Topic awaiting preservation: Lighting and Shading Theory

Hi All

As a school project I am looking into how, using software, you could work out how much daily sunlight a given area of land receives at certain times of the year, and at different global locations. Although I don?t actually have to write any 3d code, I do need to look at the computational feasibly.

Could anyone please help me identify formulas that would be needed, and what inputs I would require??

What formulas are used to shade/light an area in a 3d model with a given source of light (i.e Sunlight or spotlight, etc.)?

Without fully understanding the complexities of 3D programming, I am finding this all a bit overwhelming.

Yours hopefully

Nick James

not sure if i understood you, but the light intensity of a pixel is calculated as described here:
http://en.wikipedia.org/wiki/Rendering_equation#the_rendering_equation

In case this answers your question: the amount that a point on an object (such as the earth) is lit by a light source (like the sun) is the intensity of the light source, times the amount of light that the object reflects, times the cosine of the angle between the normal (straight up off the object) and the direction of the light source to the point.

For simplicity's sake, you can assume that the sun's intensity is 1 and that the earth recieves all of it, so all you have to calculate is the cosine of the angle. This angle is the angle between "straight up" (to a person standing on the surface of the earth) and the direction of the sun (to the same person). When the sun is over the equator (meaning the earth's axis is not tilted towards or away from the sun), this is the same as their lattitude.