I tried your code and the assert goes away. But something strange I notice is that the size of the terrain is still about the same, but the faces are missing on the outside of the mesh and ok on the top of the mesh. What should I do now?

I was following some ideas that image sizes should be power of 2 + 1 - plus the image I'm using came with Ogre. Maybe I should resize it to a power of 2 and see if it works correctly. I still have the problem also where I'm only getting 2 dimensions correct, the 3rd dimension is just repeated across the plane.
http://www.ogre3d.org/tikiwiki/Ogre+Terrain+Component+FAQ#So_if_I_have_a_height_map_of_size_512_x_1024_and_I_want_a_terrain_that_matches_it_in_world_units_512_wide_by_1024_deep_I_d_need_to_create_multiple_pages_and_put_them_together_pages_of_size_512_What_about_a_narrow_terrain_level_that_was_1000_x_300_

Switching to a terrain image of 512 x 512 still has the same assert in debug mode.

Yes, this is what I would have expected. Triangles are only generated when the extractor finds solid voxels next to empty ones. In your case you have solid voxels inside the volume and empty voxels outside - that is, the change beteen solid and empty occurs at the edge of the volume. But because my suggested change stopped it processing these edge cases you no longer see those triangles.

However, having looked at the code I now realise what is really going on. Basically, the assert you are hitting is making sure that there are no more than 1000000 vertices in the generated mesh. This is a hardcoded value which should not be there, and I will change this assert for the next release of PolyVox.

In the mean time, I believe you can sefely just comment out the relevant asserts in SurfaceExtractor.inl





I think the problem is the way you are reading your heightmap:



In my original code I use x and z rather than x and y. Try:

Cool, that fixed everything so far - I haven't tested the decimation yet though. Here's a screenshot of the output -

I tried to use a low pass filter like so -



but got an access violation in LowPassFilter.inl @ line 84

And a side note - decimation seems to be working fine

I'm going to suggest reducing the size of the region again, to avoid the edge cases. Smoothing the volume data involves averaging each voxel with it's neighbours and the voxels on the edge don't actually have some neighbours. The code should handle this but probably doesn't at the moment. Try



Also, your code snippet is smoothing the data after you have already extracted the mesh. This won't have the desired effect - you need to smooth and then extract.

Ok I tried changing the code, with no effect - same crash in LowPassFilter.inl

Notice that the region gets passed twice when creating the low pass filter and you've only changed one of them. I.e. you have:



You should try: