[英]OpenGL ES 2.0 Texture mapped, but shows as black
我試圖讓我的紋理顯示在一個基本的OpenGL視圖(UIView的子類)中,但無論我使用哪種紋理,它都顯示為黑色。 我的觀點代碼如下:
@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
頂點着色器:
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);
}
我可以通過改變gl_FragColor的值來創建一個漸變,但我嘗試了幾種不同的紋理而且不知所措。
這可能取決於你的紋理不是2的冪(即512X512)的事實
一些OpenGL驅動程序以奇怪的方式對此做出反應,其他一些只是將紋理重新縮放到最接近2的大小。
從OpenGL黃金書中,您可以找到以下內容:
你可以在OpenGL Gold Book中找到一個很好的解釋,OpenGL ES 2.0:
在OpenGL ES 2.0中,紋理可以具有非冪二(npot)維度。 換句話說,寬度和高度不需要是2的冪。 但是,如果紋理尺寸不是2的冪,OpenGL ES 2.0確實對包裝模式有限制。 也就是說,對於npot紋理,包裝模式只能是GL_CLAMP_TO_EDGE,而縮小過濾器只能是GL_NEAREST或GL_LINEAR(換句話說,不是mip-mapping)。 擴展GL_OES_texture_npot放寬了這些限制並允許GL_REPEAT和GL_MIRRORED_REPEAT的包裝模式,並且還允許使用全套縮小過濾器對npot紋理進行mipmap。
我希望這有幫助。
干杯
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