Workbench: Force Vertex Colors in Paint Mode

Vertex colors behaved differently as the paint overlay mixed the colors
in display mode and the results was multiplied on top of the original
shading.

This patch will align the implementation to texture painting where the
colors are drawn by the workbench engine so the correct shading is
applied.

This also means that we don't show the vertex colors overlay when not
in solid mode.

Reviewed By: fclem

Differential Revision: https://developer.blender.org/D6436

1 files changed, 32 insertions, 9 deletions

diff --git a/source/blender/draw/engines/workbench/workbench_private.h b/source/blender/draw/engines/workbench/workbench_private.h
index 9fcd9651f94..7c774ca7490 100644
--- a/source/blender/draw/engines/workbench/workbench_private.h
+++ b/source/blender/draw/engines/workbench/workbench_private.h
@@ -207,6 +207,7 @@ typedef struct WORKBENCH_PrivateData {
   struct GPUShader *prepass_uniform_sh;
   struct GPUShader *prepass_uniform_hair_sh;
   struct GPUShader *prepass_textured_sh;
+  struct GPUShader *prepass_vertex_sh;
   struct GPUShader *composite_sh;
   struct GPUShader *background_sh;
   struct GPUShader *transparent_accum_sh;
@@ -214,6 +215,7 @@ typedef struct WORKBENCH_PrivateData {
   struct GPUShader *transparent_accum_uniform_sh;
   struct GPUShader *transparent_accum_uniform_hair_sh;
   struct GPUShader *transparent_accum_textured_sh;
+  struct GPUShader *transparent_accum_vertex_sh;
   View3DShading shading;
   StudioLight *studio_light;
   const UserDef *preferences;
@@ -318,6 +320,15 @@ typedef struct WORKBENCH_WorldData {
   struct GPUUniformBuffer *world_ubo;
 } WORKBENCH_WorldData;
 
+/* Enumeration containing override options for base color rendering.
+ * This is used to during painting to force the base color to show what you are
+ * painting using the selected lighting model. */
+typedef enum WORKBENCH_ColorOverride {
+  WORKBENCH_COLOR_OVERRIDE_OFF = 0,
+  WORKBENCH_COLOR_OVERRIDE_TEXTURE = CTX_MODE_PAINT_TEXTURE,
+  WORKBENCH_COLOR_OVERRIDE_VERTEX = CTX_MODE_PAINT_VERTEX,
+} WORKBENCH_ColorOverride;
+
 /* inline helper functions */
 BLI_INLINE bool workbench_is_specular_highlight_enabled(WORKBENCH_PrivateData *wpd)
 {
@@ -375,23 +386,35 @@ BLI_INLINE bool workbench_is_in_texture_paint_mode(void)
   return draw_ctx->object_mode == OB_MODE_TEXTURE_PAINT;
 }
 
-/** Is texture paint mode active for the given object */
-BLI_INLINE bool workbench_is_object_in_texture_paint_mode(Object *ob)
+/** Is vertex paint mode enabled (globally) */
+BLI_INLINE bool workbench_is_in_vertex_paint_mode(void)
+{
+  const DRWContextState *draw_ctx = DRW_context_state_get();
+  return draw_ctx->object_mode == OB_MODE_VERTEX_PAINT;
+}
+
+/* Must the `View3DShading.color_type` be overriden for the given object. */
+BLI_INLINE WORKBENCH_ColorOverride workbench_object_color_override_get(Object *ob)
 {
   const DRWContextState *draw_ctx = DRW_context_state_get();
   if (ob->type == OB_MESH && (draw_ctx->obact == ob)) {
     const enum eContextObjectMode mode = CTX_data_mode_enum_ex(
         draw_ctx->object_edit, draw_ctx->obact, draw_ctx->object_mode);
-    return (mode == CTX_MODE_PAINT_TEXTURE);
+    if (mode == CTX_MODE_PAINT_TEXTURE) {
+      return WORKBENCH_COLOR_OVERRIDE_TEXTURE;
+    }
+    else if (mode == CTX_MODE_PAINT_VERTEX) {
+      return WORKBENCH_COLOR_OVERRIDE_VERTEX;
+    }
   }
 
-  return false;
+  return WORKBENCH_COLOR_OVERRIDE_OFF;
 }
 
 BLI_INLINE bool workbench_is_matdata_pass_enabled(WORKBENCH_PrivateData *wpd)
 {
   return (wpd->shading.color_type != V3D_SHADING_SINGLE_COLOR || MATCAP_ENABLED(wpd)) ||
-         workbench_is_in_texture_paint_mode();
+         workbench_is_in_texture_paint_mode() || workbench_is_in_vertex_paint_mode();
 }
 
 /**
@@ -409,7 +432,7 @@ BLI_INLINE eGPUTextureFormat workbench_color_texture_format(const WORKBENCH_Priv
       TEXTURE_DRAWING_ENABLED(wpd)) {
     result = GPU_RGBA16F;
   }
-  else if (VERTEX_COLORS_ENABLED(wpd)) {
+  else if (workbench_is_in_vertex_paint_mode() || VERTEX_COLORS_ENABLED(wpd)) {
     result = GPU_RGBA16;
   }
   else {
@@ -493,7 +516,7 @@ void workbench_material_get_image_and_mat(
 char *workbench_material_build_defines(WORKBENCH_PrivateData *wpd,
                                        bool is_uniform_color,
                                        bool is_hair,
-                                       bool is_texture_painting);
+                                       const WORKBENCH_ColorOverride color_override);
 void workbench_material_update_data(WORKBENCH_PrivateData *wpd,
                                     Object *ob,
                                     Material *mat,
@@ -504,11 +527,11 @@ int workbench_material_get_composite_shader_index(WORKBENCH_PrivateData *wpd);
 int workbench_material_get_prepass_shader_index(WORKBENCH_PrivateData *wpd,
                                                 bool is_uniform_color,
                                                 bool is_hair,
-                                                bool is_texture_painting);
+                                                const WORKBENCH_ColorOverride color_override);
 int workbench_material_get_accum_shader_index(WORKBENCH_PrivateData *wpd,
                                               bool is_uniform_color,
                                               bool is_hair,
-                                              bool is_texture_painting);
+                                              const WORKBENCH_ColorOverride color_override);
 void workbench_material_shgroup_uniform(WORKBENCH_PrivateData *wpd,
                                         DRWShadingGroup *grp,
                                         WORKBENCH_MaterialData *material,