Ambient Occlusion and Alpha Transparency

[MFVis]

Very odd - I have two models, each with a texture using alpha channel. When I turn on Ambient Occlusion, one alpha works perfectly, in the other the alpha casts a shadow. Clicking on "Evaluate Transparency" reduces the shadow artifact, but does not eliminate it. So far as I can tell the textures are the same. Why does one work and the other not?

Model link here:
https://shared-assets.adobe.com/link/be7a674e-29fe-4c32-7516-1f7cccc44bc4

BTW: This model was only 358 Kb but wouldn't upload because the textures were "too big" (in dimension not file size). That's a really small keyhole to fit through

[Dr. Sassi]

Hi MFVis,

Thank you very much for the file.

The yellow model has no alpha texture, nor anything enabled.

Please have a look here:
https://stcineversityprod02.blob.core.windows.net/$web/Cineversity_Forum_Support/2023_PROJECTS_DRS/20230624_CV4_2023_drs_23_TX_01.zip

Enjoy your weekend

[MFVis]

This shows a texture applied to the Receiver body, doesn't it? f I'm understanding you correctly.

[Dr. Sassi]

Thanks for the reply, MFVis,

I placed the plane for the background (with a little distance to the "screen"), and added to the "screen" object a new alpha image; you find it in the tex folder.

I have added an LCD background material to the Plane Object and sorted it under that parent.

https://stcineversityprod02.blob.core.windows.net/$web/Cineversity_Forum_Support/2023_PROJECTS_DRS/20230624_CV4_2023_drs_23_TX_02.zip

Let me know if that works for you.

All the best

[MFVis]

Ah! Yes, that's very effective for the receiver screen - I never noticed that issue before. However, the problem I'm wrestling with is the FLOW decal on the "Front Cover" object.

[Dr. Sassi]

Hi MFVis,

Please have a look here
https://stcineversityprod02.blob.core.windows.net/$web/Cineversity_Forum_Support/2023_PROJECTS_DRS/20230625_CV4_2023_drs_23_TX_11.zip
I have set up a Heat map to show you that the AO is working.
I tested even a Volume model (Check the two Volume objects to active and render)

Ambient Occlusion, is an old hack to create a simulation of the effect that Global Illumination has. The AO technique does not consider any lights, so even if a light source inside a corner, where AO creates dark results, the light would not change it. It just darkens (default) when polygons are at a slight angle to each other.

My best wishes for your project

[MFVis]

Ah! In other words, AO is old school. Better to use new school. Makes perfect sense. Thank you!

[Dr. Sassi]

Thanks for the reply, MFVis,

The main takeaway is to use whatever you like, but it might be too much if something doubles during rendering. Whereby GI provides more refined results, and AO is more of a hack. Anyway, whatever works.

But yes, I admit, based on the unnatural results of AO, I was never a fan of it.

Cheers