How can I go about learning to write a shader

Question

So here's the background:

I'm writing a game, just for my own amusement and education really. I've already come to the conclusion that XNA was the way to go for graphics, I've bought a couple of books, I've gotten basic game graphics going, and that's great.

Now I'm starting to get a little in-depth and I'm starting to need to do stuff not covered in my (beginner) books. In particular, I need to display a sprite using a mask. Actually, what I need to do is display a generic sprite with a different color for each player. After banging around on the web, it seems the way to go is to have a color texture (one for each player) which I display using the mask, then display the generic part of the sprite. This has to be done dynamically, i.e. at runtime because there are too many sprites to keep in memory if I try to generate all the permutations at startup.

So, I need to use a shader. Fine. I've downloaded a sample shader program, and managed to hit it with a hammer until it does something close enough to what I want so that I know I'm on the right track. And here, we come to my problem... I have no friggin' clue what I'm doing. While there are a lot of samples and such about shaders, no one ever actually explains what's going on. For instance, I can't find any real docs on Tex2D. I feel like the guys in Zoolander poking at the computer. So, my question (yes, I have a question) -- where is a good URL or what is a good book to take me from dumskie to reasonably competent to write a basic shader?

Answer 1

If you want to learn about XNA shaders, this resource might help you out:

http://forums.create.msdn.com/forums/t/27849.aspx

However, there may be an easier way to do what you described. The SpriteBatch.Draw method takes in a Color parameter which can be used to tint the color of your sprite's Texture2D. If you pass Color.White, there will be no tinting. If you pass Color.Blue, your sprite will be tinted blue.

Keeping this in mind, if you need multiple sprites rendered with different colors depending on the player, you could assign a color to each player, and when rendering the player's sprite, tint it with the player's color. Something like this:

SpriteBatch.Draw( Player.Texture,   // a Texture2D object depicting the player
                  Player.Location,  // where the Texture should be drawn
                  Player.Color );   // the color the tint the player's sprite

If you use a texture that looks like this:

All the white parts would be tinted blue, while black would be left alone. The various shades of gray would be tinted a darker blue.