Understanding camera() settings in Processing
As the documentation describes it, it looks like each group of three parameters is a vector in 3D space. The first three are the position of the “eye”, the next three are the position it’s looking at, and the last three are the “up vector”, i.e. the direction of an arrow pointing out of the top (…sort of—more detail below) of the eye. The positions aren’t related to the size of your display window—the view of your 3D geometry from the camera at that point will fill the display.

In other words, if you have a box centered at (0, 0, 0) that’s 1×1×1 units in size, then your camera should be positioned a few units away—say (2, 3, 4)—and looking roughly at the center of the box, i.e. (0, 0, 0). If the box is 100×100×100 instead, then the eye position should be on the same order of magnitude in distance, e.g. (200, 300, 400). The behavior of the up vector is a little more complicated to explain, but leaving it at (0,1,0) is fine for most purposes—it’s mostly there to help you avoid gimbal lock.