Physics patches

madman2003 · Post by **madman2003** » 05 Apr 2006 17:51

Is there any reason why this isn't included in the main tree?

Michi_cc · Post by **Michi_cc** » 05 Apr 2006 19:45

madman2003 wrote:Is there any reason why this isn't included in the main tree?

Might I make some suggestings to raise the chance it'll be trunk one day?

Post your patch on http://bugs.openttd.org/ as patch to be proofread.

Try to make some smaller pices.

Split road vehicles and trains into seperate patches.
Make another patch for real_airspeed.
An finally a patch for those GUI and code improvements.

Repeat: make small pieces, increases the chance of inclusion a lot.

If you've done all that, go to #openttd and bug a dev until he looks at the patches.

-- Michael Lutz

Wolf01 · Post by **Wolf01** » 05 Apr 2006 19:50

Michi_cc wrote: If you've done all that, go to #openttd and bug a dev until he looks at the patches.

-- Michael Lutz

err... until he says "Stop buggiiiing meeeeeee" like the ork grunt in Warcraft 2

madman2003 · Post by **madman2003** » 05 Apr 2006 20:50

There is one major problem stopping the inclusion (i had a talk with peter1138):

max speed calculation accuracy, it's done with integer calculations, but deviding a km/h by 3.6 will give inaccurate results:

example:

150/3.6=41 --> it should be 41.6666666
10/3.6=2 --> should be 2.777777777

There are maybe more conversions which cause similar problems, together they create low accuracy. The solution is to increase the scale during certain calculations so accuracy is improved, not a 100% sure (because of almost no c knowledge) what is possible without going into the floating point realm.

Floating point is a no go, because different computers make slightly different calculations, which won't work in multiplayer.

Brianetta · Post by **Brianetta** » 05 Apr 2006 22:18

You can make use of fixed point by multiplying all numbers not used as multipliers by (ten raised to the number of decimal places required) and then dividing the ultimate result by that number.

Michi_cc · Post by **Michi_cc** » 05 Apr 2006 22:31

madman2003 wrote:There is one major problem stopping the inclusion (i had a talk with peter1138):

max speed calculation accuracy, it's done with integer calculations, but deviding a km/h by 3.6 will give inaccurate results:

example:

150/3.6=41 --> it should be 41.6666666
10/3.6=2 --> should be 2.777777777

Actually, the current code correctly rounds those results to 42 and 3.
Of course, if that's not enough accuracy, fixed-point arithmetics would be an option.

Two links:
http://www.bookofhook.com/Article/GameD ... dPoin.html
http://hometown.aol.com/form1/fixed.htm.

-- Michael Lutz

madman2003 · Post by **madman2003** » 06 Apr 2006 07:05

I had something similar in mind (working on a *10^-5 (or higher) scale, essentially moving the . to get better accuracy).

madman2003 · Post by **madman2003** » 08 Apr 2006 13:39

I've modified the patch to become a bit more accurate (as far as i could see from the sourcecode). Only train stuff is modified, because the realistic truck acceleration seems ok (i don't understand some of what's happening there yet though). Moving up the resolution made some values too big for int32, so i used int64, i'd be curious to hear how it performs on a 32bits system. Compare the beheaviour of this and the original patch if you can. The airplane speed thing is gone, because it has nothing to do with this patch.

This was made against the 32bpp tree, but i think it will work for the normal one too.

Michi_cc · Post by **Michi_cc** » 08 Apr 2006 17:45

madman2003 wrote:This was made against the 32bpp tree, but i think it will work for the normal one too.

Probably yes, but you have some stray files in your patch, namely Makefile.config and rev.c.

And you should check if r4322 has any effect on the patch. Looking at that revision I'd say no, but I can be wrong.

-- Michael Lutz

madman2003 · Post by **madman2003** » 08 Apr 2006 18:10

I'll look at that too, found out it is a bit broken against current trunk. I'm working on it

madman2003 · Post by **madman2003** » 08 Apr 2006 18:26

This should apply to current trunk.

madman2003 · Post by **madman2003** » 08 Apr 2006 18:38

Discovered a minor flaw, will try to fix.

This will take longer, the problem with realistic truck accel on manually stopping the vehicle will be instant and later it will resume at old speed.

madman2003 · Post by **madman2003** » 09 Apr 2006 09:59

There turned out to be more problems, so i fixed them. This should apply against current svn, let me know if there any speed displaying issues (there was a change in trunk to km/h instead of several conversions from mph to km/h), masses of vehicles that seem too large, stuff like that. And if it works for you too.

Nappe1 · Post by **Nappe1** » 09 Apr 2006 14:14

Madman2003: acording to TortoiseSVN, any of your diff files aren't really diff files... :/

I would so much to use this patch with Subsidiaries in our private server, so could you check that you are doing right kind of diff files please?

madman2003 · Post by **madman2003** » 09 Apr 2006 15:21

They were normal diff's, this is a so called svn diff. Also did a few minor cleanups were certain things were only a space different.

Nappe1 · Post by **Nappe1** » 09 Apr 2006 16:02

madman2003 wrote:They were normal diff's, this is a so called svn diff. Also did a few minor cleanups were certain things were only a space different.

thanks.

Thief^ · Post by **Thief^** » 09 Apr 2006 16:12

As I understand it, a ".patch" file (created by the diff tool) contains the changes between 2 files or directories, and a ".diff" file (created by svn diff) contains the difference between a file / directory and a specific svn revision of that file / directory. I know that the .diff and .patch extensions are interchangable, it just seems the two tools default to the extensions I mentioned above.

I also noticed that your patch file contains the name of the directory that the files should be in, "./openttd-svn/trunk/", so it probably wouldn't have worked for anyone keeping it in a different directory. This is probably true for all patch files. By contrast a diff file doesn't store the name of the directory the files are in, only the svn-url, so it can by applied to any folder that the correct svn branch is checked out into.

madman2003 · Post by **madman2003** » 09 Apr 2006 16:24

Found a small bug, the vehicle weight when looking at a running road vehicle (not in the buying screen) was much too high.

madman2003 · Post by **madman2003** » 09 Apr 2006 16:31

I expected people to know how to use patch, patch -p2 would have worked fine. But svn diff's are easier to use and maintain i just discovered

madman2003 · Post by **madman2003** » 09 Apr 2006 19:48

Some minor things(some strings) have already been merged into trunk and the patch will continue to break in the future probably.

Removed because faulty patch.

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