You could also try the VP8 or 9 codecs made from images with alphas. that is also supported now using ffmpg4.
could you provide an example? please go to https://sheenyfile.com/posk-gallery/ to see what kind of effect I do not want. this effect is done with codecs. I need light projection effect correct projected on that corner according to topology. the code dosn’t allow me to manipulate the shader. I did it with wonderful software verge3d, which dosn’t support cookie. So know I try to adapt the script from yaustar to use it in verge3d and when I’ll be not succesful, I must build the model again and import that to playcanvas in case of using above script.
This is my reality 
Thank you guys for all your help. I am not a programmer. It is very difficult for me, to write the code.