Emissive invisible - not completely

[andy.engelkemier]

I thought I figured out a great way to Just render a basic shadow, and it still worked out OK, but not great.

But my first thought Should work. Create a new model set, and don't link materials. Apply a black emissive material to the entire thing. Turn off visible to camera, reflections, refractions.

And yay, a nice shadow on the ground. But...wait. There are a Bunch black pieces all over my model.
My Guess on what is happening, is it's visible where pieces of the model touch, but not sure.

I ended up just making the emissive plain white. Then just eliminate the white later.
The issue still is that you get half pixels that just don't really work. It's an antialiasing issue. That's why I Really want the entire shadow under my object. That way, no worries of background leaking through that selection.

The reason I did this, is it's for package rendering where the thing is cut out from the background. The lighting on the product ended up a bit dramatic. But I don't want long shadows. So I also created a Very boring environment with just one light up top to cast a Really boring shadow. I was hoping that would be less work, and potentially look better than creating a shadow in photoshop. For the time being, I was wrong.

[Niko Planke]

From your description the black patches might be related to a to low Ray bounces value.
Even though the materiel is not visible to the camera it will still count as a ray bounce for rendering.

You can try to increase the Raybounces in the Lighting tab and check if that helps.

Or maybe provide a screenshot for us to get a better idea of the issue.

[andy.engelkemier]

Ugh, Thank you. Yes, that was it.
I had to change it to 45 (but changing to 60 just in case it shows up at a slightly different angle), a value I would Really only use if someone said they wanted to see an entire assembly with internals rendered semi transparent.

And interestingly, it rendered a bit differently in custom mode than realtime, so I definitely thought it was a bug. And in the shadow pass, which doesn't seem to follow the sampling rules, the effect is Red.

Thanks for clearing that up. Not visible to camera actually = transparent to camera. So you better calculate refraction bounces, or you're in trouble.

[Bruno F]

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