after much thought about why the caustics effect is only showing on one side (for DAT file units) I came to the conclusion that the shader isn't 'interpreting' the normal map correctly. More specifically since the normal map is mirrored to the other side of the ship it will pose problems for the caustics pixel shader (upon looking at what the caustics pixel shader was doing I was correct). So I made some changes to the caustics pixel shader
Here's what I've done:
the pixel shader takes the light direction and the texel normal and does a dot product on them (both of these are vectors). It then throws this into a saturate function which just clamps the value to between 0 and 1. Do you see the problem??? I do. If the light direction and texel normal basically point in the same direction (texel is facing light) the dot product value will be > 0. If they point in basically opposite directions the dot product value will be < 0 (texel is facing away from light). Recall the saturate function clamps to between 0 and 1. Now since the normal map is mirrored on the other side of the ship, the side facing away from the light will always have a dot product value < 0 (the light direction is from the object to the light source not the other way around). PROBLEM
To fix this I made the pixel shader for the caustics check the dot product value and if it's < 0 then flip the light direction (so now the light source is coming from the other side of the unit). Now caustics are displayed on both sides of the ship
