Opacity Headache!

[josiah]

I am using 1.09.03n with 3dsmax6. Almost completely bald pulling my hair out over this!

I have an opacity map for my model, it is pure black (0,0,0) and pure white (255,255,255).

I use a Vray material on my model, put the opacity map in the refraction slot and set the IOR at 1.0.

I cannot achieve complete transparency on my model! So I tested the same map with a standard max material and same opacity map, and it looks fine, however it takes 1 hour more to render! This is for an animation and I can not afford an hour more per frame.

I read about an opacity workaround and tried it, but it didn't seem to work very well (edges very jagged). I don't think I have the wrapper set up right,

I use a Blend material
The opacity map is in the mask slot.
The color map is in the first slot
The vray material wrapper is in the second slot.
I have "matte surface" checked in the mtlwrapper.

Can anyone please lend a hand here?
Thanks!

[Tony_Morev]

that the stuff i've been asking about since v-ray material first appeared ...

no luck so far as you can see

i think my work-around was to invert the opacity map

it sucks though if you need one tga to be used on both diffuse and opacity
you can't instance them

[josiah]

Darn it anyway! I already have the map inverted. In some places the transparencey is ok (using the vray material) but in others its, uh, like 10% transparent!

Anyone familier with the blend material work around I mentioned above?
Maybe I am doing something wrong with it.

[PATER]

I have to say transparencies in Vray suck...

First - you can´t really use max standart materials, they`re incredibly slow, especially with gi. Indeed you can use prepared Vray materials instead but then you have to convert every single material by hand. (flip alpha, IOR 1) The Vray material converter can`t do this for you.
Finally, prepared Vray materials are still slow. A scene here consists of a building and four tree´s with opacity-maps. I converted all materials into Vray mats but the scene renders about 4 - 5 times longer.

Is it possible to make opacity maps faster in Vray? I know transparencies are much easyer to do with scanlining and Vray raytraces everything but isnt there a way to accelerate it? I´m sure you would find a way if enough users want it. I would prefer a new slot in the Vray material.

@josiah: you say it`s like 10% transparent? Make sure you checked "affect background" in your color mapping rollout. (if you use color mapping)

[Da_elf]

im the one who wrote the blend method. which is useless now that vray has the affect shadow and affect alpha options. seems you have the blend method setup right. but im not sure why its not working for you with the normal refraction method. are you using any reflections on this?

[josiah]

No, I am not using any reflection at all. Heres the problems I am experiencing:

Sample scene

Create a plane with a Vray material applied, set IOR to 1 and give it any kind of opacity map in the refraction slot , change the background color so you can see the plane against it, and then render. It looks fine.

Now, check the box "override max's" in the ,"refraction reflection" environment slot. (you can use any color or map). My result is the trans area takes on the enironment color.

Now uncheck "override max's" in the ,"refraction reflection" slot and turn color mapping to exponential AND uncheck "affect background". My result is that the transparent area is still affected by the color mapping so it becomes visible against the non affected background!

Can anyone else please try this experiment and verify?
Thanks for all the help here!

[Da_elf]

ooo, now i get it. hmm. not so sure if there is a work around for that

[RErender]

There is a work around

Instead of opacity use the map as a clip map using vray displacement, just set the water level to a negative number.

[josiah]

RErender, could you elaborate? I tried using the opacity map as the texmap in the dispacement modifier and set the water level less than one, but I could not get it to work.
Thanks!

[RErender]

Hmmm, Try .0001 for amount and .00001 for the water level, Basicly water level has to be less than the amount, with those small values the mesh won't move enough to be noticeable.

[josiah]

Thanks RErender, I got it to work! Unfortunately I could not get the edge detail I need even after turning up the precision and resolution. I can see where this could certainly be a workaround in alot of situations.

Darn it anyway, I think I will change the scene and do some remodeling to eliminate the need for this much opacity, I am losing too much time over this issue and I think I will not find a way anyhow. I hope true opacity mapping is introduced or at least a fix for these two issues.
I love Vray, but this &*$#s.

Thanks everyone, I appreciate the help!

[samuel_bubat]

Because of the edge details btw. the dark edges when using refraction.

I get much better results, with "reflect on backside" turned ON.
It looks like it handles internal reflections and not like expected, reflections for a double sided material wich would look and refract like
a thin glass. I think the switch should be renamed to avoid confusion.