Curves: Further implementation of new curves data structure

The general idea here is to wrap the `CurvesGeometry` DNA struct
with a C++ class that can do most of the heavy lifting for the curve
geometry. Using a C++ class allows easier ways to group methods, easier
const correctness, and code that's more readable and faster to write.
This way, it works much more like a version of `CurveEval` that uses
more efficient attribute storage.

This commit adds the structure of some yet-to-be-implemented code,
the largest thing being mutexes and vectors meant to hold lazily
calculated evaluated positions, tangents, and normals. That part might
change slightly, but it's helpful to be able to see the direction this
commit is aiming in. In particular, the inherently single-threaded
accumulated lengths and Bezier evaluated point offsets might be cached.

Ref T95355

Differential Revision: https://developer.blender.org/D14054

1 files changed, 39 insertions, 1 deletions

diff --git a/source/blender/makesdna/DNA_curves_types.h b/source/blender/makesdna/DNA_curves_types.h
index 03a587c896b..c45de832e3c 100644
--- a/source/blender/makesdna/DNA_curves_types.h
+++ b/source/blender/makesdna/DNA_curves_types.h
@@ -13,6 +13,33 @@
 extern "C" {
 #endif
 
+#ifdef __cplusplus
+namespace blender::bke {
+class CurvesGeometryRuntime;
+}  // namespace blender::bke
+using CurvesGeometryRuntimeHandle = blender::bke::CurvesGeometryRuntime;
+#else
+typedef struct CurvesGeometryRuntimeHandle CurvesGeometryRuntimeHandle;
+#endif
+
+typedef enum CurveType {
+  CURVE_TYPE_CATMULL_ROM = 0,
+  CURVE_TYPE_POLY = 1,
+  CURVE_TYPE_BEZIER = 2,
+  CURVE_TYPE_NURBS = 3,
+} CurveType;
+
+typedef enum HandleType {
+  /** The handle can be moved anywhere, and doesn't influence the point's other handle. */
+  BEZIER_HANDLE_FREE = 0,
+  /** The location is automatically calculated to be smooth. */
+  BEZIER_HANDLE_AUTO = 1,
+  /** The location is calculated to point to the next/previous control point. */
+  BEZIER_HANDLE_VECTOR = 2,
+  /** The location is constrained to point in the opposite direction as the other handle. */
+  BEZIER_HANDLE_ALIGN = 3,
+} HandleType;
+
 /**
  * A reusable data structure for geometry consisting of many curves. All control point data is
  * stored contiguously for better efficiency. Data for each curve is stored as a slice of the
@@ -34,13 +61,19 @@ typedef struct CurvesGeometry {
   float *radius;
 
   /**
+   * The type of each curve. #CurveType.
+   * \note This data is owned by #curve_data.
+   */
+  int8_t *curve_type;
+
+  /**
    * The start index of each curve in the point data. The size of each curve can be calculated by
    * subtracting the offset from the next offset. That is valid even for the last curve because
    * this array is allocated with a length one larger than the number of splines.
    *
    * \note This is *not* stored in #CustomData because its size is one larger than #curve_data.
    */
-  int *offsets;
+  int *curve_offsets;
 
   /**
    * All attributes stored on control points (#ATTR_DOMAIN_POINT).
@@ -60,6 +93,11 @@ typedef struct CurvesGeometry {
    * The number of curves in the data-block.
    */
   int curve_size;
+
+  /**
+   * Runtime data for curves, stored as a pointer to allow defining this as a C++ class.
+   */
+  CurvesGeometryRuntimeHandle *runtime;
 } CurvesGeometry;
 
 typedef struct Curves {