OpenGL ES 2.0纹理映射，但显示为黑色

Question

我试图让我的纹理显示在一个基本的OpenGL视图（UIView的子类）中，但无论我使用哪种纹理，它都显示为黑色。 我的观点代码如下：

@implementation SymGLView

typedef struct {
    float Position[3];
    float Color[4];
    float TexCoord[2];
} Vertex;

const Vertex Vertices[] = {
    {{1, -1, 0}, {1, 0, 0, 1}, {0, 0}},
    {{1, 1, 0}, {0, 1, 0, 1}, {0, 1}},
    {{-1, 1, 0}, {0, 0, 1, 1}, {1, 1}},
    {{-1, -1, 0}, {0, 0, 0, 1}, {1, 0}}
};

const GLubyte Indices[] = {
    0, 1, 2,
    2, 3, 0
};

+ (Class)layerClass {
    return [CAEAGLLayer class];
}

- (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 {    
    GLuint framebuffer;
    glGenFramebuffers(1, &framebuffer);
    glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);   
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, _colorRenderBuffer);
    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, _depthRenderBuffer);
}

- (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 {

    GLuint vertexShader = [self compileShader:@"SimpleVertex" withType:GL_VERTEX_SHADER];
    GLuint fragmentShader = [self compileShader:@"SimpleFragment" withType:GL_FRAGMENT_SHADER];

    GLuint programHandle = glCreateProgram();
    glAttachShader(programHandle, vertexShader);
    glAttachShader(programHandle, fragmentShader);
    glLinkProgram(programHandle);

    GLint linkSuccess;
    glGetProgramiv(programHandle, GL_LINK_STATUS, &linkSuccess);
    if (linkSuccess == GL_FALSE) {
        GLchar messages[256];
        glGetProgramInfoLog(programHandle, sizeof(messages), 0, &messages[0]);
        NSString *messageString = [NSString stringWithUTF8String:messages];
        NSLog(@"%@", messageString);
        exit(1);
    }

    glUseProgram(programHandle);

    _positionSlot = glGetAttribLocation(programHandle, "Position");
    _colorSlot = glGetAttribLocation(programHandle, "SourceColor");
    glEnableVertexAttribArray(_positionSlot);
    glEnableVertexAttribArray(_colorSlot);

    _modelViewUniform = glGetUniformLocation(programHandle, "Modelview");

    _texCoordSlot = glGetAttribLocation(programHandle, "TexCoordIn");
    glEnableVertexAttribArray(_texCoordSlot);
    _textureUniform = glGetUniformLocation(programHandle, "Texture");
}

- (void)setupVBOs {

    GLuint vertexBuffer;
    glGenBuffers(1, &vertexBuffer);
    glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(Vertices), Vertices, GL_STATIC_DRAW);

    GLuint indexBuffer;
    glGenBuffers(1, &indexBuffer);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffer);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(Indices), Indices, GL_STATIC_DRAW);

}

- (void)render {
    glClearColor(0, 104.0/255.0, 55.0/255.0, 1.0);
    glClear(GL_COLOR_BUFFER_BIT);

    glViewport(0, 0, self.frame.size.width, self.frame.size.height);

    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, _floorTexture);
    glUniform1i(_textureUniform, 0);    

    glDrawElements(GL_TRIANGLES, sizeof(Indices)/sizeof(Indices[0]), 
                   GL_UNSIGNED_BYTE, 0);    

    [_context presentRenderbuffer:GL_RENDERBUFFER];
}


- (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_NEAREST); 

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, spriteData);

    free(spriteData);   

    return texName;    
}


- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];

    if (self) {        
        [self setupLayer];        
        [self setupContext];    
        [self setupDepthBuffer];
        [self setupRenderBuffer];        
        [self setupFrameBuffer];     
        [self compileShaders];
        [self setupVBOs];
        [self render];        
    }
    _floorTexture = [self setupTexture:@"tile_floor.png"];
    return self;
}


@end

顶点着色器：

attribute vec4 Position;

attribute vec2 TexCoordIn;
varying vec2 TexCoordOut;

void main(void) { 
    gl_Position = Position;
    TexCoordOut = TexCoordIn;
}

片段着色器：

varying lowp vec2 TexCoordOut;
uniform sampler2D Texture;

void main(void) { 
    gl_FragColor = texture2D(Texture, TexCoordOut);
}

我可以通过改变gl_FragColor的值来创建一个渐变，但我尝试了几种不同的纹理而且不知所措。

Answer 1

这可能取决于你的纹理不是2的幂（即512X512）的事实

一些OpenGL驱动程序以奇怪的方式对此做出反应，其他一些只是将纹理重新缩放到最接近2的大小。

从OpenGL黄金书中，您可以找到以下内容：

你可以在OpenGL Gold Book中找到一个很好的解释，OpenGL ES 2.0：

在OpenGL ES 2.0中，纹理可以具有非幂二（npot）维度。 换句话说，宽度和高度不需要是2的幂。 但是，如果纹理尺寸不是2的幂，OpenGL ES 2.0确实对包装模式有限制。 也就是说，对于npot纹理，包装模式只能是GL_CLAMP_TO_EDGE，而缩小过滤器只能是GL_NEAREST或GL_LINEAR（换句话说，不是mip-mapping）。 扩展GL_OES_texture_npot放宽了这些限制并允许GL_REPEAT和GL_MIRRORED_REPEAT的包装模式，并且还允许使用全套缩小过滤器对npot纹理进行mipmap。

我希望这有帮助。

干杯