Writing a GLKBaseEffect Substitute

Question

Recently, I've been trying to learn how to use OpenGL ES 2.0 and GLKit to create simple 2D games. I've been following this tutorial by Ray Wenderlich and it's been very helpful so far. However, upon profiling my project (and his) for leaks I found that GLKBaseEffect's prepareToDraw: (specifically, GLKShaderBlockNode's copyWithZone) is leaking everywhere - I'm using ARC, by the way. After searching around quite a bit it seems that this is a bug in GLKBaseEffect and that I can't do anything about it. Is this true? The only solution I've found suggested is scrapping GLKBaseEffect entirely.

If that's the case, I have to roll my own custom vertex and fragment shaders as a result. However, I have no idea how to do this. I would appreciate any resources or help on creating custom shaders and adapting the code in the above tutorial to use those instead.

Thank you very much for your time. :)

Looks like [this answer](http://stackoverflow.com/a/11642818/1354100) might be what you're looking for. — Bejmax, Jan 13 '13 at 04:49
@Bejmax Thanks. That might help if I can find a good tutorial on OpenGL ES 2.0 shaders tomorrow as well. I find it hard to get a good understanding just going through source. :) — Metabble, Jan 13 '13 at 05:28

score 1 · Answer 1 · answered Jan 13 '13 at 05:13

For starters, in XCode do File->New Project and select "OpenGL Game".

Run it if you choose, you get 2 cubes going around each other.

Take a look at shader.fsh and shader.vsh. In viewcontroller.m, examine compilerShader, linkProgram and validateProgram (these compile the shader).

Examining that sample app should be enough to get you "in the door" on how to get a shader running, and from that point forward search for some OpenGL ES 2.0 shader tutorials or check out some of sample apps in the Apple code library.

Note: Going from Apple's built-in easy effects to shaders is a significantly wide "canyon".

+1. I looked at them earlier and couldn't quite understand. It seemed a little convoluted given that they have two cubes, one using GLKit and one using custom shaders. It has been a long day though. I'll try examining Apple's template more thoroughly tomorrow. — Metabble, Jan 13 '13 at 05:24

score 1 · Accepted Answer · edited Jun 20 '20 at 09:12

Well, after a decent amount of procrastination, I decided to bite the bullet and just do it. The leaks are gone now, although it took me a while to get it working. I read through OpenGL ES 2.0 for iPhone, Chapter 4 and learned about vertex and fragment shaders along with how to compile them and link them. After understanding how it worked, I put the author's GLProgram helper class into my project to handle all the boilerplate stuff and got to work quickly. Then, I created two shaders, nearly identical to the ones found here.

I followed his instructions on getting the attribute and uniform locations and stored them in a structure, passing them all at once to my sprite objects as they were initialized. Then, when it came time to render I passed in all the information for my attributes as I had done earlier when I was using GLKBaseEffect; the only difference (aside from manually binding the texture to a texture unit) was that I had to pass in the modelviewMatrix and projectionMatrix uniforms in myself instead of setting a GLKBaseEffect property.

Writing a GLKBaseEffect Substitute

2 Answers2