CODEWITHSUNDEEP
c++openglvertexlighting
BlueSpud
BlueSpud

Reputation: 1623

OpenGL: Easy way of stopping light at vertexes?

I have a scene built in OpenGL. When my light is in the center of the room, the outside of the room is lit. Is there any easy way to make OpenGl stop the lighting at vertexes, or will it require complex calculations. Here are pictures of my crappy, quick scene showing the lighting as it is when asking this question:

Upvotes: 1

Views: 1759

Answers (2)

darklon
darklon

Reputation: 478

One solution here would probably be to author the geometry in a way, that objects don't protrude outside walls (or separate them into inside/outside parts). Then render the interior and exterior with different lights.

You wouldn't have the problem if everything would cast shadows on everything.

If the lights are static, you might want to consider pre-calculating (baking) the lighting (together with shadows). You can do this in many 3D packages, and from a programming perspective this might be the simplest solution.

If you had a general solution for real-time rendering shadows for every light, that would also solve your problem, but that is a challenging task, and it might also not be the optimal thing to do, if you want to maintain good frame-rates.

If you want to learn about real-time shadow rendering, I recommend looking at shadow maps - they are generally the solution used in most games today. Note that for a point light you would need to render the shadow map for 6 sides of a cube-map. For practical purposes you should really consider which lights really need to cast shadows, and make some kind of trade-off.

Upvotes: 1

sheu
sheu

Reputation: 5763

Essentially, you want the walls of the room to cast a shadow. That's what you want when you want the exterior part of the object not to be lit.

Shadowing in graphics, is generally a pretty hard problem. There are a lot of good, and a lot of fast, solutions, but not both -- any one solution is going to be a tradeoff between the two. SIGGRAPH is full of all sorts of papers from Really Smart People trying to solve this problem.

If you want something quick and dirty, shadow mapping is not terribly difficult (at least the simple kind), but it is imprecise. You'll see artifacts along the intersections of your object and the walls, for one. For precision, stencil shadows will work, but you'll have hard-edged shadows.

Upvotes: 4

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