您正在查看的示例没有深度缓冲区和用于 2D GL 的透视矩阵。请查看 aurioTouch 示例。在 EAGLView 类中，您会注意到实现深度缓冲区的选项。两者结合（因为 aurioTouch 没有实现着色器）应该可以更好地理解
我认为您的方法中的操作顺序导致了问题。
这是我在我的应用程序“Live Effects Cam”中使用的代码，它将实时相机作为 GL 纹理放置在形状上：
#define DEGREES_TO_RADIANS(__ANGLE__) ((__ANGLE__) / 180.0 * M_PI)
@interface GLView : UIView
{
@private
/* The pixel dimensions of the backbuffer */
GLint backingWidth;
GLint backingHeight;
EAGLContext *context;
/* OpenGL names for the renderbuffer and framebuffers used to render to this view */
GLuint viewRenderbuffer;
GLuint viewFramebuffer;
GLuint depthRenderbuffer;
/* OpenGL name for the sprite texture */
GLuint spriteTexture;
}
@property (readonly) GLint backingWidth;
@property (readonly) GLint backingHeight;
@property (readonly) EAGLContext *context;
- (void) drawView;
- (BOOL) createFramebuffer;
- (void) destroyFramebuffer;
+ (UIImage *) snapshot:(GLView *)eaglview;
@end
@implementation GLView
@synthesize backingWidth;
@synthesize backingHeight;
@synthesize context;
+ (Class) layerClass
{
return [CAEAGLLayer class];
}
- (id)init
{
self = [[super init] initWithFrame:CGRectMake(0.0, 0.0, 480.0, 640.0)]; // size of the camera image being captures
if ( self==nil )
return self;
// Set Content Scaling
//
if ( HIRESDEVICE )
{
self.contentScaleFactor = (CGFloat)2.0;
}
// Get our backing layer
//
CAEAGLLayer *eaglLayer = (CAEAGLLayer*) self.layer;
// Configure it so that it is opaque, does not retain the contents of the backbuffer when displayed, and uses RGBA8888 color.
//
eaglLayer.opaque = YES;
eaglLayer.drawableProperties = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithBool:FALSE], kEAGLDrawablePropertyRetainedBacking,
kEAGLColorFormatRGBA8, kEAGLDrawablePropertyColorFormat,
nil];
// Create our EAGLContext, and if successful make it current and create our framebuffer.
//
context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES1];
if(!context || ![EAGLContext setCurrentContext:context] || ![self createFramebuffer])
{
[self release];
return nil;
}
// Final View Settings
//
[self setOpaque:YES];
self.multipleTouchEnabled = YES;
self.backgroundColor = [UIColor clearColor];
[EAGLContext setCurrentContext:context];
glBindFramebufferOES(GL_FRAMEBUFFER_OES, viewFramebuffer);
glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
GLfloat zNear = 1.0;
GLfloat zFar = 1000.0;
GLfloat fieldOfView = 90; // Lens Angle of View
GLfloat size = zNear * tanf(DEGREES_TO_RADIANS(fieldOfView) / 2.0);
CGRect rect = CGRectMake( (CGFloat)0.0, (CGFloat)0.0, backingWidth, backingHeight);
glFrustumf(-size, size, -size / (rect.size.width / rect.size.height), size / (rect.size.width / rect.size.height), zNear, zFar);
glViewport(0, 0, backingWidth, backingHeight);
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
glEnable(GL_MULTISAMPLE);
glEnable(GL_LINE_SMOOTH);
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
glHint(GL_LINE_SMOOTH_HINT, GL_NICEST);
glHint(GL_POINT_SMOOTH_HINT, GL_NICEST);
glDisable(GL_ALPHA_TEST);
// Turn Translucent Textures: OFF
//
glDisable(GL_BLEND);
// // Turn Translucent Textures: ON
// //
// glEnable(GL_BLEND);
// glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
return self;
}
- (void) drawView
{
[context presentRenderbuffer:GL_RENDERBUFFER_OES];
}
- (BOOL)createFramebuffer
{
// Generate IDs for a framebuffer object and a color renderbuffer
//
glGenFramebuffersOES(1, &viewFramebuffer);
glGenRenderbuffersOES(1, &viewRenderbuffer);
glBindFramebufferOES(GL_FRAMEBUFFER_OES, viewFramebuffer);
glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer);
// This call associates the storage for the current render buffer with the EAGLDrawable (our CAEAGLLayer)
// allowing us to draw into a buffer that will later be rendered to screen whereever the layer is (which corresponds with our view).
//
[context renderbufferStorage:GL_RENDERBUFFER_OES fromDrawable:(CAEAGLLayer*)self.layer];
glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_COLOR_ATTACHMENT0_OES, GL_RENDERBUFFER_OES, viewRenderbuffer);
glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_WIDTH_OES, &backingWidth);
glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_HEIGHT_OES, &backingHeight);
// If this app uses a depth buffer, we'll create and attach one via another renderbuffer.
//
if ( YES )
{
glGenRenderbuffersOES(1, &depthRenderbuffer);
glBindRenderbufferOES(GL_RENDERBUFFER_OES, depthRenderbuffer);
glRenderbufferStorageOES(GL_RENDERBUFFER_OES, GL_DEPTH_COMPONENT16_OES, backingWidth, backingHeight);
glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_DEPTH_ATTACHMENT_OES, GL_RENDERBUFFER_OES, depthRenderbuffer);
}
if(glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES) != GL_FRAMEBUFFER_COMPLETE_OES)
{
NSLog(@"failed to make complete framebuffer object %x", glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES));
return NO;
}
return YES;
}
- (void) destroyFramebuffer
{
glDeleteFramebuffersOES(1, &viewFramebuffer);
viewFramebuffer = 0;
glDeleteRenderbuffersOES(1, &viewRenderbuffer);
viewRenderbuffer = 0;
if(depthRenderbuffer)
{
glDeleteRenderbuffersOES(1, &depthRenderbuffer);
depthRenderbuffer = 0;
}
}
+ (UIImage *) snapshot:(GLView *)eaglview
{
NSInteger x = 0;
NSInteger y = 0;
NSInteger width = [eaglview backingWidth];
NSInteger height = [eaglview backingHeight];
NSInteger dataLength = width * height * 4;
// Need to do this to get it to flush before taking the snapshit
//
NSUInteger i;
for ( i=0; i<100; i++ )
{
glFlush();
CFRunLoopRunInMode(kCFRunLoopDefaultMode, (float)1.0/(float)60.0, FALSE);
}
GLubyte *data = (GLubyte*)malloc(dataLength * sizeof(GLubyte));
// Read pixel data from the framebuffer
//
glPixelStorei(GL_PACK_ALIGNMENT, 4);
glReadPixels(x, y, width, height, GL_RGBA, GL_UNSIGNED_BYTE, data);
// Create a CGImage with the pixel data
// If your OpenGL ES content is opaque, use kCGImageAlphaNoneSkipLast to ignore the alpha channel
// otherwise, use kCGImageAlphaPremultipliedLast
//
CGDataProviderRef ref = CGDataProviderCreateWithData(NULL, data, dataLength, NULL);
CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
CGImageRef iref = CGImageCreate(width, height, 8, 32, width * 4, colorspace, kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast, ref, NULL, true, kCGRenderingIntentDefault);
// OpenGL ES measures data in PIXELS
// Create a graphics context with the target size measured in POINTS
//
NSInteger widthInPoints;
NSInteger heightInPoints;
if (NULL != UIGraphicsBeginImageContextWithOptions)
{
// On iOS 4 and later, use UIGraphicsBeginImageContextWithOptions to take the scale into consideration
// Set the scale parameter to your OpenGL ES view's contentScaleFactor
// so that you get a high-resolution snapshot when its value is greater than 1.0
//
CGFloat scale = eaglview.contentScaleFactor;
widthInPoints = width / scale;
heightInPoints = height / scale;
UIGraphicsBeginImageContextWithOptions(CGSizeMake(widthInPoints, heightInPoints), NO, scale);
}
else
{
// On iOS prior to 4, fall back to use UIGraphicsBeginImageContext
//
widthInPoints = width;
heightInPoints = height;
UIGraphicsBeginImageContext(CGSizeMake(widthInPoints, heightInPoints));
}
CGContextRef cgcontext = UIGraphicsGetCurrentContext();
// UIKit coordinate system is upside down to GL/Quartz coordinate system
// Flip the CGImage by rendering it to the flipped bitmap context
// The size of the destination area is measured in POINTS
//
CGContextSetBlendMode(cgcontext, kCGBlendModeCopy);
CGContextDrawImage(cgcontext, CGRectMake(0.0, 0.0, widthInPoints, heightInPoints), iref);
// Retrieve the UIImage from the current context
UIImage *image = UIGraphicsGetImageFromCurrentImageContext(); // autoreleased image
UIGraphicsEndImageContext();
// Clean up
free(data);
CFRelease(ref);
CFRelease(colorspace);
CGImageRelease(iref);
return image;
}
@end