I’m no expert, but in the amount of playing around I’ve done with it I found the decimate tool was no good for items that require accurate geometry. It seems best suited to more freeform meshes like high-poly human figures. I’m doing a much simpler model, and am thinking I should do all the LOD’s manually to get the best result. It’ll be much cleaner for not an awful lot of extra effort.
I recently modelled a locomotive driving wheel as a practice exercise, and found it was hard to avoid some tris between spokes and the rim. FWIW, I used a Bezier to get the curve between spokes and rim, then converted it to a mesh before joining it to the other components.
I am not sure that I am following all of your logic and modelling correctly based upon your posts here, but you seem to be having enormous problems in a number of areas. With regard to rigging the suspension and the engine, I have built a number of suspension systems for aircraft mainly, but the same principles apply. I have also built a transmission and engine model and have a successful method of rigging both gearboxes and engines. These are on my website and the WIP/Tutorials sections here on BlenderArtists. if they are any use to you you might like to find them either on WIP or via my website at:
I have not done a tutorial on the engine rig yet, but can post you a file with a basic V4 test piece in it, if you think this will help. For the lighting in Cycles render, you should investigate the use of HDRI backgrounds as Environment Textures, this will greatly help in the fields of shadows and reflections. Suspension systems are quite simple to rig once you have got your head around IK chains and Stretch-To constraints, I have to agree with you that many of the suspension system tutorials out there seem to miss the fundamentals and do not work reliably once you start to move the vehicle over a terrain. You will definitely need to understand Drivers, with conditional variables to get your car to respond to ground conditions, I can help further here if required. My tutorials are written not video and as such may be easier to follow.
Anyway, take a look at some of my work and let me know if you need some more explanations of the principles.
After fiddling with a lot of options an settings, I got my pogo stick to jump around a landscape. How do I limit the x and y movement better? I wrote ±0, but Bullet seems not to obey. I lately have read lots of stuff about physics engines, and theoretically Bullett must be one of the better ones. Is the GUI to blame?
Okay now I found the number of iterations. In physics there is only an override, which had no effect on my simulation. Under scene is the global setting. I went from 60 iterations/s to 1000/s and then it looked good. I dunno why blender places per object tabs and per scene tab in the same frame. Scene Frame and Object Frame. Each one with a physics tab. The Scene Tab in Blender 2.74 is very fragmentaded.
Camera = Optics
Units = Mechanics
Key Sets = StoryTelling
Color = Optics
Gravity = okay lots of mechanics here
Simplify = Performance optimization which can also be found in Render section
