Strange artifacts with cycles render

Question

I am trying to make an effect where a building is burning down or something similar like this:

The problem is that halfway down there are some parts that does not disapear and stay black: It does not happen in the material preview, just when rendering with cycles. I need cycles because the video has to be VR compatible.

The way I am doing this is as follows. The building has this material: It has an empty plain axis attached so that when that moves one part of the building uses the given texture, the other one is transparent and there is this fire like effect in the middle.

Any ideas why there are those black artifacts?

So far I tried modifying the values of the different nodes, changing render values and removing the texture.

Does this answer your question? Black artifacts when looking through many transparent objects?. See my second answer there with further explanations. The accepted answer unfortunately talks about Transmission bounces, while this is actually a problem of Transparent bounces and so the accepted answer is actually wrong. My same answer is also here: https://blender.stackexchange.com/questions/275682/png-image-black-only-when-in-front-of-other-objects/275691#275691 — Gordon Brinkmann, Feb 14 '24 at 09:43
Oooh, yeah, that fixes it, sorry, I did not find that since it did not ocur to me to search it as a transparency problem. Thank you — Alejandro, Feb 14 '24 at 09:54

score 1 · Answer 1 · edited Feb 14 '24 at 15:44

If anyone reaches this, basically in my case the problem is that in the renderer I had the value for Transparent Light Path Bounces too low, it was at 8 and I had to increase it to 24.

As Gordon said in a comment the answer is at Black artifacts when looking through many transparent objects?.

Be careful because the answer says to modify transmission in Blender 2.8+, you still have to modify Transparent Bounces, not transmission.

Strange artifacts with cycles render

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