Normalize strands noise output range to match JS noise()

[rakesh2OO5]

This PR normalizes the output range of the strands noise implementation to match the JavaScript noise() function.

Changes:

• Normalize GLSL backend output from [-1,1] to [0,1]
• Normalize WGSL backend output from [-1,1] to [0,1]

Tested:

• Verified GPU (WEBGL and WebGPU) noise output remains within [0,1]
• Matches CPU noise() output range

Fixes #8386

[rakesh2OO5]

CI is awaiting maintainer approval since this is from a fork — happy to update the branch if needed.

[davepagurek]

I think this works, although is there a reason for doing the normalization differently in the two files? It could be easier for people in the future comparing the implementations if we use the same math in both places.

[rakesh2OO5]

Good point — there’s no strong reason for them to differ. I used the equivalent forms out of habit, but I agree it’s better for readability and future comparisons if both backends use the same expression.

I have updated both GLSL and WGSL to use the same normalization math (e.g. (result + 1.0) * 0.5) and pushed a small follow-up commit.

Now , both backends use the same normalization expression for consistency — thanks for the suggestion!

[davepagurek]

Thanks, code looks good! I think the last step before merging is just to test out a build of this doing something similar to the sketch in the original issue. I can get to that eventually, but if you have time, that would also be great. If you run npm run build, then you can upload lib/p5.js to a p5 web editor sketch, and edit the html to have <script src="p5.js"></script> rather than the usual longer CDN link to p5.

[rakesh2OO5]

Tested using the original issue sketch in the p5 Web Editor with a custom built p5.js (loaded via local p5.js file).
Tested on Windows 11 / Chrome (WebGL2 enabled).
Both paths stay normalized and match numerically:

CPU noise range: 0.0119 → 0.4960

GPU (strands/shader) noise range: 0.0119 → 0.4960

Screenshot attached showing red (GPU), blue (CPU), and console output.

[davepagurek]

That looks great, thanks @rakesh2OO5!