Objective-C iOS-使用GLKit将图像渲染到屏幕上

Question

For the life of me, I can't render an image to the iPhone simulator screen. I've simplified my code as much as possible.

The following code is in ViewController.m, a class that extends GLKViewController and is also a GLKViewDelegate.

- (void)viewDidLoad {
    [super viewDidLoad];

    /*Setup EAGLContext*/
    self.context = [self createBestEAGLContext];
    [EAGLContext setCurrentContext:self.context];

    /*Setup View*/
    GLKView *view = [[GLKView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    view.context = self.context;
    view.delegate = self;
    view.drawableDepthFormat = GLKViewDrawableDepthFormat24;
    self.view = view;
}


- (void)glkView:(GLKView *)view drawInRect:(CGRect)rect {

    /*Setup GLK effect*/
    self.effect = [[GLKBaseEffect alloc] init];
    self.effect.transform.projectionMatrix = GLKMatrix4MakeOrtho(0, 320, 480, 0, -1, 1);

    glClearColor(0.5, 1, 1, 0.0);
    glClear(GL_COLOR_BUFFER_BIT);

    NSDictionary * options = [NSDictionary dictionaryWithObjectsAndKeys:
                          [NSNumber numberWithBool:YES],
                          GLKTextureLoaderOriginBottomLeft,
                          nil];
    NSError * error;
    NSString *path = [[NSBundle mainBundle] pathForResource:@"soccerball" ofType:@"jpg"];

    GLKTextureInfo * textureInfo = [GLKTextureLoader textureWithContentsOfFile:path options:options error:&error];
    if (textureInfo == nil) {
        NSLog(@"Error loading file: %@", [error localizedDescription]);
    }

    TexturedQuad newQuad;
    newQuad.bl.geometryVertex = CGPointMake(0, 0);
    newQuad.br.geometryVertex = CGPointMake(textureInfo.width, 0);
    newQuad.tl.geometryVertex = CGPointMake(0, textureInfo.height);
    newQuad.tr.geometryVertex = CGPointMake(textureInfo.width, textureInfo.height);

    newQuad.bl.textureVertex = CGPointMake(0, 0);
    newQuad.br.textureVertex = CGPointMake(1, 0);
    newQuad.tl.textureVertex = CGPointMake(0, 1);
    newQuad.tr.textureVertex = CGPointMake(1, 1);

    self.effect.texture2d0.name = textureInfo.name;
    self.effect.texture2d0.enabled = YES;

    GLKMatrix4 modelMatrix = GLKMatrix4Identity;
    modelMatrix = GLKMatrix4Translate(modelMatrix, 100, 200, 0);

    self.effect.transform.modelviewMatrix = modelMatrix;

    [self.effect prepareToDraw];

    long offset = (long)&(newQuad);

    glEnableVertexAttribArray(GLKVertexAttribPosition);
    glEnableVertexAttribArray(GLKVertexAttribTexCoord0);
    glVertexAttribPointer(GLKVertexAttribPosition, 2, GL_FLOAT, GL_FALSE, sizeof(TexturedVertex), (void *) (offset + offsetof(TexturedVertex, geometryVertex)));
    glVertexAttribPointer(GLKVertexAttribTexCoord0, 2, GL_FLOAT, GL_FALSE, sizeof(TexturedVertex), (void *) (offset + offsetof(TexturedVertex, textureVertex)));
    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
}

and some of the structs used...

typedef struct {
    CGPoint geometryVertex;
    CGPoint textureVertex;
} TexturedVertex;

typedef struct {
    TexturedVertex bl;
    TexturedVertex br;
    TexturedVertex tl;
    TexturedVertex tr;
} TexturedQuad;

Right now the only thing that is working is

glClearColor(0.5, 1, 1, 0.0);
glClear(GL_COLOR_BUFFER_BIT);

Which does adjust the background colour. There is no 'soccerball' image.

Any help is greatly appreciated.

EDIT - The TextureVertex CGPoints were incorrect so I fixed them. The problem still persists.

Answer 1

Solution:

The TexturedVertex struct must not use CGPoint, but rather GLKVector2.

This is because there is a conversion issue from the float values stored in these points. GLKit expects float values that have single point precision, but CGPoint float values have double point precision and things get weird. Furthermore, this problem only occurs after iOS 7.0

Refer to here for more detail on the issue. OpenGL ES Shaders and 64-bit iPhone 5S