More lighting improvements
Entry posted by Josh ·
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In Leadwerks Engine 2.3, two rendering paths are used for point lights. One uses a depth cubemap (for shader model 4 hardware). The SM3 fallback uses an unwrapped cubemap on a flat texture. On SM4 hardware, a depth cubemap was used because it allowed a point light to be rendered in one pass. However, when implementing my double-buffered technique for point lights, some problems arose. As a result, I changed the renderer to draw point lights as a series of six pyramidal volumes. This is how S.T.A.L.K.E.R. drew point lights, at least in Clear Sky. There was also a problem with NVidia cards not being able to read from a color cubemap unless it had mipmaps. Think for a moment about that, and you can probably guess where I am going with this...
Now SM3 and 4 cards will use the same render routine for rendering point lights. SM3 hardware may be a bit faster, because the unwrapped flat cubemap texture coordinates took a lot of logic to figure out, but I don't think it will make any significant difference either way.
I talked earlier about separating geometry into "static" and "dynamic" objects, and how the engine gained massive savings by only redrawing dynamic objects, unless otherwise needed. I took the concept a bit further, and decided to allow a light to cast shadows from static or dynamic geometry, or both. Consider the image below. The fan is in motion, but only about 1000 shadow polys have to be drawn to update the shadow:
The large spot light projected through the fan blades is the dominant light, but the point light above the fan also casts shadows. If you look carefully, you may notice the oildrum in the foreground is not casting a shadow from the point light. The point light is set to only cast shadows from static geometry, so it never has to be redrawn (unless you move a static object in the editor). Because there are more dominant lights in the area, the viewer probably won't notice this technical error. This allows you place extra point or spot lights throughout a scene to create more detailed static lighting. The shadows will never be redrawn, and you can use them together with fully dynamic lights to create more lighting detail, without the cost of rendering more shadows.
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