What happens when two 2-sided mtl connect to parent 2-sided mtl..

[will_will]

Hello!

I recently recived a tree model, there are two 2-sided materials , as front and back material , connect to the tree leaf material (2-sidedmtl also), the leaves become transparent. (all materials are 100% opacity , no refrection)
I never did that before, but what happend?

[hermit.crab]

Could you attach (or send) a simplified scene? Seems to be something specific.

[will_will]

Sorry for the late reply , here is the simple scene.






2sidedmtl.zip

[hermit.crab]

Thanks for the report and the provided scene. The issue is reproducible. It's probably related to the "Force single-sided sub-materials" option not taking effect with nested VRay2SidedMtls. I've logged the issue (internal bug-tracker id: VMAX-12913) for developer investigation. What's the reason for using the nested 2-sided shaders when they are set to show only one side?

[will_will]

I just merged that model, and don't know why the maker did it like that. Whatever, I belive its not good way .


After then I tried GPU renderer, the model is not transparent , perhaps the maker uses GPU renderer.

[^Lele^]

You may get good results entirely without 2sided material, with the "thin" option and SSS in the base vrayMtl.

[will_will]

You may get good results entirely without 2sided material, with the "thin" option and SSS in the base vrayMtl.

I have tried steps below:
1.Set translucency to SSS
2.Check on the 'Thin-walled'
3.Copy or instance diffuse map to SSS color slot
4.Set SSS amount to 0.5.
It' looks same to 2-sidedMtl , is it a correct workflow ?

[^Lele^]

It is.
For speed, set the SSS mode to "Uniform", it'll gain you a lot of time, especially if there are many lights.
Looks will change a bit, but are likely better for foliage.

[super gnu]

this is a workflow ive not tried, is there any advantage to this over using the 2sided?

[will_will]

It is.
For speed, set the SSS mode to "Uniform", it'll gain you a lot of time, especially if there are many lights.
Looks will change a bit, but are likely better for foliage.

Thank you for your advice, its so helpful for me! I will make foliage or curtain with this workflow in future.

[will_will]

this is a workflow ive not tried, is there any advantage to this over using the 2sided?

With few tests , VrayMtl did it faster, specially in large area shadows, almost 2 times fast , and less shadow noise. its really cool.

[^Lele^]

this is a workflow ive not tried, is there any advantage to this over using the 2sided?

It should be better for all metrics: easier to set up as it's a single material, cheaper in RAM for the same reason, analogous or better for looks, and *many* times quicker than 2Sided for complex lighting situations (the "Uniform" mode.).
Speed benefits will be less obvious with simpler lighting, but still present.
However, if you have ever had complex foliage inside a lit hall, f.e., the speed difference ought to be felt.