Jeff Heidman Posted July 21, 2000 Share Posted July 21, 2000 I ran a bunch of tests to try to get some firm data on exposure for various types of terrain. I found myself while playing wondering "Is rough better than brush, and how do they compare to a light building?" So I went ahead and set up a test case and tried to figure out how CM figures this stuff. I know some people do not want to know this, as they feel it might detract from the flavor of the game, if so, quit reading now. Note: I did this in about 4 hours or so, so take it with a grain of salt. This just tried to isolate the terrain variables, so actual battlefield conditions might make these numbers vary considerably, plus it is entirely likely that I just plain screwed up some of them! Link to comment Share on other sites More sharing options...
Jeff Heidman Posted July 21, 2000 Author Share Posted July 21, 2000 All cover seems to work as a hindrance to fire based on the terrain the target is in, and the amount of terrain the line of fire (LOF) crosses. All tests were done in perfect seeing conditins (daytime, no rain or fog, etc) in order to try to isolate only the terrain dependent variables. I am listing each type of cover available, in decreasing order of effectiveness So, there are two factors involved, the terrain the target is IN, plus the amount of terrain the LOF crosses. For example, a unit in scattered trees gets a base exposure of 33%. This is for a unit in scattered tress, but no scattered trees in between the firer and target, i.e. the target is at the very edge of the cover. As the line of fire crosses more and more trees, the exposure continues to drop, until at ~50+m, the LOF is blocked completely. All numbers below assume the target is in the terrain in question. So when it says that in scattered trees the exposure drops from 33% to 25% at 50m, that means that a target in scattered trees with 50m of intervening scattered trees would have an exposure of 24%. Other notes: Cover does not appear to be additive. Being behind a wall in woods gives you the better of the two numbers, in this case 18% exposure. So here goes! Paved Road, Railroad Track, Bridges, Fords. – 100% No degradation for range. Dirt Road – 94% No degradation for range. Open Ground – 88% No degradation for range. Marsh – 76% Drops to 55% for 230m of intervening Marsh LOS is blocked at >~231m Wheatfield – 68% Drops to 49% at 230m LOS is blocked at >~231m Brush – 53% Drops to 49% at 230m LOS is blocked at >~231m Scattered Trees – 33% Drops to 24% at 50m LOS is blocked at >~51m Rough -- 28% Drops to 21% at 270m LOS is blocked at >~275m Light Building – 20% Drops to 14% Woods – 18% Drops to 13% at 25m LOS is blocked at >~26m Tall pines – 17% Drops to 13% at 25m LOS is blocked at >~26m Heavy Builiding – 11% Drops to 9% Walls – 30% and Hedges – 60% These are treated a little differently. If the LOF from firer to target crosses a wall or hedge, AND if the target is within 15m of the spot where the LOF crosses that wall or hedge, the target will get the protection offered by the wall or hedge. This protection is reciprocal, so two units firing at one another across a wall will both get the cover specified, assuming they are both within 15m of the wall or hedge. However, a unit that is atually IN a wall or hedge does NOT get that protection, they must be behind it. In fact, a unit IN a wall has an exposure level of 95%, greater even than in open ground! So be careful when your guys cross a wall, they are very vulnerable at the moment of crossing. A unit IN a headge is 88% exposed. Finally, a unit who is HIDING behind a wall has an exposure of 0%!!! Bocage – 22% Bocage is a little different. Generally it blocks fire across it, but if a unit is right up next to (or inside) the bocage, they can fire out and be fired at. If the unit is right behind the bocage, they are 22% exposed. Units IN bocage are at 88% exposure. One other difference about bocage is that if the firer is in or directly behind bocage, his target (in otherwise open ground) is at an exposure of 66% [This message has been edited by Jeff Heidman (edited 07-21-2000).] Link to comment Share on other sites More sharing options...
chrisl Posted July 21, 2000 Share Posted July 21, 2000 Nice work! Now it's time to quiz you (because I wanna know how it works): did you do any fire effectiveness tests? My guess so far is that the firepower experienced by the subject is the firepower*exposure, but it's not clear if there's a distinction between exposure of reflected photons and exposure to absorbed lead, i.e the difference between concealment and cover. As an example, a hedge might offer virtually no cover, but possibly 100% concealment. Is this abstracted into a single number that reflects the reduced probability of directing the fire into the right place to poke a hole through the twigs and hit the target? My guess is that the answer is yes, but I haven't tried any tests. Maybe this weekend if you don't beat me to it. Link to comment Share on other sites More sharing options...
Jeff Heidman Posted July 21, 2000 Author Share Posted July 21, 2000 Sorry Chris, I did not do any fire effectiveness tests. My guess is alos that effective firepower = firepower*exposure, but that is jsut a guess. Can anyone confirm or deny that? The problem is that it wil be very difficult to test, since there are random factors involved in an actuall shot. You will have to run a lot of tests and plot the results in order to get a meaningful average. Jeff Heidman Link to comment Share on other sites More sharing options...
Guest Madmatt Posted July 21, 2000 Share Posted July 21, 2000 One thing to add, there are TWO styles of Wheat. Summer wheat is taller and more dense that Winter wheat which is usually only about knee high. There are two different textures to show the difference in wheats look. You may want to check the differences between the two... Madmatt ------------------ If it's in Combat Mission, it's on Combat Mission HQ! CMHQ-Annex, The Alternative side of Combat Mission Combat Mission HQ CMHQ-Annex Proud members of the Combat Mission WebRing Link to comment Share on other sites More sharing options...
Mike Oberly Posted July 21, 2000 Share Posted July 21, 2000 Thanks for going to the trouble,Jeff.I printed out your results. Mike Link to comment Share on other sites More sharing options...
Jeff Heidman Posted July 21, 2000 Author Share Posted July 21, 2000 Another point: I did not do any testing to see what effects intervening terrain between target and firer has when the target is not in cover. THat would be nice to know. And along those same lines, what about when a target is in some cover, but the intervening terrain is a different type? Anyone got some time? Link to comment Share on other sites More sharing options...
MrPeng Posted July 21, 2000 Share Posted July 21, 2000 Very cool idea Jeff. Thanks for the info. Peng ------------------ A Journey of a thousand miles starts with a single gunshot wound to the foot. Link to comment Share on other sites More sharing options...
Joe Shaw Posted July 21, 2000 Share Posted July 21, 2000 Nice job Jeff, thanks for taking the time and sharing the results with us. Joe Link to comment Share on other sites More sharing options...
ianc Posted July 21, 2000 Share Posted July 21, 2000 Great post Jeff! Thanks for taking the time to work through this and share your results with us. Maybe I should take your figures and print out a little Terrain Effects Table. That way I can have a little ASL-like security blanket next to me as I play. ianc Link to comment Share on other sites More sharing options...
Hakko Ichiu Posted July 21, 2000 Share Posted July 21, 2000 Great stuff, Jeff. A couple of possible addenda you might want to check out, since you have the scenario all set up. -- Rubble. I'm betting it's as good or better than woods, and blocks LOS pretty well. -- The other factor is concealment. It may be more difficult to quantify, but it's useful to know whether you can actually hide successfully in wheat or brush, regardless of the cover it might provide. When you're ambushing the enemy from three sides, who needs cover. Thanks again for doing the quant work. ------------------ Ethan ----------- Das also war des Pudels Kern! -- Goethe Link to comment Share on other sites More sharing options...
Fionn Posted July 21, 2000 Share Posted July 21, 2000 Actually Jeff, There are a couple of minor errors in your table due to the following fact: 1. You obviously had some units at different distances ( into) the concealing/cover inducing terrain. To be valid you should take ALL your test results ONLY when units are at either 0 metres ( difficult to do) or 1 metre "into" the terrain type you are measuring cover into. ANY variation of distance into the terrain will screw up your LOS figures. ( Some are off by up to 10% from what I got when I ran this stuff 6 or 7 months ago.) Remember for a statistically valid result the ONLY variable can be terrain type. In your results both terrain type AND distance into the terrain "tile" varied for several tests. Also, it would appear that you didn't account for variations in height above the covering terrain in some of your figures . Run some tests with walls and units looking "down" on the unit behind the wall from different heights and you'll get some interesting results . Remember that this should be done 3-dimensionally since CM calculates these things 3-dimensionally. On the whole though this is good work and the minor errors only introduce errors of (IMO) less than 5% at largest which is quite acceptable for our purposes in giving players a "rough idea" of what's going on. So, tell me, is this something you'd be willing to spend a lot of time on ( say a week or so of plugging away night after night collecting data, collating it and sending it for analysis? ). In other words, is this something that matters to you or is this just something you dabbled with? If it is something you want to spend mucho time on creating full data and presentations for then drop me a line. Otherwise we can just discuss it superficially here. Link to comment Share on other sites More sharing options...
Lorak Posted July 22, 2000 Share Posted July 22, 2000 Jeff, Thanks for your time on running that test. Weather your results are spot on or off a bit, it gives great base to work with. I think its something that a lot of people have been kind of wondering about. Just a good list of this is better than this. Thanks again for your time. Lorak ------------------ "someone you trust is one of us"..........the illuminati * http://clubs.yahoo.com/clubs/combatmissionclub Lorak's FTX for CM <--Proud member of the Combat Mission Webring Link to comment Share on other sites More sharing options...
Randl Posted September 20, 2000 Share Posted September 20, 2000 Jeff, Have you, or has anyone gotten back to you, or does anyone have thoughts concerning, where Rubble fits into the Cover and Concealment list? Thanks, Randl Link to comment Share on other sites More sharing options...
Bastables Posted September 20, 2000 Share Posted September 20, 2000 Nice work Jeff, thanks for your time. ------------------ From the jshandorf "Why don't we compare reality to the game like Bastables likes to do all the time?" Mr T's reply "Don't touch me FOO!" Link to comment Share on other sites More sharing options...
Von Brizee Posted September 20, 2000 Share Posted September 20, 2000 Does a Foxhole in trees give u extra cover as opposed to a Foxhole in the open? Link to comment Share on other sites More sharing options...
Guest Michael emrys Posted September 20, 2000 Share Posted September 20, 2000 <BLOCKQUOTE>quote:</font><HR>Originally posted by Von Brizee: Does a Foxhole in trees give u extra cover as opposed to a Foxhole in the open?<HR></BLOCKQUOTE> I think somebody did a test a couple months back that showed being in trees gave no extra cover. While on the subject of trees, I've noticed that in the winter they don't seem to have as much impact on LOS as in summer. I wonder if the seasons also effect how much cover they give. Finally, I do kinda wish that cover was additive. I.e. a unit behind a wall in a wheat field got the benefit of both. Maybe that's too hard for the program to calculate... Michael Link to comment Share on other sites More sharing options...
Lorak Posted September 20, 2000 Share Posted September 20, 2000 Michael, IIRC I think BTS looked at the fox holes in tree coverage. I think it was just a problem in one set (tall pines maybe?) and stated that it should be additive. Then fixed it. Not sure if this was protection wise or LOS wise though. Honestly this was a long time ago.. If I'm wrong someone will point it out I'm sure. Lorak ------------------ "Do not wait to strike till the iron is hot; but make it hot by striking."--William Butler Yeats Cesspool Link to comment Share on other sites More sharing options...
Guest Michael emrys Posted September 20, 2000 Share Posted September 20, 2000 Now that you mention it, Lorak, I believe you're right. I should go back and read the ReadMe file for the last couple of updates. And I think the issue was for protection. Michael Link to comment Share on other sites More sharing options...
Mother Theresa Posted September 20, 2000 Share Posted September 20, 2000 I can just picture all of these military scientists shooting at dummies in the woods, and buildings. "Gee Jim, i would say that dummy is 32% exposed there." Link to comment Share on other sites More sharing options...
GreasyPig Posted September 20, 2000 Share Posted September 20, 2000 Thanks Jeff, This is the very stuff I've wanted to know for quite a while but too lazy to figure it out. By the way, Im a little surprised Tall Pines provide so much cover. I would have thunk that a typical pine forest would not have that much low ground cover (especialy "Tall Pines). I lived near lots of pine timber and the conditions on the forest floor don't usually support alot of shrubs or low growth. But hey, thats here and I have no idea over there. Thanks again Jeff GreasyPig Link to comment Share on other sites More sharing options...
RudeLover Posted September 20, 2000 Share Posted September 20, 2000 <BLOCKQUOTE>quote:</font><HR>While on the subject of trees, I've noticed that in the winter they don't seem to have as much impact on LOS as in summer. I wonder if the seasons also effect how much cover they give.<HR></BLOCKQUOTE> This is true I believe. IIRC, in the alpha AAR Moon comments on how much worse the cover/concealment was in 'woods' in the winter. Grain also behaves differently depending on the season. Link to comment Share on other sites More sharing options...
Renaud Posted September 21, 2000 Share Posted September 21, 2000 It is disappointing that cover is not additive. It seems that in real life being in woods behind a low brick wall would be better than just one or the other alone for both concealment and protection. I imagine bts chose not to allow this due to the possibility it might create of unhittable 'super-positions' existing with certain terrain combinations. Speaking of protection, I sure hope bts adds some other fortification features to later cm's such as log-covered foxholes, bunkers troops and weapons can be moved in and out of (like mount vehicles perhaps), dedicated anti-tank ditches, dragons-teeth, dug out defensive pits and berms for tanks, etc. -Ren Link to comment Share on other sites More sharing options...
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