[Bf-committers] Clay Tool Bug

[Jason Wilkins]

Ah, didn't realize attachments won't work, here:

http://www.pasteall.org/22585

The bug is that it is inconsistent the way it builds up when it is in
the default mode (Accumulate Off).  Also, both modes (accumulate on
and off), both accumulate :)
The patch is very simple.

On Wed, Jun 22, 2011 at 8:34 AM, Vox Lapin <voxelbunny at gmail.com> wrote:
> I definitely like the sound of that. I thought that the high "build-up" of
> the clay brush was part of the design, but I would welcome access to a patch
> to fix a bug and create a mode that does more "filling in" than "building
> up". Could you post a link to the patch? I think the listserv eats
> attachments.
>
> On Wed, Jun 22, 2011 at 8:23 AM, Jason Wilkins <jason.a.wilkins at gmail.com>wrote:
>
>> I ran into this while re-factoring sculpt.
>>
>> The clay tool in sculpt is supposed to obey the 'accumulate' flag.
>> This flag tells sculpt if it should base the brush location on the
>> original mesh before a stroke started (Accumulate Off) or use the new
>> position of the mesh that it gets during the stroke (Accumulate On).
>> Subjectively, accumulate 'off' looks like a brush has less and less
>> effect as you use it on the same spot without starting a new stroke,
>> sort of like how painting over the same area over and over doesn't
>> change the color as much.  You can build up a sculpt in this mode if
>> you release and restart your stroke in the same spot, but not if you
>> just hold down the button and keep going over the same area.  With
>> accumulate 'on' the sculpt will just build higher and higher without
>> releasing the button but it is harder to get a smooth result.
>>
>> An option like 'Accumulate' is needed because unlike adding or
>> blending a color, where it will eventually saturate to 1 or converge
>> (respectively), a sculpting displacement can be applied indefinitely
>> with continued effect.  Setting accumulate to 'off' lets sculpting
>> simulate this saturation to some degree (could possibly be better),
>> but it isn't obvious that this is always what should be done, because
>> sculpting isn't painting.
>>
>> The bug is that clay is partially ignoring the Accumulate setting.
>> When Accumulate is 'off' the brush location is correctly placed on the
>> original mesh position, and the displacement vector is correctly
>> determined from the original surface, however the amount that the clay
>> brush raises the surface is computed from the new positions when it
>> should come from the original positions.  The result is that even with
>> Accumulate 'off', the brush still looks kind of like Accumulate is
>> 'on', but because it is still using the original brush position and
>> normals it simply isn't doing the right thing.
>>
>> I would just fix this, but I am unsure because somebody may really
>> like how clay works now and by changing it to be 'correct' they will
>> feel that I broke it.  However, I do think it should be fixed.  The
>> old behavior can be mostly gotten back by turning 'Accumulate On' for
>> clay, and it will accumulate correctly instead of in the potentially
>> broken way it is now.  The subjective strength of clay with
>> 'Accumulate Off' will seem weaker after this fix, but it will also be
>> possible to get much smoother results because it won't build up on top
>> of itself, allowing you to fill in gaps without applying too much
>> clay.
>>
>> I've attached a patch, if anybody would like to test the difference
>> just try un-patched and patched blender with accumulate turned on and
>> off for the clay tool and tell me what you think.
>>
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