Show HN: Reverse perspective camera for OpenGL (Three.js)
3 months ago (github.com)
I've extended the standard OpenGL camera to allow smooth transition between normal perspective, orthographic, and reverse perspective projection. To demonstrate the effect, I built a demo using Three.js.
Reverse perspective can feel a bit disorienting at first, but this demo is meant to highlight a few of its interesting advantages:
1. An extended Dolly zoom effect. https://en.wikipedia.org/wiki/Dolly_zoom
You can think of it as an extrapolation of the classic Dolly zoom into negative space. It produces a cinematic sense of vertigo or sudden insight, and also lets you pull the camera back from an object without distracting the viewer with surrounding geometry.
2. A wider and more complete spatial view.
Near objects no longer obscure distant ones; the viewer can see both the façade of a building and what’s happening on its roof, or even behind it.
Code and details: https://github.com/bntre/reverse-perspective-threejs
Link to live demo linked on the github -> https://bntre.github.io/reverse-perspective-threejs/
Well that is just the right amount of nauseating, trippy and interesting
For an extra dose of nausea, there's also a cross-eye stereo version: https://bntr.planet.ee/temp/rp/
(Alt + mouse wheel changes the eye distance)
That's so cool! I want more cross-eye content.
this is really neat. going to try it out with a creative coding tool I've been playing with.
are there any performance considerations to consider here relative to standard three cameras (either perspective or orthographic) ?
No performance hit - it's just a custom projection matrix. The rest of the rendering pipeline works exactly the same as with a normal camera.
Makes me feel the z-test should be reversed in reverse perspective mode but maybe it would just be even weirder?
That seems like it's just normal perspective from the opposite direction.
Exactly. Reversing the z-test is one way to get a reverse-perspective effect, but it doesn't allow for a smooth transition between projections (like dolly zoom).