Text with OpenGL

[krisix]

Hi,

I've created a project from default iPhone OpenGL project template. I'd like to place text on the view, so I'm trying to use Texture2D class provided by Apple.

In initWithCoder method I've added line:

testText = [[Texture2D alloc] initWithString:@"Test" dimensions:CGSizeMake(100, 100) alignment:UITextAlignmentLeft fontName:@"Helvetica" fontSize:30];

I've modified drawView method - it looks like this:

- (void)drawView {
    // Replace the implementation of this method to do your own custom drawing
    const GLfloat squareVertices[] = {
        -0.5f, -0.5f,
        0.5f,  -0.5f,
        -0.5f,  0.5f,
        0.5f,   0.5f,
    };
    const GLubyte squareColors[] = {
        255, 255,   0, 255,
        0,   255, 255, 255,
        0,     0,   0,   0,
        255,   0, 255, 255,
    };

    [EAGLContext setCurrentContext:context];

    glBindFramebufferOES(GL_FRAMEBUFFER_OES, viewFramebuffer);

/*    
    glViewport(0, 0, backingWidth, backingHeight);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrthof(-1.0f, 1.0f, -1.5f, 1.5f, -1.0f, 1.0f);

    glMatrixMode(GL_MODELVIEW);
    glRotatef(3.0f, 0.0f, 0.0f, 1.0f);

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

    glVertexPointer(2, GL_FLOAT, 0, squareVertices);
    glEnableClientState(GL_VERTEX_ARRAY);
    glColorPointer(4, GL_UNSIGNED_BYTE, 0, squareColors);
    glEnableClientState(GL_COLOR_ARRAY);

    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

*/

    glColor4f(1.0f, 1.0f, 1.0f, 1.0f);

    glEnable(GL_TEXTURE_2D);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    [testText drawAtPoint:CGPointMake(0.0f, 0.0f)];
         glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);


    glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer);
    [context presentRenderbuffer:GL_RENDERBUFFER_OES];

}

Could you help? I'm developing with OS 3.0. I've searched this forum for solution but everything I've found doesn't work for me. What am I doing wrong?

Thx

Krzychu

[Jamvert]

What is happening wrong? Is it compiling? Does it display anything? Does it crash when it start running?

Is the commented out part yours or the default stuff?


Also, I am not sure if you have already found it or not but if you are starting out OpenGL on iphone Simon Maurices Blog is really good: iPhone OpenGL ES Tutorial Series ?

[krisix]

Commented out part is default stuff - I've just removed it. The project is compiling fine but none text is displaying.

Thanks for the link - it's really useful!

Dou you have any idea what I'm doing wrong?

[kingbombs]

yeah you need to give information on what is going wrong
although calling the glBlendfunc twice won't help, although don't think it will really effect anything but remove them both and see what happens (not sure what the 2nd blendFunc is doing?)

[Jamvert]

It might be just cause I am not that good at openGL but I think it is very difficult to tell what you are doing wrong just from that.

For starters, some of the commented out code, starting with the glViewPort, do you have equivalent code somewhere else in your code or did you just eliminate it all together? You can throw away some of that stuff but some of it you need to do before you draw.

I don't know about the Texture2D class though, I can't find the documentation for it.

[Jamvert]

What might be easier is if you first just try to draw your text on top of Apples starting shape, then once you have you text drawing start removing apples stuff. That way you can break it down into smaller parts and have a better idea where things start going wrong.

[krisix]

Hi,

I've found solution Please check this page. You can download source code there.

Please take a look at setupView method and gluPerspective method. When I've implemented both methods in my code the text is on the screen!

Thx for help!

[kingbombs]

Originally Posted by kingbombs

yeah you need to give information on what is going wrong
although calling the glBlendfunc twice won't help, although don't think it will really effect anything but remove them both and see what happens (not sure what the 2nd blendFunc is doing?)

Originally Posted by gotorightway123

you need to give information on what is going wrong
although calling the glBlendfunc twice won't help, although don't think it will really effect anything but remove them both and see what happens (not sure what the 2nd blendFunc is doing?)

You quoted me directly without the quote tags? and didn't say anything else? (and without the 'yeah' at the start)

[smasher]

Originally Posted by kingbombs

You quoted me directly without the quote tags? and didn't say anything else? (and without the 'yeah' at the start)

I think gotorightway123 is a spambot pretending to be human. All his posts are quotes of previous posts.