Textured Procedural Planet

…aka back to square one albeit the terrain is round this time, so back to round one? I added some textures to the planet, generated on the GPU, they look ok but still lots of work to do. First some outtakes, looked like a load of shite at the start…

… then a bit like an old leather ball…

… then all contoury …

… (which is actually not too bad looking) then it started to come together a bit …

The problem with this though is that the source texture is applied at the same scale for each patch so there’s a noticeable jump when changing levels, a higher level might show a rock but when it subdivides there are 4 rocks. This gif shows the gifferences when approaching, it looks like the centre patch uses a completely different texture.

So it made sense to scale them according to the level (texCoords *= pow(2, maxlevels – patchlevel)), but this introduced some pretty nasty artefacts when zoomed out due to tiling the same texture over and over. Applying mipmapping to the texture I was using helped a bit but it’s still very obvious.

The transitions looked very layered so I added a bit of noise:

All in all it’s not bad for a first go but could be a lot better. I was having fun flying about the place so I made a little video:

 

…then noticed a problem I had neglected from before that’s obvious in lines going through the brown pit on the right at 0:34.

I thought it was cracking at first because it only seemed to occur when creating other patches but investigating it further it wasn’t cracking, but something to do with textures. Another gif to show the gifferences…

The points are fine, it’s the texture on top that’s creating the artefact. What it ended up being was a leftover setting from creating patches. In order to get the heights from the GPU I draw the noise for each vertex in a patch to an image and read them back to reset the vertices. In order for neighbouring patches to have the same height values I draw it as a point-clamped list of lines. When this was happening a subsequent draw would use the point-clamped sampler and create the artefact. Looking for how to fix led to some good advice, don’t assume sampler states when drawing, explicitly set them every time you need them.

I’ve found a few other very impressive procedural planet projects so I might trawl their blogs to see if they mention how to do textures so well. So for next time…

• Adding noise to the texture isn’t great, needs a good bit of tweaking. I could try to do a look-up table & incorporate slope as in this old post from Ysaneya (Infinity).
• I need to hide tiling somehow, it occurs and is dealt with in the old post from Ysaneya above but the description is just “lighting, shadowing, other effects”.
• I’ll need a better noise algo, the one I’m using is very homogenous (“samey”). This project called lithosphere might help find a good one quickly.
• The FPS are struggling whenever creating patches & I’m not showing that many polys so I might need to do some optimisation. I pass data around a lot between CPU and GPU so I think these articles by Shawn Hargreaves might help find out if I’m CPU or GPU bound and try to balance both.

Lots to do!