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I want to render mirror balls. In the real world you would hit each mirror ball with a spot light.

To test if this would work in Cycles, I made a mirror ball and hit it with two spot lights (shown with red and green arrows) as shown here: enter image description here

However, although you can see the direct spot light effect on the walls, the mirror balls show no light and no light is reflected onto the walls from the mirror balls.

enter image description here What I would want to see is light on the other side of the wall (i.e. in the area circled in red) because that is the direction the second spot light is pointing, and directly perpendicular to the normal of a few faces of the sphere.

Why don't I see any light reflected from the balls?

Here is the project file:

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  • $\begingroup$ The first image is very very confusing... can you screenshot more clearly? $\endgroup$
    – Master Heavy
    Nov 7, 2019 at 6:52
  • $\begingroup$ I clarified the image. The point is that light is shown directly onto the mirror ball and yet you can't see it. $\endgroup$
    – Startec
    Nov 7, 2019 at 8:20

1 Answer 1

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If you wish light to be reflected and illuminate other objects, you need to enable reflective caustics:

enter image description here

These calculations take a lot of time in Cycles and are inefficient, because of the way tehy are calculated. For better caustics one would need to use a render engine that supports bidirectional pathtracing. I think LuxCoreRender can do a better job with this.

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  • $\begingroup$ What do you mean "mesh lights"? You are saying that light reflections are not calculated by cycles? $\endgroup$
    – Startec
    Nov 7, 2019 at 8:36
  • $\begingroup$ Visible reflections are only calculated if lights are made of geometry, light emission reflections are calculated if Reflective Caustics are enabled, but Cycles does not do that very well - it's slow inefficient and inaccurate with caustics unfortunately. $\endgroup$
    – Martynas Žiemys
    Nov 7, 2019 at 8:43
  • $\begingroup$ @MartynasŽiemys Okay, this question is very old, I just stumbled across it while searching something different. I just wanted to point out that lights don't have to be meshes to be visible in reflections. Point, Spot and Area lights are visible in reflections, even back then when this answer was written. The radius (point/spot) or size X/Y and shape (area) you set will determine how the reflection looks like. $\endgroup$
    – Gordon Brinkmann
    Nov 15, 2022 at 11:11
  • $\begingroup$ Seems like I was young and stupid back then those many years ago. :D Thanks for noticing. $\endgroup$
    – Martynas Žiemys
    Nov 15, 2022 at 14:01

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