SDF Fractal Noise • Hacker News Board

Re: SDF Fractal Noise

#11

Post by pasabagi » Tue, Jul 13, 2021, 9:15 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

If you want to generate textures which you then read at runtime, this kind of technique is very useful - for instance, imagine you want to create the normal map of a cloud, or create a height map to displace vertices with (for a procedural landscape).

Re: SDF Fractal Noise

#12

Post by twic » Tue, Jul 13, 2021, 9:23 AM UTC

> As Signed Distance Functions start making it into mainstream and commercial applications, it's important to find replacements or alternatives to common things artists used to do in polygon-land.

So are SDFs really going to replace polygons then? Is this for just the demoscene, or for some specific applications, or do experts think this is the future for all 3D graphics?

I know enough about SDFs to know that they are really cool, but i have no idea what the practical considerations are now, let alone likely to be in five years' time.

Re: SDF Fractal Noise

#13

Post by SonOfLilit » Tue, Jul 13, 2021, 9:30 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

It's an easy to use and general mathematical language for describing geometry. It lends itself easily to parametrization for things like procedural generation of infinite variations or for animation. And it is very "local" so requires O(1) memory to evaluate.

For a nonstandard use of the idea, see font rendering on the GPU with signed distance field textures:

https://aras-p.info/blog/2017/02/15/Font-Rendering-is-Gettin...

Re: SDF Fractal Noise

#14

Post by maeln » Tue, Jul 13, 2021, 9:38 AM UTC

twic wrote: post #12

> As Signed Distance Functions start making it into mainstream and commercial applications, it's important to find replacements or alternatives to common things artists used to do in polygon-land. So are SDFs really going to replace polygons then? Is this for just the demoscene, or for some specific applications, or do experts think this is the future for all 3D graphics? I know enough about SDFs to know that they ar…

It won't replace polygons. But it has been a very useful tool in the gfx programmer toolbox. It can be used for font/vector rendering, modelling / rendering complex shapes that are difficult to do using traditional modelling methods, and it has a lot of niche usages (I remember one talk about using some SDF to procedurally generates fakes).

Re: SDF Fractal Noise

#15

Post by enriquto » Tue, Jul 13, 2021, 9:38 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

> Can someone help me understand why SDF-only techniques are valuable

Out of computer graphics, I have used them a lot for modeling the evolution of curves and surfaces in a topologically-oblivious way. The terminology is slightly different (they go by silly names like "implicit snakes"), but it is the same thing. If you have ever used an "adaptive select" or "intelligent scissors" tool of a drawing program, it was probably implemented using this technique.

Re: SDF Fractal Noise

#16

Post by pxf » Tue, Jul 13, 2021, 10:02 AM UTC

SDFs are another tool. Very useful for content creation, for example, although there are still very few tools to create SDFs. You can't create SDFs in Blender for example. SDFs will be more used in the future, polygons are a mess... :) Games like Dreams (PS4 / PS5) make extensive use of SDFs

Re: SDF Fractal Noise

#17

Post by pxf » Tue, Jul 13, 2021, 10:07 AM UTC

Blender still does not support SDFs, but you can use MagicaCSG to play with SDFs https://ephtracy.github.io/index.html?page=magicacsg Also you can use my nodes at https://github.com/paulofalcao/MaterialMakerRayMarching for MaterialMaker for making procedural nodebased SDFs in Material Maker

Re: SDF Fractal Noise

#18

Post by anentropic » Tue, Jul 13, 2021, 10:08 AM UTC

pasabagi wrote: post #11

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

If you want to generate textures which you then read at runtime, this kind of technique is very useful - for instance, imagine you want to create the normal map of a cloud, or create a height map to displace vertices with (for a procedural landscape).

But using noise to generate textures isn't directly related to SDF (I think?)

from other replies I think the point here is there are no "vertices", i.e. no mesh geometry

Re: SDF Fractal Noise

#19

Post by dimatura » Tue, Jul 13, 2021, 10:18 AM UTC

Interestingly, SDFs have also become a widely used tool for analysis of 3D sensors such as lidar and RGBD (kinect, realsense). Specifically, truncated SDF's, which put an upper limit on the magnitude of function, which helps with outliers and makes the representation sparser. They're a nice way to summarize noisy range measurements in a way that makes it easy to extract surfaces for visualization/further processing. The technique has been out there for a while, going at least back to Curless' space carving paper in the 90s [1], but kinect fusion [2] made it a lot more popular in recent years.

[1] https://graphics.stanford.edu/papers/volrange/volrange.pdf

[2] https://www.microsoft.com/en-us/research/publication/kinectf...

Re: SDF Fractal Noise

#20

Post by tinus_hn » Tue, Jul 13, 2021, 10:23 AM UTC

Cool, but this looks like it’s really the same as the old side scrolling mountain landscape screensaver (which I can’t seem to find anymore).

Is it just a new technique to achieve the same?