Converting simplex noise values into a vibrant spectrum of colors

I'm attempting to generate a 256x256 heightmap using simplex noise. The simplex noise function produces values ranging from -1 to 1, and I'm struggling to convert these values into grayscale for my canvas.

    import { SimplexNoise } from "three/examples/jsm/math/SimplexNoise";

    const ctx = document.createElement("canvas").getContext("2d");
    ctx.canvas.width = 256;
    ctx.canvas.height = 256;

    const simplex = new SimplexNoise();
    for(let y = 0; y < ctx.canvas.width; y++) {
        for(let x = 0; x < ctx.canvas.width; x++) {
            let noise = simplex.noise(x, y);
            noise = (noise + 1) / 2;
            ctx.fillStyle = `rgba(0, 0, 0, ${noise})`;
            ctx.fillRect(x, y, 1, 1)
        }
    }

The current approach is not working as expected, and I'm unsure how to properly translate the noise value into a suitable color representation for rendering on the canvas. Any assistance or guidance on this matter would be greatly appreciated!

Answer №1

To modify the opacity of a black color, it is recommended to convert noise into grayscale. This can be achieved by adjusting the R, G, and B components to values ranging from 0 to 255, treating the noise value as a percentage. For instance, you can obtain the absolute value of the noise and multiply it by 255 while setting the opacity to 1:

import { SimplexNoise } from "three/examples/jsm/math/SimplexNoise";

const ctx = document.createElement("canvas").getContext("2d");
ctx.canvas.width = 256;
ctx.canvas.height = 256;

const simplex = new SimplexNoise();
for(let y = 0; y < ctx.canvas.width; y++) {
    for(let x = 0; x < ctx.canvas.width; x++) {
        let noise = simplex.noise(x, y);
        noise = (noise + 1) / 2;
        let color = Math.abs(noise) * 255;
        ctx.fillStyle = `rgba(${color}, ${color}, ${color}, 1)`;          
        ctx.fillRect(x, y, 1, 1)
    }
}

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