EEVEE: support Curves attributes rendering

This adds support to render Curves attributes in EEVEE.

Each attribute is stored in a texture derived from a VBO. As the
shading group needs the textures to be valid upon creation, the
attributes are created and setup during its very creation, instead
of doing it lazily via create_requested which we cannot rely on
anyway as contrary to the mesh batch, we do cannot really tell if
attributes need to be updated or else via some `DRW_batch_requested`.

Since point attributes need refinement, and since attributes are all
cast to vec4/float4 to account for differences in type conversions
between Blender and OpenGL, the refinement shader for points is
used as is. The point attributes are stored for each subdivision level
in CurvesEvalFinalCache. Each subdivision level also keeps track of the
attributes already in use so they are properly updated when needed.

Some basic garbage collection was added similar to what is done
for meshes: if the attributes used over time have been different
from the currently used attributes for too long, then the buffers
are freed, ensuring that stale attributesare removed.

This adds `CurvesInfos` to the shader creation info, which stores
the scope in which the attributes are defined. Scopes are stored
as booleans, in an array indexed by attribute loading order which
is also the order in which the attributes were added to the material.
A mapping is necessary between the indices used for the scoping, and
the ones used in the Curves cache, as this may contain stale
attributes which have not been garbage collected yet.

Common utilities with the mesh code for handling requested
attributes were moved to a separate file.

Differential Revision: https://developer.blender.org/D14916

1 files changed, 14 insertions, 0 deletions

diff --git a/source/blender/draw/intern/draw_shader_shared.h b/source/blender/draw/intern/draw_shader_shared.h
index db128fffde7..94c0c53dab7 100644
--- a/source/blender/draw/intern/draw_shader_shared.h
+++ b/source/blender/draw/intern/draw_shader_shared.h
@@ -1,12 +1,14 @@
 /* SPDX-License-Identifier: GPL-2.0-or-later */
 
 #ifndef GPU_SHADER
+#  include "GPU_shader.h"
 #  include "GPU_shader_shared_utils.h"
 
 typedef struct ViewInfos ViewInfos;
 typedef struct ObjectMatrices ObjectMatrices;
 typedef struct ObjectInfos ObjectInfos;
 typedef struct VolumeInfos VolumeInfos;
+typedef struct CurvesInfos CurvesInfos;
 #endif
 
 #define DRW_SHADER_SHARED_H
@@ -16,6 +18,10 @@ typedef struct VolumeInfos VolumeInfos;
 /* Define the maximum number of grid we allow in a volume UBO. */
 #define DRW_GRID_PER_VOLUME_MAX 16
 
+/* Define the maximum number of attribute we allow in a curves UBO.
+ * This should be kept in sync with `GPU_ATTR_MAX` */
+#define DRW_ATTRIBUTE_PER_CURVES_MAX 15
+
 struct ViewInfos {
   /* View matrices */
   float4x4 persmat;
@@ -79,6 +85,14 @@ struct VolumeInfos {
 };
 BLI_STATIC_ASSERT_ALIGN(VolumeInfos, 16)
 
+struct CurvesInfos {
+  /* Per attribute scope, follows loading order.
+   * NOTE: uint as bool in GLSL is 4 bytes. */
+  uint is_point_attribute[DRW_ATTRIBUTE_PER_CURVES_MAX];
+  int _pad;
+};
+BLI_STATIC_ASSERT_ALIGN(CurvesInfos, 16)
+
 #define OrcoTexCoFactors (drw_infos[resource_id].drw_OrcoTexCoFactors)
 #define ObjectInfo (drw_infos[resource_id].drw_Infos)
 #define ObjectColor (drw_infos[resource_id].drw_ObjectColor)