Smoothly transition from orthographic projection to perspective projection?

Question

I'm developing a game that consists of 2 stages, one of these has an orthographic projection, and the other stage has a perspective projection.

Currently when we go between modes we fade to black, and then come back in the new camera mode.

How would I go about smoothly transitioning between the two?

Answer 1

There are probably a handful of ways of accomplishing this, the two I found that seemed like they would work the best were:

1. Lerping all the matrix elements from one matrix to the other. Apparently this works pretty well all things considered. I don't believe this transition will appear linear, though. You could try to give it an easing function instead of doing the interpolation linearly

2. A dolly zoom on the perspective matrix going to/from a near 0 field of view. You would pop from the orthographic matrix to the near 0 perspective matrix and lerp the fov out to your target, and probably be heavily tweaking the near/far planes as you go. In reverse you would lerp to 0 and then pop to the orthographic matrix. The idea behind this being that things appear flatter with a lower fov and that a fov of 0 is essentially an orthographic projection. This is more complex but can also be tweaked a whole lot more.