opengl启动过程

Posted 2020-07-12 全绍辉

- (BOOL)loadShaders
{
GLuint vertShader, fragShader;
NSString *vertShaderPathname, *fragShaderPathname;

// Create shader program.
_program = glCreateProgram();

// Create and compile vertex shader.
vertShaderPathname = [[NSBundle mainBundle] pathForResource:@"Shader" ofType:@"vsh"];
if (![self compileShader:&vertShader type:GL_VERTEX_SHADER file:vertShaderPathname]) {
NSLog(@"Failed to compile vertex shader");
return NO;
}

// Create and compile fragment shader.
fragShaderPathname = [[NSBundle mainBundle] pathForResource:@"Shader" ofType:@"fsh"];
if (![self compileShader:&fragShader type:GL_FRAGMENT_SHADER file:fragShaderPathname]) {
NSLog(@"Failed to compile fragment shader");
return NO;
}

// Attach vertex shader to program.
glAttachShader(_program, vertShader);

// Attach fragment shader to program.
glAttachShader(_program, fragShader);

// Bind attribute locations.
// This needs to be done prior to linking.
glBindAttribLocation(_program, GLKVertexAttribPosition, "position");
glBindAttribLocation(_program, GLKVertexAttribColor, "color");
glBindAttribLocation(_program, GLKVertexAttribNormal, "a_normal");

// Link program.
if (![self linkProgram:_program]) {
NSLog(@"Failed to link program: %d", _program);

if (vertShader) {
glDeleteShader(vertShader);
vertShader = 0;
}
if (fragShader) {
glDeleteShader(fragShader);
fragShader = 0;
}
if (_program) {
glDeleteProgram(_program);
_program = 0;
}

return NO;
}

// Get uniform locations.
uniforms[UNIFORM_MODELVIEWPROJECTION_MATRIX] = glGetUniformLocation(_program, "modelViewProjectionMatrix");
uniforms[UNIFORM_NORMAL_MATRIX] = glGetUniformLocation(_program, "normalMatrix");
uniforms[UNIFORM_COLOR_MATRIX] = glGetUniformLocation(_program, "colorMatrix");
// Release vertex and fragment shaders.
if (vertShader) {
glDetachShader(_program, vertShader);
glDeleteShader(vertShader);
}
if (fragShader) {
glDetachShader(_program, fragShader);
glDeleteShader(fragShader);
}

return YES;
}

- (BOOL)compileShader:(GLuint *)shader type:(GLenum)type file:(NSString *)file
{
GLint status;
const GLchar *source;

source = (GLchar *)[[NSString stringWithContentsOfFile:file encoding:NSUTF8StringEncoding error:nil] UTF8String];
if (!source) {
NSLog(@"Failed to load vertex shader");
return NO;
}

*shader = glCreateShader(type);
glShaderSource(*shader, 1, &source, NULL);
glCompileShader(*shader);

#if defined(DEBUG)
GLint logLength;
glGetShaderiv(*shader, GL_INFO_LOG_LENGTH, &logLength);
if (logLength > 0) {
GLchar *log = (GLchar *)malloc(logLength);
glGetShaderInfoLog(*shader, logLength, &logLength, log);
NSLog(@"Shader compile log:\n%s", log);
free(log);
}
#endif

glGetShaderiv(*shader, GL_COMPILE_STATUS, &status);
if (status == 0) {
glDeleteShader(*shader);
return NO;
}

return YES;
}

- (BOOL)linkProgram:(GLuint)prog
{
GLint status;
glLinkProgram(prog);

#if defined(DEBUG)
GLint logLength;
glGetProgramiv(prog, GL_INFO_LOG_LENGTH, &logLength);
if (logLength > 0) {
GLchar *log = (GLchar *)malloc(logLength);
glGetProgramInfoLog(prog, logLength, &logLength, log);
NSLog(@"Program link log:\n%s", log);
free(log);
}
#endif

glGetProgramiv(prog, GL_LINK_STATUS, &status);
if (status == 0) {
return NO;
}

return YES;
}