I’m working on a test scene and there’s a strip of capsules on a ‘working’ turntable. The capsules are white and transparent blue but how they react on light is a bit confusing to me.
In this video you see…
- Scene lit by an HDRI, white side of the pills is looking fine.
- I turn the HDRI off and turn on the planar lights
- The white side of the pills turns black, it’s just white plastic
- The blue side on the other hand looks totally fine
- At the end I remove the transparent plastic and white side is white again.
I noticed that turning on caustics will let light pass again but I don’t understand why there’s not an issue if I use an HDRI and whatever I use the blue side of the capsules looks fine.
I would for example expect that the same will happen to the blue side since that’s even a more complex material.
Would love to hear if someone actually knows what’s happening and why the differences occur.
Also tried the same in an older 2024 but same result.
Was just trying a bit more… if I disable global illumination the capsules get dark, think that makes sense. The movie below has the HDRI enabled all the time and at first the planar lights are not active. As soon as I enable them the capsules got darker. I’m confused 
Hi Oscar, that is pretty unintuitive, I agree. I don’t have an immediate idea what exactly is going on but if you could share the scene with me, I will ask a developer to investigate and verify if what is happening here is correct and expected or if you’ve found a bug!
I’ve send you an email Jan. For those who run into the same issue, it seems to have to do with the ‘self shadows’ under the lighting options.
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Are you in 2025.2? Too funny I made a capsule like yours a few weeks ago and noticed similar behavior, with the clear glass casting shadows on the meds inside. I wasn’t using planer lights though. There was a bug with translucent materials being opaque, but it was fixed in 2025.2. Your issue differs and I can replicate it and fix it, at least my issue.
I attached a video, and brief descriptions of my findings, with fix are below.
What I noticed in my instance with the glass material is:
- CPU mode appears as expected in both Product and Interior Modes.
- GPU mode does not.
- The type of physical light made no difference.
- The Label with an Advanced Material Texture with PNG Transparency was causing the issue.
My Fix:
- Assign the PNG (with Alpha) Label graphic to the diffuse color.
- Under Label Properties Scroll down to Use Diffuse Map Alpha and check the box, it should now appear correct. Also, from the drop down select Alpha. < Main Issue
- I needed the label for transparency not the diffuse color when I removed the label from diffuse back to transparency the Advanced material “Use Diffuse Map Alpha” remained checked and the materials appeared as expected with physical lights.
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Hey @don.tuttle!
That’s really funny, capsules are hot! I didn’t really think of it as a bug but thought I just forgot something about certain limitations with materials and light. Currently I do think it’s a bug, I tested it in 2024.2, 2025.1 and 2025.2 and behaviour is all the same.
I’ve now sent Jan a test scene so the developers can take a look at it. While preparing a bit less heavy test scene I played with the light options again and I noticed if I disable the ‘self shadows’ the problem will go away, well also the realistic lighting 
I think it’s actually the combination between the transparent material, think I used the default polycarbonate and the Self Shadows or the physical lights and the self shadows. The transparent layer is actually a solid and first I thought it might be because some geometry intersects but moving the capsules down didn’t make any difference.
I’ve more than enough bounces so it shouldn’t suddenly appear dark. If you like I can give you a link to the scene as well.
Gotcha! I overlooked your comment about the shadows. That I cannot reproduce. It sounds like you found the issue, so I don’t need a link. 