程序化星空生成器

Use a seeded PRNG so a text seed always yields the same sky. For each of the six cube faces, render into a framebuffer: first thousands of tiny point stars at random directions, then several additive nebula layers computed in a fragment shader from 3D fractal noise sampled by the view direction with a random colour and offset, then a handful of bright stars with soft radial falloff. Store the six textures as a cubemap and display it on a skybox the user can orbit, with an export button that saves each face.