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I need to do a shadow study for a residential project showing shadows at different times on different days of the year. I am using the 'set sun position' command but am having a difficult time understanding the 'elevation' result. How does the degree number given correspond to the sun's height (or z dimension) in the drawing assuming my ground plane is at 0'-0"? When I use the command the sun seems to be pointing the right way in plan view but seems to be sitting on the ground in elevation. Can somebody give me some pointers on how this works- the manual does'nt say much. Thanks. [Confused]

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The sun is a directional light source, meaning its physical position has no bearing on the source. Directional lights mimic the effect of the sun by emitting rays in a parallel direction indicated by the light object.

What this means in normal language is the physical location of the sun dosent matter. the light given by the object will all come from the same direction. The light has no source, and the object that represents the light is only there so you can select something, and adjust its attributes.

Does this make any sense?

Good Luck

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  • Vectorworks, Inc Employee

Hello Thom, Davis Design:

The rays run parallel to the direction arrow on the light object.

As Mike says, the direction vector is the only parameter needed to determine the effect from this light source. Our sun is so far away that it can reasonably be assumed to be a point light source at inifinity, which would produce parallel light rays so the position (millions of miles away) doesn't matter, only the angular direction. The real sun also covers an area of the sky and so should be simulated as a central direction plus or minus a certain number of degrees, but it is much simpler and usually good enough for computer rendering to do it as a single direction vector.

As an aside, as far as not simulating the sun as a disk of light in the sky, I saw an eclipse once and shadows from the leaves of our tree were crescent-shaped instead of the usual! It was freaky!

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