glTranslatef / 2D视口设置问题

Question

当我尝试glTranslatef（1，-1,0）;它将我的四边形的左手角推到了屏幕的中心而不是我想要做的事情，向左移动1个像素，向下移动1个像素。我很确定这是因为我的视口没有正确设置，但我不确定为什么。 pic，查看下面的设置代码和绘图代码。

setupView函数：

-(void)setupView:(GLView*)view
 {
printf("setup view");
glClearColor(0,1,1, 1);
// Enable Smooth Shading, default not really needed.
glShadeModel(GL_SMOOTH);
// Depth buffer setup.
glClearDepthf(1.0f);


//enable textures.
glEnable(GL_TEXTURE_2D);
glHint(GL_PERSPECTIVE_CORRECTION_HINT,GL_FASTEST);
glEnable(GL_BLEND); 
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
CGRect rect = view.bounds;
glOrthof( 0,rect.size.width,-rect.size.height, 0, -1, 1 ) ;  
glViewport(0, 0,rect.size.width,rect.size.height);

glMatrixMode(GL_PROJECTION); 


// Bind the number of textures we need, in this case one.
glGenTextures(1, &texture[0]);
glBindTexture(GL_TEXTURE_2D, texture[0]);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_GENERATE_MIPMAP,GL_TRUE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glLoadIdentity();


NSString *path = [[NSBundle mainBundle] pathForResource:@"cm2" ofType:@"jpg"];
NSData *texData = [[NSData alloc] initWithContentsOfFile:path];
UIImage *image = [[UIImage alloc] initWithData:texData];

if (image == nil)
    NSLog(@"Do real error checking here");

GLuint width = CGImageGetWidth(image.CGImage);
GLuint height = CGImageGetHeight(image.CGImage);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
void *imageData = malloc( height * width * 4 );
CGContextRef context = CGBitmapContextCreate( imageData, width, height, 8, 4 * width, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big );

// Flip the Y-axis
CGContextTranslateCTM (context, 0, height);
CGContextScaleCTM (context, 1.0, -1.0);

CGColorSpaceRelease( colorSpace );
CGContextClearRect( context, CGRectMake( 0, 0, width, height ) );
CGContextDrawImage( context, CGRectMake( 0, 0, width, height ), image.CGImage );

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageData);

CGContextRelease(context);

free(imageData);
[image release];
[texData release];


 }

drawView函数：

- (void)drawView:(GLView*)view 
 {
 //draw calls

glColor4f(1,1,1,1);
glClear(GL_COLOR_BUFFER_BIT);

glLoadIdentity();

glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);

static const Vertex3D vertices[] = {
    {0, 0, 1}, //TL
    { 1024.0f,0, 1}, //TR
    {0, -1024.0f, 1}, //BL
    { 1024.0f, -1024.0f, 1}  //BR
};


static const GLfloat texCoords[] = {
    0.0, 1.0,
    1.0, 1.0,
    0.0, 0.0,
    1.0, 0.0
};
glTranslatef(1,-1, 1);
glScalef(scale,scale,1);

glBindTexture(GL_TEXTURE_2D, texture[0]);
glVertexPointer(3, GL_FLOAT, 0, vertices);
glTexCoordPointer(2, GL_FLOAT, 0, texCoords);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);

}

Answer 1

您需要先设置视口，然后将矩阵模式设置为投影，然后调用glOrtho，如下所示：

glViewPort (0, 0, width, height);
glMatrixMode (GL_PROJECTION);
glLoadIdentity ();
glOrtho (0, width, 0, height, -1, 1); // Usually this is -width/2,width/2,-height/2,height/2

此外，您可能希望在此之后将矩阵模式设置为ModelView以绘制模型。