Issue With Opacity Maps & VRay Fog Rendering

[kweechy]

Messing with some World of Warcraft maps I ripped into Maya...good way to play with lighting large environments without having to make them yourself.

Anyway, I've got opacity mapped branches and leaves geometry from the Blizzard assets. They looked totally fine until I rendered with fog on, once that was added, they appear to look more like frosted glass with a texture on them rather than proper cutouts:



I must be missing some settings that I haven't thought of. Anyone here run into something similar before?

The fog is being done with a Maya Fluid Container that has simply been flooded via Paint Fluids.

[vlado]

Hm, it looks odd, we have to try and reproduce this here.

Best regards,
Vlado

[yolov]

Hi kweechy,

What is the setting for your max transparency levels (Render globals > Global options > Materials > Max transparency levels)?
Also what image format are you using for the textures, what lights? And what v-ray/maya versions / os ?

[kweechy]

Hi Vlado and Yolov,

My max transparency right now is the default 50 levels, which is also my best guess as to the problem too...doing some testing to experiment with that as well. When I get home tonight, I'll try a test with this scene again and see what happens if I set it to 1000+.

The lights are a dome light with HDRI plugged in, and a VRay Sun to supplement it.

Textures image format is .png, but I did a test with a polygon plane using a procedural checkerboard plugged into the cutoff opacity, ended up with the same results.

Maya 2012, VRay build I don't remember right now but it's a more recently nightly build, and in Windows 7.

[yolov]

It'll also be helpful if you can share the scene here or send it to vraymaya@chaosgroup.com because we tried to reproduce this (also using dome and sun + png/exr) but with no luck. Any further info on this will be helpful to pin point the problem.

[kweechy]

I'll package it up tonight and send it along. Thanks guys.

[kweechy]

Here's a zipped file with the scene: https://docs.google.com/file/d/0B2cv...it?usp=sharing

[yolov]

I see that you're using the vray fluid attributes on the maya fluid container.. You need to lower your step size. The smaller the value there, the more correct result you'll get. The default 0.1 will render properly but you can go up to 1 in your case to speed up the render.
See our help for reference.
I hope that solves the problem.

[kweechy]

Isn't that very dependent on the scene scale though? If you had a small scale scene where a step size of 0.1 give you nice results and a quick render...if you scale everything up 10x, wouldn't you also scale your step size 10x to avoid ballooning render times out of control?

[vlado]

It is scene dependent indeed. Perhaps we need to lock it relative to the fluid container cell size...

Best regards,
Vlado

[kweechy]

I tested some more renders last night. My scene was overexposed before by a couple of stops, so I cut the light intensity by half or so...everything rendered much cleaner. I can't really figure why that would work the way it does, but the frosted glass card issue is a lot less apparent.

[estefez]

I know this is an old problem, but if anyone's still having it (where opacity maps on sprites/cards are showing up weird through fog, here's what fixed it for me: it turns out the object I was using to house the fog gizmo had been scaled- once it scales I guess it scales the fog noise inside with it, except when viewed through objects with opacity. So to fix it we went to Utilities, Reset Xform and collapsed it, now it works fine!