[sillysaurusx]

Whoaaa. If you look from the bottom up through the glass floor, it looks crazy awesome.

I think that's the most impressive little demo I've seen in ... quite some time. I can think of more impressive ones, but they're all extraordinarily complicated in comparison.

How'd you do the glass if there are no meshes? I'm about to pass out, else I'd dig in.

I'm especially curious how you're getting the refraction right. I forget my basic physics, but is it as simple as deflecting the ray slightly? But then how does it work on a curved surface? I guess it happens per pixel, so it shouldn't be too surprising, but... still, I was expecting a lot more aliasing than this: https://i.imgur.com/fdDVcCT.jpg

I guess I've never seen a real time raytracer that happened to trace through ripply glass, which is why it feels so neat.

[vikingerik]

The sibling comment explains it too, but here's a simple description: The object still has a geometric definition, it just isn't a mesh. It has equations describing the curves. Yes, per pixel, using the curve geometry, you calculate where the ray intersects that curve, and at what angle to figure out the deflection from there.

Think of a simplification in 2D. Sunlight comes from directly vertical above a sine wave. For every x-coordinate where you cast a sun ray, you just need the slope of the sine-wave at that x-coordinate to calculate the angle for what will happen at the intersection.

A mesh isn't any fundamental unit of physics or geometry, it's just our customary way of approaching the rendering to get good-enough fast-enough results from our current hardware.

[elihu]

Not the person you're replying to, but in general refraction is pretty easy to do in a ray tracer. When the ray hits the object you use the normal vector, the incident ray direction, and the index of refraction of the material (or materials, if you're transitioning from one substance to another with different index of refractions) to calculate the new ray direction and continue from there. Usually there's some amount of reflection, too (the amount varying based on the angle of the incoming ray with respect to the surface), so you might spawn two rays: one continuing through the object, and the other bouncing off.

What's much harder to do is simulating the light that's refracted or reflected off of objects (called "caustics"), like the light on the bottom of a swimming pool. To do that in a physically correct way generally requires falling back on some kind of global illumination technique like path tracing or photon mapping.

[otaviogood]

The geometry in my raytracer can either be ray-traced primitives, like spheres or boxes, or it can be "signed distance functions" (SDFs), which let you define all kinda of crazy shapes. Inigo Quilez does a good job of explaining SDFs here: https://www.iquilezles.org/www/articles/distfunctions/distfu... The refraction math in my code is around line 799 or 809 depending on what you're looking for. There are a few errors in the refraction code in this version. :/ But caustics are handled well by my renderer.

[trollied]

If you think that shader is impressive this one will blow your mind: https://www.shadertoy.com/view/3lsSzf