Curves: Add sculpt selection overlay

This commit adds visualization to the selection in curves sculpt mode.
Previously it was only possible to see the selection when it was
connected to a material.

In order to obstruct the users vision as little as possible, the
selected areas of the curve are left as is, but a dark overlay
is drawn over unselected areas.

To make it work, the overlay requests the selection attribute and then
ensures that the evaluation is complete for curves. Then it retrieves
the evaluated selection GPU texture and passes that to the shader.
This reuses the existing generic attribute extraction system because
there currently wouldn't be any benefits to dealing with selection
separately, and because it avoids duplication of the logic that
extracts attributes from curves and evaluates them if necessary.

Differential Revision: https://developer.blender.org/D15219

7 files changed, 187 insertions, 0 deletions

diff --git a/source/blender/draw/engines/overlay/overlay_engine.c b/source/blender/draw/engines/overlay/overlay_engine.c
index f8c28394b16..9ec0398e5cb 100644
--- a/source/blender/draw/engines/overlay/overlay_engine.c
+++ b/source/blender/draw/engines/overlay/overlay_engine.c
@@ -192,6 +192,8 @@ static void OVERLAY_cache_init(void *vedata)
       OVERLAY_edit_curves_cache_init(vedata);
       break;
     case CTX_MODE_SCULPT_CURVES:
+      OVERLAY_sculpt_curves_cache_init(vedata);
+      break;
     case CTX_MODE_OBJECT:
       break;
     default:
@@ -310,6 +312,8 @@ static void OVERLAY_cache_populate(void *vedata, Object *ob)
                              (draw_ctx->object_mode & OB_MODE_ALL_PAINT);
   const bool in_sculpt_mode = (ob == draw_ctx->obact) && (ob->sculpt != NULL) &&
                               (ob->sculpt->mode_type == OB_MODE_SCULPT);
+  const bool in_curves_sculpt_mode = (ob == draw_ctx->obact) &&
+                                     (ob->mode == OB_MODE_SCULPT_CURVES);
   const bool has_surface = ELEM(ob->type,
                                 OB_MESH,
                                 OB_CURVES_LEGACY,
@@ -428,6 +432,9 @@ static void OVERLAY_cache_populate(void *vedata, Object *ob)
   if (in_sculpt_mode) {
     OVERLAY_sculpt_cache_populate(vedata, ob);
   }
+  else if (in_curves_sculpt_mode) {
+    OVERLAY_sculpt_curves_cache_populate(vedata, ob);
+  }
 
   if (draw_motion_paths) {
     OVERLAY_motion_path_cache_populate(vedata, ob);
@@ -591,6 +598,9 @@ static void OVERLAY_draw_scene(void *vedata)
     case CTX_MODE_SCULPT:
       OVERLAY_sculpt_draw(vedata);
       break;
+    case CTX_MODE_SCULPT_CURVES:
+      OVERLAY_sculpt_curves_draw(vedata);
+      break;
     case CTX_MODE_EDIT_MESH:
     case CTX_MODE_POSE:
     case CTX_MODE_PAINT_WEIGHT:
diff --git a/source/blender/draw/engines/overlay/overlay_private.h b/source/blender/draw/engines/overlay/overlay_private.h
index 23c20a186a0..667e443932c 100644
--- a/source/blender/draw/engines/overlay/overlay_private.h
+++ b/source/blender/draw/engines/overlay/overlay_private.h
@@ -116,6 +116,7 @@ typedef struct OVERLAY_PassList {
   DRWPass *particle_ps;
   DRWPass *pointcloud_ps;
   DRWPass *sculpt_mask_ps;
+  DRWPass *sculpt_curves_selection_ps;
   DRWPass *volume_ps;
   DRWPass *wireframe_ps;
   DRWPass *wireframe_xray_ps;
@@ -279,6 +280,7 @@ typedef struct OVERLAY_PrivateData {
   DRWShadingGroup *particle_shapes_grp;
   DRWShadingGroup *pointcloud_dots_grp;
   DRWShadingGroup *sculpt_mask_grp;
+  DRWShadingGroup *sculpt_curves_selection_grp;
   DRWShadingGroup *volume_selection_surface_grp;
   DRWShadingGroup *wires_grp[2][2];      /* With and without coloring. */
   DRWShadingGroup *wires_all_grp[2][2];  /* With and without coloring. */
@@ -669,6 +671,10 @@ void OVERLAY_sculpt_cache_init(OVERLAY_Data *vedata);
 void OVERLAY_sculpt_cache_populate(OVERLAY_Data *vedata, Object *ob);
 void OVERLAY_sculpt_draw(OVERLAY_Data *vedata);
 
+void OVERLAY_sculpt_curves_cache_init(OVERLAY_Data *vedata);
+void OVERLAY_sculpt_curves_cache_populate(OVERLAY_Data *vedata, Object *ob);
+void OVERLAY_sculpt_curves_draw(OVERLAY_Data *vedata);
+
 void OVERLAY_wireframe_init(OVERLAY_Data *vedata);
 void OVERLAY_wireframe_cache_init(OVERLAY_Data *vedata);
 void OVERLAY_wireframe_cache_populate(OVERLAY_Data *vedata,
@@ -750,6 +756,7 @@ GPUShader *OVERLAY_shader_paint_wire(void);
 GPUShader *OVERLAY_shader_particle_dot(void);
 GPUShader *OVERLAY_shader_particle_shape(void);
 GPUShader *OVERLAY_shader_sculpt_mask(void);
+GPUShader *OVERLAY_shader_sculpt_curves_selection(void);
 GPUShader *OVERLAY_shader_volume_velocity(bool use_needle, bool use_mac);
 GPUShader *OVERLAY_shader_volume_gridlines(bool color_with_flags, bool color_range);
 GPUShader *OVERLAY_shader_wireframe(bool custom_bias);
diff --git a/source/blender/draw/engines/overlay/overlay_sculpt_curves.cc b/source/blender/draw/engines/overlay/overlay_sculpt_curves.cc
new file mode 100644
index 00000000000..b8021124f27
--- /dev/null
+++ b/source/blender/draw/engines/overlay/overlay_sculpt_curves.cc
@@ -0,0 +1,96 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright 2022 Blender Foundation. */
+
+/** \file
+ * \ingroup draw_engine
+ */
+
+#include "DRW_render.h"
+
+#include "draw_cache_impl.h"
+#include "overlay_private.h"
+
+#include "BKE_curves.hh"
+
+void OVERLAY_sculpt_curves_cache_init(OVERLAY_Data *vedata)
+{
+  OVERLAY_PassList *psl = vedata->psl;
+  OVERLAY_PrivateData *pd = vedata->stl->pd;
+
+  const DRWState state = DRW_STATE_WRITE_COLOR | DRW_STATE_DEPTH_EQUAL | DRW_STATE_BLEND_ALPHA;
+  DRW_PASS_CREATE(psl->sculpt_curves_selection_ps, state | pd->clipping_state);
+
+  GPUShader *sh = OVERLAY_shader_sculpt_curves_selection();
+  pd->sculpt_curves_selection_grp = DRW_shgroup_create(sh, psl->sculpt_curves_selection_ps);
+  DRWShadingGroup *grp = pd->sculpt_curves_selection_grp;
+
+  /* Reuse the same mask opacity from sculpt mode, since it wasn't worth it to add a different
+   * property yet. */
+  DRW_shgroup_uniform_float_copy(grp, "selection_opacity", pd->overlay.sculpt_mode_mask_opacity);
+}
+
+static bool everything_selected(const Curves &curves_id)
+{
+  if (!(curves_id.flag & CV_SCULPT_SELECTION_ENABLED)) {
+    /* When the selection is disabled, conceptually everything is selected. */
+    return true;
+  }
+  const blender::bke::CurvesGeometry &curves = blender::bke::CurvesGeometry::wrap(
+      curves_id.geometry);
+  blender::VArray<float> selection;
+  switch (curves_id.selection_domain) {
+    case ATTR_DOMAIN_POINT:
+      selection = curves.selection_point_float();
+      break;
+    case ATTR_DOMAIN_CURVE:
+      selection = curves.selection_curve_float();
+      break;
+  }
+  return selection.is_single() && selection.get_internal_single() == 1.0f;
+}
+
+void OVERLAY_sculpt_curves_cache_populate(OVERLAY_Data *vedata, Object *object)
+{
+  OVERLAY_PrivateData *pd = vedata->stl->pd;
+  Curves *curves = static_cast<Curves *>(object->data);
+
+  /* As an optimization, return early if everything is selected. */
+  if (everything_selected(*curves)) {
+    return;
+  }
+
+  /* Retrieve the location of the texture. */
+  const char *name = curves->selection_domain == ATTR_DOMAIN_POINT ? ".selection_point_float" :
+                                                                     ".selection_curve_float";
+
+  bool is_point_domain;
+  GPUTexture **texture = DRW_curves_texture_for_evaluated_attribute(
+      curves, name, &is_point_domain);
+  if (texture == nullptr) {
+    return;
+  }
+
+  /* Evaluate curves and their attributes if necessary. */
+  DRWShadingGroup *grp = DRW_shgroup_curves_create_sub(
+      object, pd->sculpt_curves_selection_grp, nullptr);
+  if (*texture == nullptr) {
+    return;
+  }
+
+  DRW_shgroup_uniform_bool_copy(grp, "is_point_domain", is_point_domain);
+  DRW_shgroup_uniform_texture(grp, "selection_tx", *texture);
+}
+
+void OVERLAY_sculpt_curves_draw(OVERLAY_Data *vedata)
+{
+  OVERLAY_PassList *psl = vedata->psl;
+  OVERLAY_PrivateData *pd = vedata->stl->pd;
+  OVERLAY_FramebufferList *fbl = vedata->fbl;
+
+  if (DRW_state_is_fbo()) {
+    GPU_framebuffer_bind(pd->painting.in_front ? fbl->overlay_in_front_fb :
+                                                 fbl->overlay_default_fb);
+  }
+
+  DRW_draw_pass(psl->sculpt_curves_selection_ps);
+}
diff --git a/source/blender/draw/engines/overlay/overlay_shader.c b/source/blender/draw/engines/overlay/overlay_shader.c
index 48146fbddfb..7b7e84c307b 100644
--- a/source/blender/draw/engines/overlay/overlay_shader.c
+++ b/source/blender/draw/engines/overlay/overlay_shader.c
@@ -90,6 +90,7 @@ typedef struct OVERLAY_Shaders {
   GPUShader *particle_shape;
   GPUShader *pointcloud_dot;
   GPUShader *sculpt_mask;
+  GPUShader *sculpt_curves_selection;
   GPUShader *uniform_color;
   GPUShader *volume_velocity_needle_sh;
   GPUShader *volume_velocity_mac_sh;
@@ -792,6 +793,18 @@ GPUShader *OVERLAY_shader_sculpt_mask(void)
   return sh_data->sculpt_mask;
 }
 
+GPUShader *OVERLAY_shader_sculpt_curves_selection(void)
+{
+  const DRWContextState *draw_ctx = DRW_context_state_get();
+  OVERLAY_Shaders *sh_data = &e_data.sh_data[draw_ctx->sh_cfg];
+  if (!sh_data->sculpt_curves_selection) {
+    sh_data->sculpt_curves_selection = GPU_shader_create_from_info_name(
+        draw_ctx->sh_cfg == GPU_SHADER_CFG_CLIPPED ? "overlay_sculpt_curves_selection_clipped" :
+                                                     "overlay_sculpt_curves_selection");
+  }
+  return sh_data->sculpt_curves_selection;
+}
+
 struct GPUShader *OVERLAY_shader_uniform_color(void)
 {
   const DRWContextState *draw_ctx = DRW_context_state_get();
diff --git a/source/blender/draw/engines/overlay/shaders/infos/overlay_sculpt_curves_info.hh b/source/blender/draw/engines/overlay/shaders/infos/overlay_sculpt_curves_info.hh
new file mode 100644
index 00000000000..46e3943b293
--- /dev/null
+++ b/source/blender/draw/engines/overlay/shaders/infos/overlay_sculpt_curves_info.hh
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "gpu_shader_create_info.hh"
+
+GPU_SHADER_INTERFACE_INFO(overlay_sculpt_curves_selection_iface, "")
+    .smooth(Type::FLOAT, "mask_weight");
+
+GPU_SHADER_CREATE_INFO(overlay_sculpt_curves_selection)
+    .do_static_compilation(true)
+    .push_constant(Type::BOOL, "is_point_domain")
+    .push_constant(Type::FLOAT, "selection_opacity")
+    .sampler(0, ImageType::FLOAT_BUFFER, "selection_tx")
+    .vertex_out(overlay_sculpt_curves_selection_iface)
+    .vertex_source("overlay_sculpt_curves_selection_vert.glsl")
+    .fragment_source("overlay_sculpt_curves_selection_frag.glsl")
+    .fragment_out(0, Type::VEC4, "out_color")
+    .additional_info("draw_hair", "draw_globals");
+
+GPU_SHADER_CREATE_INFO(overlay_sculpt_curves_selection_clipped)
+    .do_static_compilation(true)
+    .additional_info("overlay_sculpt_curves_selection", "drw_clipped");
diff --git a/source/blender/draw/engines/overlay/shaders/overlay_sculpt_curves_selection_frag.glsl b/source/blender/draw/engines/overlay/shaders/overlay_sculpt_curves_selection_frag.glsl
new file mode 100644
index 00000000000..7af6bdb9fdb
--- /dev/null
+++ b/source/blender/draw/engines/overlay/shaders/overlay_sculpt_curves_selection_frag.glsl
@@ -0,0 +1,5 @@
+
+void main()
+{
+  out_color = vec4(vec3(0.0), 1.0 - mask_weight);
+}
diff --git a/source/blender/draw/engines/overlay/shaders/overlay_sculpt_curves_selection_vert.glsl b/source/blender/draw/engines/overlay/shaders/overlay_sculpt_curves_selection_vert.glsl
new file mode 100644
index 00000000000..9ed959b5ea1
--- /dev/null
+++ b/source/blender/draw/engines/overlay/shaders/overlay_sculpt_curves_selection_vert.glsl
@@ -0,0 +1,35 @@
+#pragma BLENDER_REQUIRE(common_hair_lib.glsl)
+#pragma BLENDER_REQUIRE(common_view_clipping_lib.glsl)
+#pragma BLENDER_REQUIRE(common_view_lib.glsl)
+
+
+float retrieve_selection()
+{
+  if (is_point_domain) {
+    return texelFetch(selection_tx, hair_get_base_id()).r;
+  }
+  return texelFetch(selection_tx, hair_get_strand_id()).r;
+}
+
+void main()
+{
+  bool is_persp = (ProjectionMatrix[3][3] == 0.0);
+  float time, thick_time, thickness;
+  vec3 world_pos, tan, binor;
+  hair_get_pos_tan_binor_time(is_persp,
+                              ModelMatrixInverse,
+                              ViewMatrixInverse[3].xyz,
+                              ViewMatrixInverse[2].xyz,
+                              world_pos,
+                              tan,
+                              binor,
+                              time,
+                              thickness,
+                              thick_time);
+
+  gl_Position = point_world_to_ndc(world_pos);
+
+  mask_weight = 1.0 - (selection_opacity - retrieve_selection() * selection_opacity);
+
+  view_clipping_distances(world_pos);
+}