Fisheye effect

[rostidev]

I think the formula is incomplete. How I know this? I've ported your demonstration code to C with SDL3 library and made it showing more than one object. In my case there is one penguin and eight cubes - all rotating together. I've also made it rotating round both xz and yz. With more objects the fisheye effect could be seen better.

To workaround the fisheye effect I added a focal distance factor:

point_t project(point3d_t p) {
    const float focal = 2.5f;  // Focal distance of virtual lens
    return (point_t){
        x: (p.x / p.z) * focal,
        y: (p.y / p.z) * focal
    };
}

You can find the whole code of this port in my GitHub: https://github.com/rostidev/formula

It looks like this: