Build Modifier - Add "Reversed" Option

This commit introduces the ability to make the Build Modifier operate in reverse,
essentially allowing it to be used as a "deconstruction" effect.

(See D219 for more details about use cases for this)

5 files changed, 41 insertions, 6 deletions

diff --git a/release/scripts/startup/bl_ui/properties_data_modifier.py b/release/scripts/startup/bl_ui/properties_data_modifier.py
index f9684794b79..bca613be866 100644
--- a/release/scripts/startup/bl_ui/properties_data_modifier.py
+++ b/release/scripts/startup/bl_ui/properties_data_modifier.py
@@ -160,6 +160,7 @@ class DATA_PT_modifiers(ModifierButtonsPanel, Panel):
         col = split.column()
         col.prop(md, "frame_start")
         col.prop(md, "frame_duration")
+        col.prop(md, "use_reverse")
 
         col = split.column()
         col.prop(md, "use_random_order")
diff --git a/source/blender/blenloader/intern/versioning_260.c b/source/blender/blenloader/intern/versioning_260.c
index 768e0ba5e68..218313ebb44 100644
--- a/source/blender/blenloader/intern/versioning_260.c
+++ b/source/blender/blenloader/intern/versioning_260.c
@@ -2655,6 +2655,22 @@ void blo_do_versions_260(FileData *fd, Library *UNUSED(lib), Main *main)
 			}
 		}
 	}
+	
+	if (!MAIN_VERSION_ATLEAST(main, 269, 9)) {
+		Object *ob;
+		
+		for (ob = main->object.first; ob; ob = ob->id.next) {
+			ModifierData *md;
+			for (md = ob->modifiers.first; md; md = md->next) {
+				if (md->type == eModifierType_Build) {
+					BuildModifierData *bmd = (BuildModifierData *)md;
+					if (bmd->randomize) {
+						bmd->flag |= MOD_BUILD_FLAG_RANDOMIZE;
+					}
+				}
+			}
+		}
+	}
 
 	if (!DNA_struct_elem_find(fd->filesdna, "BevelModifierData", "float", "profile")) {
 		Object *ob;
diff --git a/source/blender/makesdna/DNA_modifier_types.h b/source/blender/makesdna/DNA_modifier_types.h
index 6756a18e382..06e75ca62de 100644
--- a/source/blender/makesdna/DNA_modifier_types.h
+++ b/source/blender/makesdna/DNA_modifier_types.h
@@ -167,9 +167,18 @@ typedef struct BuildModifierData {
 	ModifierData modifier;
 
 	float start, length;
-	int randomize, seed;
+	short flag;
+	
+	short randomize;      /* (bool) whether order of vertices is randomized - legacy files (for readfile conversion) */
+	int seed;             /* (int) random seed */
 } BuildModifierData;
 
+/* Build Modifier -> flag */
+enum {
+	MOD_BUILD_FLAG_RANDOMIZE = (1 << 0),  /* order of vertices is randomized */
+	MOD_BUILD_FLAG_REVERSE   = (1 << 1),  /* frame range is reversed, resulting in a deconstruction effect */
+};
+
 /* Mask Modifier */
 typedef struct MaskModifierData {
 	ModifierData modifier;
diff --git a/source/blender/makesrna/intern/rna_modifier.c b/source/blender/makesrna/intern/rna_modifier.c
index 73db7adb8cb..89fb24145a6 100644
--- a/source/blender/makesrna/intern/rna_modifier.c
+++ b/source/blender/makesrna/intern/rna_modifier.c
@@ -1092,8 +1092,13 @@ static void rna_def_modifier_build(BlenderRNA *brna)
 	RNA_def_property_ui_text(prop, "Length", "Total time the build effect requires");
 	RNA_def_property_update(prop, 0, "rna_Modifier_update");
 
+	prop = RNA_def_property(srna, "use_reverse", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_sdna(prop, NULL, "flag", MOD_BUILD_FLAG_REVERSE);
+	RNA_def_property_ui_text(prop, "Reversed", "Deconstruct the mesh instead of building it");
+	RNA_def_property_update(prop, 0, "rna_Modifier_update");
+	
 	prop = RNA_def_property(srna, "use_random_order", PROP_BOOLEAN, PROP_NONE);
-	RNA_def_property_boolean_sdna(prop, NULL, "randomize", 1);
+	RNA_def_property_boolean_sdna(prop, NULL, "flag", MOD_BUILD_FLAG_RANDOMIZE);
 	RNA_def_property_ui_text(prop, "Randomize", "Randomize the faces or edges during build");
 	RNA_def_property_update(prop, 0, "rna_Modifier_update");
 
diff --git a/source/blender/modifiers/intern/MOD_build.c b/source/blender/modifiers/intern/MOD_build.c
index d74044fa1ef..58fcbf76e8d 100644
--- a/source/blender/modifiers/intern/MOD_build.c
+++ b/source/blender/modifiers/intern/MOD_build.c
@@ -119,7 +119,11 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *UNUSED(ob),
 
 	frac = (BKE_scene_frame_get(md->scene) - bmd->start) / bmd->length;
 	CLAMP(frac, 0.0f, 1.0f);
-
+	
+	if (bmd->flag & MOD_BUILD_FLAG_REVERSE) {
+		frac = 1.0 - frac;
+	}
+	
 	numFaces_dst = numPoly_src * frac;
 	numEdges_dst = numEdge_src * frac;
 
@@ -129,7 +133,7 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *UNUSED(ob),
 		MLoop *ml, *mloop;
 		MEdge *medge;
 		
-		if (bmd->randomize) {
+		if (bmd->flag & MOD_BUILD_FLAG_RANDOMIZE) {
 			BLI_array_randomize(faceMap, sizeof(*faceMap),
 			                    numPoly_src, bmd->seed);
 		}
@@ -174,7 +178,7 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *UNUSED(ob),
 	else if (numEdges_dst) {
 		MEdge *medge, *me;
 
-		if (bmd->randomize)
+		if (bmd->flag & MOD_BUILD_FLAG_RANDOMIZE)
 			BLI_array_randomize(edgeMap, sizeof(*edgeMap),
 			                    numEdge_src, bmd->seed);
 
@@ -207,7 +211,7 @@ static DerivedMesh *applyModifier(ModifierData *md, Object *UNUSED(ob),
 	else {
 		int numVerts = numVert_src * frac;
 
-		if (bmd->randomize) {
+		if (bmd->flag & MOD_BUILD_FLAG_RANDOMIZE) {
 			BLI_array_randomize(vertMap, sizeof(*vertMap),
 			                    numVert_src, bmd->seed);
 		}