Geometry Nodes: Support modifier on curve objects

With this commit, curve objects support the geometry nodes modifier.

Curves objects now evaluate to `CurveEval` unless there was a previous
implicit conversion (tessellating modifiers, mesh modifiers, or the
settings in the curve "Geometry" panel). In the new code, curves are
only considered to be the wire edges-- any generated surface is a mesh
instead, stored in the evaluated geometry set.

The consolidation of concepts mentioned above allows remove a lot of
code that had to do with maintaining the `DispList` type temporarily
for modifiers and rendering. Instead, render engines see a separate
object for the mesh from the mesh geometry component, and when the
curve object evaluates to a curve, the `CurveEval` is always used for
drawing wire edges.

However, currently the `DispList` type is still maintained and used as
an intermediate step in implicit mesh conversion. In the future, more
uses of it could be changed to use `CurveEval` and `Mesh` instead.

This is mostly not changed behavior, it is just a formalization of
existing logic after recent fixes for 2.8 versions last year and two
years ago. Also, in the future more functionality can be converted
to nodes, removing cases of implicit conversions. For more discussion
on that topic, see T89676.

The `use_fill_deform` option is removed. It has not worked properly
since 2.62, and the choice for filling a curve before or after
deformation will work much better and be clearer with a node system.

Applying the geometry nodes modifier to generate a curve is not
implemented with this commit, so applying the modifier won't work
at all. This is a separate technical challenge, and should be solved
in a separate step.

Differential Revision: https://developer.blender.org/D11597

1 files changed, 30 insertions, 123 deletions

diff --git a/source/blender/draw/intern/draw_cache_impl_curve.cc b/source/blender/draw/intern/draw_cache_impl_curve.cc
index 1efe0c080be..0804745fab5 100644
--- a/source/blender/draw/intern/draw_cache_impl_curve.cc
+++ b/source/blender/draw/intern/draw_cache_impl_curve.cc
@@ -112,43 +112,6 @@ static void curve_render_overlay_verts_edges_len_get(ListBase *lb,
   }
 }
 
-static void curve_render_wire_verts_edges_len_get(const CurveCache *ob_curve_cache,
-                                                  int *r_curve_len,
-                                                  int *r_vert_len,
-                                                  int *r_edge_len)
-{
-  BLI_assert(r_vert_len || r_edge_len);
-  int vert_len = 0;
-  int edge_len = 0;
-  int curve_len = 0;
-  LISTBASE_FOREACH (const BevList *, bl, &ob_curve_cache->bev) {
-    if (bl->nr > 0) {
-      const bool is_cyclic = bl->poly != -1;
-      edge_len += (is_cyclic) ? bl->nr : bl->nr - 1;
-      vert_len += bl->nr;
-      curve_len += 1;
-    }
-  }
-  LISTBASE_FOREACH (const DispList *, dl, &ob_curve_cache->disp) {
-    if (ELEM(dl->type, DL_SEGM, DL_POLY)) {
-      BLI_assert(dl->parts == 1);
-      const bool is_cyclic = dl->type == DL_POLY;
-      edge_len += (is_cyclic) ? dl->nr : dl->nr - 1;
-      vert_len += dl->nr;
-      curve_len += 1;
-    }
-  }
-  if (r_vert_len) {
-    *r_vert_len = vert_len;
-  }
-  if (r_edge_len) {
-    *r_edge_len = edge_len;
-  }
-  if (r_curve_len) {
-    *r_curve_len = curve_len;
-  }
-}
-
 static void curve_eval_render_wire_verts_edges_len_get(const CurveEval &curve_eval,
                                                        int *r_curve_len,
                                                        int *r_vert_len,
@@ -243,7 +206,7 @@ enum {
 };
 
 /*
- * ob_curve_cache can be NULL, only needed for CU_DATATYPE_WIRE
+ * ob_curve_cache can be NULL
  */
 static CurveRenderData *curve_render_data_create(Curve *cu,
                                                  CurveCache *ob_curve_cache,
@@ -267,12 +230,6 @@ static CurveRenderData *curve_render_data_create(Curve *cu,
                                                  &rdata->wire.vert_len,
                                                  &rdata->wire.edge_len);
     }
-    else {
-      curve_render_wire_verts_edges_len_get(rdata->ob_curve_cache,
-                                            &rdata->wire.curve_len,
-                                            &rdata->wire.vert_len,
-                                            &rdata->wire.edge_len);
-    }
   }
 
   if (cu->editnurb) {
@@ -594,6 +551,10 @@ void DRW_curve_batch_cache_free(Curve *cu)
 /* GPUBatch cache usage. */
 static void curve_create_curves_pos(CurveRenderData *rdata, GPUVertBuf *vbo_curves_pos)
 {
+  if (rdata->curve_eval == nullptr) {
+    return;
+  }
+
   static GPUVertFormat format = {0};
   static struct {
     uint pos;
@@ -606,46 +567,26 @@ static void curve_create_curves_pos(CurveRenderData *rdata, GPUVertBuf *vbo_curv
   GPU_vertbuf_init_with_format(vbo_curves_pos, &format);
   GPU_vertbuf_data_alloc(vbo_curves_pos, vert_len);
 
-  if (rdata->curve_eval != nullptr) {
-    const CurveEval &curve_eval = *rdata->curve_eval;
-    Span<SplinePtr> splines = curve_eval.splines();
-    Array<int> offsets = curve_eval.evaluated_point_offsets();
-    BLI_assert(offsets.last() == vert_len);
-
-    for (const int i_spline : splines.index_range()) {
-      Span<float3> positions = splines[i_spline]->evaluated_positions();
-      for (const int i_point : positions.index_range()) {
-        GPU_vertbuf_attr_set(
-            vbo_curves_pos, attr_id.pos, offsets[i_spline] + i_point, positions[i_point]);
-      }
-    }
-  }
-  else {
-    BLI_assert(rdata->ob_curve_cache != nullptr);
-
-    int v_idx = 0;
-    LISTBASE_FOREACH (const BevList *, bl, &rdata->ob_curve_cache->bev) {
-      if (bl->nr <= 0) {
-        continue;
-      }
-      const int i_end = v_idx + bl->nr;
-      for (const BevPoint *bevp = bl->bevpoints; v_idx < i_end; v_idx++, bevp++) {
-        GPU_vertbuf_attr_set(vbo_curves_pos, attr_id.pos, v_idx, bevp->vec);
-      }
-    }
-    LISTBASE_FOREACH (const DispList *, dl, &rdata->ob_curve_cache->disp) {
-      if (ELEM(dl->type, DL_SEGM, DL_POLY)) {
-        for (int i = 0; i < dl->nr; v_idx++, i++) {
-          GPU_vertbuf_attr_set(vbo_curves_pos, attr_id.pos, v_idx, &((float(*)[3])dl->verts)[i]);
-        }
-      }
+  const CurveEval &curve_eval = *rdata->curve_eval;
+  Span<SplinePtr> splines = curve_eval.splines();
+  Array<int> offsets = curve_eval.evaluated_point_offsets();
+  BLI_assert(offsets.last() == vert_len);
+
+  for (const int i_spline : splines.index_range()) {
+    Span<float3> positions = splines[i_spline]->evaluated_positions();
+    for (const int i_point : positions.index_range()) {
+      GPU_vertbuf_attr_set(
+          vbo_curves_pos, attr_id.pos, offsets[i_spline] + i_point, positions[i_point]);
     }
-    BLI_assert(v_idx == vert_len);
   }
 }
 
 static void curve_create_curves_lines(CurveRenderData *rdata, GPUIndexBuf *ibo_curve_lines)
 {
+  if (rdata->curve_eval == nullptr) {
+    return;
+  }
+
   const int vert_len = curve_render_data_wire_verts_len_get(rdata);
   const int edge_len = curve_render_data_wire_edges_len_get(rdata);
   const int curve_len = curve_render_data_wire_curve_len_get(rdata);
@@ -655,54 +596,20 @@ static void curve_create_curves_lines(CurveRenderData *rdata, GPUIndexBuf *ibo_c
   GPUIndexBufBuilder elb;
   GPU_indexbuf_init_ex(&elb, GPU_PRIM_LINE_STRIP, index_len, vert_len);
 
-  if (rdata->curve_eval != nullptr) {
-    const CurveEval &curve_eval = *rdata->curve_eval;
-    Span<SplinePtr> splines = curve_eval.splines();
-    Array<int> offsets = curve_eval.evaluated_point_offsets();
-    BLI_assert(offsets.last() == vert_len);
-
-    for (const int i_spline : splines.index_range()) {
-      const int eval_size = splines[i_spline]->evaluated_points_size();
-      if (splines[i_spline]->is_cyclic() && splines[i_spline]->evaluated_edges_size() > 1) {
-        GPU_indexbuf_add_generic_vert(&elb, offsets[i_spline] + eval_size - 1);
-      }
-      for (const int i_point : IndexRange(eval_size)) {
-        GPU_indexbuf_add_generic_vert(&elb, offsets[i_spline] + i_point);
-      }
-      GPU_indexbuf_add_primitive_restart(&elb);
-    }
-  }
-  else {
-    BLI_assert(rdata->ob_curve_cache != nullptr);
+  const CurveEval &curve_eval = *rdata->curve_eval;
+  Span<SplinePtr> splines = curve_eval.splines();
+  Array<int> offsets = curve_eval.evaluated_point_offsets();
+  BLI_assert(offsets.last() == vert_len);
 
-    int v_idx = 0;
-    LISTBASE_FOREACH (const BevList *, bl, &rdata->ob_curve_cache->bev) {
-      if (bl->nr <= 0) {
-        continue;
-      }
-      const bool is_cyclic = bl->poly != -1;
-      if (is_cyclic) {
-        GPU_indexbuf_add_generic_vert(&elb, v_idx + (bl->nr - 1));
-      }
-      for (int i = 0; i < bl->nr; i++) {
-        GPU_indexbuf_add_generic_vert(&elb, v_idx + i);
-      }
-      GPU_indexbuf_add_primitive_restart(&elb);
-      v_idx += bl->nr;
+  for (const int i_spline : splines.index_range()) {
+    const int eval_size = splines[i_spline]->evaluated_points_size();
+    if (splines[i_spline]->is_cyclic() && splines[i_spline]->evaluated_edges_size() > 1) {
+      GPU_indexbuf_add_generic_vert(&elb, offsets[i_spline] + eval_size - 1);
     }
-    LISTBASE_FOREACH (const DispList *, dl, &rdata->ob_curve_cache->disp) {
-      if (ELEM(dl->type, DL_SEGM, DL_POLY)) {
-        const bool is_cyclic = dl->type == DL_POLY;
-        if (is_cyclic) {
-          GPU_indexbuf_add_generic_vert(&elb, v_idx + (dl->nr - 1));
-        }
-        for (int i = 0; i < dl->nr; i++) {
-          GPU_indexbuf_add_generic_vert(&elb, v_idx + i);
-        }
-        GPU_indexbuf_add_primitive_restart(&elb);
-        v_idx += dl->nr;
-      }
+    for (const int i_point : IndexRange(eval_size)) {
+      GPU_indexbuf_add_generic_vert(&elb, offsets[i_spline] + i_point);
     }
+    GPU_indexbuf_add_primitive_restart(&elb);
   }
 
   GPU_indexbuf_build_in_place(&elb, ibo_curve_lines);