Vray "ID Generator Tex" - Transparency effect

[legi008]

Hello,

I would like to recreate the transparency effect that i saw in the doc using the VrayMultiSubTex and ID Generator Tex. As it would work as the opacity in Photoshop as i understand. Not like the classic "Visibility Object" where we see the backface.
See here : https://docs.chaos.com/display/VMAX/...IDGeneratorTex

I follow the steps but did not manage to have the same effects, i still see the backface of my mesh.


Is it a bug ? Am i missing something ?

Thank you
Max 2024 - Vray 6.20.02

[dlparisi]

I'm not exactly sure how it is supposed to work based off the example, but it works as expected if you have 2 slots (3 including the default) and make the default and no. 1 slot black and control the front facing opacity with the no. 2 slot color.

[legi008]

I can get full transparency with full black color, but no intermediate transparency.
And with your proposition, if i set the Default to full black, the shadow disappear totally.
In the doc, you can see they are still present.

i wish i could have the scene in the doc to see how it's has been set-up.

[dlparisi]

Something like this doesn't work for you? (Sorry the forum replace the slot notations with "Home" and "Forum", now fixed).

[legi008]

Can you upload your scene ti test on my side ? Because i get a different render even with your setup

[legi008]

This setup is working for a simple box :


But if the mesh is more complex as with the extrude on the top part, it doesn't work :
We still see behing the front face (Not like the ref in the docs)

[legi008]

Weird effect, for testing purpose i create several slot with a black color, and it's now kind a working.
I had to make 7 black slot. Something is clearly unusual.



Would appreciate a feedback from Chaos developpers to clarifiy things

[dlparisi]

Yeah, weird. I couldn't get it to work either with a more complicated object. It also gets weird once once you start viewing multiple transparent objects through each other so you can probably forget using this for trees or something like that with a lot of overlaying geometry.

[legi008]

Here a 100 frame animation test from 100% to 0% opacity.
It's kind of working but in a strange way. The darker area looks like to disappear first.

[legi008]

Too bad, it not working if a light is between the object and the camera....

[hermit.crab]

When using the VRayMultiSubTex's ID generator tex., the additional slots control the color, based on transparency hits.

In the attached image, the big plane is shaded with a VRayMtl and VRayMultiSubTex plugged in its Diffuse. Above it, six fully transparent little planes are stacked on top of each other. When a transparency ray goes through one plane: the rendered color is from VRayMultiSubTex slot 1. When it goes through two planes - slot 2 and so on.

The disappearing effect works by controlling the opacity, based on the 0th transparency hit (direct). ̶F̶o̶r̶ ̶t̶h̶i̶s̶ ̶r̶e̶a̶s̶o̶n̶,̶ ̶c̶o̶m̶p̶l̶e̶x̶ ̶o̶b̶j̶e̶c̶t̶s̶ ̶(̶w̶h̶i̶c̶h̶ ̶r̶e̶q̶u̶i̶r̶e̶ ̶m̶o̶r̶e̶ ̶t̶r̶a̶n̶s̶p̶a̶r̶e̶n̶c̶y̶ ̶h̶i̶t̶s̶)̶ ̶n̶e̶e̶d̶ ̶t̶o̶ ̶h̶a̶v̶e̶ ̶a̶d̶d̶i̶t̶i̶o̶n̶a̶l̶ ̶"̶b̶l̶a̶c̶k̶"̶ ̶s̶l̶o̶t̶s̶ ̶s̶o̶ ̶a̶s̶ ̶t̶o̶ ̶s̶a̶y̶ ̶t̶o̶ ̶V̶-̶R̶a̶y̶ ̶t̶h̶a̶t̶ ̶t̶h̶o̶s̶e̶ ̶t̶r̶a̶n̶s̶p̶a̶r̶e̶n̶c̶y̶ ̶h̶i̶t̶s̶ ̶s̶h̶o̶u̶l̶d̶ ̶b̶e̶ ̶i̶n̶d̶e̶e̶d̶ ̶t̶r̶a̶n̶s̶p̶a̶r̶e̶n̶t̶.̶ ̶O̶t̶h̶e̶r̶w̶i̶s̶e̶,̶ ̶a̶n̶y̶ ̶h̶i̶t̶s̶ ̶a̶b̶o̶v̶e̶ ̶t̶h̶e̶ ̶s̶t̶a̶t̶e̶d̶ ̶o̶n̶e̶s̶ ̶i̶n̶h̶e̶r̶i̶t̶ ̶t̶h̶e̶ ̶d̶e̶f̶a̶u̶l̶t̶ ̶c̶o̶l̶o̶r̶.̶

Too bad, it not working if a light is between the object and the camera....

The thing to note is that VRaySamplerInfoTex's Transparency Levels get the data so to say globally, for the rendering. Since the light (if invisible) is transparent, it counts as a transparency hit, hence the object is shaded according to the VRayMultiSubTex slot of the transp. level.

---

Overall, this may be confusing and I agree. I'll discuss the case with the product owner, maybe we can make this functionality more intuitive.

EDIT: There is an easy way to do this already written in the Docs, without the need for more than one slot. Simply set the default color to black so that all levels without an ID are transparent and manually set the number of the first slot to 0 (direct). Afterward, you control the transparency through the first slot's color. Screencap added.

[legi008]

Thanks for the feedback.
Maybe all this information need to be add in the docs to avoid confusion in the future.
And yes, it would be great to have an exeption hit for the lights (or even better, all invisible objects) so that the effects could be use at its maximum potential.

And also, as i have managed to have it works on my project. I have had a last problem with a lot of black edge appearing when several fading objects where in front of each others.
I had to increase the "Max transp; levels" in the Global Switches rollout to make them disapears. Hope that helps for others !

[dimitar_panayotov]

We will add the scene with the cups in the documentation.

[DCHA34]

We will add the scene with the cups in the documentation.

Thank you.
It's a very good idea and goes along with my message posted a few minutes ago. : https://forums.chaos.com/forum/docum...es#post1221690

[hermit.crab]

legi008 Check the edit of my post above.