金属 - 符号距离函数中的相机旋转

Question

我正在学习this tutorial并获得此metal代码，并稍微改动以使用鼠标来控制相机的位置：

struct Ray {
    float3 origin;
    float3 direction;
    Ray(float3 o, float3 d) {
        origin = o;
        direction = d;
    }
};

struct Sphere {
    float3 center;
    float radius;
    Sphere(float3 c, float r) {
        center = c;
        radius = r;
    }
};

float distToSphere(Ray ray, Sphere s) {
    return length(ray.origin - s.center) - s.radius;
}

float distToScene(Ray r) {
    Sphere s = Sphere(float3(1.), 0.5);
    Ray repeatRay = r;
    repeatRay.origin = fmod(r.origin, 2.);
    return distToSphere(repeatRay, s);
}

kernel void compute(texture2d<float, access::write> output [[texture(0)]],
                    constant float &mouseX [[buffer(1)]],
                    constant float &mouseY [[buffer(2)]],
                    uint2 gid [[thread_position_in_grid]]) {
    int width = output.get_width();
    int height = output.get_height();
    float2 uv = float2(gid) / float2(width, height);

    uv = uv * 2.0 - 1.0;

    float3 camPos = float3(1000+mouseX*-0.05, 1000-mouseY*0.05, 1);

    Ray ray = Ray(camPos, normalize(float3(uv.x,uv.y, 1.)));
    float3 col = float3(0.);
    for (int i=0.; i<100.; i++) {
        float dist = distToScene(ray);
        if (dist < 0.001) {
            col = float3(1.);
            break;
        }
        ray.origin += ray.direction * dist;
    }
    float3 posRelativeToCamera = ray.origin - camPos;
    output.write(float4(col * abs((posRelativeToCamera) / 10.0), 1.), gid);
}

一切正常。现在，我想用鼠标旋转相机而不是位置。我从shadertoy.com做了一些研究，并将setCamera()代码转换为metal：

float3x3 setCamera( float3 origin,  float3 target, float rotation) {
    float3 forward = normalize(target - origin);
    float3 orientation = float3(sin(rotation), cos(rotation), 0.0);
    float3 left = normalize(cross(forward, orientation));
    float3 up = normalize(cross(left, forward));
    return float3x3(left, up, forward);
}

但是，我不知道如何注入我的代码以使其工作。

我该如何使其发挥作用？