A canvas radial gradient with two different centres paints a cone, not a soft blob

Fact

createRadialGradient(x0, y0, r0, x1, y1, r1) interpolates between two circles. When the centres differ and the start circle is not inside the end circle, the gradient is a cone between them: filling a whole rectangle with it paints a wedge or fan shape that runs off to the edge, not a round glow.

Why it matters

Procedural textures often scatter soft blotches by calling the function with fresh random numbers for each argument. Every blotch then becomes a sharp-edged fan, and on a tiled or 3D surface the fans read as lighting or shadow artifacts (faceted patches round objects), sending the debugging toward lights, shadow maps or reflections instead of the texture.

How to apply

For a soft round blotch, use one centre for both circles:

const cx = rand() * w, cy = rand() * h, r = 60 + rand() * 90;
const g = ctx.createRadialGradient(cx, cy, 0, cx, cy, r);

Offset the inner centre only on purpose (a highlight off to one side), and keep it inside the outer circle. When a 3D scene shows patches that survive turning off the environment light and the shadows, look at the textures next.