Specular Bouncing of Light Source (Spotlight)

I'm trying to bounce (specularly reflect) a focused, small width spot light off a mirror to get a spotlight-like spot on an object via the reflection. I'm not sure IRender nXt can do it. My forum searches & example browsing haven't found a solution in any case. I haven't figured out how to do it in Chief Architect or Punch! Architectural Series either.

I'm using SketchUp Pro 2017 as my modeler with a trial version of IRender nXt.

Any comments? Thank you.

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Permalink Reply by Render Plus on February 19, 2017 at 7:19am

You can place another spot light behind the mirror - but at the same height and "mirrored" location as the first spotlight, and aim the at the same place. (I drew a construction line to make it easy to aim them)

Then, in SketchUp, I set the mirror itself not to cast shadows.

Then, when you render, the beam from the second spot appears on the back wall as if reflected.

the reflection of the beam on the wall is also seen in the mirror.

If you want an even more enhanced effect, use our "visible light path" trick to add a visible path to both spot lights, and the visible path will appear to be mirrored in the mirror.

http://www.renderplus.com/wp2/wk/Visible_Light_Paths.htm

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Permalink Reply by David Barrows on March 12, 2017 at 10:52pm

Thanks for your help. I've been experimenting with various methods of achieving what I wanted.

I was hoping not to have to use a workaround for specularly reflecting illumination sources. It appears that illumination is only diffusely reflected. A spot (for a spotlight) appears on the mirror where the spot hits the surface and that spot illuminates other surfaces. It appears that making the mirror 100% reflective and the material color totally black results in no illumination from the mirror surface (other than the picture that is seen in the mirror which doesn't illuminate other surfaces).

Am I doing something wrong, or is it true that there is no specular reflection of illumination sources in your rendering algorithms?

Thanks.