Any tips for indoor night time renders?

DDCreate

I have no lights in my scene except for one point light set to very low lumenence but it's still fairly lit. My ideal set up would just be moonlight coming in through the window. Not a moon beam really, just that level of light. Does anyone have any tips on how to achieve this?

 

Catherine3678ab

Rendering in 3Delight, Iray or ?

lamoid_5f20d3e469

I do a fair number of low light indoor renders. No domes or HRI; scene lights only. The main thing is to allow for many iterations, 5000 to 15000, and many hours of computation time even with a fast GPU, 8 to 24.  Giving the process time gives excellent results. 

Regarding moonlight: Probably the easiset way to achieve what you want is to find an HDR image of a moonlit landscape. In the render settings use an enviroment mode that includes a dome and put the HDR image in the environment map.

If you would prefer a phyics-based approach, read on.

The angle covered by the diameter of the full moon is about 31 arcmin or 1/2°, so astronomers would say the Moon's angular diameter is 31 arcmin, or the Moon subtends an angle of 31 arcmin. (from https://lco.global/spacebook/sky/using-angles-describe-positions-and-apparent-sizes-objects/).

So if you were to use a spotlight set to be a disk a distance r from the scene origin and oriented perpendicularly to a line through the origin, the diameter, d, of the disk should be 0.0087r. For example if you place the spot 10m away, its diameter should be 8.7mm. The color temperature of the moon is 4100K which is redder than sunlight at 5000K, But it appears to be bluer than sunlight because of the psychophysics of vision. Heres a good discussion on that: https://physics.stackexchange.com/questions/244922/why-does-moonlight-have-a-lower-color-temperature,

The luminant flux of the moon depends on many factors. Here's one example: https://www.spaceweather.com/swpod2009/13jan09/Perigee_moon_2009_01_11_corr.pdf. In general on a clear night with a full moon about 3.7 lux. See https://www.rapidtables.com/calc/light/lux-to-lumen-calculator.html to convert that to lumens.

All that being said. I would experiement using a spot light in photometric mode with Light Geometry set to Disk and a diameter of 1cm. Move it to where you want the light to come from. Make sure it is pointed at the origin. (The easiest way to do that is to create a null primitive with default settings and set the spotlight to point at that null.) Then experiment with the color temperature luminous flux until you get what you want.

Bear in mind that the spotlight acts like it is in a vaccum so you get no atmospheric scattering.