gldrawelements bad access in xcode when used outside of GLKViewController - ios

Question

I'm pretty new to OpenGL ES, but all I'm trying to do is draw indexed vertices using glDrawElements in a Character class. I've gotten this to work before inside of my GLKViewController class, but when I tried creating a Character class which would perform its own rendering, I got nothing but BAD_ACCESS. Here is my Character class:
#import "Character.h"
#interface Character()
{
GLuint _vertexBuffer;
GLuint _indexBuffer;
GLuint _vertexArray;
}
#property(nonatomic, weak) GLKBaseEffect *effect;
#end
typedef struct {
float Position[3];
float Color[4];
} Vertex;
const Vertex Vertices[] = {
{{1, -1, 0}, {1, 0, 0, 1}},
{{1, 1, 0}, {0, 1, 0, 1}},
{{-1, 1, 0}, {0, 0, 1, 1}},
{{-1, -1, 0}, {0, 0, 0, 1}}
};
const GLushort Indices[] = {
0, 1, 2,
2, 3, 0
};
#implementation Character
- (id)initWithEffect:(GLKBaseEffect *)effect
{
if (self = [super init])
{
self.effect = effect;
[self setupGL];
}
return self;
}
- (void)setupGL
{
glGenVertexArraysOES(1, &_vertexArray);
glBindVertexArrayOES(_vertexArray);
glGenBuffers(1, &_vertexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(Vertices), Vertices, GL_STATIC_DRAW);
glGenBuffers(1, &_indexBuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _indexBuffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(Indices), Indices, GL_STATIC_DRAW);
glEnableVertexAttribArray(GLKVertexAttribPosition);
glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid *) offsetof(Vertex, Position));
glEnableVertexAttribArray(GLKVertexAttribColor);
glVertexAttribPointer(GLKVertexAttribColor, 4, GL_FLOAT, GL_FALSE, sizeof(Vertex), (const GLvoid *) offsetof(Vertex, Color));
glBindVertexArrayOES(0);
}
- (void)teardownGL
{
glDeleteBuffers(1, &_vertexBuffer);
glDeleteBuffers(1, &_indexBuffer);
}
- (void)render
{
self.effect.transform.modelviewMatrix = GLKMatrix4Translate(GLKMatrix4Identity, self.position.x, self.position.y, self.position.z);
self.effect.transform.modelviewMatrix = GLKMatrix4Rotate(self.effect.transform.modelviewMatrix, self.rotation, 0.0f, 0.0f, 1.0f);
[self.effect prepareToDraw];
glBindVertexArrayOES(_vertexArray);
glDrawElements(GL_TRIANGLES, sizeof(Indices) / sizeof(Indices[0]), GL_UNSIGNED_SHORT, 0);
}
#end
Then in ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
self.context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
GLKView *view = (GLKView *)self.view;
view.context = self.context;
character = [[Character alloc] initWithEffect:self.effect];
character.position = GLKVector3Make(self.view.bounds.size.width / 2, self.view.bounds.size.height / 2, 0.0f);
[self setupGL];
}
rendered using:
- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect
{
glClearColor(0.65f, 0.65f, 0.65f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
[character render];
}
I know it isn't something as simple as a miscalculation of byte-size or something because I've been at this for a couple days now.

Answer 1

Hard to say for sure on a quick read, but it looks like the problem is that you don't have a current GL context when you're setting up your VAO in -[Character setupGL].
Creating an EAGLContext object doesn't make it the current context. If the rest of the code in your view controller looks like that from the Xcode "OpenGL Game" template, ViewController doesn't set the current context until its own setupGL method, which you call only after calling into your Character class and its attempts to set up OpenGL ES resources.