grass displacement issue

[DaForce]

Looking better

You could always mix a few displacement maps together in a mix map. That could help breakup the even look to it all.

[pentool]

Hi,

I've found this thread about 2 days ago, and ever since I read through it about 5 times and still can't fix my stupid grass issues. Actually the problems are similar but based on this thread recommendation(s), it still doesn't go away.

I have a very simple scene, it's just a flat plane equally divided in all directions. In this first image, the YELLOW squares are the grass. It's one single plane object (with some square polys removed). The RED squares is also a plane object. That is the ground. So I have 2 SEPARATE meshes. Yellow (grass) and red (ground). I have a planar UVW mod applied to the grass:



When I render, I get this:



Notice that on the right lower side stripe, it seems to have a repeating pattern. That is the odd phenomena. The actual grass AND grass displacement textures are repeating 4 times on this whole mesh. So the obvious question would be why is it seem to be repeating only there, but it's ok anywhere else? Before you try to answer, let me just rotate the view around a little, like on this image below. Now, the repeating seems to be wondered off to a different location. Now it seems to be repeating even more and even on places where it was fine before (compare it with the image above).



This is my grass texture.
This is my grass displacement texture.
In case you wonder, I've tried to use bigger (1024x1024) version of these. (The displacement I made in photoshop.)

I'd like to point out, that originally I've used noise maps for both the grass colors AND the displacement map as well. They gave similar results.

I have rebuilt the mesh 3 times so far, but what the heck is there to rebuild? It's a plane object with 9 divisions and some division segments removed (to make place for the separate ground plane).

I've tried both the textures and the noise maps with and without tiling. Nothing helps. They seem to be generating this repeating pattern (even when they are not tiled) differently, depending on the view.

I have not been doing anything else in the past 2 days but messing with this stupid grass, and I'm ready to smash my computer at this point. I am very angry and pissed to waste so much time with this seemingly little issue.

Just in case... this is my setting for the VRayDisplacementMod.


I've tried DaForce's recommendation and swapped the maps with a checker map tiled 50 times and it was just fine. The problem crops up when I start to use noise, or noise-like displacements (either texture or map) and a small level - meaning I either tile the displacement a few times, or, in case of a noise map, I make the noise size small, such as 1.

In the last comment, inslaight said that it's all in the mapping. Well, it's only a planar UV map on a plane object. There's really nothing magical about it - so I'd think.

I'm using Max 8 SP3
VRay 1.5 final.

Any tips from the grass pros out there?

Thanks!

[DaForce]

Will give it a shot with your maps shortly..

stay tuned

[DaForce]

Well it seemed to work as expected here (no problems)

I created the plane.
added uvwmap.
collapsed it to editable poly
Selected the faces for the path area
detached those.
added a vraydisplacement mod and setup as your settings indicated.

And it rendered fine.

Can you perhaps upload the file your having problems with.

<edit> mmmm
just rendered above the grass and can now see the patterning in one corner very clearly.
Weird.

<edit2>
Ok its the filtering as soon as you turn the filtering and blur of it gets all repetitive. Best to leave it on or place it into a vraybmpfilter and then set the tiling via the uvwmap.

[pentool]

DaForce, thanks for checking!

Well, further experiments show that if I turn the light off and only use skylight, the patterning disappears regardless of the view angle, tiling, or whether I use textures or noise maps.

I used VRay sun for ligthing, then I switched it out to a direct light. No change. Then I turned all lights off, and left only the default vray skylight (multiplied it a little so I can see) and no patterns.

I have no clue how does lighting has to do with displacement patterns appearing or disappearing depending on whether direct light is present or not in the scene...

[DaForce]

heheh no problem. it seems with even the vraybmpfilter the visible tiling is still there, just alot fainter.

I tried teselating the mesh that didnt really make any difference either.

Maybe its a matter of not tiling the displacement map.. i think thats maybe where its coming from.

Im just going to try something now.

[pentool]

I uploaded the file here.

well, when I try using a noise map (or any kind of procedurals) for the displacement and/or the actual grass color, i don't tile it. yet, the pattern is still visible.

[DaForce]

Yeah.. my thoughts of having a pre-tiled displacement map didnt work at all.. haha

Well it seems to render fine with 2d anyway, which is good as its generally faster and uses less memory. Just set precision to 1 if your displacing a flat surface and up it as your displace surface gets more curved.

[vlado]

The problem with these patterns starts from the fact that the displacement maps are too noisy; if you blur them a bit, it should get a lot better.

Best regards,
Vlado

[pentool]

well, this was the original displace:



after blurring:



and the result. no change what-so-ever.



the point is, i'm not married to this technique, i just wanted some nice grassy lawn (from bird's eye view) and just can't get it working because of these stupid patterns showing up. but I've seen very nice grasses people make, so it's gotta work one way or the other.

i might just take a break from it and come back a few days later when my brain will not be cluttered with grass.

[vlado]

It works fine for me with the blurred map and 2d displacement; to make it work with the 3d displacement, you'll need very low edge length, which will be too slow.

Best regards,
Vlado