I am creating an ARCore application in Unity where I want to make lighting shadows that match the real lighting outside.

For this, I have made a rotational directional light that simulations the real sun. The suns altitude and azimuth angles is found from the phones GPS coordinates. In combination with the rotational sun, I will also have a hemisphere of directional lights simulation the sky. These directional lights will have different colors and intensities. The color and intensity of these I have found using the model presented by Preetham in the paper A Practical Analytic Model for Daylight. I need to properly scale the intensity of the sun and these sky lights to make the lighting conditions look as realistic as possible.

In order to make the Augmented objects have the same lightning conditions as the real objects, I need to make the intensity of the sun in Unity similar to the real sun. The Unity documentation reads that for light intensity:

The value can be between 0 and 8.

I have been told that parameters like these in Unity have no coloration to the real world conditions. Are you aware of any good practices for setting the intensity of a sun in Unity or do you know of scientific method for this?

  • 1
    I suspect what will matter most here is not the absolute magnitude of your sun's directional light, but the ratio in intensity between this light and your ambient lights. This will determine the contrast ratio between the lit & shadowed regions. Your AR display device will likely lack the vast dynamic range needed to display the contrast ratios of actual sunlight & shadow though, so you may be forced to judge by eye what looks good enough. – DMGregory Dec 6 at 1:12

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