Where is the Scene in terms of the z-coordinate?

OpenGL OpenGL: Basic Coding
1

Simple question, I thought. But I found this:
http://profs.sci.univr.it/~colombar/html_openGL_tutorial/en/03basic_transforms_018.html

Is this accurate? Is the scene calculated at the near clipping?

Thanks for any help.

2

yes, that is how it works. the image (what you call scene) that is rendered is the one that is projected onto the near plane; anything in front of that plane is not rendered. anything behind the far plane is also no rendered.

3

You can think of it like this:
The 3d scene… exists…
Then you go with the camera frustum, you “cut” from the whole scene only what’s inside this frustrum and then you “squish” what you have in the frustrum onto the near “rectangle” (it’s not a plane, because a plane is infinite).
What you get is your image.

4

Ah thanks. I understand “how” the scene is rendered to my screen but I never knew that the near clipping was the plane by which screen coordinates are drawn. I’m not exactly sure if this helps me much yet but it has shun some more light on this.

Thanks.

5

well, actually that’s only part of the story. your near “plane” is more like a rectangle, that will be “stretched” inside whatever coords you pass to glViewport and then rasterised and pixel shaded :smiley: