Index: source/blender/include/BSE_trans_types.h
===================================================================
--- source/blender/include/BSE_trans_types.h	(revision 15376)
+++ source/blender/include/BSE_trans_types.h	(working copy)
@@ -74,7 +74,8 @@
 } TransVert;
 
 typedef struct VPaint {
-	float r, g, b, a;
+	float r, g, b, alpha;
+	float a; /* amount of pressure */
 	float size;			/* of brush */
 	float gamma, mul;
 	short mode, flag;
Index: source/blender/src/buttons_editing.c
===================================================================
--- source/blender/src/buttons_editing.c	(revision 15376)
+++ source/blender/src/buttons_editing.c	(working copy)
@@ -6104,10 +6104,13 @@
 		uiDefButF(block, NUMSLI, B_NOP, "R ",			979,170,150,19, &Gvp.r, 0.0, 1.0, B_VPCOLSLI, 0, "The amount of red used for painting");
 		uiDefButF(block, NUMSLI, B_NOP, "G ",			979,150,150,19, &Gvp.g, 0.0, 1.0, B_VPCOLSLI, 0, "The amount of green used for painting");
 		uiDefButF(block, NUMSLI, B_NOP, "B ",			979,130,150,19, &Gvp.b, 0.0, 1.0, B_VPCOLSLI, 0, "The amount of blue used for painting");
+		uiBlockEndAlign(block);
+
+		uiDefButF(block, NUMSLI, B_NOP, "A ",			979,105,150,19, &Gvp.alpha, 0.0, 1.0, B_VPCOLSLI, 0, "The amount of alpha used for painting");
 		
 		uiBlockBeginAlign(block);
-		uiDefButF(block, NUMSLI, B_NOP, "Opacity ",		979,105,222,19, &Gvp.a, 0.0, 1.0, 0, 0, "The amount of pressure on the brush");
-		uiDefButF(block, NUMSLI, B_NOP, "Size ",		979,85,222,19, &Gvp.size, 2.0, 64.0, 0, 0, "The size of the brush");
+		uiDefButF(block, NUMSLI, B_NOP, "Pressure ",		979,75,222,19, &Gvp.a, 0.0, 1.0, 0, 0, "The amount of pressure on the brush");
+		uiDefButF(block, NUMSLI, B_NOP, "Size ",		979,55,222,19, &Gvp.size, 2.0, 64.0, 0, 0, "The size of the brush");
 		uiBlockEndAlign(block);
 		
 		uiDefButF(block, COL, B_REDR, "",				1140,150,60,40, &(Gvp.r), 0, 0, 0, B_VPCOLSLI, "");
Index: source/blender/src/vpaint.c
===================================================================
--- source/blender/src/vpaint.c	(revision 15376)
+++ source/blender/src/vpaint.c	(working copy)
@@ -110,8 +110,8 @@
 
 #define MAXINDEX	512000
 
-VPaint Gvp= {1.0, 1.0, 1.0, 0.2, 25.0, 1.0, 1.0, 0, VP_AREA+VP_SOFT+VP_SPRAY, 0};
-VPaint Gwp= {1.0, 1.0, 1.0, 1.0, 25.0, 1.0, 1.0, 0, VP_AREA+VP_SOFT, 0};
+VPaint Gvp= {1.0, 1.0, 1.0, 1.0, 0.2, 25.0, 1.0, 1.0, 0, VP_AREA+VP_SOFT+VP_SPRAY, 0};
+VPaint Gwp= {1.0, 1.0, 1.0, 1.0, 1.0, 25.0, 1.0, 1.0, 0, VP_AREA+VP_SOFT, 0};
 
 static int *get_indexarray(void)
 {
@@ -157,7 +157,7 @@
 
 static unsigned int vpaint_get_current_col(VPaint *vp)
 {
-	return rgba_to_mcol(vp->r, vp->g, vp->b, 1.0f);
+	return rgba_to_mcol(vp->r, vp->g, vp->b, vp->alpha);
 }
 
 void do_shared_vertexcol(Mesh *me)
@@ -532,6 +532,7 @@
 		Gvp.r= cp[0]/255.0f;
 		Gvp.g= cp[1]/255.0f;
 		Gvp.b= cp[2]/255.0f;
+		/* do not sample alpha channel? */
 	}
 	else {
 		Brush *brush= G.scene->toolsettings->imapaint.brush;
@@ -540,6 +541,7 @@
 			brush->rgb[0]= cp[0]/255.0f;
 			brush->rgb[1]= cp[1]/255.0f;
 			brush->rgb[2]= cp[2]/255.0f;
+			/* do not sample alpha channel? */
 
 			allqueue(REDRAWVIEW3D, 0);
 			allqueue(REDRAWIMAGE, 0);
@@ -565,7 +567,7 @@
 	cp2= (char *)&col2;
 	cp=  (char *)&col;
 	
-	cp[0]= 255;
+	cp[0]= (mfac*cp1[0]+fac*cp2[0])>>8; /* mix alpha channels */
 	cp[1]= (mfac*cp1[1]+fac*cp2[1])>>8;
 	cp[2]= (mfac*cp1[2]+fac*cp2[2])>>8;
 	cp[3]= (mfac*cp1[3]+fac*cp2[3])>>8;
@@ -585,7 +587,7 @@
 	cp2= (char *)&col2;
 	cp=  (char *)&col;
 	
-	cp[0]= 255;
+	cp[0]= cp1[0]; /* keep original alpha */
 	temp= cp1[1] + ((fac*cp2[1])>>8);
 	if(temp>254) cp[1]= 255; else cp[1]= temp;
 	temp= cp1[2] + ((fac*cp2[2])>>8);
@@ -608,7 +610,7 @@
 	cp2= (char *)&col2;
 	cp=  (char *)&col;
 	
-	cp[0]= 255;
+	cp[0]= cp1[0]; /* keep original alpha */
 	temp= cp1[1] - ((fac*cp2[1])>>8);
 	if(temp<0) cp[1]= 0; else cp[1]= temp;
 	temp= cp1[2] - ((fac*cp2[2])>>8);
@@ -634,7 +636,7 @@
 	cp=  (char *)&col;
 	
 	/* first mul, then blend the fac */
-	cp[0]= 255;
+	cp[0]= cp1[0]; /* keep original alpha */
 	cp[1]= (mfac*cp1[1] + fac*((cp2[1]*cp1[1])>>8)  )>>8;
 	cp[2]= (mfac*cp1[2] + fac*((cp2[2]*cp1[2])>>8)  )>>8;
 	cp[3]= (mfac*cp1[3] + fac*((cp2[3]*cp1[3])>>8)  )>>8;
@@ -663,7 +665,7 @@
 	if (cp1[1]+cp1[2]+cp1[3] > cp2[1]+cp2[2]+cp2[3])
 		return col1;
 	
-	cp[0]= 255;
+	cp[0]= cp1[0]; /* keep original alpha */
 	cp[1]= (mfac*cp1[1]+fac*cp2[1])>>8;
 	cp[2]= (mfac*cp1[2]+fac*cp2[2])>>8;
 	cp[3]= (mfac*cp1[3]+fac*cp2[3])>>8;
@@ -691,7 +693,7 @@
 	if (cp1[1]+cp1[2]+cp1[3] < cp2[1]+cp2[2]+cp2[3])
 		return col1;
 	
-	cp[0]= 255;
+	cp[0]= cp1[0]; /* keep original alpha */
 	cp[1]= (mfac*cp1[1]+fac*cp2[1])>>8;
 	cp[2]= (mfac*cp1[2]+fac*cp2[2])>>8;
 	cp[3]= (mfac*cp1[3]+fac*cp2[3])>>8;