Quirky colour and light behaviour

Something kinda silly I noticed last night, fooling around with a couple wood boxes.

I dunno if anyone else noticed this, but a prim set to material type 'light' (assuming you have local lighting turned on), will cast the colour of light corresponding to the colour of face 0 on the prim. So if I have a cube, colour the whole thing red except I make face 0 blue, it will cast only blue light. That looks very odd when I put two of these together end-to-end to hide the blue faces.

This also allows one to make 'unlit' objects, ie. those that 'glow in the dark' but don't cast any actual light. Just set face 0 to be black in colour; it won't throw any local lighting, but all the faces will be fully lit. Weird.

I hope that made some sorta sense. I'm too scatterbrained to make much more sense than that. Or I'm just crazy. Has anyone else observed this sorta thing?

which side is face 0?

the 0 side... silly mommie...

That's interesting. Back when "light glows" was enabled by default (1.2 and earlier I think) the glow color at least was the color of the most visible face.

I for one am glad each face does not cast its own light. What a performance-robber that would be.

However, I would think that the color of the cast light should be the average of all faces before applying textures. Eh well. Does the texture color play a role? For instance, the standard cube is colored white, but textured uh... woodish. What color is the light that's cast? Up until now I haven't really cared. heh.

I hope this is not a bug. It sounds like a neat effect.
Thanks for sharing.

Good questions.... Lindens??? AHEM???

Arti

I think it's a rather handy unexpected feature, instead of a bug.

As far as I'm aware, the texture placed on any prim is irrelevant, as far as local lighting goes. It only seems to care about what colour face 0 is, and casts that colour of light. So, interestingly, you could apply a pure black texture to a prim, but set its colour to white, and it would always appear completely black, but would illuminate its surroundings with white light.

The following bit of code will set face 0 on any prim to be pure white, if you need help finding which face is which.

default
{
     state_entry()
     {
          llSetColor( < 1, 1, 1 >, 0 ) ;
     }
}

Another bizarre thing that I never realized I could do before, as well, is change the transparency of individual sides of a prim. I suppose I should've clued in when llSetAlpha() has a parameter to determine which face to apply it to.

Also, for a cube, face 0 is the upwards facing side, for a freshly-created cube.

It was good to see you demo this yesterday in action, Cross.

Cheers.

Woot Ty!

Way cool, Cross.
Thanks for sharing