SDF Fractal Noise

I know very little gfx but so far I mostly saw SDFs used for accomplishing stuff in fragment shader that would otherwise be done with geometry, kind of as a workaround for limitation of shadertoy environment

Re: SDF Fractal Noise

#7

Post by monk_e_boy » Tue, Jul 13, 2021, 9:03 AM UTC

It's an interesting and very clever technique. But those landscapes don't look real in any sense. They look like painted clouds. Uncanny valley? Maybe not even that close to reality.

Re: SDF Fractal Noise

#8

Post by frabert » Tue, Jul 13, 2021, 9:10 AM UTC

anentropic wrote: post #6

This is fascinating. Can someone help me understand why SDF-only techniques are valuable (aside from being interesting in their own right)? I know very little gfx but so far I mostly saw SDFs used for accomplishing stuff in fragment shader that would otherwise be done with geometry, kind of as a workaround for limitation of shadertoy environment

I believe the reason is because they allow for efficient raytracing via a technique called raymarching, which requires a way for it to tell what's the minimum distance from a surface given any arbitrary point, hence the need for a SDF. Quilez has many examples of this technique on his site

Re: SDF Fractal Noise

#9

Post by anentropic » Tue, Jul 13, 2021, 9:12 AM UTC

frabert wrote: post #8

anentropic wrote: post #6

This is fascinating. Can someone help me understand why SDF-only techniques are valuable (aside from being interesting in their own right)? I know very little gfx but so far I mostly saw SDFs used for accomplishing stuff in fragment shader that would otherwise be done with geometry, kind of as a workaround for limitation of shadertoy environment

I believe the reason is because they allow for efficient raytracing via a technique called raymarching, which requires a way for it to tell what's the minimum distance from a surface given any arbitrary point, hence the need for a SDF. Quilez has many examples of this technique on his site

Ah, thank you!

Re: SDF Fractal Noise

#10

Post by tiborsaas » Tue, Jul 13, 2021, 9:14 AM UTC

anentropic wrote: post #6

This is fascinating. Can someone help me understand why SDF-only techniques are valuable (aside from being interesting in their own right)? I know very little gfx but so far I mostly saw SDFs used for accomplishing stuff in fragment shader that would otherwise be done with geometry, kind of as a workaround for limitation of shadertoy environment

One huge benefit is the way you describe them. It's very concise.

    // This is a sphere
    length(p) - size;

There are no polygons, just surfaces described with math. You can do operations with them, like addition, subtraction, deformation quite easily, which is also much more complex with polygon based 3D models.

https://iquilezles.untergrund.net/www/articles/distfunctions...