iPhone上的OpenGL：ES-Texture2D大小和显示问题

Question

I'm having issues with Texture2D and I'd like to understand how to use it better.

I've taken the Crashlander Texture2D class from here and a default OpenGL project in XCode 4, forcing it to load OpenGL ES1.1

First, a conceptual question. The size on the Texture2D init method is clearly an OpenGL size, but what relation to the OpenGL world does the fontSize parameter have?

Second, debugging. The result I get from the code below is a black (Or whatever colour I set in glColor) square where the text should be.

Here's the changes I've made in my code:

- (void)awakeFromNib
{
    EAGLContext *aContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES1];

    if (!aContext) {
        aContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES1];
    }

    self.labelAtTheTop = [[[Texture2D alloc] initWithString:@"Some Text" dimensions:CGSizeMake(1, 1) alignment:UITextAlignmentLeft fontName:@"Helvetica" fontSize:14.0f] autorelease];

    if (!aContext)
        NSLog(@"Failed to create ES context");
    else if (![EAGLContext setCurrentContext:aContext])
        NSLog(@"Failed to set ES context current");

    self.context = aContext;
    [aContext release];

    [(EAGLView *)self.view setContext:context];
    [(EAGLView *)self.view setFramebuffer];

    animating = FALSE;
    animationFrameInterval = 1;
    self.displayLink = nil;
}

- (void)drawFrame
{
    [(EAGLView *)self.view setFramebuffer];

    // Replace the implementation of this method to do your own custom drawing.

    glClearColor(0.5f, 0.5f, 0.5f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);
    glEnableClientState(GL_VERTEX_ARRAY);
    glEnable(GL_TEXTURE_2D);
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glColor4f(0.0f, 0.0f, 0.0f, 1.0f);
    glPushMatrix();
    glLoadIdentity();
    [self.labelAtTheTop drawAtPoint:CGPointMake(0, 0)];
    glPopMatrix();
    glDisable(GL_COLOR_MATERIAL);
    // Disable modes so they don't interfere with other parts of the program
    glDisableClientState(GL_TEXTURE_COORD_ARRAY);
    glDisableClientState(GL_VERTEX_ARRAY);
    glDisable(GL_TEXTURE_2D);
    glDisable(GL_BLEND);                


    [(EAGLView *)self.view presentFramebuffer];


}

Answer 1

Crashlander is really an old code base, so I would suggest avoiding it. There is a perfectly good 2D engine for the iPhone called Cocos2D http://www.cocos2d-iphone.org/ . About the code, try commenting glDisable(GL_COLOR_MATERIAL); plus glColor4f(0,0,0,1); actually represents black color, try commenting this too. I think fontSize is the size of font in screen points.

[EDIT]

If you want to learn something about OpenGLES here is a good intro tutorial http://iphonedevelopment.blogspot.com/2009/05/opengl-es-from-ground-up-table-of.html