Additive snap for Transform. Easy snapping between two vertices, in the middle of three faces, ...

A to add the current snapping point to the list
Alt-A to remove the last one

The resulting snapping point is the average of all snap points in the list (and the one under the mouse pointer, if valid).

Snapping between two verts is a matter of moving over the first, pressing A, moving over the other, confirming transform.

1 files changed, 72 insertions, 10 deletions

diff --git a/source/blender/editors/transform/transform_snap.c b/source/blender/editors/transform/transform_snap.c
index d36b7c9b903..7f1e67b62ac 100644
--- a/source/blender/editors/transform/transform_snap.c
+++ b/source/blender/editors/transform/transform_snap.c
@@ -123,9 +123,14 @@ int BIF_snappingSupported(Object *obedit)
 	return status;
 }
 
+int validSnap(TransInfo *t) {
+	return (t->tsnap.status & (POINT_INIT|TARGET_INIT)) == (POINT_INIT|TARGET_INIT) ||
+			(t->tsnap.status & (MULTI_POINTS|TARGET_INIT)) == (MULTI_POINTS|TARGET_INIT);
+}
+
 void drawSnapping(const struct bContext *C, TransInfo *t)
 {
-	if ((t->tsnap.status & (POINT_INIT|TARGET_INIT)) == (POINT_INIT|TARGET_INIT) &&
+	if (validSnap(t) &&
 		(t->modifiers & MOD_SNAP))
 		{
 		
@@ -134,6 +139,7 @@ void drawSnapping(const struct bContext *C, TransInfo *t)
 		glColor4ub(col[0], col[1], col[2], 128);
 		
 		if (t->spacetype == SPACE_VIEW3D) {
+			TransSnapPoint *p;
 			View3D *v3d = CTX_wm_view3d(C);
 			RegionView3D *rv3d = CTX_wm_region_view3d(C);
 			float tmat[4][4], imat[4][4];
@@ -141,14 +147,18 @@ void drawSnapping(const struct bContext *C, TransInfo *t)
 			
 			glDisable(GL_DEPTH_TEST);
 	
-			size = get_drawsize(t->ar, t->tsnap.snapPoint);
-			
-			size *= 0.5f * UI_GetThemeValuef(TH_VERTEX_SIZE);
+			size = 0.5f * UI_GetThemeValuef(TH_VERTEX_SIZE);
 			
 			copy_m4_m4(tmat, rv3d->viewmat);
 			invert_m4_m4(imat, tmat);
 
-			drawcircball(GL_LINE_LOOP, t->tsnap.snapPoint, size, imat);
+			for (p = t->tsnap.points.first; p; p = p->next) {
+				drawcircball(GL_LINE_LOOP, p->co, size * get_drawsize(t->ar, p->co), imat);
+			}
+
+			if (t->tsnap.status & POINT_INIT) {
+				drawcircball(GL_LINE_LOOP, t->tsnap.snapPoint, size * get_drawsize(t->ar, t->tsnap.snapPoint), imat);
+			}
 			
 			/* draw normal if needed */
 			if (usingSnappingNormal(t) && validSnappingNormal(t))
@@ -302,7 +312,7 @@ void applySnapping(TransInfo *t, float *vec)
 	
 			t->tsnap.last = current;
 		}
-		if ((t->tsnap.status & (POINT_INIT|TARGET_INIT)) == (POINT_INIT|TARGET_INIT))
+		if (validSnap(t))
 		{
 			t->tsnap.applySnap(t, vec);
 		}
@@ -331,7 +341,7 @@ int usingSnappingNormal(TransInfo *t)
 
 int validSnappingNormal(TransInfo *t)
 {
-	if ((t->tsnap.status & (POINT_INIT|TARGET_INIT)) == (POINT_INIT|TARGET_INIT))
+	if (validSnap(t))
 	{
 		if (dot_v3v3(t->tsnap.snapNormal, t->tsnap.snapNormal) > 0)
 		{
@@ -502,11 +512,59 @@ void setSnappingCallback(TransInfo *t, short snap_target)
 	}
 }
 
+void addSnapPoint(TransInfo *t)
+{
+	if (t->tsnap.status & POINT_INIT) {
+		TransSnapPoint *p = MEM_callocN(sizeof(TransSnapPoint), "SnapPoint");
+
+		VECCOPY(p->co, t->tsnap.snapPoint);
+
+		BLI_addtail(&t->tsnap.points, p);
+
+		t->tsnap.status |= MULTI_POINTS;
+	}
+}
+
+void removeSnapPoint(TransInfo *t)
+{
+	if (t->tsnap.status & MULTI_POINTS) {
+		BLI_freelinkN(&t->tsnap.points, t->tsnap.points.last);
+
+		if (t->tsnap.points.first == NULL)
+			t->tsnap.status &= ~MULTI_POINTS;
+	}
+}
+
+void getSnapPoint(TransInfo *t, float vec[3])
+{
+	if (t->tsnap.points.first) {
+		TransSnapPoint *p;
+		int total = 0;
+
+		vec[0] = vec[1] = vec[2] = 0;
+
+		for (p = t->tsnap.points.first; p; p = p->next, total++) {
+			add_v3_v3(vec, p->co);
+		}
+
+		if (t->tsnap.status & POINT_INIT) {
+			add_v3_v3(vec, t->tsnap.snapPoint);
+			total++;
+		}
+
+		mul_v3_fl(vec, 1.0f / total);
+	} else {
+		VECCOPY(vec, t->tsnap.snapPoint)
+	}
+}
+
 /********************** APPLY **************************/
 
 void ApplySnapTranslation(TransInfo *t, float vec[3])
 {
-	sub_v3_v3v3(vec, t->tsnap.snapPoint, t->tsnap.snapTarget);
+	float point[3];
+	getSnapPoint(t, point);
+	sub_v3_v3v3(vec, point, t->tsnap.snapTarget);
 }
 
 void ApplySnapRotation(TransInfo *t, float *vec)
@@ -515,7 +573,9 @@ void ApplySnapRotation(TransInfo *t, float *vec)
 		*vec = t->tsnap.dist;
 	}
 	else {
-		*vec = RotationBetween(t, t->tsnap.snapTarget, t->tsnap.snapPoint);
+		float point[3];
+		getSnapPoint(t, point);
+		*vec = RotationBetween(t, t->tsnap.snapTarget, point);
 	}
 }
 
@@ -525,7 +585,9 @@ void ApplySnapResize(TransInfo *t, float vec[3])
 		vec[0] = vec[1] = vec[2] = t->tsnap.dist;
 	}
 	else {
-		vec[0] = vec[1] = vec[2] = ResizeBetween(t, t->tsnap.snapTarget, t->tsnap.snapPoint);
+		float point[3];
+		getSnapPoint(t, point);
+		vec[0] = vec[1] = vec[2] = ResizeBetween(t, t->tsnap.snapTarget, point);
 	}
 }