
+
 template<typename T> struct DefaultMixerStruct {
   /* Use void by default. This can be checked for in `if constexpr` statements. */
   using type = void;
@@ -307,7 +348,10 @@ template<> struct DefaultMixerStruct<float3> {
 template<> struct DefaultMixerStruct<ColorGeometry4f> {
   /* Use a special mixer for colors. ColorGeometry4f can't be added/multiplied, because this is not
    * something one should usually do with colors. */
-  using type = ColorGeometryMixer;
+  using type = ColorGeometry4fMixer;
+};
+template<> struct DefaultMixerStruct<ColorGeometry4b> {
+  using type = ColorGeometry4bMixer;
 };
 template<> struct DefaultMixerStruct<int> {
   static int double_to_int(const double &value)