Direct modeling is cool and Fillet, Chamfer, Boolean some strong!
Moi to Shape is easy by SKP format inbetweener
Render of course SimLab Composer lite (free)
PS If you export as DAE to SKetchUP, seems there is a bug even both programs are in unity meter!
You must scale * 1000 in Shape before the exportation!
else you will have some faces no filled!
With free BricsCad Shape! (function Quick draw) :)
Draw 2-3 volumes Make a Snapshot - dupplicate / rotate / resize the few volumes on a PNG transparent background Image and drag & drop the result on my own little tricky free prog https://editor.p5js.org/Pilou/full/y1GHaBqyT
Put it inside MagicaVoxel + File2Vox by Zarbuz et voilà! :)