Curves: Changes to the new curves data-block

This patch refactors the "Hair" data-block, which will soon be renamed
to "Curves". The larger change is switching from an array of `HairCurve`
to find indices in the points array to simply storing an array of offsets.
Using a single integer instead of two halves the amount of memory for that
particular array.

Besides that, there are some other changes in this patch:
- Split the data-structure to a separate `CurveGeometry`
  DNA struct so it is usable for grease pencil too.
- Update naming to be more aligned with newer code and the style guide.
- Add direct access to some arrays in RNA
-- Radius is now retrieved as a regular attribute in Cycles.
-- `HairPoint` has been renamed to `CurvePoint`
-- `HairCurve` has been renamed to `CurveSlice`
- Add comments to the struct in DNA.

The next steps are renaming `Hair` -> `Curves`, and adding support
for other curve types: Bezier, Poly, and NURBS.

Ref T95355

Differential Revision: https://developer.blender.org/D13987

1 files changed, 4 insertions, 4 deletions

diff --git a/source/blender/blenkernel/intern/customdata.cc b/source/blender/blenkernel/intern/customdata.cc
index e4c18325d76..d235e6d15e1 100644
--- a/source/blender/blenkernel/intern/customdata.cc
+++ b/source/blender/blenkernel/intern/customdata.cc
@@ -1793,10 +1793,10 @@ static const LayerTypeInfo LAYERTYPEINFO[CD_NUMTYPES] = {
     {sizeof(float[3]), "vec3f", 1, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr},
     /* 44: CD_RADIUS */
     {sizeof(float), "MFloatProperty", 1, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr},
-    /* 45: CD_HAIRCURVE */
-    {sizeof(HairCurve), "HairCurve", 1, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr},
-    /* 46: CD_HAIRMAPPING */
-    {sizeof(HairMapping), "HairMapping", 1, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr},
+    /* 45: CD_HAIRCURVE */ /* DEPRECATED */
+    {-1, "HairCurve", 1, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr},
+    /* 46: CD_HAIRMAPPING */ /* DEPRECATED */
+    {-1, "HairMapping", 1, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr},
     /* 47: CD_PROP_COLOR */
     {sizeof(MPropCol),
      "MPropCol",