2D Displacement losing quality/details when tiled.

[Short_Fuse]

Running into a problem when tiling a texture used in VRay 2d displacement for an ocean surface. I need to tile the image across the surface and the more i tile it the less quality/details there are in the displacement. Tried everything i can think of include bitmap filtering, texture resolution and quality and displacement quality.

The attached image explains it better. Left side of image is the texture tiled once which matches the UV's. Right side shows the texture tiling increased 32 times and the UV's increased 32 times to keep scale. You can see the scale of the displacement map matches but the quality of displacement drops drastically.



If your wondering why i need to tile the texture in this manor, i need to mask the displacement in areas and 2d displacement only allows for 1 UV channel. And 3D displacement is too heavy.

Max 2010, VRay 1.50 sp5

[kriscabrera15]

i think whats happening is that your displacement is getting really fine and really small maybe 1/5 of a pixel and vray is having a hard time sampling it. Depending on your shot i would use a bump map or a normal map for ocean ripple, if i was animated i might use a wave modifier with some noise to break it up. Also if your displacement map is really crisp, try adding some blur so it could falloff a bit smother. Hope that helps!

[Short_Fuse]

Thanks for the pointers kriscabrera15.

The weird thing is the displacement on the left of the image works perfect, I'm completely satisfied with it. The only values I'm changing in the right side of the image is the Texture tiling value and the UVW size. The size, scale and position of the texture in the scene is exactly the same, yet the result is very different.

This is a simplified version of the final result just isolating the 2d displacement problem, i am using wave modifiers and bump maps in the final result.

[Dubbie99]

Try using the VRay HDRI bitmap loader instead.

[Short_Fuse]

Excellent suggestion but unfortunately the VRay HDRi bitmap loader doesn't have the tiling feature, which i need to tile the texture over the ocean surface.

[Morne]

Try subdividing your geometry some more by slapping on a "quadrify mesh" or "subdivide" modifier below vraydisplacement in the stack. This worked for me in a recent project

[Short_Fuse]

Good idea thanks, but the underlying mesh is already heavily subdivided as I'm using a simple max displace with noise on top of that for bigger waves (not shown in the example).

[Sushidelic]

Bitmap filtering is not the problem - in 2D displacement there's the 2D resolution spinner, that sets the size of the 2D displacement map for the whole UV space, not for the bitmap you use. So if you set your displacement map size to 1024 and use a 1024x1024 bitmap tiled twice in each direction, you basically are only using 4x 512x512px bitmaps. To retain the original bitmap detail, you would have to go to a displacement map size of 2048. Tiling 32x32 times will give you, well, a drastic number and an incredible memory footprint. So maybe 3D displacement would in fact be the right way to go here, as it might render longer, but it does LOD, which seems to me exactly what you need here.
Another try could be to tile your UV layout 32x32 instead of tiling the map, but i never did this with vray 2D displacement, so i cannot tell you what the outcome would be.
Best regards,
Michael