Add weight preview to WeightVG modifiers, and first, simple/basic refactor of how modifiers can generate preview.

User side:
* Preview for DynamicPaint should keep the same behavior (for now). Weight preview should be somawhat quicker, though.
* Preview for WeightVG modifiers is only active in WeightPaint mode, and if the affected vgroup is the active one.
* Last active preview modifier in stack wins!

Note: that modifier preview topic is yet to be further refined, quite raw/incomplete for now.

Dev side:
* In draw code, renamed DRAW_DYNAMIC_PAINT_PREVIEW flag to DRAW_MODIFIERS_PREVIEW
* Removed use of MOD_DPAINT_PREVIEW_READY in DynamicPaint code (seems unecessary, and if it was, should be of more general scope).
* Added eModifierTypeFlag_UsesPreview to ModifierTypeFlag, for modifiers that can generate some preview data.
* Added three new modifier funcs, to handle preview modifiers in draw code / mod stack.
* For weights preview: added the generic DM_update_weight_mcol func, which can update WEIGHT_MCOL layer with either a given array of weights (currently used by DynamicPaint only), or from current active vgroup(s).

So now, draw code is fully generic (i.e. no more modifier-type checking in it). Mod stack code is generic to some extent, but will need more work.

3 files changed, 9 insertions, 21 deletions

diff --git a/source/blender/editors/space_view3d/drawmesh.c b/source/blender/editors/space_view3d/drawmesh.c
index 5f521cc3dd1..62c12500aa8 100644
--- a/source/blender/editors/space_view3d/drawmesh.c
+++ b/source/blender/editors/space_view3d/drawmesh.c
@@ -713,7 +713,7 @@ void draw_mesh_textured_old(Scene *scene, View3D *v3d, RegionView3D *rv3d, Objec
 	}
 	else {
 		if(GPU_buffer_legacy(dm)) {
-			if (draw_flags & DRAW_DYNAMIC_PAINT_PREVIEW)
+			if (draw_flags & DRAW_MODIFIERS_PREVIEW)
 				dm->drawFacesTex(dm, draw_mcol__set_draw_legacy, NULL, NULL);
 			else 
 				dm->drawFacesTex(dm, draw_tface__set_draw_legacy, NULL, NULL);
@@ -849,7 +849,7 @@ static int tex_mat_set_face_editmesh_cb(void *UNUSED(userData), int index)
 
 void draw_mesh_textured(Scene *scene, View3D *v3d, RegionView3D *rv3d, Object *ob, DerivedMesh *dm, int draw_flags)
 {
-	if((!scene_use_new_shading_nodes(scene)) || (draw_flags & DRAW_DYNAMIC_PAINT_PREVIEW)) {
+	if((!scene_use_new_shading_nodes(scene)) || (draw_flags & DRAW_MODIFIERS_PREVIEW)) {
 		draw_mesh_textured_old(scene, v3d, rv3d, ob, dm, draw_flags);
 		return;
 	}
diff --git a/source/blender/editors/space_view3d/drawobject.c b/source/blender/editors/space_view3d/drawobject.c
index f7f67bd4e73..1482340632e 100644
--- a/source/blender/editors/space_view3d/drawobject.c
+++ b/source/blender/editors/space_view3d/drawobject.c
@@ -36,7 +36,6 @@
 #include "DNA_camera_types.h"
 #include "DNA_curve_types.h"
 #include "DNA_constraint_types.h" // for drawing constraint
-#include "DNA_dynamicpaint_types.h"
 #include "DNA_lamp_types.h"
 #include "DNA_lattice_types.h"
 #include "DNA_material_types.h"
@@ -3081,27 +3080,16 @@ static void draw_mesh_fancy(Scene *scene, ARegion *ar, View3D *v3d, RegionView3D
 	eWireDrawMode draw_wire= OBDRAW_WIRE_OFF;
 	int /* totvert,*/ totedge, totface;
 	DerivedMesh *dm= mesh_get_derived_final(scene, ob, scene->customdata_mask);
-	ModifierData *md = NULL;
 	const short is_obact= (ob == OBACT);
 	int draw_flags = (is_obact && paint_facesel_test(ob)) ? DRAW_FACE_SELECT : 0;
 
 	if(!dm)
 		return;
 
-	/* check to draw dynamic paint colors */
-	if ((md = modifiers_findByType(ob, eModifierType_DynamicPaint)))
-	{
-		/* check if target has an active dpaint modifier	*/
-		if(md && (md->mode & eModifierMode_Realtime))					
-		{
-			DynamicPaintModifierData *pmd = (DynamicPaintModifierData *)md;
-			/* if canvas is ready to preview vertex colors */
-			if (pmd->canvas && pmd->canvas->flags & MOD_DPAINT_PREVIEW_READY &&
-				DM_get_face_data_layer(dm, CD_WEIGHT_MCOL)) {
-				draw_flags |= DRAW_DYNAMIC_PAINT_PREVIEW;
-			}
-		}
-	}
+	/* Check to draw dynamic paint colors (or weights from WeightVG modifiers).
+	 * Note: Last "preview-active" modifier in stack will win! */
+	if(DM_get_face_data_layer(dm, CD_WEIGHT_MCOL) && modifiers_isPreview(ob))
+		draw_flags |= DRAW_MODIFIERS_PREVIEW;
 
 	/* Unwanted combination */
 	if (draw_flags & DRAW_FACE_SELECT) {
@@ -3142,7 +3130,7 @@ static void draw_mesh_fancy(Scene *scene, ARegion *ar, View3D *v3d, RegionView3D
 			draw_mesh_object_outline(v3d, ob, dm);
 		}
 
-		if(draw_glsl_material(scene, ob, v3d, dt) && !(draw_flags & DRAW_DYNAMIC_PAINT_PREVIEW)) {
+		if(draw_glsl_material(scene, ob, v3d, dt) && !(draw_flags & DRAW_MODIFIERS_PREVIEW)) {
 			glFrontFace((ob->transflag&OB_NEG_SCALE)?GL_CW:GL_CCW);
 
 			dm->drawFacesGLSL(dm, GPU_enable_material);
@@ -3193,7 +3181,7 @@ static void draw_mesh_fancy(Scene *scene, ARegion *ar, View3D *v3d, RegionView3D
 			/* since we already draw wire as wp guide, dont draw over the top */
 			draw_wire= OBDRAW_WIRE_OFF;
 		}
-		else if (draw_flags & DRAW_DYNAMIC_PAINT_PREVIEW) {
+		else if (draw_flags & DRAW_MODIFIERS_PREVIEW) {
 			/* for object selection draws no shade */
 			if (flag & (DRAW_PICKING|DRAW_CONSTCOLOR)) {
 				dm->drawFacesSolid(dm, NULL, 0, GPU_enable_material);
diff --git a/source/blender/editors/space_view3d/view3d_intern.h b/source/blender/editors/space_view3d/view3d_intern.h
index f6c82b0ba9d..07754c0883c 100644
--- a/source/blender/editors/space_view3d/view3d_intern.h
+++ b/source/blender/editors/space_view3d/view3d_intern.h
@@ -59,7 +59,7 @@ struct wmNDOFMotionData;
 #define DRAW_SCENESET	4
 
 /* draw_mesh_fancy/draw_mesh_textured draw_flags */
-#define DRAW_DYNAMIC_PAINT_PREVIEW 1
+#define DRAW_MODIFIERS_PREVIEW 1
 #define DRAW_FACE_SELECT 2
 
 /* view3d_header.c */