I think that 3D is one of best features developers made for iGP Manager. There is some room for improvement of performance and visual, but currently I love it. I have some suggestions to how improve visual of 3D, these include:
Car model: put sponsor and supplier logos on car
Tyres: should be visibly distinguishable from one another (dry-weather tyres, intermediates and wet-weather tyres are already distinguishable by grooves, just add colour to rings at sides of tyres: supersoft=red, soft=yellow, medium=white, hard=orange, intermediate=green, full wet=blue).
Pit lane: add beginning of pit lane and end of pit lane lines, separate fast lane and inner lane (done on some tracks, but not on all) and put pit boxes
Grid: put grid boxes and increase distance between rows on grid
DRS: add DRS activation point markers and make DRS activation animation (Suspension movements, driver steering, tyre change, wheel rotation and steering are already animated, opening of rear wing flap shouldn't be any harder to do)