Canvas 3D viewer's perspective

Question

I am working on rendering a 3D world in a 2D space. I found this article: https://en.m.wikipedia.org/wiki/3D_projection . In the perspective projection sub-category, it talks about "the viewer's position relative to the display surface" which is represented by e. Where is e. Is it where the viewer is looking ( the center of the screen), the viewer's actual position relative to the screen(if so how this is gotten), or something completely different?

Answer 1

Position of e depends of coordinate system (space) we consider to be the camera in. In world space e has different coordinates, in view space or screen space it is always located at the origin.

But the thing is that in computer graphics there's no such thing as camera (same as viewer, eye, e from your article), so transforming (rotating, translating or scaling) the camera actually means applying the appropriate transformations for the whole scene just with opposite values. for instance to rotate the camera around y axis by alpha radians you should rotate the scene around same axis by -alpha radians, thus camera always stays in the same position therefore emulating real world camera where scene stays in the same position but camera keeps transforming.