使用 glReadPixels 映射内存中的纹理时发生崩溃

Question

我正在尝试使用 glReadPixels 映射内存中的纹理，以便能够使用 openGL 的不可变存储功能。

我正在使用延迟着色，所以我按如下方式准备 G-Buffer：

glGenFramebuffers(1, &_gBuffer);
glBindFramebuffer(GL_FRAMEBUFFER, _gBuffer);
glGenTextures(1, &_pos3dTex);
glBindTexture(GL_TEXTURE_2D, _pos3dTex);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA32F, width, height, 0, GL_RGBA, GL_FLOAT, NULL);
GLuint layout = glGetFragDataLocation(_progID, "positionTexture");
...
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0 + layout, GL_TEXTURE_2D, _pos3dTex, 0);
...
unsigned int attachments[1] = { GL_COLOR_ATTACHMENT0 + layout };
glDrawBuffers(1, attachments);

glGenRenderbuffers(1, &_rboDepth);
glBindRenderbuffer(GL_RENDERBUFFER, _rboDepth);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, width, height);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, _rboDepth);

然后我想在内存中映射我的纹理，这样我就可以使用不可变存储：

//Bind Data
glGenBuffers(1, &_pos3dPbo);
glBindBuffer(GL_PIXEL_PACK_BUFFER, _pos3dPbo);
//w*h*4 (Channels)*4(size of float)
glBufferData(GL_PIXEL_PACK_BUFFER,width*height*4* 4, 0, GL_STREAM_READ);
glBindBuffer(GL_PIXEL_PACK_BUFFER, 0);

glBindFramebuffer(GL_FRAMEBUFFER, _gBuffer);
glReadBuffer(GL_COLOR_ATTACHMENT0 + layout);
glPixelStorei(GL_PACK_ALIGNMENT, 4);//4 channels

glReadPixels(0, 0, width, height, GL_RGBA,GL_FLOAT,NULL);
glBindBuffer(GL_PIXEL_PACK_BUFFER, 0);

//Reading
glBindBuffer(GL_PIXEL_PACK_BUFFER, _pos3dPbo);
void* outPos3d = glMapBuffer(GL_PIXEL_PACK_BUFFER, GL_READ_ONLY);
glBindBuffer(GL_PIXEL_PACK_BUFFER, 0);

//Releasing 
glBindBuffer(GL_PIXEL_PACK_BUFFER, _pos3dPbo);
glUnmapBuffer(GL_PIXEL_PACK_BUFFER);
glBindBuffer(GL_PIXEL_PACK_BUFFER, 0);

我在 glReadPixels 函数之后得到一个 "Access Violation"。请问我做错了什么？

Answer 1

您在 glReadPixels 之前取消绑定您的 GL_PIXEL_PACK_BUFFER，因此 NULL 指针将相对于您的客户端内存地址 space 进行解释，并尝试复制那里的数据几乎肯定会导致崩溃。

使用 glReadPixels 映射内存中的纹理时发生崩溃

getting a crash while using glReadPixels to map texture in memory

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