Photoshop  CS4 Extended - Lights on a 3D Layer
© 2009 Robin Wood
This is the second movie in this tutorial, and deals with lighting in Photoshop CS4 Extended. If you’ve been following along, you already have your model open. If you don’t, you might want to do that. If you don’t know how, please watch the first movie.
You can set the lights, and the other properties of the 3D layer, in the 3D Palette. If you don’t have it visible in your  Layout, you can find it under Window > 3D, right at the top.
There are sections for several things. The one for lights is here on the far right. 
You can edit them in the scene panel too, but I think it’s easier to have them isolated, especially when you’re beginning.
From here you can add lights, delete them, change the type or color, and move them around.
First, let’s change the color of Infinite Light 2, which is the one that’s lighting up the model in this case.
We can do that in one of two ways.
We can use the slider, here, to increase the intensity of the light, like this. But it’s easy to get it too bright, as you can see, so let’s undo that.
We can click on the color swatch, here, and set the light to white. Let me move the color picker so you can see. Now click on white. There we go. That looks good, so let’s leave it at that.
We’re going to change the other two default lights, too, so I can show you something in the next movie.
First, we’ll change Light 1 to yellow. You can’t see the color picker, but you know what I’m doing.
And light 3 to blue.
You can add new lights by clicking on the New icon here at the bottom of the panel.
It looks like the New icon in most of the rest of Adobe’s panels, so it’s easy to spot.
You can delete them with this trash icon, of course.
The Lights Toggle, here next to the New icon, lets you see markers that show you where your lights are pointing.
That makes it easier when you’re moving them around, like this.
You can get the tools to move the lights from the left side of the panel, here.
For now, though, we’ll just toggle all that off, so the lines and things don’t distract us.
Now, the thing about lights is that they cause shadows. It’s possible, when you are painting on a mesh, that you won’t want any shadows at all.
Fortunately, it’s easy to make them all go away, and have flat illumination.
To do so, just go to 3D > Render Settings. (This will be available if a 3D layer is selected.)
That opens a dialog.
We’re not going to go into most of this now; that can wait for another tutorial.
But if you go to this first section, and change the Face Style to Unlit Texture, here in the drop down menu, you will have an utterly shadowless canvas, with no coloring from any of your lights, to paint on. (It’ll act like Full Bright, in Second Life, if you’re familiar with that.) You can leave all the rest of this just as it is.
For now, I'm going to change the Face Style back to Solid, so I can show you some other things.
Once you have the mesh set up just the way you like it, Save it as a .psd file. That way, you’ll be able to open it at any time, and all this work will already be done. You’ll be able to just start painting!