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.

4 files changed, 51 insertions, 10 deletions

diff --git a/source/blender/modifiers/intern/MOD_dynamicpaint.c b/source/blender/modifiers/intern/MOD_dynamicpaint.c
index 773e93a22ad..c7b4d41e646 100644
--- a/source/blender/modifiers/intern/MOD_dynamicpaint.c
+++ b/source/blender/modifiers/intern/MOD_dynamicpaint.c
@@ -170,8 +170,10 @@ ModifierTypeInfo modifierType_DynamicPaint = {
 	/* structSize */        sizeof(DynamicPaintModifierData),
 	/* type */              eModifierTypeType_Constructive,
 	/* flags */             eModifierTypeFlag_AcceptsMesh
-							| eModifierTypeFlag_UsesPointCache
-							| eModifierTypeFlag_Single,
+/*	                       |eModifierTypeFlag_SupportsMapping*/
+	                       |eModifierTypeFlag_UsesPointCache
+	                       |eModifierTypeFlag_Single
+	                       |eModifierTypeFlag_UsesPreview,
 
 	/* copyData */          copyData,
 	/* deformVerts */       NULL,
diff --git a/source/blender/modifiers/intern/MOD_weightvgedit.c b/source/blender/modifiers/intern/MOD_weightvgedit.c
index e090ad78e59..e4d1d7d0eb0 100644
--- a/source/blender/modifiers/intern/MOD_weightvgedit.c
+++ b/source/blender/modifiers/intern/MOD_weightvgedit.c
@@ -114,6 +114,8 @@ static CustomDataMask requiredDataMask(Object *UNUSED(ob), ModifierData *md)
 	if(wmd->mask_tex_mapping == MOD_DISP_MAP_UV)
 		dataMask |= CD_MASK_MTFACE;
 
+	/* No need to ask for CD_WEIGHT_MCOL... */
+
 	return dataMask;
 }
 
@@ -186,8 +188,12 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *ob, DerivedMesh *der
 	int defgrp_idx;
 	int i;
 	/* Flags. */
-	int do_add = (wmd->edit_flags & MOD_WVG_EDIT_ADD2VG) != 0;
-	int do_rem = (wmd->edit_flags & MOD_WVG_EDIT_REMFVG) != 0;
+	int do_add  = (wmd->edit_flags & MOD_WVG_EDIT_ADD2VG) != 0;
+	int do_rem  = (wmd->edit_flags & MOD_WVG_EDIT_REMFVG) != 0;
+	/* Only do weight-preview in Object, Sculpt and Pose modes! */
+#if 0
+	int do_prev = (wmd->modifier.mode & eModifierMode_DoWeightPreview);
+#endif
 
 	/* Get number of verts. */
 	numVerts = dm->getNumVerts(dm);
@@ -244,6 +250,12 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *ob, DerivedMesh *der
 	weightvg_update_vg(dvert, defgrp_idx, dw, numVerts, NULL, org_w, do_add, wmd->add_threshold,
 	                   do_rem, wmd->rem_threshold);
 
+	/* If weight preview enabled... */
+#if 0 /* XXX Currently done in mod stack :/ */
+	if(do_prev)
+		DM_update_weight_mcol(ob, dm, 0, org_w, 0, NULL);
+#endif
+
 	/* Freeing stuff. */
 	MEM_freeN(org_w);
 	MEM_freeN(new_w);
@@ -267,8 +279,9 @@ ModifierTypeInfo modifierType_WeightVGEdit = {
 	/* structSize */        sizeof(WeightVGEditModifierData),
 	/* type */              eModifierTypeType_NonGeometrical,
 	/* flags */             eModifierTypeFlag_AcceptsMesh
-/*	                       |eModifierTypeFlag_SupportsMapping*/
-	                       |eModifierTypeFlag_SupportsEditmode,
+	                       |eModifierTypeFlag_SupportsMapping
+	                       |eModifierTypeFlag_SupportsEditmode
+	                       |eModifierTypeFlag_UsesPreview,
 
 	/* copyData */          copyData,
 	/* deformVerts */       NULL,
diff --git a/source/blender/modifiers/intern/MOD_weightvgmix.c b/source/blender/modifiers/intern/MOD_weightvgmix.c
index 28f9f503966..38de944cf45 100644
--- a/source/blender/modifiers/intern/MOD_weightvgmix.c
+++ b/source/blender/modifiers/intern/MOD_weightvgmix.c
@@ -156,6 +156,8 @@ static CustomDataMask requiredDataMask(Object *UNUSED(ob), ModifierData *md)
 	if(wmd->mask_tex_mapping == MOD_DISP_MAP_UV)
 		dataMask |= CD_MASK_MTFACE;
 
+	/* No need to ask for CD_WEIGHT_MCOL... */
+
 	return dataMask;
 }
 
@@ -229,6 +231,10 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *ob, DerivedMesh *der
 	int *tidx, *indices = NULL;
 	int numIdx = 0;
 	int i;
+	/* Flags. */
+#if 0
+	int do_prev = (wmd->modifier.mode & eModifierMode_DoWeightPreview);
+#endif
 
 	/* Get number of verts. */
 	numVerts = dm->getNumVerts(dm);
@@ -372,6 +378,12 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *ob, DerivedMesh *der
 	 */
 	weightvg_update_vg(dvert, defgrp_idx, dw1, numIdx, indices, org_w, TRUE, -FLT_MAX, FALSE, 0.0f);
 
+	/* If weight preview enabled... */
+#if 0 /* XXX Currently done in mod stack :/ */
+	if(do_prev)
+		DM_update_weight_mcol(ob, dm, 0, org_w, numIdx, indices);
+#endif
+
 	/* Freeing stuff. */
 	MEM_freeN(org_w);
 	MEM_freeN(new_w);
@@ -399,8 +411,9 @@ ModifierTypeInfo modifierType_WeightVGMix = {
 	/* structSize */        sizeof(WeightVGMixModifierData),
 	/* type */              eModifierTypeType_NonGeometrical,
 	/* flags */             eModifierTypeFlag_AcceptsMesh
-/*	                       |eModifierTypeFlag_SupportsMapping*/
-	                       |eModifierTypeFlag_SupportsEditmode,
+	                       |eModifierTypeFlag_SupportsMapping
+	                       |eModifierTypeFlag_SupportsEditmode
+	                       |eModifierTypeFlag_UsesPreview,
 
 	/* copyData */          copyData,
 	/* deformVerts */       NULL,
diff --git a/source/blender/modifiers/intern/MOD_weightvgproximity.c b/source/blender/modifiers/intern/MOD_weightvgproximity.c
index 55b625f7865..c1aa68d1544 100644
--- a/source/blender/modifiers/intern/MOD_weightvgproximity.c
+++ b/source/blender/modifiers/intern/MOD_weightvgproximity.c
@@ -268,6 +268,8 @@ static CustomDataMask requiredDataMask(Object *UNUSED(ob), ModifierData *md)
 	if(wmd->mask_tex_mapping == MOD_DISP_MAP_UV)
 		dataMask |= CD_MASK_MTFACE;
 
+	/* No need to ask for CD_WEIGHT_MCOL... */
+
 	return dataMask;
 }
 
@@ -353,6 +355,10 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *ob, DerivedMesh *der
 	int *tidx, *indices = NULL;
 	int numIdx = 0;
 	int i;
+	/* Flags. */
+#if 0
+	int do_prev = (wmd->modifier.mode & eModifierMode_DoWeightPreview);
+#endif
 
 #if DO_PROFILE
 	TIMEIT_START(perf)
@@ -505,6 +511,12 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *ob, DerivedMesh *der
 	/* Update vgroup. Note we never add nor remove vertices from vgroup here. */
 	weightvg_update_vg(dvert, defgrp_idx, dw, numIdx, indices, org_w, FALSE, 0.0f, FALSE, 0.0f);
 
+	/* If weight preview enabled... */
+#if 0 /* XXX Currently done in mod stack :/ */
+	if(do_prev)
+		DM_update_weight_mcol(ob, dm, 0, org_w, numIdx, indices);
+#endif
+
 	/* Freeing stuff. */
 	MEM_freeN(org_w);
 	MEM_freeN(new_w);
@@ -535,8 +547,9 @@ ModifierTypeInfo modifierType_WeightVGProximity = {
 	/* structSize */        sizeof(WeightVGProximityModifierData),
 	/* type */              eModifierTypeType_NonGeometrical,
 	/* flags */             eModifierTypeFlag_AcceptsMesh
-/*	                       |eModifierTypeFlag_SupportsMapping*/
-	                       |eModifierTypeFlag_SupportsEditmode,
+	                       |eModifierTypeFlag_SupportsMapping
+	                       |eModifierTypeFlag_SupportsEditmode
+	                       |eModifierTypeFlag_UsesPreview,
 
 	/* copyData */          copyData,
 	/* deformVerts */       NULL,