I'm struggling with rendering a plane on which a PNG texture with alpha channel scrolls (it's basically an arrow indicating the direction of flow of a liquid) in front of a material set up as sort of an hologram (the node setup of which I have found online and I'm attaching here below) to let the user see the inner part of the pump. The material is composed by an emission mixed with a transparent BSDF based on the Fresnel IOR value, all mixed with a transparent BSDF depending on the "Transparent depth" of the mesh.

"Hologram" material setup

What I would like to have is that the two planes with the scrolling PNG are rendered on top of this material in the same way as they are rendered when the pump material is a normal BSDF one (material setup also attached) like in this image:

enter image description here

Unfortunately, when the two materials "overlap" (in the view, not in reality, as there's no physical overlapping of the two meshes), the second one (the "holo") renders completely transparent where the PNG is transparent, like so:

enter image description here

I tried every sort of trick that I know but I haven't been able to solve. Do anyone have any suggestion about how to setup the two materials to obtain the result I need? Here's what I tried:

  • setting all the possible combinations of alpha on both materials blend mode and shadow mode
  • increasing the transparency bounces (which in the beginning was causing artifacts in other parts because of the image because of them being set too low)
  • removing the "Transparent" flag from the Film section
  • removing the Simplify flag.


  • $\begingroup$ The "Transparent Depth" on the Light Path is the number of transparent surfaces the ray has passed through. The Less Than node checks if this is 1 or greater, and if it is, makes the material fully transparent. So it makes sense it will be invisible when it is behind the transparent part of the arrow. Get rid of that part of the graph and see what happens. You may want to cull backfacing polys or something instead. $\endgroup$
    – scurest
    Mar 11 at 15:34
  • $\begingroup$ i would recommend providing a blend file, if you wanna have an answer which really helps you because we could verify it by testing. It is often pretty difficult, to "guess" a solution if you don't know all details. $\endgroup$
    – Chris
    Mar 11 at 15:41
  • $\begingroup$ Thanks for your feedabcks. @scurest that setup is basic to having the holo effect and therefore I can't remove it. $\endgroup$ Mar 11 at 16:47
  • $\begingroup$ @Chris the file can be dowloaded from here: drive.google.com/file/d/1tJks8jTp6iRBaoUQrXZCXSIKVkyLC3un/… in the worst case, I'll end up rendering the two things separately and compositing them but I would've liked to do everything in the same pass. $\endgroup$ Mar 11 at 16:48
  • $\begingroup$ can u pls use file->external data -> pack resources before uploading, so we can also see your png? thx. $\endgroup$
    – Chris
    Mar 11 at 17:46


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