Hello there, this is my first time in the forums.
Thanks for the Z-depth code - i'm wondering if i can use it for Animations without modifying
the Slick2D library? I'm now having my own version of Slick2D which supports glDepth for Animations.
I'm not even sure if i'm doing this the right way, but at least it is working.
I have modified files Graphics.java and Image.java.
Image.java is basically having same code than SortedImage.java, but function "public void draw(float x, float y, float width, float height, Color filter)" always draws using depth, which is taken from Y-axis (and this have been sufficient for me so far). If i don't want to use depth, then i just don't call startDepthUse().
Then i added startDepthUse() and endDepthUse() to Graphics.java so i can call g.startDepthUse() etc.
I hope that someday Slick2D has native support for Z-axis - at least i'm planning to use it a lot!

Oh and thanks for this great java library - i'm not yet building games with it, just fooling around and building my own test engine.