Hi,

Is it possible to have a flexible number of say point lights in one effect (.fx/shader)?

With of course some sort of maximum.

I was thinking about the following approach:

- define max lights is 8 or 10

- effect includes float3 lightposition[max lights]

- effect includes float lightrange[max lights]

- set lightrange to 0.0 in the effect, set to needed value while processing shaders in my engine

- loop through max lights and if range != 0, calculate attenation in float att[8]

- add them all up at the end and voila, goal achieved

(or not?)

I'm using d3dxeffects and vs/ps 2.0 (or 3.0, also working).

I'm planning to develop my engine to 'push' max nr. of pointlights to the shader, based on spatial culling in the active scene/ viewpoint.

What are your thoughts on this?

So if you use a #define to set your limit, it's absolutely possible, though the branch may be a little costly. Especially in SM 2.0. Though it's definitely possible.

If you try and make the number of lights variable, (like passing in a shader constant for it), you may run into issues because the loop can't be unrolled.

It can definitely work! Though I'd still be abit worried about the branch, shaders in SM 3.0 aren't a big fan of them. It might be cheaper just to do the calculations with a "black" light.