适用于OpenGL离屏渲染上下文的初始化代码

说明

代码

h文件

#ifndef GL_GLCONTEXT_H
#define GL_GLCONTEXT_H
class GLContext {
public:
static bool init(int version=2);
static void destroy();
};
#endif

cpp文件

#include "GL/GLContext.h"
#include <assert.h>

#ifdef GL_BUILD_FOR_ANDROID
//适用于 Android 和其他使用 EGL 标准的平台
#include <EGL/egl.h>
static EGLContext gContext;
static EGLDisplay gDisplay;
static EGLSurface gSurface;
bool GLContext::init(int version)
{
gDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY);
EGLint majorVersion;
EGLint minorVersion;
eglInitialize(gDisplay, &majorVersion, &minorVersion);
EGLint numConfigs;
static const EGLint configAttribs[] = {
EGL_SURFACE_TYPE, EGL_PBUFFER_BIT,
EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
EGL_RED_SIZE, 8,
EGL_GREEN_SIZE, 8,
EGL_BLUE_SIZE, 8,
EGL_ALPHA_SIZE, 8,
EGL_NONE
};

EGLConfig surfaceConfig;
eglChooseConfig(gDisplay, configAttribs, &surfaceConfig, 1, &numConfigs);

static const EGLint contextAttribs[] = {
EGL_CONTEXT_CLIENT_VERSION, version,
EGL_NONE
};
gContext = eglCreateContext(gDisplay, surfaceConfig, NULL, contextAttribs);

static const EGLint surfaceAttribs[] = {
EGL_WIDTH, 1,
EGL_HEIGHT, 1,
EGL_NONE
};
gSurface = eglCreatePbufferSurface(gDisplay, surfaceConfig, surfaceAttribs);
eglMakeCurrent(gDisplay, gSurface, gSurface, gContext);
return true;
}

void GLContext::destroy()
{
eglMakeCurrent(gDisplay, EGL_NO_SURFACE , EGL_NO_SURFACE , EGL_NO_CONTEXT);
eglDestroyContext(gDisplay, gContext);
eglDestroySurface(gDisplay, gSurface);
eglTerminate(gDisplay);
gDisplay = EGL_NO_DISPLAY;
}
#else
/*适用于Mac平台*/
#ifdef __APPLE__
#include <OpenGL/OpenGL.h>
CGLContextObj gContext;
bool GLContext::init(int version)
{
CGLPixelFormatAttribute attributes[] = {
kCGLPFADoubleBuffer,
(CGLPixelFormatAttribute)0
};
CGLPixelFormatObj pixFormat;
GLint npix;

CGLChoosePixelFormat(attributes, &pixFormat, &npix);
assert(NULL!=pixFormat);

CGLCreateContext(pixFormat, NULL, &gContext);
CGLReleasePixelFormat(pixFormat);
assert(NULL!=gContext);
CGLSetCurrentContext(gContext);
return true;
}
void GLContext::destroy()
{
CGLReleaseContext(gContext);
}
#else
/*这个是以前用在Ubuntu系统中的，使用了glew以打开shader功能，适用于 XDisplay*/
#include <GL/glew.h>
#include <GL/glut.h>
#include <X11/Xlib.h>
#include <GL/glx.h>
static GLXContext gContext;
static Pixmap gPixmap;
static GLXPixmap gGlxPixmap;
static Display* gDisplay = XOpenDisplay(0);
bool GLContext::init(int version)
{
int fbcount;
static int visual_attribs[] = {
GLX_X_RENDERABLE    , True,
GLX_DRAWABLE_TYPE   , GLX_PIXMAP_BIT,
None
};
GLXFBConfig *fbc = glXChooseFBConfig(gDisplay, DefaultScreen(gDisplay),
visual_attribs, &fbcount);
int best_fbc = -1, best_num_samp = -1;

int i;
for (i = 0; i < fbcount; ++i) {
XVisualInfo *vi = glXGetVisualFromFBConfig(gDisplay, fbc[i]);
if (vi) {
int samp_buf, samples;
glXGetFBConfigAttrib(gDisplay, fbc[i], GLX_SAMPLE_BUFFERS, &samp_buf);
glXGetFBConfigAttrib(gDisplay, fbc[i], GLX_SAMPLES, &samples);
if (best_fbc < 0 || (samp_buf && samples > best_num_samp))
best_fbc = i, best_num_samp = samples;
}
XFree(vi);
}
GLXFBConfig bestFbc = fbc[best_fbc];
XFree(fbc);
XVisualInfo *vi = glXGetVisualFromFBConfig(gDisplay, bestFbc);
gPixmap = XCreatePixmap(gDisplay, RootWindow(gDisplay, vi->screen), 10, 10, vi->depth);
gGlxPixmap = glXCreateGLXPixmap(gDisplay, vi, gPixmap);
XFree(vi);
gContext = glXCreateNewContext(gDisplay, bestFbc, GLX_RGBA_TYPE, 0, True);
glXMakeCurrent(gDisplay, gGlxPixmap, gContext);
glewInit();
return true;
}

void GLContext::destroy()
{
glXMakeCurrent(gDisplay, 0,0);
glXDestroyContext(gDisplay, gContext);
glXDestroyGLXPixmap(gDisplay, gGlxPixmap);
XFreePixmap(gDisplay, gPixmap);
gDisplay = NULL;
XCloseDisplay(gDisplay);
}
#endif
#endif