Sun Spread Angles

by | January 11th, 2011 | Articles | 6 Comments »

Just a quick one today to clear up something that possibly isn’t experimented with much when considering lighting, the spread angle from the light_environment. The entity itself recommends a value of 5 degrees to start with however, as my attention was drawn recently to, this is actually quite a large angle. You’ll see on a sunny day, the shadow from a tall building is incredibly crisp. The angular size of the sun, a non-point light source, is about 32 arcminutes in the sky, which is just over half a degree. So picking a sun spread angle smaller than 5 degrees is a good idea if there is little to no cloud cover in your skybox.

The images after the jump are examples of sun spread angles 0, 1, 3, 5, 10 and 20 degrees. 3 degrees is the limit of what you want for a sunny day or a full moon (which is usually only a 60th of a degree smaller than the sun in the sky). 0 degrees looks blotchy on the lightmap scale 16 because of the chainlink, just smoothing that by 1 degree gets rid of that. If a cloud covers up the sun then the light source gets smeared out to nearly the size of the cloud, for such a skybox a larger value like 10 would be more accurate and for an overcast day 20 degrees is almost not enough.

Left hand side is using a lightmap scale of 16 and right hand side is on 1.

sun spread 0 degrees

sun spread 1 degrees

sun spread 3 degrees

sun spread 5 degree

sun spread 10 degrees

sun spread 20 degrees

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6 Responses to “Sun Spread Angles”

  1. StickZer0 says:

    Hooray! I inspired this article!

    Thanks for testing this yourself and throwing it out for the masses to see, while I don’t think that anyone will ever conciously (or even subconciously) notice or care about a difference between setting it to 5 or setting it to 1, it’s still nice to set it in my own maps just to know that I’m right 😉

  2. […] featured an article about sunSpreadAngles in the Source Engine, inspired by my original tests with them. It’s good to see a site […]

  3. StickZer0 says:

    The fuck, how did it automatically steal that off my blog and post that here? :S *awkward*

  4. You use wordpress, and haven’t disabled it’s automatic trackback system. Since Nodraw also uses wordpress… well, you figure it out 😉

  5. Moose says:

    Never really considered sunspreadangle in my maps before. I’ll probably end up changing it for my next alpha. Thanks!

  6. honeymustard says:

    Nice! Never knew how this worked, great help – thanks.

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