Looking for some suggestions on how best to show projections of multiple conical beams (of light, or in my case, signals from satellites) onto the surface of an earth sphere.  I have had limited success with placing a point light inside an open-ended cylinder and allowing it to cast the shadow onto the earth.

For the material on the surface of the earth I am using the techniques and bitmaps from the Globe Materials Tutorial, and applying earthMaterial.shadowMethod = new HardShadowMapMethod(pointLight);

That looks OK inside the “hole” where pointLight shines through, but in the shadow, the earth is completely black unless I reduce the alpha, but that does not look great, especially if I use a colored point light.  And I don’t see a way to have multiple of these beams in different places on the earth (i.e. you can apply only one shadowMethod to a material?)

So… am I doing this the wrong way?  Or should I not try to get shadows to do this job, and instead build partial-sphere primitives and lay them on the earth like small colored caps?

BTW this all needs to be scripted rather than externally modeled, as the positions of the satellites and their beams will be in motion and interactive.

Thanks!
Ralph

First off, I think you will need to use a cone primitive to represent the “beam”, from the satellite to the earth. To light the earth independently, you could use a Point Light to represent the sun, or assign no lights to get it’s Diffuse color (i.e. the globe map).

If your beams are a semi-transparent pale color, that might be enough to give you the effect you are looking for, lightening the area on the earth where the cone and sphere intersect. (or with your capping idea

Good Luck!

Thanks!  I infer you agree that trying to use shadows is not going to work well.

The semi-transparent cone does look pretty good, together with “caps” (which I figured out how to make as new custom primitives… very different from 3.6 which is what I am used to!)

By the way, Away3D 4 handles intersecting objects SO much better than 3.6! I can let the cone dive right through the earth and it makes a clean intersection contour.  In 3.6 there would be all sorts of weird artificacts, depending on the renderer.  And mixing line segments with 3D objects, and moving their endpoints around, works great too, now.  Thank you developers!