What's the proper way to limit css3d sprite's width and height on screen

Questions
1

I use orbitontrols to zoom in/out the scene,but it can make sprites too big on screen.
I want to give my sprites maxlimits,like:
if it’s width(actual width,the one you get by using getBoundingClientRect), is over 50%of the width
of the screen ,then the sprites won’t get bigger even i zoom in .
I’ve tried this,manage the element of mesh.
1.const computedStyle = window.getComputedStyle(sprite.element);
const transform = computedStyle.transform;
const scale = getScaleFromMatrix(transform);
2.next time when the sprites is too big ,i use these:
sprite.element.style.transform = scale3d(${scale.scaleX}, ${scale.scaleY},${scale.scaleZ});
3.but it can make the sprites not face my screen,not in the right position