OpenGL ES 2.0 - iOS -使用FBO渲染纹理

Question

根据教程:

" http://www.raywenderlich.com/4404/opengl-es-2-0-for-iphone-tutorial-part-2-textures "

和《Open GL ES 2.0 Programming Guide》这本书

我试图渲染一个场景到一个FBO纹理，然后渲染该FBO纹理在显示窗口。

我不知道为什么，但是我的屏幕是白的。

编辑1:白屏是由于在渲染循环中绑定深度缓冲区造成的。现在的问题是，在FBO纹理中渲染的立方体不会在屏幕上渲染。编辑2:更新代码并添加着色器文件 下面是我的代码:

OpenGLView.h:

#import <UIKit/UIKit.h>
#import <QuartzCore/QuartzCore.h>
#include <OpenGLES/ES2/gl.h>
#include <OpenGLES/ES2/glext.h>
@interface OpenGLView : UIView {
    CAEAGLLayer* _eaglLayer;
    EAGLContext* _context;
    GLuint _viewFrameBuffer;
    GLuint _colorRenderBuffer;
    GLuint _depthRenderBuffer;

    float _cubeCurrentRotation;
    GLuint _cubeTexture;
    GLuint _cubeVertexBuffer;
    GLuint _cubeIndexBuffer;
    GLuint _viewportSizedQuadVertexBuffer;
    GLuint _viewportSizedQuadIndexBuffer;
    GLuint _FBO;
    GLuint _FBOTexture;
    GLuint _FBODepthBuffer;
    // shaders
    // simple shader
    GLuint _simpleShaderProgram;
    GLuint _simpleVertexShader;
    GLuint _simpleFragmentShader;
    GLuint _positionSlot;
    GLuint _colorSlot;
    GLuint _projectionUniform;
    GLuint _modelViewUniform;
    GLuint _texCoordSlot;
    GLuint _textureUniform;
    // texture shader
    GLuint _textureShaderProgram;
    GLuint _textureVertexShader;
    GLuint _texturePositionSlot;
    GLuint _textureColorSlot;
    GLuint _textureTexCoordSlot;
    GLuint _textureTextureUniform;
}
@end

OpenGLView。m:

    //
//  OpenGLView.m
//  HelloOpenGL
//
//  Created by Ray Wenderlich on 5/24/11.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//
#import "OpenGLView.h"
#import "CC3GLMatrix.h"
@implementation OpenGLView
typedef struct {
    float Position[3];
    float Color[4];
    float TexCoord[2];
} Vertex;
#define TEX_COORD_MAX 1
const Vertex cubeVertices[] = {
    // Front
    {{1, -1, 0}, {1, 0, 0, 1}, {TEX_COORD_MAX, 0}},
    {{1, 1, 0}, {0, 1, 0, 1}, {TEX_COORD_MAX, TEX_COORD_MAX}},
    {{-1, 1, 0}, {0, 0, 1, 1}, {0, TEX_COORD_MAX}},
    {{-1, -1, 0}, {0, 0, 0, 1}, {0, 0}},
    // Back
    {{1, 1, -2}, {1, 0, 0, 1}, {TEX_COORD_MAX, 0}},
    {{-1, -1, -2}, {0, 1, 0, 1}, {TEX_COORD_MAX, TEX_COORD_MAX}},
    {{1, -1, -2}, {0, 0, 1, 1}, {0, TEX_COORD_MAX}},
    {{-1, 1, -2}, {0, 0, 0, 1}, {0, 0}},
    // Left
    {{-1, -1, 0}, {1, 0, 0, 1}, {TEX_COORD_MAX, 0}},
    {{-1, 1, 0}, {0, 1, 0, 1}, {TEX_COORD_MAX, TEX_COORD_MAX}},
    {{-1, 1, -2}, {0, 0, 1, 1}, {0, TEX_COORD_MAX}},
    {{-1, -1, -2}, {0, 0, 0, 1}, {0, 0}},
    // Right
    {{1, -1, -2}, {1, 0, 0, 1}, {TEX_COORD_MAX, 0}},
    {{1, 1, -2}, {0, 1, 0, 1}, {TEX_COORD_MAX, TEX_COORD_MAX}},
    {{1, 1, 0}, {0, 0, 1, 1}, {0, TEX_COORD_MAX}},
    {{1, -1, 0}, {0, 0, 0, 1}, {0, 0}},
    // Top
    {{1, 1, 0}, {1, 0, 0, 1}, {TEX_COORD_MAX, 0}},
    {{1, 1, -2}, {0, 1, 0, 1}, {TEX_COORD_MAX, TEX_COORD_MAX}},
    {{-1, 1, -2}, {0, 0, 1, 1}, {0, TEX_COORD_MAX}},
    {{-1, 1, 0}, {0, 0, 0, 1}, {0, 0}},
    // Bottom
    {{1, -1, -2}, {1, 0, 0, 1}, {TEX_COORD_MAX, 0}},
    {{1, -1, 0}, {0, 1, 0, 1}, {TEX_COORD_MAX, TEX_COORD_MAX}},
    {{-1, -1, 0}, {0, 0, 1, 1}, {0, TEX_COORD_MAX}},
    {{-1, -1, -2}, {0, 0, 0, 1}, {0, 0}}
};
const GLubyte cubeIndices[] = {
    // Front
    0, 1, 2,
    2, 3, 0,
    // Back
    4, 5, 6,
    6, 7, 4,
    // Left
    8, 9, 10,
    10, 11, 8,
    // Right
    12, 13, 14,
    14, 15, 12,
    // Top
    16, 17, 18,
    18, 19, 16,
    // Bottom
    20, 21, 22,
    22, 23, 20
};
const Vertex viewPortQuadVertices[] = {
    {{1, -1, 0}, {1, 1, 1, 1}, {TEX_COORD_MAX, 0}},
    {{1, 1, 0}, {1, 1, 1, 1}, {TEX_COORD_MAX, TEX_COORD_MAX}},
    {{-1, 1, 0}, {1, 1, 1, 1}, {0, TEX_COORD_MAX}},
    {{-1, -1, 0}, {1, 1, 1, 1}, {0, 0}}
};
const GLubyte viewPortQuadIndices[] = {
    0, 1, 2,
    2, 3, 0,
};
+ (Class)layerClass {
    return [CAEAGLLayer class];
}
- (void)dealloc {
    [_context release];
    _context = nil;
    [super dealloc];
}
- (id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self) {
        [self setupLayer];
        [self setupContext];
        [self setupDepthBuffer];
        [self setupRenderBuffer];
        [self setupFrameBuffer];
        [self setupFBOs];
        [self compileShaders];
        [self setupVBOs];
        [self setupDisplayLink];
        _cubeTexture = [self setupTexture:@"tile_floor.png"];
    }
    return self;
}
- (void)setupDisplayLink {
    CADisplayLink* displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(render:)];
    [displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
}
- (void)setupLayer {
    _eaglLayer = (CAEAGLLayer*) self.layer;
    _eaglLayer.opaque = YES;
}
- (void)setupContext {
    EAGLRenderingAPI api = kEAGLRenderingAPIOpenGLES2;
    _context = [[EAGLContext alloc] initWithAPI:api];
    if (!_context) {
        NSLog(@"Failed to initialize OpenGLES 2.0 context");
        exit(1);
    }
    if (![EAGLContext setCurrentContext:_context]) {
        NSLog(@"Failed to set current OpenGL context");
        exit(1);
    }
}
- (void)setupRenderBuffer {
    glGenRenderbuffers(1, &_colorRenderBuffer);
    glBindRenderbuffer(GL_RENDERBUFFER, _colorRenderBuffer);
    [_context renderbufferStorage:GL_RENDERBUFFER fromDrawable:_eaglLayer];
}
- (void)setupDepthBuffer {
    glGenRenderbuffers(1, &_depthRenderBuffer);
    glBindRenderbuffer(GL_RENDERBUFFER, _depthRenderBuffer);
    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, self.frame.size.width, self.frame.size.height);
}
- (void)setupFrameBuffer {
    glGenFramebuffers(1, &_viewFrameBuffer);
    glBindFramebuffer(GL_FRAMEBUFFER, _viewFrameBuffer);
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, _colorRenderBuffer);
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, _depthRenderBuffer);
}
-(void)setupFBOs {
    GLint maxRenderBufferSize;
    glGetIntegerv(GL_MAX_RENDERBUFFER_SIZE, &maxRenderBufferSize);
    GLuint textureWidth = self.frame.size.width;
    GLuint textureHeight = self.frame.size.height;
    if(maxRenderBufferSize <= textureWidth
       || maxRenderBufferSize <= textureHeight) {
            NSLog(@"FBO cant allocate that much space");
    }
    glGenFramebuffers(1, &_FBO);
    glGenRenderbuffers(1, &_FBODepthBuffer);
    glGenTextures(1, &_FBOTexture);
    glBindTexture(GL_TEXTURE_2D, _FBOTexture);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, textureWidth, textureHeight,
                 0, GL_RGB, GL_UNSIGNED_SHORT_5_6_5, NULL);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glBindRenderbuffer(GL_RENDERBUFFER, _FBODepthBuffer);
    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, textureWidth, textureHeight);
    glBindFramebuffer(GL_FRAMEBUFFER, _FBO);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, _FBOTexture, 0);
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, _FBODepthBuffer);
    GLuint status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
    if(status != GL_FRAMEBUFFER_COMPLETE) {
        NSLog(@"FBO is not complete :%u", status);
    }
}
- (GLuint)compileShader:(NSString*)shaderName withType:(GLenum)shaderType {
    NSString* shaderPath = [[NSBundle mainBundle] pathForResource:shaderName ofType:@"glsl"];
    NSError* error;
    NSString* shaderString = [NSString stringWithContentsOfFile:shaderPath encoding:NSUTF8StringEncoding error:&error];
    if (!shaderString) {
        NSLog(@"Error loading shader: %@", error.localizedDescription);
        exit(1);
    }
    GLuint shaderHandle = glCreateShader(shaderType);
    const char * shaderStringUTF8 = [shaderString UTF8String];
    int shaderStringLength = [shaderString length];
    glShaderSource(shaderHandle, 1, &shaderStringUTF8, &shaderStringLength);
    glCompileShader(shaderHandle);
    GLint compileSuccess;
    glGetShaderiv(shaderHandle, GL_COMPILE_STATUS, &compileSuccess);
    if (compileSuccess == GL_FALSE) {
        GLchar messages[256];
        glGetShaderInfoLog(shaderHandle, sizeof(messages), 0, &messages[0]);
        NSString *messageString = [NSString stringWithUTF8String:messages];
        NSLog(@"%@", messageString);
        exit(1);
    }
    return shaderHandle;
}
- (void)compileShaders {
    _simpleVertexShader = [self compileShader:@"SimpleVertex" withType:GL_VERTEX_SHADER];
    _simpleFragmentShader = [self compileShader:@"SimpleFragment" withType:GL_FRAGMENT_SHADER];
    _textureVertexShader = [self compileShader:@"TextureVertex" withType:GL_VERTEX_SHADER];
    _simpleShaderProgram = glCreateProgram();
    glAttachShader(_simpleShaderProgram, _simpleVertexShader);
    glAttachShader(_simpleShaderProgram, _simpleFragmentShader);
    glLinkProgram(_simpleShaderProgram);
    GLint linkSuccess;
    glGetProgramiv(_simpleShaderProgram, GL_LINK_STATUS, &linkSuccess);
    if (linkSuccess == GL_FALSE) {
        GLchar messages[256];
        glGetProgramInfoLog(_simpleShaderProgram, sizeof(messages), 0, &messages[0]);
        NSString *messageString = [NSString stringWithUTF8String:messages];
        NSLog(@"%@", messageString);
        exit(1);
    }
    glUseProgram(_simpleShaderProgram);
    _positionSlot = glGetAttribLocation(_simpleShaderProgram, "Position");
    _colorSlot = glGetAttribLocation(_simpleShaderProgram, "SourceColor");
    glEnableVertexAttribArray(_positionSlot);
    glEnableVertexAttribArray(_colorSlot);
    _projectionUniform = glGetUniformLocation(_simpleShaderProgram, "Projection");
    _modelViewUniform = glGetUniformLocation(_simpleShaderProgram, "Modelview");
    _texCoordSlot = glGetAttribLocation(_simpleShaderProgram, "TexCoordIn");
    glEnableVertexAttribArray(_texCoordSlot);
    _textureUniform = glGetUniformLocation(_simpleShaderProgram, "Texture");

    // Texture shader
    _textureShaderProgram = glCreateProgram();
    glAttachShader(_textureShaderProgram, _textureVertexShader);
    glAttachShader(_textureShaderProgram, _simpleFragmentShader);
    glLinkProgram(_textureShaderProgram);
    glGetProgramiv(_textureShaderProgram, GL_LINK_STATUS, &linkSuccess);
    if (linkSuccess == GL_FALSE) {
        GLchar messages[256];
        glGetProgramInfoLog(_textureShaderProgram, sizeof(messages), 0, &messages[0]);
        NSString *messageString = [NSString stringWithUTF8String:messages];
        NSLog(@"%@", messageString);
        exit(1);
    }
    glUseProgram(_textureShaderProgram);
    _texturePositionSlot = glGetAttribLocation(_textureShaderProgram, "texPosition");
    _textureColorSlot = glGetAttribLocation(_textureShaderProgram, "texSourceColor");
    glEnableVertexAttribArray(_texturePositionSlot);
    glEnableVertexAttribArray(_textureColorSlot);
    _textureTexCoordSlot = glGetAttribLocation(_textureShaderProgram, "texTexCoordIn");
    glEnableVertexAttribArray(_textureTexCoordSlot);
    _textureTextureUniform = glGetUniformLocation(_textureShaderProgram, "Texture");
}
- (void)setupVBOs {
    glGenBuffers(1, &_cubeVertexBuffer);
    glBindBuffer(GL_ARRAY_BUFFER, _cubeVertexBuffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(cubeVertices), cubeVertices, GL_STATIC_DRAW);
    glGenBuffers(1, &_cubeIndexBuffer);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _cubeIndexBuffer);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(cubeIndices), cubeIndices, GL_STATIC_DRAW);
    glGenBuffers(1, &_viewportSizedQuadVertexBuffer);
    glBindBuffer(GL_ARRAY_BUFFER, _viewportSizedQuadVertexBuffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(viewPortQuadVertices), viewPortQuadVertices, GL_STATIC_DRAW);
    glGenBuffers(1, &_viewportSizedQuadIndexBuffer);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _viewportSizedQuadIndexBuffer);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(viewPortQuadIndices), viewPortQuadIndices, GL_STATIC_DRAW);
}
- (GLuint)setupTexture:(NSString *)fileName {
    CGImageRef spriteImage = [UIImage imageNamed:fileName].CGImage;
    if (!spriteImage) {
        NSLog(@"Failed to load image %@", fileName);
        exit(1);
    }
    size_t width = CGImageGetWidth(spriteImage);
    size_t height = CGImageGetHeight(spriteImage);
    GLubyte * spriteData = (GLubyte *) calloc(width*height*4, sizeof(GLubyte));
    CGContextRef spriteContext = CGBitmapContextCreate(spriteData, width, height, 8, width*4, CGImageGetColorSpace(spriteImage), kCGImageAlphaPremultipliedLast);
    CGContextDrawImage(spriteContext, CGRectMake(0, 0, width, height), spriteImage);
    CGContextRelease(spriteContext);
    GLuint texName;
    glGenTextures(1, &texName);
    glBindTexture(GL_TEXTURE_2D, texName);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, spriteData);
    free(spriteData);
    return texName;
}
- (void)render:(CADisplayLink*)displayLink {
    glBindFramebuffer(GL_FRAMEBUFFER, _FBO);
    //glBindRenderbuffer(GL_RENDERBUFFER, _FBODepthBuffer);
    glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
    glEnable(GL_BLEND);
    glClearColor(255.0/255.0, 255.0/255.0, 255.0/255.0, 1.0);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glEnable(GL_DEPTH_TEST);
    glViewport(0, 0, self.frame.size.width, self.frame.size.height);
    glUseProgram(_simpleShaderProgram);
    // Cube draw in FBO
    CC3GLMatrix *projection = [CC3GLMatrix matrix];
    float h = 4.0f * self.frame.size.height / self.frame.size.width;
    [projection populateFromFrustumLeft:-2 andRight:2 andBottom:-h/2 andTop:h/2 andNear:4 andFar:1000];
    glUniformMatrix4fv(_projectionUniform, 1, 0, projection.glMatrix);
    CC3GLMatrix *modelView = [CC3GLMatrix matrix];
    [modelView populateFromTranslation:CC3VectorMake(sin(CACurrentMediaTime()), 0, -7)];
    _cubeCurrentRotation += displayLink.duration * 90;
    [modelView rotateBy:CC3VectorMake(_cubeCurrentRotation, _cubeCurrentRotation, 0)];
    glUniformMatrix4fv(_modelViewUniform, 1, 0, modelView.glMatrix);
    glBindBuffer(GL_ARRAY_BUFFER, _cubeVertexBuffer);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _cubeIndexBuffer);
    glVertexAttribPointer(_positionSlot, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0);
    glVertexAttribPointer(_colorSlot, 4, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLvoid*) (sizeof(float) * 3));
    glVertexAttribPointer(_texCoordSlot, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLvoid*) (sizeof(float) * 7));
    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, _cubeTexture);
    glUniform1i(_textureUniform, 0);
    glDrawElements(GL_TRIANGLES, sizeof(cubeIndices)/sizeof(cubeIndices[0]), GL_UNSIGNED_BYTE, 0);
    glBindFramebuffer(GL_FRAMEBUFFER, 0);
    // ---------------------------------------------------------------
    // FBO -> window
    glBindFramebuffer(GL_FRAMEBUFFER, _viewFrameBuffer);
    glBindRenderbuffer(GL_RENDERBUFFER, _colorRenderBuffer);
    glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
    glEnable(GL_BLEND);
    glClearColor(0.0/255.0, 0.0/255.0, 0.0/255.0, 1.0);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glEnable(GL_DEPTH_TEST);
    glViewport(0, 0, self.frame.size.width, self.frame.size.height);
    glUseProgram(_textureShaderProgram);
    glBindBuffer(GL_ARRAY_BUFFER, _viewportSizedQuadVertexBuffer);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _viewportSizedQuadIndexBuffer);
    glVertexAttribPointer(_texturePositionSlot, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0);
    glVertexAttribPointer(_textureColorSlot, 4, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLvoid*) (sizeof(float) * 3));
    glVertexAttribPointer(_textureTexCoordSlot, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex), (GLvoid*) (sizeof(float) * 7));
    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, _FBOTexture);
    glUniform1i(_textureTextureUniform, 0);
    glDrawElements(GL_TRIANGLES, sizeof(viewPortQuadIndices)/sizeof(viewPortQuadIndices[0]), GL_UNSIGNED_BYTE, 0);
    [_context presentRenderbuffer:GL_RENDERBUFFER];
    glBindFramebuffer(GL_FRAMEBUFFER, 0);
    glBindRenderbuffer(GL_RENDERBUFFER, 0);
}
@end

SimpleVertex。glsl:

attribute vec4 Position; 
attribute vec4 SourceColor; 
varying vec4 DestinationColor; 
uniform mat4 Projection;
uniform mat4 Modelview;
attribute vec2 TexCoordIn;
varying vec2 TexCoordOut;
void main(void) { 
    DestinationColor = SourceColor; 
    gl_Position = Projection * Modelview * Position;
    TexCoordOut = TexCoordIn;
}

TextureVertex。glsl:

attribute vec4 texPosition;
attribute vec4 texSourceColor;
varying vec4 DestinationColor;
attribute vec2 texTexCoordIn;
varying vec2 TexCoordOut;
void main(void) { 
    DestinationColor = texSourceColor;
    gl_Position = texPosition;
    TexCoordOut = texTexCoordIn;
}

SimpleFragment。glsl:

varying lowp vec4 DestinationColor;
varying lowp vec2 TexCoordOut;
uniform sampler2D Texture;
void main(void) {
    gl_FragColor = DestinationColor * texture2D(Texture, TexCoordOut);
}

Answer 1

我解决了这个问题，纠正了视图端口，没有在渲染循环中绑定深度缓冲区，感谢@FelixK !