Creating a Ray for a Click Location

void GetWorldRayFromClick(const Camera *camera, const Point& p, Ray *ray)
{
    // Get the viewport rect for the camera.
    const Rect& viewRect = camera->GetObject()->GetViewRect();
 
    // Normalize the click coordinates.
    float x = p.x / (float) viewRect.Width();
    float y = p.y / (float) viewRect.Height();
 
    // Cast a local ray from the camera.
    camera->CastRay(x, y, ray);
 
    // Transform the ray into world space.
    const Transform4D& cameraTransform = camera->GetNodeTransform();
    ray->origin = cameraTransform * ray->origin;
    ray->direction = (cameraTransform * ray->direction).Normalize();
 
    // Set the rest of the ray fields.
    ray->radius = 0.0F;
    ray->tmin = 0.0F;
    ray->tmax = 100.0F;   // Set to max distance ray will go.
}