Zatikon is back and free to play! https://www.chroniclogic.com/zatikon.htm
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Not posting a detailed description of your system (speed, gfx card, operating system).
The graphics of Pontifex registered are no different than those of Pontifex demo, but you should have more levels, a choice of "normal", "complex" and "map" when you "Start game", and an option to "elevel" edit in the edit screen.
I am running a 12.40 series detonator; have you downloaded and installed a detonator from nvidia or are you running with W2000 default drivers?
Pfx demolition
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Take a given bridge, add members to it (at the least additional cost) so it self-destructs instead of settling :-) The task is completed if all deck pieces are on the ground afterwards; those connected directly to anchors may still be, but must drop down as far as they can go.
Are the explosions the same if you use heavy steel?
I have used the slowness of my system to advantage, and have, on low detail so you can see the members betters, made shots of the frames immediately preceeding the collapse for the box and two towers of 80 and 120 meters in height, constructed like entroper's 160m tower. It is all very puzzling.... (Edited by mendel at 7:04 pm on Oct. 28, 2001)
http://pontifex.mendelsohn.de/forum/Xploico.JPG" border="0">
http://pontifex.mendelsohn.de/forum/xplobox.GIF" target="_blank">Xplobox (68kB gif) shows the box right before and after the explosion
http://pontifex.mendelsohn.de/forum/XploTwr2.GIF" target="_blank">XploTwr2 (87kB gif) shows the 4 frames that encompass the demise of the 80m tower
http://pontifex.mendelsohn.de/forum/XploTwr3.GIF" target="_blank">XploTwr3 (84kB gif) shows 4 frames leading up to the downfall of the 120m tower
Notes:
0) My neutral stress color is gray, red is compression, blue is tension. I oversized the level (128x64 or something) to choke speed on my machine.
1) The box beams are under tension; I imagine the bottom wants to fall off the top? I have seen similar things in my hanging experiments mentioned on the "Short links bug" thread. Strangely enough, the top linkboxes show some compression.
2) The 80m tower explodes under compression. This does not mean this failure is unrelated to the box; this may just be the same forces acting upside down this time. The small size of the tower makes it unlikely that the explosion has been caused by simply too much weight.
3) On the 120m tower, the middle section explodes first; the top explodes 1 frame later (not shown here); although it is now freely in air, it is destroyed by compression (or a very rapid snapback into tension that occurs "between" frames if the physics engine is faster than the framerate). You can see clearly the tension in the linkboxes - opposite behaviour from the box, again.
The idea about "explosive charges" is to add some beams to an existing structure to take out some structural supports. If you've ever seen a high-rise demolished (e.g. on TV), you'll notice that the charges doesn't pulverize it all, but rather take out some structural elements so the thing falls down in a controlled manner.
The length of cable seems to affect the strength of the link box it attaches to.
If you're using a cable which has two joint = 3 section, and only the middle section is short, it will hold much more weight than it would if you attached a box to the short piece (or switched the short section down).
Of course, with an anchor at top, you don't need a top section really.
You can also use a cable joint to attach more cables, like an inverted Y. Even if they're the same length, the lower cables will tear first (from the box).
See http://pontifex.mendelsohn.de/forum/sthang1.pxb" target="_blank">http://pontifex.mendelsohn.de/forum/sthang1.pxb and sthang2.pxb.
[corrected URL]
(Edited by mendel at 9:08 pm on Oct. 23, 2001)
I used to think this was physically ok, because the short box diagonals are at more of an angle (45° for 1x1 as opposed to 14° for a 4x1 box). However, setting 100% as the bar breaking load, a 4-box can take 1176% against 1-box 965%, and even with the added relative weight of short boxes (15.3 vs. 12.2 per unit length), this does not account for the strength loss you've observed.
In real life, the longer a (solid) bar gets, the more likely it is to fail by buckling outward, so the compresive strength actually decreases with length. (If you pull, you have no buckling, so strength against tension remains constant).
All this points to a common physics engine problem: as the construction gets stiffer, it is more likely to explode due to numerical instability of the engine.
During simulation, it may happen that beam ends move away from the joints; the engine then applies force to the beam to close that gap again, and that force can rip the beam apart if you're unlucky (and it is particularly stiff).
This problem may get worse by the non-real strain of the members as it may be prone to produce bigger gaps, especially with the diagonal cross-bracing.
Moral: don't construct stiff structures, make them loose! :-)
(I wonder if these guesses will turn out to be true... ;-)
Actually, congratulations on your well-reasoned article, much more exact than my off-the-cuff estimates of the percentages involved.
I don't have time right now to go into this more, so here are some suggestions:
1) Breaking strengths of 3HD and 6HD box can be narrowed down further by shortening the stick below the 2-bar at the top of the breaking column.
2) Relating cable weight to light steel weight and using short cable sections to refine things would be a bad idea because changing the connections on a structure has strange side effects. (witness replacing the 2 heavy steel sticks with light sticks and a heavy crossbeam, and both HD8 towers pop boxes)
3) Calculating Y for HD8 is erroneous because it's not the bar that breaks on this tower, it's the link box that pops. (Link boxes are still an open research question at this time.) Same goes for HD7.
I think pontifex would be more accessible (if not more fun) if the physics was more intuitive. A beginner will optimize his bridge by shortening bars to save weight (worked well in BB); pros will replace two long bars with one long bar and be more effective, but it's not easy to find that out.
If you think you'd get link boxes for free, that's not true because small bars are heavier per unit length - this is because of the proportionally longer diagonals and the absolute weight of the link boxes. Weight per unit 2HD=41, 4HD=26, 8HD=19 using VRBones's figures. Since a link box is stronger than a 2 HD bar, they're probably even heavier in proportion, making the penalty worse. And then there's the strength loss because of the diagonals' angle...
I made up another http://pontifex.mendelsohn.de/forum/tspring.pxb" target="_blank">experiment to check. It compares loading both a 20m and a 40m bar equally, and if you look closely, you see the top of the 20m bar is actually lower than that of the other! It seems it compresses even more. Stress seems to be 40% vs. 10%.
My current guess is: spring constant is unchanged for all lengths, so the short bar strains as much as the long bar (absolute length change); actually, a bit more, since the diagonals are at more of an angle. Then, stress is calculated by strain, not by strain/rest length. This would result in stress being inversely proportional to the square of the bar length (applied force being constant), which is in line with the somewhat inaccurate stress measurement.
All this is just so much guesswork; can anybody come up with better experiments to confirm this?
Notes on measuring with http://pontifex.mendelsohn.de/forum/tspring.pxb" target="_blank">tspring.pxb: I used 1024x768; "Low Detail" to make the bars show up as pixel-wide lines; much "R" in edit mode so I can really zoom up close in Test mode; make a screenshot with the heights I want to compare in the same picture, preferably near the horizon; then measure pixel displacement using a gfx program; that also measures RGB values of the stress color to get the percentages.
