Smear brush destroys alpha #46560

New Issue

Keith Boshoff · 2015-10-21T22:33:40+02:00

Keith Boshoff commented

2015-10-21 22:33:40 +02:00

When texture painting in the UV editor, the Smear brush doesn't smear the Alpha channel, it paints it like a regular brush.

Test 1:

Create a blank texture with 0 alpha.
Draw a spot with the TexDraw brush.

With the Smear tool selected, smear the spot.

Test 2:

Create a blank texture with 0 alpha
With the Smear tool selected, paint on the image.

Tested in Blender 2.76 Official.

Thanks.

When texture painting in the UV editor, the Smear brush doesn't smear the Alpha channel, it paints it like a regular brush. Test 1: - Create a blank texture with 0 alpha. - Draw a spot with the TexDraw brush. # With the Smear tool selected, smear the spot. Test 2: - Create a blank texture with 0 alpha - With the Smear tool selected, paint on the image. Tested in Blender 2.76 Official. Thanks.

Keith Boshoff commented

2015-10-21 22:33:40 +02:00

Changed status to: 'Open'

Keith Boshoff commented

2015-10-21 22:33:40 +02:00

Added subscriber: @Wahooney

Campbell Barton commented

2015-10-22 12:19:16 +02:00

Added subscriber: @ideasman42

Marcelo Mutzbauer commented

2015-10-30 20:50:37 +01:00

Added subscriber: @Marcelo-Mutzbauer

Marcelo Mutzbauer commented

2015-10-30 20:50:37 +01:00

This seems to solve it
P281: Smear Alpha

diff --git a/source/blender/editors/sculpt_paint/paint_image_2d.c b/source/blender/editors/sculpt_paint/paint_image_2d.c
index c5a066e..0e5a1ba 100644
--- a/source/blender/editors/sculpt_paint/paint_image_2d.c
+++ b/source/blender/editors/sculpt_paint/paint_image_2d.c
@@ -994,7 +994,7 @@ static void paint_2d_lift_smear(ImBuf *ibuf, ImBuf *ibufb, int *pos, short tile)
 		IMB_rectblend(ibufb, ibufb, ibuf, NULL, NULL, NULL, 0, region- [x].destx, region- [x].desty,
 		              region- [x].destx, region- [x].desty,
 		              region- [x].srcx, region- [x].srcy,
-		              region- [x].width, region- [x].height, IMB_BLEND_COPY_RGB, false);
+		              region- [x].width, region- [x].height, IMB_BLEND_COPY, false);
 }
 
 static ImBuf *paint_2d_lift_clone(ImBuf *ibuf, ImBuf *ibufb, int *pos)

This seems to solve it [P281: Smear Alpha](https://archive.blender.org/developer/P281.txt) ```diff diff --git a/source/blender/editors/sculpt_paint/paint_image_2d.c b/source/blender/editors/sculpt_paint/paint_image_2d.c index c5a066e..0e5a1ba 100644 --- a/source/blender/editors/sculpt_paint/paint_image_2d.c +++ b/source/blender/editors/sculpt_paint/paint_image_2d.c @@ -994,7 +994,7 @@ static void paint_2d_lift_smear(ImBuf *ibuf, ImBuf *ibufb, int *pos, short tile) IMB_rectblend(ibufb, ibufb, ibuf, NULL, NULL, NULL, 0, region- [x].destx, region- [x].desty, region- [x].destx, region- [x].desty, region- [x].srcx, region- [x].srcy, - region- [x].width, region- [x].height, IMB_BLEND_COPY_RGB, false); + region- [x].width, region- [x].height, IMB_BLEND_COPY, false); } static ImBuf *paint_2d_lift_clone(ImBuf *ibuf, ImBuf *ibufb, int *pos) ```

Campbell Barton commented

2015-11-02 07:53:31 +01:00

@Marcelo-Mutzbauer, I tried this too and while it gives improved results, its still overriding the alpha, you can't for eg, smear a 50% alpha region (while maintaining the 50% alpha).

Gwenael Le Page commented

2016-04-16 23:56:42 +02:00

Added subscriber: @gwentiv

Gwenael Le Page commented

2016-04-16 23:57:02 +02:00

Tried it as well, and it seems to me that "soften" behaves the same way.

Sergey Sharybin commented

2016-07-28 15:14:49 +02:00

Added subscriber: @Sergey

Sergey Sharybin commented

2016-07-28 15:14:49 +02:00

@campbellabrton, this is because of smear buffer will be mixed together with original image, and current blend_color_mix_byte() will lift the alpha up.

Guess we want some sort of "leak" of alpha between smear buffer and original one, so we can smear opaque reigons into transparent ones. Real quick test:

P379: Smear Alpha Mix

diff --git a/source/blender/blenlib/intern/math_color_blend_inline.c b/source/blender/blenlib/intern/math_color_blend_inline.c
index 048ab71..68835ed 100644
--- a/source/blender/blenlib/intern/math_color_blend_inline.c
+++ b/source/blender/blenlib/intern/math_color_blend_inline.c
@@ -68,7 +68,7 @@ MINLINE void blend_color_mix_byte(unsigned char dst- [x], const unsigned char src1
 		dst- [x] = (unsigned char)divide_round_i(tmp- [x], tmp[3]);
 		dst- [x] = (unsigned char)divide_round_i(tmp- [x], tmp[3]);
 		dst- [x] = (unsigned char)divide_round_i(tmp- [x], tmp[3]);
-		dst- [x] = (unsigned char)divide_round_i(tmp- [x], 255);
+		dst- [x] = max_ii(src1- [x], (((int)src1- [x] + src2- [x]) / 2));
 	}
 	else {
 		/* no op */
diff --git a/source/blender/editors/sculpt_paint/paint_image_2d.c b/source/blender/editors/sculpt_paint/paint_image_2d.c
index 9474a46..83fa148 100644
--- a/source/blender/editors/sculpt_paint/paint_image_2d.c
+++ b/source/blender/editors/sculpt_paint/paint_image_2d.c
@@ -995,7 +995,7 @@ static void paint_2d_lift_smear(ImBuf *ibuf, ImBuf *ibufb, int *pos, short tile)
 		IMB_rectblend(ibufb, ibufb, ibuf, NULL, NULL, NULL, 0, region- [x].destx, region- [x].desty,
 		              region- [x].destx, region- [x].desty,
 		              region- [x].srcx, region- [x].srcy,
-		              region- [x].width, region- [x].height, IMB_BLEND_COPY_RGB, false);
+		              region- [x].width, region- [x].height, IMB_BLEND_COPY, false);
 }
 
 static ImBuf *paint_2d_lift_clone(ImBuf *ibuf, ImBuf *ibufb, int *pos)

Warning: colors are probably incorrectly unpremulled here.

If we want to go this way we can create some special mix blend for this.

@campbellabrton, this is because of smear buffer will be mixed together with original image, and current `blend_color_mix_byte()` will lift the alpha up. Guess we want some sort of "leak" of alpha between smear buffer and original one, so we can smear opaque reigons into transparent ones. Real quick test: [P379: Smear Alpha Mix](https://archive.blender.org/developer/P379.txt) ``` diff --git a/source/blender/blenlib/intern/math_color_blend_inline.c b/source/blender/blenlib/intern/math_color_blend_inline.c index 048ab71..68835ed 100644 --- a/source/blender/blenlib/intern/math_color_blend_inline.c +++ b/source/blender/blenlib/intern/math_color_blend_inline.c @@ -68,7 +68,7 @@ MINLINE void blend_color_mix_byte(unsigned char dst- [x], const unsigned char src1 dst- [x] = (unsigned char)divide_round_i(tmp- [x], tmp[3]); dst- [x] = (unsigned char)divide_round_i(tmp- [x], tmp[3]); dst- [x] = (unsigned char)divide_round_i(tmp- [x], tmp[3]); - dst- [x] = (unsigned char)divide_round_i(tmp- [x], 255); + dst- [x] = max_ii(src1- [x], (((int)src1- [x] + src2- [x]) / 2)); } else { /* no op */ diff --git a/source/blender/editors/sculpt_paint/paint_image_2d.c b/source/blender/editors/sculpt_paint/paint_image_2d.c index 9474a46..83fa148 100644 --- a/source/blender/editors/sculpt_paint/paint_image_2d.c +++ b/source/blender/editors/sculpt_paint/paint_image_2d.c @@ -995,7 +995,7 @@ static void paint_2d_lift_smear(ImBuf *ibuf, ImBuf *ibufb, int *pos, short tile) IMB_rectblend(ibufb, ibufb, ibuf, NULL, NULL, NULL, 0, region- [x].destx, region- [x].desty, region- [x].destx, region- [x].desty, region- [x].srcx, region- [x].srcy, - region- [x].width, region- [x].height, IMB_BLEND_COPY_RGB, false); + region- [x].width, region- [x].height, IMB_BLEND_COPY, false); } static ImBuf *paint_2d_lift_clone(ImBuf *ibuf, ImBuf *ibufb, int *pos) ``` Warning: colors are probably incorrectly unpremulled here. If we want to go this way we can create some special mix blend for this.

Bastien Montagne was assigned by Aaron Carlisle

2016-09-04 20:33:44 +02:00

Bastien Montagne removed their assignment 2016-09-05 09:52:54 +02:00

Bastien Montagne commented

2016-09-05 09:52:54 +02:00

Added subscribers: @Blendify, @mont29

Bastien Montagne commented

2016-09-05 09:52:54 +02:00

@Blendify I’d like to know why me? Last guy working on this was @Sergey afaict, and texture painting is not especially my area?

blender-admin commented

2017-07-21 00:16:59 +02:00

This issue was referenced by 0d4fd7528f

This issue was referenced by 0d4fd7528f9bfdf88eb3623b1e1e6cdf749b397d

Brecht Van Lommel commented

2017-07-21 01:09:01 +02:00

Changed status from 'Open' to: 'Resolved'

Brecht Van Lommel closed this issue

2017-07-21 01:09:01 +02:00

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Smear brush destroys alpha #46560

With the Smear tool selected, smear the spot.