Good evening twitter

I have raymarched an Orb

Hello everyone

Now I have raymarched The Absence of an Orb

Hello again

As you have no doubt surmised, I have now raymarched a Vast Profusion of Orbs

For real though; pick a few colors that look nice together and use those for all your graphics tests. Makes boring experiments look cool

This was supposed to be a fisheye projection but uh

There are some super weird fish though so hey maybe

What If M. C. Escher Had Very Little Idea What He Was Doing

Raymarching has super interesting artifacts. Surfaces start attracting/interfering with each other at acute view angles

Don't understand the technique deeply enough to know exactly what causes this/how to fix it but not sure I want to right now

Oh okay I figured it out: To keep a cap on execution time, algo limits to how many steps it'll march before giving up. If a ray passes

super close to a surface but doesn't quite hit it, the step size ends up super tiny and you expend all remaining steps before getting

any significant distance past the surface. So curved surfaces end up with a halo of unresolved pixels around their edges

Cool!

Have seen some stuff on shadertoy that doesn't have this problem so I guess a solution exists

I guess as a last resort temporal filtering could fix it in most cases. Overkill for my purposes though

The camera code in the tutorial I started with is total garbage but my attempts at writing my own are proving... interesting

Hey this looks correct

*increases fov*

Hmm

If nothing else, raymarching bugs are certainly more interesting than vertex shader bugs

Hmmmm

Weird thought: Hypothetically, an alien brain could make perfect sense of these images

They contain the same information as a "normal" perspective image; the projection's just totally different from what we're used to

The worst part is when I actually get this working it'll look like a totally normal render instead of all this cool weirdness

Okay here we go; finally got fisheye projection working

Told you it wouldn't look as cool as the bugs

Also added some dither fog which helps a lot with differentiating surfaces

Forgot to do the make-one-pixel-transparent-to-force-twitter-to-use-PNG trick for most of these so jpeg's kinda pooping on the dithering :(

Greetings once again

At last, the image you have waited for: A Vast Profusion of Orbs in Five-Point Perspective

Wait crap I screwed up the gif export it was supposed to have shading but now it already has RTs

It was supposed to look like this

540-DEGREE FIELD OF VIEW

SUCK IT GAMERS

I should point out that this is literally impossible with normal game rendering. Games use a pinhole projection, which is linear

Side effect is you can't render a fov larger than 180 degrees. Even if you set it to 1000 in the ini and post a screenshot on reddit. 180

This is why I get IRRATIONALLY ANGRY when people refer to the distortion from wide fovs in games as "fisheye"

FISHEYE IS A COMPLETELY DIFFE

The distortion in a game with 180 fov is so bad specifically because it's NOT fisheye. Can't curve straight lines so it loses its mind

"loses its mind" is the formal term mathematicians use to describe things that involve the asymptote of the tangent function, btw

(this also means gaming on curved monitors or wraparound multi-monitor rigs is Dumb. You're not fixing the distortion; you're *adding more*)

(if you want to use multiple monitors to view a wider in-game fov they need to be flat on the wall perpendicular to your view to be correct)

(assuming you sit 2 feet away, for a fov of 120 you need about a seven-foot wide monitor wall

160: 23 feet

170: 46 feet

Asymptotes!)

I guess this is too many tweets to be considered parenthetical anymore

In a similar way, fisheye is only distorted on flat displays

A curved monitor and a properly-calibrated fisheye projection would be perfect: All fovs <=360 supported with zero distortion

Problem is all the ways of doing fisheye in games are really complicated and have significant performance considerations

Also nobody makes ring-shaped 360-degree monitors

Ooh stereographic projection does really cool stuff at large angles

(earlier images were using equiangular)

So the term "fisheye" generically refers to any number of curvilinear perspective projections

My aim here has been to figure out a generic camera for raymarching where I can just plug in any old projection and see the result

And I have succeeded!

Currently going off this list:

Would like to find more expressed in that form

Will post shadertoy in a bit; gotta make the code at least vaguely readable first

Also "fisheye" is a dumb name; your actual human eyes see curvilinear perspective. Brain just interprets it flawlessly

Stand perpendicular in a hallway some time and stare at the wall. Can see it converge towards both vanishing points in peripheral vision

The part in front of you *looks* straight because Brain Stuff but you can force yourself to notice the curvature if you focus on periphery

Okay, it's done! Code for raymarching using various curvilinear perspective projections:

Looking forward to making tweets that aren't part of this three-day-long reply thread