Volumes Of Fun

PagedVolume Geometry Issue
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Author:  ChillyFlashER [ Sat Aug 22, 2015 6:20 pm ]
Post subject:  PagedVolume Geometry Issue

I am running the code for PagingExample.
I am using the latest develop commit.

The example creates this

But when I use it there are missing faces. Like the blue layer is only one-sided.

Author:  David Williams [ Mon Aug 24, 2015 8:42 am ]
Post subject:  Re: PagedVolume Geometry Issue

There are actually two issues I would like to address here. Firstly, the PolyVox example is already rather strange and I'm not sure if it is supposed to look like that. I didn't write that code, but a quick skim indicates it's supposed to be a Perlin noise volume. I don't know where the sine wave effect is coming from, perhaps it is hidden in the code somewhere or maybe it is a bug. Possibly a clamping/wrapping error at the volume bounds? I'll need to poke the code to see.

The second question is why your version looks different. However, it's only the sine wave which looks wrong, so if that's a bug anyway then we shouldn't worry about it yet. For example, the buggy geometry could simply have wrong winding or normals.

I'll try to look at the PolyVox example after LudumDare.

Author:  ChillyFlashER [ Mon Aug 24, 2015 9:00 pm ]
Post subject:  Re: PagedVolume Geometry Issue

It seems that the PolyVox example has double sided rendering, so the issue is the same.
The only thing that is different is that I set a random color to the voxels.

Author:  David Williams [ Wed Aug 26, 2015 10:11 pm ]
Post subject:  Re: PagedVolume Geometry Issue

Hi, just a note that I haven't forgotten about this. Had a busy weekend with Ludum Dare and there's still some stuff going on regarding that.

I have had a quick look at the PolyVox example and it does seem like something strange is going on. I tried to modify it to generate just a plain Perlin-noise height-field but I'm still seeing the weird sine-wave style effects. I'd really like to get the PolyVox example doing something sensible before worrying about why your Unreal version doesn't match

However, if you really want to investigate the Unreal version further you could check how many vertices/indices are being output in each case, and whether you can change the winding order or back-face culling in Unreal in case that is an issue?

Author:  ChillyFlashER [ Wed Aug 26, 2015 11:06 pm ]
Post subject:  Re: PagedVolume Geometry Issue

Hi, there is nothing wrong with my Unreal code. Maybe this image will be more helpful.

As you can see the example has double sided rendering. My unreal example doesn't.


Author:  David Williams [ Thu Aug 27, 2015 7:30 pm ]
Post subject:  Re: PagedVolume Geometry Issue

If you are concerned about the double sided rendering then it seems unlikely that PolyVox is the problem - more likely the issue is with Unreal. But to test this you should really use a simpler volume. For example, what if you set a single voxel in the volume to be solid? This should generate eight vertices and a number of indices (24 I think?) so you can easily look at the data in the Unreal debugger or even just print it out. Then you can see if Unreal is getting bad data from PolyVox, or if it is just a rendering issue.

Author:  David Williams [ Mon Sep 07, 2015 8:56 pm ]
Post subject:  Re: PagedVolume Geometry Issue

I'm not sure if you are still following this but unfortunately I'm not finding time to investigate it further at the moment. I've logged it as an issue for future reference: https://bitbucket.org/volumesoffun/poly ... rs-corrupt

Author:  David Williams [ Sat Dec 19, 2015 3:41 pm ]
Post subject:  Re: PagedVolume Geometry Issue

This was caused by the example code trying to extract a region which was too large. The example has been fixed and the issue closed: https://bitbucket.org/volumesoffun/poly ... rs-corrupt

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