uniform vec3 uForward;
uniform vec3 uRight;
uniform vec3 uUp;
uniform float uAspect;
uniform float uTanHalfFov;
uniform vec3 uRayJitter;
vec3 cameraRay(vec2 uv) {
    vec2 xy=((uv-uRayJitter.xy)*2.0-1.0)*uTanHalfFov;
    return normalize(uForward+uRight*xy.x*uAspect+uUp*xy.y);
}