I've got my single-pass multi-light shader working using phong illumination model. I also have another working lighting shader that does bump mapping, but this one only uses one light source at the moment. I've recently tried to blend the two together in order to get a single-pass multi-light shader that supports bump-mapping. However, Im running into difficulties when it comes to passing the interpolants required for each light source to the fragment shader. It was easy with the 1-light source version - Here's the structure that gets outputed by the vertex shader and received as input by the fragment shader (HLSL): struct vertexOutput { float4 hpos : POSITION; float2 baseCoords : TEXCOORD0; float2 lightmapCoords : TEXCOORD1; float3 viewDirTS : TEXCOORD2; // dir = Vertex to Camera float3 lightDirTS : TEXCOORD3; // dir = Vertex to Light }; TS stands for Tangent Space. Obviously, the only light-dependant interpolant is lightDirTS. Now the tricky part is modifying this to support more than one light. Ideally, instead of passing a single lightDirTS to the fragment shader, I'd like to pass an array of lightDirTS, with each entry corresponding to a different light source. Is there any clean way of doing this, or do I have to go lightDirTS1, lightDirTS2, lightDirTS3, etc..? How is this done in state-of-the-art engines? Also, Ive got another question related to multi-pass/single-pass lighting shaders. I'm planning on adding support for shadow mapping to my engine soon, and someone in another thread suggested that in this case it's better to have single-pass approach to lighting (as in, one light per shader pass). I remember the guy knew what he was talking about, but he didnt give a more detailed explanation. Can anyone provide more insights on this topic please? And as anyone doing graphics programming loves to show off their work, here are some of the most recent shots of my humble D3D engine that supports several quake formats: mastok_md5_4_HQ.jpg mastok_md5_5_HQ.jpg Thanks in advance for your help! [Edited by - Spk on January 31, 2007 9:30:44 AM]

There's indeed a limit on the number of interpolants you can provide to the fragment shader. The exact number must depend on the shader model or the hardware itself. I guess this is also why most single-pass multi-light shaders don't seem to be able to support more than 3-4 lights at the same time, depending on the extra techniques supported. The multi pass approach sounds a lot more flexible to me, but Im curious about how people get it working in a single pass.

This won't work here, the light sources Im using are dynamic, and the liighting parameters required by the bump map change on a per-pixel basis, so they definately need to go the "interpolant" way.

As xycsoscyx said, but you will need to TBN matrix inside the pixel shader, pass that to the pixel shader using 3 float4 TEXTURE fields and reassemble inside the ps. Have fun !!

Hello Spk. I've done something similar to what you're doing. I created a 3DS Viewer application that does multiple lights, bump mapping, and other things in a single pass.

The light data (positions, directions, colors, etc) are stored as effect parameters. Doing lighting in a single pass like this, on a per pixel basis, requires very long pixel shader instruction sequences, so the rendering only looks nice on shader model 3.0 hardware, though I do have a fallback for shader model 2.0 hardware that uses vertex lighting. The fallback looks pretty bad, as you might imagine.

I've posted the application with the full source code, so you may want to take a look at it. I'd be glad to answer any questions you have about the approach that I took for other aspects of the program.