Most efficient way to render transparent materials (complex scene)

[Joyvel Osorio]

I’m rendering an animation of mechanical parts and components, similar to the YouTube channel Animagraffs like in this video https://www.youtube.com/watch?v=hjsrqMe0B3s The idea is to be able to see the interior of an airplane or machine and put many of the outer layers semi transparent or totally transparent, but I’ve noticed it takes way longer, the GPU has to calculate a lot more, or maybe it is because now some geometry that wasn’t visible now is.

My technique now is using a ‘Mix Shader’ node with a transparent node to dial in how much transparency I want. I’ve also tried the alpha section of the ‘Principled BSDF’ but I think that one takes even longer to render.

What do you guys suggest for faster rendering? And, how can I also group objects to be affected by the same transparency if that’s possible?

Thank you.

[Omar Domenech]

I guess it’s in the nature of the beast, even worst if you have to bump up the transparency bounces. Are you using Eevee or Cycles?

I guess one thing you can do is render in layers and in compositing dial down the opacity of the layer you want less visible. Also maybe do Eevee viewport renders if you can sacrifice the reality component.

[Joyvel Osorio]

Thanks, I’m using cycles, it looks more realistic. I thought of doing the layers and compositing, maybe I’ll do that in some parts. I think the guy from that video I shared uses the fresnel node to keep the outline of the materials and keep transparency. I’m pretty sure there are many ways to do something like that efficiently but I’m still learning.

[Omar Domenech]

So you’re planning on staying with Cycles? Based on the animation you shared, looks like you can totally use Eevee. Another idea can be to break blend files into shots. So if you’re just showing the stuff that is under the main chassis of the plane, the only thing that needs transparency is the chassis, no need to have lots of stuff in transparency one on top of the other.

[Martin Bergwerf]

It depends a lot on the look that you want…

You can try a single Transparent Shader and change the Color…for instance use a Mix Color Node with Pure white and one other Color and change the Factor to control how transparent it appears.

And if Objects use the same Material, they have the same transparency….don’t really know what you mean by grouping objects to have the same transparency…

[Joyvel Osorio]

I’m staying with Cycles, I’ve used EEVEE several times but when it comes to transparencies there are some glitches I don’t like, like objects disappearing behind the transparent objects, etc. I’m planning to use it on some shots of my animation where it will make sense. Thanks for your help.

[Joyvel Osorio]

Martin, thanks for your help. I was just wondering if there’s another way to control transparency/visibility to a group of objects. Thanks.

[Omar Domenech]

Well basically if that group of objects share the same transparent material, change one parameter in one they all change in unison.

[Joyvel Osorio]

Here we go Guys, the guy from Animagraffs himself made a video explaining his workflow, and the transparency approach he makes is custom-made and amazing. He just published the video. https://www.youtube.com/watch?v=T7Hb8kRUHEI Around minute 10 he explains the transparency approach with python.

[Omar Domenech]

Well sounds like in the end he is turning visibility or transparency from a tool he built, but it’s more like a handy way to reach it, not that transparency in itself is different. I don’t know, Martin will know better.

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