[wagurto]

I am using one of the grass displacement material form the maxwell library and for some strange reason I am getting strange reflection on my walls. Please take a look and this image and let me know if there is any reason why this is happening?
thanks

[frosty_ramen]

wagurto,
do a quick test with the default material on your grass, and see if the reflections are still there.

[wagurto]

I change the material to diffuse and the reflections desappear. I am sure the displacement material is causing the problem.
thanks

[Mihai]

Difficult to tell without a scene file. Could you please email the scene with the materials?

[Mihai]

In the scene you sent me, it doesn't matter what material I apply, the problem is still there. So I think it's something strange in the ground plane geometry. Since it's not perfectly flat but low poly it's making some strange reflections with physical sky. And it's the same with/without direct sunlight.
If I instead put a regular flat plane in the scene, it renders fine.

Perhaps you could export the ground plane as higher resolution geometry and see.

[wagurto]

Thanks for the sugestions Mihai. I tried to increse the poly number on the ground but the reflections persist. In addition, I am notice strange triangulation on the grass displacements. Does anybody else knows whats going on in this scene?
thanks

[Bubbaloo]

Can you post a wire frame?

[wagurto]

Thanks bubbaloo for the interest in my problem. I hope you can see clear the wireframe.

[Bubbaloo]

Ok, I'm not 100% sure that this is your problem, but some of the triangles of the grass mesh are very large while some are small. Also, some are elongated. This, for some reason, causes some triangles to lose their displacement (contact NL about that). Couple that with the very fine detailed grass displacement map you must be using, and I'd imagine you would have to set that precision VERY high. The differing sizes of triangles are possibly causing these patterns in the grass (which are probably areas of displacement vs. no displacement), also explaining the reflections on the structure (from the triangles with no displacement). Have you considered using instanced grass planes or grass blades instead of displacement? Making high precision displacement on such a large surface is just asking for trouble if you ask me.

[Richard]

I'll have a guess and suggest that the displacement is opening up at the seams where the planes differ in angle and what you are seeing on the walls may well be light coming up through these portals!

I would try a flat diffuse plane under your ground geometry as a seal and see if the problem persists.