bugfix #18187

Using "Key Alpha" didn't work when using MBlur render. The accumulation
code was assuming regular alpha then. Now it corrects for it.

Still it's a bit of a weak spot in Blender's render system. I will look 
in the future to make this a real post process; converting all RGBA 
buffers in the system, including for all passes, to "key alpha". 
Combined with that our compositor should become alpha type aware too. 
Everything in Blender assumes premul alpha, which still just will work 
best in general...

1 files changed, 45 insertions, 4 deletions

diff --git a/source/blender/render/intern/source/pipeline.c b/source/blender/render/intern/source/pipeline.c
index 5c3c954aa8e..96edb4ee73c 100644
--- a/source/blender/render/intern/source/pipeline.c
+++ b/source/blender/render/intern/source/pipeline.c
@@ -1639,6 +1639,42 @@ static void do_render_3d(Render *re)
 	RE_Database_Free(re);
 }
 
+/* called by blur loop, accumulate RGBA key alpha */
+static void addblur_rect_key(RenderResult *rr, float *rectf, float *rectf1, float blurfac)
+{
+	float mfac= 1.0f - blurfac;
+	int a, b, stride= 4*rr->rectx;
+	int len= stride*sizeof(float);
+	
+	for(a=0; a<rr->recty; a++) {
+		if(blurfac==1.0f) {
+			memcpy(rectf, rectf1, len);
+		}
+		else {
+			float *rf= rectf, *rf1= rectf1;
+			
+			for( b= rr->rectx; b>0; b--, rf+=4, rf1+=4) {
+				if(rf1[3]<0.01f)
+					rf[3]= mfac*rf[3];
+				else if(rf[3]<0.01f) {
+					rf[0]= rf1[0];
+					rf[1]= rf1[1];
+					rf[2]= rf1[2];
+					rf[3]= blurfac*rf1[3];
+				}
+				else {
+					rf[0]= mfac*rf[0] + blurfac*rf1[0];
+					rf[1]= mfac*rf[1] + blurfac*rf1[1];
+					rf[2]= mfac*rf[2] + blurfac*rf1[2];
+					rf[3]= mfac*rf[3] + blurfac*rf1[3];
+				}				
+			}
+		}
+		rectf+= stride;
+		rectf1+= stride;
+	}
+}
+
 /* called by blur loop, accumulate renderlayers */
 static void addblur_rect(RenderResult *rr, float *rectf, float *rectf1, float blurfac, int channels)
 {
@@ -1662,8 +1698,9 @@ static void addblur_rect(RenderResult *rr, float *rectf, float *rectf1, float bl
 	}
 }
 
+
 /* called by blur loop, accumulate renderlayers */
-static void merge_renderresult_blur(RenderResult *rr, RenderResult *brr, float blurfac)
+static void merge_renderresult_blur(RenderResult *rr, RenderResult *brr, float blurfac, int key_alpha)
 {
 	RenderLayer *rl, *rl1;
 	RenderPass *rpass, *rpass1;
@@ -1672,8 +1709,12 @@ static void merge_renderresult_blur(RenderResult *rr, RenderResult *brr, float b
 	for(rl= rr->layers.first; rl && rl1; rl= rl->next, rl1= rl1->next) {
 		
 		/* combined */
-		if(rl->rectf && rl1->rectf)
-			addblur_rect(rr, rl->rectf, rl1->rectf, blurfac, 4);
+		if(rl->rectf && rl1->rectf) {
+			if(key_alpha)
+				addblur_rect_key(rr, rl->rectf, rl1->rectf, blurfac);
+			else
+				addblur_rect(rr, rl->rectf, rl1->rectf, blurfac, 4);
+		}
 		
 		/* passes are allocated in sync */
 		rpass1= rl1->passes.first;
@@ -1703,7 +1744,7 @@ static void do_render_blur_3d(Render *re)
 		
 		blurfac= 1.0f/(float)(re->r.osa-blur);
 		
-		merge_renderresult_blur(rres, re->result, blurfac);
+		merge_renderresult_blur(rres, re->result, blurfac, re->r.alphamode & R_ALPHAKEY);
 		if(re->test_break()) break;
 	}