My panel textures consist of just a generic noise texture for the surface structure, so they can be swapped out (or set up with different material properties) without effort. The labels and shadows are separate alpha-blended textures rendered on top of the panel background. The labels are rendered with standard diffuse material during daytime, and with emissive material and additive flag set when instrument illumination is switched on.
So, if I understand correctly, there are three textures:
the diffuse base texture,
a texture that applies shade, multiply blended, and
a texture that contains the labels and floodlights, which in daytime is multiply blended, and in nighttime is additive blended
Am I close?
How would you do transition from night to day, other textures ?
Basically, the night textures are controlled by the sunlight strength. During the day, the night textures are invisible, and the normal textures show. As the sun sets and gets weaker, the night textures begin to fade in, until the sun is gone. The reverse happens at sunrise.
I don't think there's a way to control the panel lights with a switch or keyboard shortcut (yet), so the lights automatically fade in and out with the sun.
Right now, I'm experimenting with two rendering methods, and I will be working on more as ideas arise.
1. The _emis texture contains only shadows, floodlit areas, and illuminated instruments and labels. This texture is multiplied with the diffuse texture and emissive material property at night to provide the output.
2. The _emis texture contains everything. This texture replaces the diffuse texture at night.