같은 픽셀에서 여러 물체중 어떤걸 표출할지 정하기 위해but not enough memory to store all objectray tracing 에서는 그냥 제일 가까운 거 찾음 camera to origin matrix composed with unit axis vectorfrustum to box box to unit box www.cs.ucr.eduhttps://www.cs.ucr.edu/~craigs/courses/2022-fall-cs-130/lectures/pipeline-transforms.pdf