Major Work - Using other digital models (1 Viewer)

[Tony Stark]

So I'm making a blender animation for my major work, and I have used textures by other people (though in all instances I have changed the actual material, for example adding depth and such instead of a flat image). However, now there is a model I would like to use, but I'm not sure about the license and whether NESA would allow me to directly import it into my animation. It would only be on frame for a few seconds, however.

So, what type of rules/procedures are there for using other people's digital works in my own work? Would I have to get permission from the publisher, or include credits at the end, or am I not allowed?