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Cubiquity pixel artifacts
http://www.volumesoffun.com/phpBB3/viewtopic.php?f=23&t=709
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Author:  xtitus [ Fri May 25, 2018 4:16 pm ]
Post subject:  Cubiquity pixel artifacts

So, I'm using the OpenGL renderer for Cubiquity. I'm writing my own game engine for fun around it and when I added a Skybox, I notice pixel artifacts shining through the voxel model at cube seams. I attached a pic of it (look at the whitish dots in the brown blocks). Hard to capture it as well on an image, but as you move around the artifacts all twinkle at you. I've had something similar happen to me in the past when I used texture coordinates and there was rounding issues. But, since there's no textures, this seem more like floating point precision issues or something... Is there a way around this?

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Author:  David Williams [ Sat May 26, 2018 2:26 pm ]
Post subject:  Re: Cubiquity pixel artifacts

The artefacts which you are seeing are caused by T-junctions in the extracted mesh. This is a difficult problem to avoid and affects many voxel engines. There is a nice blog series about voxel mesh extraction below, and part three talk briefly about this issue:


The conclusion is basically that it is hard to fix, and the author references my suggested approach of simply fixing up the problems in a image post-processing step. I haven't actually tried this myself but the author seemed to have success with it.

You may also find the flickering pixels are particular annoying when you have large areas of plain colour, but once you add lighting and possibly normal maps it may be less obvious. I never noticed them in Voxeliens, for example, but I also had the advantage of a dark skybox there.

But ultimately it is a problem with PolyVox/Cubiquity, it is not something you are doing wrong.

Hope that helps!

Author:  xtitus [ Sat May 26, 2018 4:39 pm ]
Post subject:  Re: Cubiquity pixel artifacts

Ok, yeah I remember reading about t junctions in your wiki. I didn’t remember seeing them in my ogre3d/polyvox experiments. Sounds like I should hit them in there too, so glad it’s not something unique in my setup. I’ll read up on the link you sent. Thanks!

Author:  David Williams [ Sat May 26, 2018 9:06 pm ]
Post subject:  Re: Cubiquity pixel artifacts

xtitus wrote:
I didn’t remember seeing them in my ogre3d/polyvox experiments. Sounds like I should hit them in there too...


In principle you should, but there can be a number of factors at play. Early version of PolyVox did not perform the 'greedy meshing' (adjacent quads were not combined) which would probably have avoided T-junctions but at the expense of high triangle counts. Also, because the issue is related to floating point precision it will be more serious further from the origin, and may depend on other factors such as whether you combine your model/view/projection matrices into a single matrix before applying them.

On an unrelated note (just because you are one of the few users of Cubiquity) I recently posted a little insight into my work on Cubiquity 2 on Reddit:


Also, I'm going to be away for the next couple of weeks so I may not be able to reply to any questions.

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