enter image description hereI found there is a circle when the point light through my glass material using the circle render. How could I solve it? enter image description here


When looking through glass, the light path is considered a transmission ray instead of a camera ray, and the full sphere of the point light is visible to transmission rays. Point lights in Cycles are not true point lights unless size is set to 0 (as these are non-physical and usually look bad). If size is > 0, you instead get what's technically a spherical area light. And like a regular area light, the surface is visible through glass (and in reflections). As far as getting rid of it, there's a bunch of possible solutions:

You can just hide the lamp from transmission rays by unchecking object data > Cycles Settings > Transmission. But this will also make the lamp not cast light when viewed through glass, which I suspect isn't the result you want.

A better solution is to change your glass to not be true glass. Some render engines have an "architectural glass" shader designed to fix this sort of issue. Cycles doesn't have one, but the node system allows you to recreate one pretty well:

architectural glass example, mixing glossy and transparent with fresnel

This glass will not refract, but otherwise looks exactly like the glass shader. For very thin and flat panes of glass, the refractive effect isn't very noticeable anyway, so you can get away with this. It will still reflect like glass, but as far as light rays are concerned, objects seen through it are still viewed directly ("camera rays"). Not only will this keep lamp objects hidden, but it also has some other nice side effects, like passing the alpha channel through, and preventing clamp indirect from affecting things seen through the glass.

Technical mumbo jumbo P.S.

The geometry > backfacing node is to prevent reflections on the backface, which would otherwise appear black. There's actually a slightly neater way to do this, as fresnel - backfacing, rather than fresnel * 1-backfacing as in the other setup. Doesn't really matter, but it's a little cleaner on the nodegraph at the cost of being slightly less intuitive: arch glass node, with subtract and no invert


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