How to get Z values from Z Buffer

I'm having problems with drawing in OpenGL and I need开发者_运维问答 to see exactly what values are being placed in the depth buffer. Can anyone tell me how to retrieve these values? Thanks Chris

---

Use glReadPixels with format = GL_DEPTH_COMPONENT, for example:

float depth;
glReadPixels(0, 0, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &depth);

Will get the depth of pixel (0, 0).