CODEWITHSUNDEEP
objective-ciosopengl-esglkit
Fonix
Fonix

Reputation: 11597

GLKBaseEffect prepareToDraw GL ERROR: 0x0501

So ive been doing some iphone development with some OpenglES in it, but i am getting a rather weird error when i call prepareToDraw on my effect. My program in short simulates dice rolling (trying to learn objective-c and opengl). The program works fine for the most part, i can use everything ive programmed my app to do (with its bugs in the physics but ill fix that later). The problem comes in after ive used the part that contains the OpenGL.

The program contains 2 menu's you have to go through in order to reach the screen that is using OpenGL, once you have used the apps OpenGL part and go back to the previous menu, then try go back to the OpenGL part again, i get a print out saying GL ERROR: 0x0501. ive narrowed it down to be caused by the prepareToDraw method from my effect. The other weird part about it, is if i go back, then forward again, the OpenGL works again, and can be repeated again and again for it to be working and breaking every second time you go into the OpenGL part.

I've been searching around for similar problems to mine, but each time its got something to do with loading textures that are not a power-of-two texture, which doesnt help me because im not even using textures yet, just colored vertices.

ive pastebin'd my two code files where the problem should lie

Dice.m: http://pastebin.com/ze1DEEzs in the draw method you'll see my printouts have narrowed down where the problem lies, which is the prepareToDraw method. (line 308)

RollViewController.m: http://pastebin.com/VycwAh3R this file is where i setup the effect and the context etc, so i must be doing something wrong in here to cause the prepareToDraw method to mess up every 2nd time i run the OpenGL part of the program. i have a feeling it has something to do with not letting go some kind of resource to do with the context and the effect, but i cant find anything about deleting context and effect (probably because you dont need to but im not sure).

I hope there is someone out there that has run into the same problem and can answer my question and i hope its not just a silly mistake because ive been trying to solve this for a while now :)

thanks

Upvotes: 3

Views: 1844

Answers (2)

user371260
user371260

Reputation: 71

The error seems general and might be because of different issues. I avoided it(for now) by not using mipmaps. I commented the following code I had and don't have the error anymore.

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,GL_LINEAR_MIPMAP_NEAREST); glGenerateMipmap(GL_TEXTURE_2D)

Upvotes: 0

Fonix
Fonix

Reputation: 11597

After much pain and suffering i finally found a fix to the problem. Im not exactly sure why this is a problem, but creating the context within the OpenGL part (aka RollViewController.m) is not the way to do it. Instead you should create it once throughout the lifetime of your program and just set your current context for your glkview to be the context you have made. Maybe someone can enlighten me why recreating the context is a bad idea.

In my code i have a profile object that gets passed around between views and menu's so that they can all communicate with the same data, so i just defined a public context within my profile object so that everything can get access to the context instead of creating their own (and breaking).

Upvotes: 10

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