Aperion
Refactoring slidenodes, drivetrain, and framework
by , 01-28-13 at 10:53 PM (3388 Views)
Since I've been doing some coding I thought I'd share what I'm working on. First and foremost my goal right now is to rework the drive-train code, this includes the tires. But I am sort of taking a round about approach to this which includes some pretty heavy refactoring. I've written a lot of concept code in the past for a new drive-train but never put it to use. I also wrote it in a reusable manner and am expanding this design.
History
The drive-train code I did write works on it's own, it just needed to be integrated into RoR. The new drive train code is built on the same principle as RoR, nodes and beams. Instead of nodes and beam in a 3 dimensional space we have nodes and beams in a 1 dimensional space. replace position with angle, velocity with moment, and force with torque and you have the same equations. This is where I started.
So I am basically building a parallel "world" for the drive train that works similar to nodes and beams. My starting point was going to be the wheels, since they essentially act like the gate way between the node/beam world and the drive-train world. My approach here is to simulate a drive-train wheel object which is nothing more than an an angle, then calculate where the nodes should be positioned based on that angle. While I was working on this, I realized that this is drive-train same concept I'm using for slide nodes: calculate where a node should be, calculate beam-like forces from where the node is, and where the node should be and distribute forces appropriately. So I started hacking away at some concept that I could use for both when I dawned on me that I had already written this code a long time ago for the drive train.
Theory
So here is a bit about my theory behind the drive-train code, and what will most likely be used in many many more places than the drive-train. As I've worked in the BeamForcesEuler routine I've realized that it boils down to two actions, updating the forces that act on a node, and updating the nodes position. I call them sources, and sinks; sources generate/calculate the forces based on the environment and are applied to the sinks, the sinks take the forces and decide what to do with them. In RoR terms sources are beams, engine, wings, commands, collisions, etc, etc, and sinks are nodes.
One of the cool ideas I will be able to introduce with this new idea is per-node integrators, I feel this will be handy because some weight/spring combinations are not stable but would be if a different integration method is used.
Way Forward (aka the plan)
- Replace slidenode code with outside drive-train code
- Refactor current wheel calculation
- Rewrite current drive-train to make use of new code
- Add new drive train features
Replace slidenode code with outside drive-train code
I'm doing this first because it's an existing system so I will be able to just test out the new code against existing slide node behavior to tell if it is working. This will be the biggest change all other items will make use of the concepts implemented here.
Refactoring this code will also have the added benefit of slide node damping since it's already built into the code I will be integrating.
Refactor current wheel calculation
Current wheels aren't very reliable, we average the speed of each node to calculate the rotation of the wheel, this is subject to fluctuation. Instead I will have one object that represents the wheel as a whole, it acts more like a traditional tire model in a game where it's simply a cylinder. This is very similar to slidenodes is that there is an ideal state, and a state the wheels actually are at.
I'm expecting this to help solve a few issues RoR currently faces such as vehicles slipping down a slop when they should be braked. Also under this approach folding wheels should be a thing of the past.
Rewrite current drive-train to make use of new code
Make sure the current drive train code works and behaves as is with the new wheel model, and make use of new code to perform drive train calculations. The current code is a bit of a mess and there is a bug where the first two axles are locked together but none others, this should solve that problem.
Add new drive train features
Multiple engines, torque converters, clutches, lockers, limited slip, multiple gear boxes, transfer-case, brakes, etc
My goal here is to model any and all kinds of different power, be it a traditional engine and 4 wheels, a parallel hybrid with two different engine types, or a helicopter with one engine powering two different rotors. Or who knows what. I want to flip over a car, spin one wheel with the mouse and watch the other wheel spin in the opposite direction when using an open diff. the best part IMO is that I've already got some of this working. I've test locked, open, and LS diffs. I've tested with one power source, and I've tested with two power sources.
And Beyond!
I plan on using this framework throughout RoR, hoping to achieve better performance, multiprocessor support, more organized, and easier to alter.
I'm excited
My work and progress is viewable here: http://sourceforge.net/u/aperion/rig...0fd7a443/tree/
What I will be using for much of my refactoring is here: http://sourceforge.net/u/aperion/rig...ics/framework/
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