Weight Paint: Blur brush performs paint with average rather than true blur. #34596

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Josh Wedlake · 2013-03-11T14:24:48+01:00

Josh Wedlake commented

2013-03-11 14:24:48 +01:00

%%%After an email conversation with Antony Riakiotakis, he suggested that I submit this issue to the tracker. IMHO this is likely to be closed or marked low priority as it is more of a design flaw with the current system than an accidental bug. Please let me know if there is a more appropriate place for this report or how to file a TODO. Antony wrote to me:

"this indeed looks hard to solve properly. But it could be done. Thanks, but I would really prefer this was in the tracker. I may not be able to handle the bug in a timely manner (remember, I'm doing this on a voluntary basis and I have a ton of other stuff to do and fix already!) And it would be good if others are at least aware of it."

My original email to Antony...

It seems to me from reading the code that the blur brush actually does a 'paint with average' rather than a true blur. I think it just samples the average of all the weights/vcols/pixels under the brush and then paints every vertex/pixel under the brush with the sample result. So if you use blender's blur brush over a contrasty border in weight paint mode...
(see http://www.pasteall.org/pic/46983 , top), rather than softening the edge as a blur brush would in GIMP or PS, it paints the whole under-brush region with the average value under the brush.

In the lower half of the image (http://www.pasteall.org/pic/46983 again) I've simulated (with python) the effect a blur brush should (IMHO) have, where verts/pixels get blended towards the weights/vcols/values of their neighbours (topological neighbours or within a screen space radius?). I guess to work really well there would need to be a separate control for the blur radius and brush radius. The blur radius being the distance from each vertex/pixel for which the neighbours are sampled.

Another nasty (or perhaps desirable in some cases?) side effect of the current blur brush is that it has a directional effect. In this next image ( http://www.pasteall.org/pic/46984 ) the top stroke was painted L to R, while the bottom stroke was painted R to L. So "scrubbing" back and forth with the blur brush over a contrasty border which you want to smooth can be quite tricky and you need to remember which way to drag the brush last.

I expect many users have got used to the current toolset and I realise that a proper blur brush might be very slow (though I believe that the smooth brush in sculpt mode must use a "tend to neighbours" algorithm, except in sculpt mode obviously vertex co's are 'blurred' rather than vcol/vweight etc).

I've attached a blend file with instructions to recreate the images linked here, as well as a python script which does a true blur.

Thanks!%%%

%%%After an email conversation with Antony Riakiotakis, he suggested that I submit this issue to the tracker. IMHO this is likely to be closed or marked low priority as it is more of a design flaw with the current system than an accidental bug. Please let me know if there is a more appropriate place for this report or how to file a TODO. Antony wrote to me: "this indeed looks hard to solve properly. But it could be done. Thanks, but I would really prefer this was in the tracker. I may not be able to handle the bug in a timely manner (remember, I'm doing this on a voluntary basis and I have a ton of other stuff to do and fix already!) And it would be good if others are at least aware of it." My original email to Antony... It seems to me from reading the code that the blur brush actually does a 'paint with average' rather than a true blur. I think it just samples the average of all the weights/vcols/pixels under the brush and then paints every vertex/pixel under the brush with the sample result. So if you use blender's blur brush over a contrasty border in weight paint mode... (see http://www.pasteall.org/pic/46983 , top), rather than softening the edge as a blur brush would in GIMP or PS, it paints the whole under-brush region with the average value under the brush. In the lower half of the image (http://www.pasteall.org/pic/46983 again) I've simulated (with python) the effect a blur brush should (IMHO) have, where verts/pixels get blended towards the weights/vcols/values of their neighbours (topological neighbours or within a screen space radius?). I guess to work really well there would need to be a separate control for the blur radius and brush radius. The blur radius being the distance from each vertex/pixel for which the neighbours are sampled. Another nasty (or perhaps desirable in some cases?) side effect of the current blur brush is that it has a directional effect. In this next image ( http://www.pasteall.org/pic/46984 ) the top stroke was painted L to R, while the bottom stroke was painted R to L. So "scrubbing" back and forth with the blur brush over a contrasty border which you want to smooth can be quite tricky and you need to remember which way to drag the brush last. I expect many users have got used to the current toolset and I realise that a proper blur brush might be very slow (though I believe that the smooth brush in sculpt mode must use a "tend to neighbours" algorithm, except in sculpt mode obviously vertex co's are 'blurred' rather than vcol/vweight etc). I've attached a blend file with instructions to recreate the images linked here, as well as a python script which does a true blur. Thanks!%%%

Josh Wedlake commented

2013-03-11 14:24:48 +01:00

Changed status to: 'Open'

Antonis Ryakiotakis commented

2013-03-11 15:10:52 +01:00

%%%Reminder to others: This is vertex/weight, not texture paint.%%%

Antonis Ryakiotakis commented

2013-03-11 15:13:14 +01:00

%%%Correction: Vertex paint seems to work. Weight paint does not.%%%

Campbell Barton commented

2013-04-23 19:52:14 +02:00

%%%Since this is working as intended, I dont think its a bug, but thanks for the comprehensive info and this is a good TODO.

Noted here:
http://wiki.blender.org/index.php/Dev:2.5/Source/Development/Todo/Tools#Weight_Paint%%%

%%%Since this is working as intended, I dont think its a bug, but thanks for the comprehensive info and this is a good TODO. Noted here: http://wiki.blender.org/index.php/Dev:2.5/Source/Development/Todo/Tools#Weight_Paint%%%

Campbell Barton commented

2013-04-23 19:52:15 +02:00

Changed status from 'Open' to: 'Archived'

Campbell Barton closed this issue

2013-04-23 19:52:15 +02:00

Josh Wedlake commented

2013-04-23 19:58:22 +02:00

%%%Thanks Campbell & Antony,
best wishes, Josh%%%

%%%Thanks Campbell & Antony, best wishes, Josh%%%

Campbell Barton commented

2016-07-21 22:20:00 +02:00

Changed status from 'Archived' to: 'Resolved'