Cool to see its effect on the bottom!
But does it have a lens?
Yes, there is a lens at the top. When rendering, the sun is placed directly overhead so that it shines straight down which projects the text on the bottom. The projected image is actually created by the rendering software … it’s not in the model itself.
I think @Aerilius was referring to the original camera obscura which has only a hole instead of a lens? But nice result anyhow!
I should have made that clearer … it’s still a camera obscura, but not a pinhole camera. I’ll change the title to clarify that distinction.
So the rendering software does the proper refraction in the glass for the lens to work, huh? What render is this? …or more broadly, which renders are capable of this and which aren’t?
All good renderers do this. Although surface models are hollow inside, when a ray goes through a frontface that has a refractive material, the renderer applies the ratio of the refractive indices of glass and air to Snell’s law, and when the ray goes through the backface (outwards) it applies the inverse. This is trivial. At the moment, I can’t even think of a renderer that does not do this.
However what differentiates renderers is whether they can break up white light into a spectrum of colors. Therefore a renderer needs to consider 1. that white light consists of a spectrum of many frequencies of light and 2. that light rays refract to a different degree depending on their frequency. Instead of casting a single ray, the renderer needs to follow rays of many color components (to approximate a continuous spectrum).
For example Thea can do this.
I use KerkyThea because it’s priced right for my budget. As @Aerilius noted, the ability to refract light through glass is a pretty standard function.
So far I’ve only played with Podium, but not really accomplished with it yet.