[chbot] Scene description language for GPU's - a project failure

[Mark Atherton]

Thanks Geoffrey.

quote of the day "and a touch of the nightmare that is the web 
development ecosystem"

-Mark

On 12/06/2020 9:23 PM, Geoff wrote:
> Hey all,
>
> I recently discovered that the power of a modern GPU allows 
> brute-forcing constructive solid geometry 
> <https://en.wikipedia.org/wiki/Constructive_solid_geometry> (aka how 
> CAD programs work) on a per-pixel basis. As I know a bit of GLSL, I 
> endeavoured to create a small CAD program.
>
> For those who know nothing about a GPU: you can treat it like a CPU 
> with a thousand cores, with the caveat that all the cores are 
> performing the same instruction at the same time. Typically you write 
> a "shader" program that gets executed for a region on the screen.
>
> My idea was to define primitives (box, sphere), transformations 
> (translate, rotate) and boolean operations (union, intersect, 
> difference) in a declarative language. For example, you may say:
>
>   * Create An Entity
>   * Move the entity 3 units along the X axis
>   * The entity is a box
>   * The entity should be joined to the existing entities with a
>     "difference" operation
>
> A mini version you can play with is available online here: 
> https://www.shadertoy.com/view/ttXcWH
> The scene description begins on line 52.
>
> Unfortunately I couldn't get the system performant enough to be 
> useful. I think this is because of the (by shader standards) high 
> amount of memory fetches required, or perhaps the instruction cache is 
> getting hammered? (There is zero information on the size of the 
> instruction cache on modern GPU's).
>
> Anyway, there's a random failure that failed. If I could be bothered 
> continuing with making a CAD program, I'd probably dynamically 
> generate the shader. This would be slower when you edit the scene (as 
> it would have to recompile the shader), but would be faster on execution.
>
> If nothing else, I learned a bunch of Rust, WebAssembly and WebGL and 
> a touch of the nightmare that is the web development ecosystem. Full 
> project repository https://github.com/sdfgeoff/sdf_designer_failed
>
> Geoffrey
>
>
>
>
>
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