Grass Issue - 3D displacement

[peakyfreak80]

I am using 3D displacement grass for an exterior scene and getting some weird geometric patterns showing up. Not sure what's going on here. Hopefully someone can help out. I'll post the settings, mesh, etc. so all the information is available.

The reason for using the 3D displacement is because I have a large mix map for the grass/mulch and a small map for the actual displacement map. Both need to use different UVW mapping channels.

If anything looks wrong here, or if there's a different method of doing this, I'm open for suggestions.

Thanks!
peakyfreak

[vlado]

Which V-Ray version is this?

Best regards,
Vlado

[peakyfreak80]

I'm using SP2

[vlado]

It happens because the little triangles that make up the displacement have different orientation, depending on the source mesh. You can try using smaller Edge length for the displacement, or using a source mesh that is made up of quads.

Best regards,
Vlado

[Morbid Angel]

or you can bake your mix maps into 1 map and use 2d displacement.

[peakyfreak80]

Thanks vlado. I've actually tried both of those options. And, even though adjusting the edge length down to .67 looked great, it took a lifetime to render! I guess I was looking for a happy-medium between rendertimes and quality. With 2d displacement you can adjust the sampling to make it not quite as perfect looking, but good enough for what is needed, and I was hoping the edge length would do the same. When I adjust edge length to larger numbers the result seems to have more inconsistencies.

morbid angel - I can look into doing that, but my map will have to be extremely large! My displacement texture is 4'x4' and my site is 500' by 500'. But who knows, maybe that will offset the need to make the edge length so small.

just a though...would I need to crank up the resolution of the displacement for that to work?

I'll keep plugging away at this. Its a great house and I'd hate for the grass to ruin the image.

peakyfreak

[Morbid Angel]

either way, you are tiling the texture right?
So long as the displacement map is large enough for your camera view (frame size) it should be all you need. I don't really understand imperial units so I cant really say respectively to the size you got.

[peakyfreak80]

Right now my displacement map is 500px x 500px and used at ~1m x 1m. The subdivision on my displacement is at 500. If I make a new map with that covers an area ~160m x 160m does that mean I have to increase my subdivision by 160 times to get the same results? Seems a bit crazy, but if that's what it takes, I'll do it.

I guess I don't completely understand the subdivision setting on 2d displacement. This is just my interpretation.

Thanks for the help, btw, and quick responses!

peakyfreak

[MoonDoggie]

You realize that your picture of your VraydisplacementMod settings you don't have any texture applied?

[peakyfreak80]

Yeah...that's when I was using the 3D displacement. i have the "Use mtl" checkbox on for that. That way I can use multiple UVW mapping for the same displacement (1 for the large mix map and 1 for the small displacement map)

I'm testing a much larger displacement map right now with 2d displacement. My subdivisions are at 7000! Seems to be working better, and thank goodness for 8GB of ram!!

I really wish I could get the 3D to work, though. This seems like an unnecessary kind of workaround.

-peakyfreak

[RErender]

3D displacement is overkill for grass imo, you could mix the two maps with the same uv channel by just setting the tiling locally in the smaller bitmap.

[peakyfreak80]

I can do that, and that's what I'm playing with right now. I've just never taken my subdivisions so high before. Its makin' me nervous!! that, and above 7000 subdivisions its crashing my machine. Still tweaking. I'll have an image here pretty soon.

[peakyfreak80]

Here's the new image. A little different perspective to get closer to the ground. I think this is a good compromise between the quality I'm looking for and the rendering time. Actually dropped the time by quite a bit.

Now if I could only buy a house like that with a lawn that size!!


peakyfreak