GFXwithSDLPart3

GFX with SDL

Lesson 3: Sprites

by Marius Andra

Hello and welcome to this yet-another-tutorial. This lesson will be about the

things that most 2D games use - sprites. In a way sprites are like objects. I'm

background is simply a background - you can't touch it in any way. Sometimes

some sprites are parts of the background (eg: a sun that is moving/rotating, but

can't affect you in any way). Let's call them passive sprites. And let's call the

sprites that can affect the player (and the player itself) active sprites. In our little

sprite demo that we will create today, we won't seperate active and passive

sprites. Altough the vikings could very well be active sprites and the sun a

passive sprite. Active sprites need to collide with each other. And if a collision

occurs, respond. That's all called collision detection and response. More on it in a

future lesson. Besides being active and passive, sprites can also be animated or

non-animated. And all sprites can have the possibility to change their x and y

position), a blinking traffic light, a lighthouse, etc, etc.

This little statement will make some RGB value equal transparency:

Where surface is the surface you want to modify and r, g and b are the r, g, b of

do that simply replace SDL_SRCCOLORKEY with 0.

So, let's get coding the sprite classes.

{

So let's start with the sprite base class. It's called CSpriteBase. CSpriteBase

has one function, init() to initialize the class - load in all the frames.

CSpriteBase also has one pointer to the structure of type CSpriteFrame that

The init function is the core of the CSpriteBase class. init() takes one

from. init() then looks for the file "info" from that directory and reads in some

to init.

{

prints the output into a string, not the screen. We print the full location of the info

file into the string filename and then try to open it.

We'll then grab one line from the file into the string buffer. Since we know that

this is the first line of the file and that it starts with "FILES: nr", where nr is the

sscanf is just like scanf, only it gets the input from a string. We'll store the