DIsplacement tips?

[alexyork]

Hi folks,

Using VRayDisplacementMod on a bunch of very large objects, in this case big swaths of sand.

Any tips for keeping memory usage down? The render without displacement enabled is around 10GB, including max itself, but when I enable it it climbs up and fills my 32GB and crashes. I can't really get away with disabling it and I don't really have time to go through and convert everything to normal maps instead. Also I need real displacement to make the water over sand look correct.

Any quick tips for keeping RAM usage down with displacement?

Any help ASAP would be appreciated!

Cheers,

[Morbid Angel]

what kind of displacement is it 3d/3d? you may try 2d if its not, also if you want to stick to 3d reduce number of subdivisions and increase edge length those control quality...creating too many polys will raise the ram. Lastly, do look to set your dynamic memory limit so it does not go too high.

[alexyork]

what kind of displacement is it 3d/3d? you may try 2d if its not, also if you want to stick to 3d reduce number of subdivisions and increase edge length those control quality...creating too many polys will raise the ram. Lastly, do look to set your dynamic memory limit so it does not go too high.

Thanks Morbid. Using 3d, which I need to for this, with only 32 subdivisions and edge length default of 4 pixels. I think this last value must be what's throwing it all off.

Also, even when I set dynamic mem limit to, say 10GB, it still climbs way way up to 30+ for some reason. Quite odd!

Will experiment with the edge length.

Cheers!

[Rens]

You could try 8 subdivs, depending on how high-poly your geo is before displacement. Edge length should be ok or maybe even a bit too high depending in how much detail you want to see.

[alexyork]

You could try 8 subdivs, depending on how high-poly your geo is before displacement. Edge length should be ok or maybe even a bit too high depending in how much detail you want to see.

thanks. just increasing edge length from 4 pixels to 10 pixels made an enormous difference to ram usage, now down to around 10gb and still looks fine. will keep tweaking.

thanks for the help, chaps.

[joconnell]

Is it for a high res still or an animation?

[Neilg]

32 subdivisions is still a little high. I subdivide my meshes and keep it around 8 or lower.

the default of 256/4 is really misleading, it doesn't work at all on any high res render.

[alexyork]

It's for high res stills.

I can't subdivide the mesh - it's come in from (wait for it....) sketchup! And any adjusments are a real nightmare. It's already fairly dense, so I reckon 8 will work, yep.

I agree that the defaults are not very helpful at all.

[joconnell]

256 is probably a really big catch all value, 4 as an edge length is kind of a lot for print too!

[Morbid Angel]

Well, the 4 pixels was originally I suppose to fine detail at more or less close up. It was also, as I remember that the subdivs were ignored when not using 3d motion blur. But I think that changed a while back. So now one must be careful with those values.

think of it like this, how many turbosmooth subdivisions you would have to put on a mesh before you think you will see reasonable result? You can surely test that by using 3ds max displacement + turbosmooth. You can then derive that subdivision value as your max. The edge length determines when to reach that max value. So, if your original mesh is highly subdivided already, probably you don't need high edge length.

[Morne]

but lowering the edge lenght (not touching the subdivision), pushes render times sky high. For example something that on edge lenght 4 that renders in 5 min (but looks bad), suddenly renders for 40 min on edge lenght 1 (but looks good)

[alexyork]

I think there's a balance to be made between subdivisions and edge length. Much like everything else in Vray!

Edit. I have realised that the way to go here is to disable Pixel for the edge length, so it uses scene scale instead. That way things look and behave the same when you scale up from low-res tests to full res.

[Morbid Angel]

Edit. I have realised that the way to go here is to disable Pixel for the edge length, so it uses scene scale instead. That way things look and behave the same when you scale up from low-res tests to full res.

using scene units can be dangerous also, because there will be even subdivision from far and up close, something you want to avoid on large meshes.

[alexyork]

using scene units can be dangerous also, because there will be even subdivision from far and up close, something you want to avoid on large meshes.

Cheers Morbid. Hadn't considered that. I've had great success with scene units on this huge expanse of sand, though, so working well here. RAM usage is down considerably, too, and rendering fast.