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Dynamic Paint - Paintmap dissolve not working (cycles)
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Description

--- Operating System, Graphics card ---
osx 10.8.4, macbook pro 6.2, 8GB Ram, gt330m

--- Blender version with error, and version that worked ---
error: official 2.68a r 60186, own r60385M

--- Short description of error ---
Viewport shows Dynamic Paint Advanced Dissolve, Cycles Material Attribute dp_paintmap doesn't
dp_wetmap works
--- Steps for others to reproduce the error (preferably based on attached .blend file) ---
open BUG_DynamicPaint.blend
run animation to frame 60
render
compare render with viewport

Event Timeline

I don't know the expected behavior here, but the wetmap is marked red because there is no dp_wetmap vertex color layer in the Mesh?

The issue is not the wetmap. It's the paintmap. If you look how it looks in Viewport and compare this to how the cycles render looks like you will see that the dissolve effect only takes place in viewport, but not in the render.

Dynamic paint uses RGBA vertex colors in order to appear invisible unless paint is applied. It seems that Cycles isn't using the alpha component at all... And because dissolve only manipulates alpha it doesn't show up in Cycles render.

I'm not quite sure if there is a nice way to fix this assuming Cycles color socket only uses RGB? Maybe it could output alpha from the Fac socket? Anyway, assigning to Brecht as this is render engine related issue.

Is this the same problem as why a Shader normal can't be put through a Color MixRGB Node?

Is there a way to "mix" normals? (the blue node socket)

That's unrelated, and you can put a normal through a mix node, but you have to normalize it afterwards with the vector math node.

Alpha for vertex colors isn't supported in vertex paint mode, Blender internal shading nodes or the python api. Dynamic paint may be the only place in Blender that actually uses it, with a modification in Blender internal to make this particular case work? At the moment I'm not even sure that alpha can be expected to be set to a reasonable value in old files.

I suppose its because dynamic paint is the only tool in Blender that actually needs vertex color alpha in order to work properly. And yeah, Blender internal has used vertex color alpha ever since dynamic paint was added.

But good point regarding old files... I never realized they may not have the alpha component initialized correctly. :s

"That's unrelated, and you can put a normal through a mix node, but you have to normalize it afterwards with the vector math node."

Not working for me:

http://www.pasteall.org/pic/60061

It works for me in a simple test, I can't tell from that screenshot what the full setup is that you use.

..that's the full setup...

http://www.pasteall.org/blend/24358

for me it seems to be a bug. should i report it as such?

seem to be a bigger issue, since sometimes it render the object black and sometimes "just" darker as a it should.

the point seems to be that i have not connected anything to the Group Normal input.
But then again it works fine if you have no Mix node in between...

This is not a bug. The BSDF node knows to use the default normal if you don't plug anything in, but for other nodes you need to plug it in yourself. It would be convenient if there was a way to specify this for node groups, but that's not supported at the moment.

Ok, thanks.

(Still, it would make Node Groups more usable though ;-)

Brecht Van Lommel (brecht) changed the task status from Unknown Status to Unknown Status.Jan 23 2014, 7:04 PM