手动设置纹理动画时SKSpriteNode拉伸

I have a fairly simple animation with 8 identically sized images. I'm not using the built in animation methods as I want to manually control the speed of the animation on the fly. I'm using preloaded SKTexture's and doing [object setTexture:texture]; inside of the update:currentTime method.I have a fairly simple animation with 8 identic