GWR 81xx for OpenBVE

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GWR 81xx for OpenBVE

Post by leezer3 on Thu May 23, 2013 1:15 pm

So, I'm going to mostly parrot my own site here Laughing

This first release of the 81xx for OpenBVE represents the culmination of over 18 months worth of hard work.
Oddly enough, this all started when I looked at my steam locomotive
models for passing trains- I decided that they needed a 'little' work,
and started building this 81xx.
From there, things rather snowballed, and I've ended up with a result
which I think is probably among the most detailed locomotive models
currently available for OpenBVE!


Of course, no locomotive would be complete without a train to pull, and
so I've added into the mix a 10-wagon unfitted freight for her to pull,
again all built to a high detail standard.



Now available at my site Smile

Cheers

Chris Lees

http://www.bvecornwall.co.uk

leezer3

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Re: GWR 81xx for OpenBVE

Post by mrknowitall on Fri May 24, 2013 1:38 pm

Surprised no body has commented on this mate, I've been watching closely on your WIP shots and videos, its a truly amazing achievement to create something this technical, I spent many weeks trying the animation on the A4 and time after time i hit the 'wall' and had to re think the animation code, so will be interesting to have a look at just how you have gone about the animation for this, im downloading as i type this but well done anyway, it just shows with work as complex as this and hand mesh coding becoming more efficient from certain developers that OpenBVE is in no means dying, but actually starting to grow in terms of knowledge and technicality. will enjoy running this, well done.

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Re: GWR 81xx for OpenBVE

Post by Quork on Fri May 24, 2013 2:27 pm

I'll download it soon as well, looks promising, the question remains though, whether my computer will be able to run it anyway Laughing

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Re: GWR 81xx for OpenBVE

Post by mobile1 on Fri May 24, 2013 3:13 pm

Well done Chris, i`ve tried it and it runs well on my laptop, the time you`ve spent on this has been worth while, you`re understanding of the animation coding is up with the best, and i should know...anyway congratulations another good addition to our hobby...mobile1

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Re: GWR 81xx for OpenBVE

Post by leezer3 on Mon May 27, 2013 9:37 pm

mrknowitall wrote:Surprised no body has commented on this mate, I've been watching closely on your WIP shots and videos, its a truly amazing achievement to create something this technical, I spent many weeks trying the animation on the A4 and time after time i hit the 'wall' and had to re think the animation code, so will be interesting to have a look at just how you have gone about the animation for this, im downloading as i type this but well done anyway, it just shows with work as complex as this and hand mesh coding becoming more efficient from certain developers that OpenBVE is in no means dying, but actually starting to grow in terms of knowledge and technicality. will enjoy running this, well done.

When it came down to it, the animation wasn't actually that difficult, just time consuming.
The main motion is easy- All you need to do is a TranslateAll command at the end of each individual animation frame.
The connecting rod is a little bit more of a pain and should be built when the main motion is working correctly:
Assuming you're using a 32-frame animation, then take your piston stroke length and divide by 16, and build it so your piston moves out for the first 16, and in again for the second 16 frames.
When this works correctly, build your connecting rod, with the point where it pivots from the piston at 0,0,0
I found it easier to add use two cylinders to position the rod correctly- Add one sticking out from the main motion, and another slightly smaller one from the connecting rod.
A little trial and error with your RotateAll command should position the rod correctly.
Rinse and repeat 32 times Cool

You can either build the main motion, piston and pushrod as a single objects or separate objects, it makes no odds- I used one for the piston and pushrod and one for the main motion.
Walschaerts motion is doable as per the A4, just requires careful thought and a little excel coding- If you build yourself the right spreadsheet, it'll do most of the trigonometry for you, and all you need to do is shift the values into your object file.
Basically, remember that the connection point for the pushrod is also the pivot point for your eccentric crank. From there, if you get the travel distance of the link rod and do the same, you have the second point required to connect the eccentric crank.
You ought to be also able to work back from the travel of the link rod to get the appropriate motion for the radius bar.
Similarly, the travel of the piston should translate to the drop link and anchor link with some rotation tweaking.

It'll be a time-consuming pig to build, but it's eminently possible.
The other option would be to use 2D images for some of the motion (Drop link, anchor link and link rod I'd say), and just build the main motion, pushrod and piston in 3D.

Cheers

Chris Lees

http://www.bvecornwall.co.uk

leezer3

Posts : 749
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Re: GWR 81xx for OpenBVE

Post by kwijiboenator on Mon May 27, 2013 10:07 pm

Drove as per the instructions on your page, but after a few mins is just slows down and stops, and I can't seem to get it running again. It more or less looses momentum?

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Re: GWR 81xx for OpenBVE

Post by leezer3 on Mon May 27, 2013 10:33 pm

kwijiboenator wrote:Drove as per the instructions on your page, but after a few mins is just slows down and stops, and I can't seem to get it running again. It more or less looses momentum?

Shouldn't do that.
First, try with auto-cutoff on- This rules out any sort of bug, although I don't think that's what's happening here.
Using the 'wrong' reverser setting or too much power causes the steam pressure to drop through the floor, just like the real thing. No steam pressure= No movement (You should be aiming to stay above 150psi minimum, idle pressure is c. 220psi)

Basically though, it's down to driving style.
By about 35mph or so, you should be down to near the minimum cutoff.
You also want to drop the throttle wherever possible- Keeping it wide open eats steam pressure.
It's also important to remember that the brakes aren't particularly efficient and this loco has a good deal of momentum, so you can drop off the power a lot earlier than in more modern trains.
My final thought for the moment, is to keep on listening to the sounds. The OpenBVE sound model doesn't really cater too well for steam engines, but in essence you should be able to backoff on the cutoff until you hear the volume start to dropoff, and that's close to the optimum level.

Cheers

Chris Lees

http://www.bvecornwall.co.uk

leezer3

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Re: GWR 81xx for OpenBVE

Post by kwijiboenator on Sat Jun 08, 2013 10:25 pm

Ah so that's where I was going wrong! It all makes sense now - keep the water level happy, and you're fine.

Yes it's a little tricky to work in on the 81xxx because everything is everywhere and not all in one place, but I've managed to be able to drive the SRPS's J36 with ease now - so it's only a matter of time before I'll be merrily driving the 81xxx. Very Happy

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Re: GWR 81xx for OpenBVE

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