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, 164 insertions, 68 deletions

diff --git a/source/blender/blenkernel/intern/DerivedMesh.c b/source/blender/blenkernel/intern/DerivedMesh.c
index b670a360a6a..27aeeb95903 100644
--- a/source/blender/blenkernel/intern/DerivedMesh.c
+++ b/source/blender/blenkernel/intern/DerivedMesh.c
@@ -722,24 +722,23 @@ void vDM_ColorBand_store(ColorBand *coba)
  * note that we could save some memory and allocate RGB only but then we'd need to
  * re-arrange the colors when copying to the face since MCol has odd ordering,
  * so leave this as is - campbell */
-static unsigned char *calc_weightpaint_vert_array(Object *ob, int const draw_flag, ColorBand *coba)
+static unsigned char *calc_weightpaint_vert_array(Object *ob, DerivedMesh *dm, int const draw_flag, ColorBand *coba)
 {
-	Mesh *me = ob->data;
-	unsigned char *wtcol_v = MEM_mallocN (sizeof(unsigned char) * me->totvert * 4, "weightmap_v");
+	MDeformVert *dv = DM_get_vert_data_layer(dm, CD_MDEFORMVERT);
+	int numVerts = dm->getNumVerts(dm);
+	unsigned char *wtcol_v = MEM_mallocN (sizeof(unsigned char) * numVerts * 4, "weightmap_v");
 
-	if (me->dvert) {
+	if (dv) {
 		unsigned char *wc = wtcol_v;
-		MDeformVert *dv= me->dvert;
 		unsigned int i;
 
-		/* varisbles for multipaint */
+		/* variables for multipaint */
 		const int defbase_tot = BLI_countlist(&ob->defbase);
 		const int defbase_act = ob->actdef-1;
 		char *dg_flags = MEM_mallocN(defbase_tot * sizeof(char), __func__);
 		const int selected = get_selected_defgroups(ob, dg_flags, defbase_tot);
-		/* const int unselected = defbase_tot - selected; */ /* UNUSED */
 
-		for (i = me->totvert; i != 0; i--, wc += 4, dv++) {
+		for (i = numVerts; i != 0; i--, wc += 4, dv++) {
 			calc_weightpaint_vert_color(wc, dv, coba, defbase_tot, defbase_act, dg_flags, selected, draw_flag);
 		}
 
@@ -748,48 +747,94 @@ static unsigned char *calc_weightpaint_vert_array(Object *ob, int const draw_fla
 	else {
 		int col_i;
 		weightpaint_color((unsigned char *)&col_i, coba, 0.0f);
-		fill_vn_i((int *)wtcol_v, me->totvert, col_i);
+		fill_vn_i((int *)wtcol_v, numVerts, col_i);
 	}
 
 	return wtcol_v;
 }
 
-static void add_weight_mcol_dm(Object *ob, DerivedMesh *dm, int const draw_flag)
+/* return an array of vertex weight colors from given weights, caller must free.
+ *
+ * note that we could save some memory and allocate RGB only but then we'd need to
+ * re-arrange the colors when copying to the face since MCol has odd ordering,
+ * so leave this as is - campbell */
+static unsigned char *calc_colors_from_weights_array(const int num, float *weights)
 {
-	ColorBand *coba= stored_cb;	/* warning, not a local var */
+	unsigned char *wtcol_v = MEM_mallocN(sizeof(unsigned char) * num * 4, "weightmap_v");
+	unsigned char *wc = wtcol_v;
+	int i;
 
-	Mesh *me = ob->data;
-	unsigned char *wtcol_v = calc_weightpaint_vert_array(ob, draw_flag, coba);
-	unsigned char *wtcol_f = MEM_mallocN (sizeof(unsigned char) * me->totface*4*4, "weightmap_f");
-	unsigned char *wtcol_f_step = wtcol_f;
+	for (i = 0; i < num; i++, wc += 4, weights++)
+		weightpaint_color((unsigned char *) wc, NULL, *weights);
+
+	return wtcol_v;
+}
 
-	MFace *mf = me->mface;
+void DM_update_weight_mcol(Object *ob, DerivedMesh *dm, int const draw_flag,
+                           float *weights, int num, const int *indices)
+{
+	ColorBand *coba= stored_cb;	/* warning, not a local var */
+
+	MFace *mf = dm->getFaceArray(dm);
+	int numFaces = dm->getNumFaces(dm);
+	int numVerts = dm->getNumVerts(dm);
+	unsigned char *wtcol_v;
+	unsigned char *wtcol_f = dm->getFaceDataArray(dm, CD_WEIGHT_MCOL);
 	int i;
 
-	for (i=0; i<me->totface; i++, mf++, wtcol_f_step += (4 * 4)) {
+	/* If no CD_WEIGHT_MCOL existed yet, add a new one! */
+	if (!wtcol_f)
+		wtcol_f = CustomData_add_layer(&dm->faceData, CD_WEIGHT_MCOL, CD_CALLOC, NULL, numFaces);
+
+	if (wtcol_f) {
+		unsigned char *wtcol_f_step = wtcol_f;
+
+		/* Weights are given by caller. */
+		if (weights) {
+			float *w = weights;
+			/* If indices is not NULL, it means we do not have weights for all vertices,
+			 * so we must create them (and set them to zero)... */
+			if(indices) {
+				w = MEM_callocN(sizeof(float)*numVerts, "Temp weight array DM_update_weight_mcol");
+				i = num;
+				while(i--)
+					w[indices[i]] = weights[i];
+			}
+
+			/* Convert float weights to colors. */
+			wtcol_v = calc_colors_from_weights_array(numVerts, w);
+
+			if(indices)
+				MEM_freeN(w);
+		}
+
+		/* No weights given, take them from active vgroup(s). */
+		else
+			wtcol_v = calc_weightpaint_vert_array(ob, dm, draw_flag, coba);
+
+		/* Now copy colors in all face verts. */
+		for (i = 0; i < numFaces; i++, mf++, wtcol_f_step += (4 * 4)) {
 #if 0
-		unsigned int fidx= mf->v4 ? 3:2;
+			unsigned int fidx= mf->v4 ? 3:2;
 
 #else	/* better zero out triangles 4th component. else valgrind complains when the buffer's copied */
-		unsigned int fidx;
-		if (mf->v4) {
-			fidx = 3;
-		}
-		else {
-			fidx = 2;
-			*(int *)(&wtcol_f_step[3 * 4]) = 0;
-		}
+			unsigned int fidx;
+			if (mf->v4) {
+				fidx = 3;
+			}
+			else {
+				fidx = 2;
+				*(int *)(&wtcol_f_step[3 * 4]) = 0;
+			}
 #endif
 
-		do {
-			copy_v4_v4_char((char *)&wtcol_f_step[fidx * 4],
-			                (char *)&wtcol_v[4 * (*(&mf->v1 + fidx))]);
-		} while (fidx--);
+			do {
+				copy_v4_v4_char((char *)&wtcol_f_step[fidx * 4],
+						        (char *)&wtcol_v[4 * (*(&mf->v1 + fidx))]);
+			} while (fidx--);
+		}
+		MEM_freeN(wtcol_v);
 	}
-
-	MEM_freeN(wtcol_v);
-
-	CustomData_add_layer(&dm->faceData, CD_WEIGHT_MCOL, CD_ASSIGN, wtcol_f, dm->numFaceData);
 }
 
 /* new value for useDeform -1  (hack for the gameengine):
@@ -803,7 +848,7 @@ static void mesh_calc_modifiers(Scene *scene, Object *ob, float (*inputVertexCos
 								int needMapping, CustomDataMask dataMask, int index, int useCache)
 {
 	Mesh *me = ob->data;
-	ModifierData *firstmd, *md;
+	ModifierData *firstmd, *md, *previewmd = NULL;
 	LinkNode *datamasks, *curr;
 	CustomDataMask mask, nextmask, append_mask = 0;
 	float (*deformedVerts)[3] = NULL;
@@ -816,8 +861,17 @@ static void mesh_calc_modifiers(Scene *scene, Object *ob, float (*inputVertexCos
 	int has_multires = mmd != NULL, multires_applied = 0;
 	int sculpt_mode = ob->mode & OB_MODE_SCULPT && ob->sculpt;
 
-	int draw_flag= ((scene->toolsettings->multipaint ? CALC_WP_MULTIPAINT : 0) |
-	                (scene->toolsettings->auto_normalize ? CALC_WP_AUTO_NORMALIZE : 0));
+	const int draw_flag= ((scene->toolsettings->multipaint ? CALC_WP_MULTIPAINT : 0) |
+	                      (scene->toolsettings->auto_normalize ? CALC_WP_AUTO_NORMALIZE : 0));
+	/* Generic preview only in object mode! */
+	const int do_mod_mcol = (ob->mode == OB_MODE_OBJECT);
+#if 0 /* XXX Will re-enable this when we have global mod stack options. */
+	const int do_final_wmcol = (scene->toolsettings->weights_preview == WP_WPREVIEW_FINAL) && do_wmcol;
+#endif
+	const int do_final_wmcol = FALSE;
+	int do_init_wmcol = ((dataMask & CD_MASK_WEIGHT_MCOL) && (ob->mode & OB_MODE_WEIGHT_PAINT) && !do_final_wmcol);
+	/* XXX Same as above... For now, only weights preview in WPaint mode. */
+	const int do_mod_wmcol = do_init_wmcol;
 
 	if(mmd && !mmd->sculptlvl)
 		has_multires = 0;
@@ -842,6 +896,14 @@ static void mesh_calc_modifiers(Scene *scene, Object *ob, float (*inputVertexCos
 	datamasks = modifiers_calcDataMasks(scene, ob, md, dataMask, required_mode);
 	curr = datamasks;
 
+	if(do_mod_wmcol || do_mod_mcol) {
+		/* Find the last active modifier generating a preview, or NULL if none. */
+		/* XXX Currently, DPaint modifier just ignores this.
+		 *     Needs a stupid hack...
+		 *     The whole "modifier preview" thing has to be (re?)designed, anyway! */
+		previewmd = modifiers_getLastPreview(scene, md, required_mode);
+	}
+
 	if(deform_r) *deform_r = NULL;
 	*final_r = NULL;
 
@@ -997,8 +1059,8 @@ static void mesh_calc_modifiers(Scene *scene, Object *ob, float (*inputVertexCos
 					CDDM_calc_normals(dm);
 				}
 
-				if((dataMask & CD_MASK_WEIGHT_MCOL) && (ob->mode & OB_MODE_WEIGHT_PAINT))
-					add_weight_mcol_dm(ob, dm, draw_flag); 
+				if(do_init_wmcol)
+					DM_update_weight_mcol(ob, dm, draw_flag, NULL, 0, NULL);
 
 				/* Constructive modifiers need to have an origindex
 				 * otherwise they wont have anywhere to copy the data from.
@@ -1085,8 +1147,14 @@ static void mesh_calc_modifiers(Scene *scene, Object *ob, float (*inputVertexCos
 			}
 
 			/* in case of dynamic paint, make sure preview mask remains for following modifiers */
+			/* XXX Temp and hackish solution! */
 			if (md->type == eModifierType_DynamicPaint)
 				append_mask |= CD_MASK_WEIGHT_MCOL;
+			/* In case of active preview modifier, make sure preview mask remains for following modifiers. */
+			else if ((md == previewmd) && (do_mod_wmcol)) {
+				DM_update_weight_mcol(ob, dm, draw_flag, NULL, 0, NULL);
+				append_mask |= CD_MASK_WEIGHT_MCOL;
+			}
 		}
 
 		isPrevDeform= (mti->type == eModifierTypeType_OnlyDeform);
@@ -1114,10 +1182,19 @@ static void mesh_calc_modifiers(Scene *scene, Object *ob, float (*inputVertexCos
 		CDDM_apply_vert_coords(finaldm, deformedVerts);
 		CDDM_calc_normals(finaldm);
 
-		if((dataMask & CD_MASK_WEIGHT_MCOL) && (ob->mode & OB_MODE_WEIGHT_PAINT))
-			add_weight_mcol_dm(ob, finaldm, draw_flag);
+#if 0 /* For later nice mod preview! */
+		/* In case we need modified weights in CD_WEIGHT_MCOL, we have to re-compute it. */
+		if(do_final_wmcol)
+			DM_update_weight_mcol(ob, finaldm, draw_flag, NULL, 0, NULL);
+#endif
 	} else if(dm) {
 		finaldm = dm;
+
+#if 0 /* For later nice mod preview! */
+		/* In case we need modified weights in CD_WEIGHT_MCOL, we have to re-compute it. */
+		if(do_final_wmcol)
+			DM_update_weight_mcol(ob, finaldm, draw_flag, NULL, 0, NULL);
+#endif
 	} else {
 		finaldm = CDDM_from_mesh(me, ob);
 
@@ -1126,8 +1203,9 @@ static void mesh_calc_modifiers(Scene *scene, Object *ob, float (*inputVertexCos
 			CDDM_calc_normals(finaldm);
 		}
 
-		if((dataMask & CD_MASK_WEIGHT_MCOL) && (ob->mode & OB_MODE_WEIGHT_PAINT))
-			add_weight_mcol_dm(ob, finaldm, draw_flag);
+		/* In this case, we should never have weight-modifying modifiers in stack... */
+		if(do_init_wmcol)
+			DM_update_weight_mcol(ob, finaldm, draw_flag, NULL, 0, NULL);
 	}
 
 	/* add an orco layer if needed */
diff --git a/source/blender/blenkernel/intern/dynamicpaint.c b/source/blender/blenkernel/intern/dynamicpaint.c
index 6a2207d455c..18c8d0f0106 100644
--- a/source/blender/blenkernel/intern/dynamicpaint.c
+++ b/source/blender/blenkernel/intern/dynamicpaint.c
@@ -1574,7 +1574,6 @@ static struct DerivedMesh *dynamicPaint_Modifier_apply(DynamicPaintModifierData
 
 		DynamicPaintSurface *surface = pmd->canvas->surfaces.first;
 		int update_normals = 0;
-		pmd->canvas->flags &= ~MOD_DPAINT_PREVIEW_READY;
 
 		/* loop through surfaces */
 		for (; surface; surface=surface->next) {
@@ -1651,7 +1650,6 @@ static struct DerivedMesh *dynamicPaint_Modifier_apply(DynamicPaintModifierData
 										}
 									}
 								}
-								pmd->canvas->flags |= MOD_DPAINT_PREVIEW_READY;
 							}
 						}
 
@@ -1711,29 +1709,7 @@ static struct DerivedMesh *dynamicPaint_Modifier_apply(DynamicPaintModifierData
 						if (surface->flags & MOD_DPAINT_PREVIEW) {
 							/* Save preview results to weight layer, to be
 							*   able to share same drawing methods */
-							MFace *mface = result->getFaceArray(result);
-							int numOfFaces = result->getNumFaces(result);
-							int i;
-							MCol *col = result->getFaceDataArray(result, CD_WEIGHT_MCOL);
-							if (!col) col = CustomData_add_layer(&result->faceData, CD_WEIGHT_MCOL, CD_CALLOC, NULL, numOfFaces);
-
-							if (col) {
-								#pragma omp parallel for schedule(static)
-								for (i=0; i<numOfFaces; i++) {
-									float temp_color[3];
-									int j = (mface[i].v4) ? 4 : 3;
-									while (j--) {
-										int index = *((&mface[i].v1)+j);
-
-										weight_to_rgb(temp_color, weight[index]);
-										col[i*4+j].r = FTOCHAR(temp_color[2]);
-										col[i*4+j].g = FTOCHAR(temp_color[1]);
-										col[i*4+j].b = FTOCHAR(temp_color[0]);
-										col[i*4+j].a = 255;
-									}
-								}
-								pmd->canvas->flags |= MOD_DPAINT_PREVIEW_READY;
-							}
+							DM_update_weight_mcol(ob, result, 0, weight, 0, NULL);
 						}
 
 						/* apply weights into a vertex group, if doesnt exists add a new layer */
diff --git a/source/blender/blenkernel/intern/modifier.c b/source/blender/blenkernel/intern/modifier.c
index 5a389019519..911d303b4cf 100644
--- a/source/blender/blenkernel/intern/modifier.c
+++ b/source/blender/blenkernel/intern/modifier.c
@@ -142,6 +142,19 @@ int modifier_supportsMapping(ModifierData *md)
 			(mti->flags & eModifierTypeFlag_SupportsMapping));
 }
 
+int modifier_isPreview(ModifierData *md)
+{
+	ModifierTypeInfo *mti = modifierType_getInfo(md->type);
+
+	if (!(mti->flags & eModifierTypeFlag_UsesPreview))
+		return FALSE;
+
+	if (md->mode & eModifierMode_Realtime)
+		return TRUE;
+
+	return FALSE;
+}
+
 ModifierData *modifiers_findByType(Object *ob, ModifierType type)
 {
 	ModifierData *md = ob->modifiers.first;
@@ -385,6 +398,21 @@ LinkNode *modifiers_calcDataMasks(struct Scene *scene, Object *ob, ModifierData
 	return dataMasks;
 }
 
+ModifierData *modifiers_getLastPreview(struct Scene *scene, ModifierData *md, int required_mode)
+{
+	ModifierData *tmp_md = NULL;
+
+	if (required_mode != eModifierMode_Realtime)
+		return tmp_md;
+
+	/* Find the latest modifier in stack generating preview. */
+	for(; md; md = md->next) {
+		if(modifier_isEnabled(scene, md, required_mode) && modifier_isPreview(md))
+			tmp_md = md;
+	}
+	return tmp_md;
+}
+
 ModifierData *modifiers_getVirtualModifierList(Object *ob)
 {
 		/* Kinda hacky, but should be fine since we are never
@@ -545,6 +573,20 @@ int modifiers_isCorrectableDeformed(Object *ob)
 	return 0;
 }
 
+/* Check whether the given object has a modifier in its stack that uses WEIGHT_MCOL CD layer
+ * to preview something... Used by DynamicPaint and WeightVG currently. */
+int modifiers_isPreview(Object *ob)
+{
+	ModifierData *md = ob->modifiers.first;
+
+	for (; md; md = md->next) {
+		if (modifier_isPreview(md))
+			return TRUE;
+	}
+
+	return FALSE;
+}
+
 int modifiers_indexInObject(Object *ob, ModifierData *md_seek)
 {
 	int i= 0;