A Bridge Too Far?

[kumaryu]

Please forgive my ignorance (, laziness, and impertinence) if this is a topic that's been discussed countless number of times in the last two millennia, but what's the situation with bridges and to a lesser extent roads?

Although the list of possible structures that can be introduced is endless, bridges and roads have been of crucial, overriding military importance for a number of civilisations. What's the current take on the matter?

[fabio]

For reference roads were discussed here.

[kumaryu]

Understood. I get that the roads are not a priority at present for the reasons given in the discussion linked above. I still feel that an ability to build bridges might be interesting for some factions and on many maps.

Edited March 20, 2015 by kumaryu

[sanderd17]

Units going over each other will never be supported. The pathfinder is 2D, and the position component doesn't store the height, but calculates it based on the terrain. So if you place a bridge over the water, you must be sure that no boats can pass under it, or that no other entities (like fish) are at that place.

For roads, the new pathfinder will be faster, because it uses a uniform speed grid. That uniform grid allows for certain optimisations severely reducing the number of calculations needed. When that grid would be non-uniform (f.e. because speed is higher on roads), then the new pathfinder will be worthless. The possible intermediate way would be that the pathfinder ignores, but that the speed does increase when units walk on roads. However, that would require a lot of micro to keep the units on the road.

[kumaryu]

Units going over each other will never be supported. The pathfinder is 2D, and the position component doesn't store the height, but calculates it based on the terrain. So if you place a bridge over the water, you must be sure that no boats can pass under it, or that no other entities (like fish) are at that place.

For roads, the new pathfinder will be faster, because it uses a uniform speed grid. That uniform grid allows for certain optimisations severely reducing the number of calculations needed. When that grid would be non-uniform (f.e. because speed is higher on roads), then the new pathfinder will be worthless. The possible intermediate way would be that the pathfinder ignores, but that the speed does increase when units walk on roads. However, that would require a lot of micro to keep the units on the road.

Understood... then again perhaps I've misunderstood but would there be a need for units in water, such as boats or fishes to go under the bridge? To all intents and purposes, a bridge would merely be a terrain that could be "built" by the player. And once the water terrain has miraculously been transformed in to a land terrain with suitable "bridge" renders, it would allow units to pass over them just like any other flat terrain.

Indeed the type of bridges I had in mind, such as Xerxes' pontoon bridge across Hellespont (480 BCE), or Caesar's bridge over the Rhine (55, 53 BCE) would not have permitted vessels of any significant size to go under them. For larger bridges at a later date, perhaps that would be a "nice-to-have" cosmetic touch but hardly a "must have" for a tactical tool/feature.

In time, it may be good to allow the bridges to be destroyed by enemy action, deteriorate over time or be garrisoned in some way but those are all secondary to the function of allowing them to be built and walked over. Fishes, like so much sushi, are likewise luxuries that I can personally do without.

Edited March 21, 2015 by kumaryu

[ubik]

I love where this thread is headed.

Bridges and roads could be a benefit to traders, and help mobilize armies faster. I keep thinking it would be great eye candy to allow units to leave footprints that could turn into nature paths and betray the comings and goings of the enemy. Although I fear this might hinder performance.

[Lion.Kanzen]

I said this before: Roads can be make/ made by units common paths , this ways works in Rise of Nations but with bonus from Empire Earth 2, now the bridges can work similar as empire earth 2 / praetorians

In Pretorians the bridges is like a building and can be destroyed

Min 5:31

Edited March 21, 2015 by Lion.Kanzen

[historic_bruno]

Units going over each other will never be supported. The pathfinder is 2D, and the position component doesn't store the height, but calculates it based on the terrain. So if you place a bridge over the water, you must be sure that no boats can pass under it, or that no other entities (like fish) are at that place.

Technically, they are and they do, with planes and other flying things The answer is simply to have a separate "pathfinder" for such cases (walking on entities, be they bridges, walls, or other things). The hardest part would be combining them so units can transition between the different pathfinders, but it would be extremely cool. On a related note, I think we'll end up with multiple pathfinders anyway, I'm quite skeptical that one alone can handle infantry, cavalry, vehicles, and boats in a reasonable manner, but we'll see.

Building bridges would be tough as well, making them adjust to different heights and lengths.

[greenknight32]

The problem of adjusting to different heights reminds me of a game I got for Christmas, Grand Ages of Rome (gold edition). In it, to build on land that's too steep, you build platforms - you can add layers to the platform until it's large enough.

Maybe, to build a bridge, you'd first build bridge footings, the elevations of which have to match before you can build a bridge on them. If they didn't match, you'd add an approach ramp to the lower one to make it higher - ramps would have a fixed slope, and you could add layers to them to make them tall enough. When heights matched, you could then stretch a bridge from one to the other like building a wall.

This way, you could bridge between different elevations if there was enough space for the ramp, which would be longer the taller it needed to be, and the cost would be higher. The bridge footings could be graphically very simple, only the bridge itself would need an elaborate design.

Also, the bridge could be a destroyable structure, the bridge footings not - which would be realistic.

Edited March 22, 2015 by greenknight32

[wowgetoffyourcellphone]

Building bridges would be tough as well, making them adjust to different heights and lengths.

Hmm, I don't see problem with the height thing, maybe clarify? Length--Just have min and max length. About boats, ancient bridge were not the big bridge of today. Only small watercraft would fit beneath them, certainly not warships! So, the bridge could block boat movement and be perfect realistic.

[kumaryu]

Building bridges would be tough as well, making them adjust to different heights and lengths.

I'm sure the ancient military engineers built bridges in places where it required the least amount of engineering effort. Wherever they could, they would build bridges across the narrowest stretches of calm water, where the ground on both banks were level and of about the same height. This is the rule of thumb that should be applied in the game as well. Having an engineering solution to meet every foreseeable challenge under all natural conditions (or for that matter, the whim of the consumer/player) is a very modern concern. In other words, a bridge spanning two cliff-tops separated by half a day's sailing distance should not be allowed in the game.

There were exceptions of course. Civil engineering feats such as aqueducts that spanned chasms between very different heights, but they served different purposes and were built to different constraints. In the make-believe world of 0 A.D. bridges should first and foremost serve a military/tactical function. For this reason, that there may be restrictions on how and where a bridge might be built; that they can only span narrow widths between banks of equal height should not be considered as a issue but a constraint that more accurately reflects historical reality.

Edited March 22, 2015 by kumaryu

[FeXoR]

I agree. Howeve, that dosn't make it easier to implement.

Bridges could be placed like walls for their length - while checking for placability like e.g. docks at their ends (and ground passability as well). To be even the bridge parts has to be adjusted in height over ground though (other things snap to the ground).

And still the "entities walking on entities" thing needs to be done. (I don't really like the curent implementation of units on walls. If units would actually be able to walk on walls we had the same needs for walls as for bridges)

Even the current default entity/actor placement is not very clever. It simply adjust the height by snapping the ancor - likely the center - to the ground. IMO the average height of the area covered by a entity/actor should actually be used to snap its height to. (and still there will be visual issues becuse not all buildings - and especially actors like stones - are not reaching deep enough into the ground - that's an art task though)

Edited March 22, 2015 by FeXoR

[Stan`]

I agree. Howeve, that dosn't make it easier to implement.

Bridges could be placed like walls for their length - while checking for placability like e.g. docks at their ends (and ground passability as well). To be even the bridge parts has to be adjusted in height over ground though (other things snap to the ground).

And still the "entities walking on entities" thing needs to be done. (I don't really like the curent implementation of units on walls. If units would actually be able to walk on walls we had the same needs for walls as for bridges)

Even the current default entity/actor placement is not very clever. It simply adjust the height by snapping the ancor - likely the center - to the ground. IMO the average height of the area covered by a entity/actor should actually be used to snap its height to. (and still there will be visual issues becuse not all buildings - and especially actors like stones - are not reaching deep enough into the ground - that's an art task though)

I tried to make my props, (eyecandy mod) be long enough for this not happen however, having a list of bad props would be nice

I'd like to see bridge aswell, for gameplay, especially if weather gets implemented, (frozen lakes)(and non freezing ones for the sake of it, with different water color support, and different water heights, In another game, water is tiled and you can raise all the waters of the same type.

[historic_bruno]

Hmm, I don't see problem with the height thing, maybe clarify? Length--Just have min and max length. About boats, ancient bridge were not the big bridge of today. Only small watercraft would fit beneath them, certainly not warships! So, the bridge could block boat movement and be perfect realistic.

I'm referring to the riverbanks being at different heights. Possible solutions would be to restrict bridge placement or terrain flattening. I'm guessing the main structure of the bridge would be built like walls, but unlike walls, it should be a single finished structure.

[wowgetoffyourcellphone]

I'm referring to the riverbanks being at different heights. Possible solutions would be to restrict bridge placement or terrain flattening. I'm guessing the main structure of the bridge would be built like walls, but unlike walls, it should be a single finished structure.

Hmmm, I think it could be like Docks. Docks cannot built on shoreline that is too tall. Bridge can use same placement code?. Have Bridge always be same height above water table, with ends that taper down like ramp (usually hidden by terrain but if terrain low the ramp will show, just like the back side of Greek dock). The span in middle gets "segments" added seamlessly like a wall that doesn't have towers.

EDIT: With imagination I see this. Can click one end of the bridge at shoreline (has shoreline placement requirement like dock), then drag to the other side of river. If drag too far, bridge spirit goes red (have tooltip like walls that tells you how far bridge is and cost, it tell you if you go too far too). Click the end at the opposite shoreline, then units start building the bridge from starting end. If you have units on the opposite bank you can click them onto the end they can start building from their end to cut building time in half. Foundation before they start building looks like pylons in the water. Persian one can be wider and look like pontoon bridge (see: Xerxes; it can go longer, but is weaker; say most civs can go 5 segments long, but Persia can go 7). Roman one can have stone pylons but wooden span (they tend to make their bridges wooden so they can fire the bridge in case of enemy invasion).

Red ends ramp downward. If bank slope upward then it just clip the ramp no problem. If the bank is too steep or cliff, it be like dock and cannot be built. Yellow spans are short, medium, long, just like walls and swap into place depending on need of length.

Once build, any player can use it, but only owner can delete it (maybe it can be "capture" when captuiring implemente). Romans can upgrade their bridge to be full stone like this:

Edited March 22, 2015 by wowgetoffyourcellphone

[auron2401]

I think he meant you draw it like a wall. (drag from one end to another) But you place it like a dock.

Nice sketch, btw.

[Lion.Kanzen]

The bridge can be palisade type and upgradable to stone, and easy to destroy by archers and fire siege engines.

Edited March 23, 2015 by Lion.Kanzen

[kumaryu]

Bridge Feature Work points

Here's a tentative list of things I thought might be worth considering from features perspective. It would be good if we can develop it further, prioritised from community perspective and commented by the developers as to their feasibility.

Must-have Features

• Ability to build bridges across waterways.
• The bridges may be traversed by most units.

In-game prerequisites?:

• Restricted to specific civilisations?
• Town or city level should be a basic requirement?
• Engineering tech development may also be a prerequisite?
• Perhaps longer lengths ought to be dependent on tech dev?
• Introduce engineer units (pros/cons?)
• Certain bridges (pontoon and smaller stone bridges) may not allow siege engine movement?

Types

Perhaps it would be best to start with the simplest and the most basic bridge type first to test the concept and its impact on the game as well as facilitating quicker implementation.

1. Wooden bridges (degradeable)
2. Pontoon bridges (degradeable)
3. Short stone bridges (permanent)
4. Long-span stone bridges (permanent)

Here's a good cross section of Roman bridges that have survived to the present day. That they've lasted means that they're all stone bridges and many have later modifications which would not be suitable for 0AD.

Nice-to-haves:

1. Degradation
2. Destruction through enemy action
3. Between different elevations
4. Overlapping movement
5. Integration with roads

Edited March 23, 2015 by kumaryu

[sanderd17]

So idea for adding low bridges:

* Change Obstruction component into an ObstructionModifier. Instead of just adding a general obstruction, this could add or remove obstructions of different size per passability class.

* Implement a virtual terrain, bridges could modify the virtual terrain to let units follow that instead of the real terrain. By default, values are null, but when non-null, these terrain heights are preferred over the non-virtual terrains.

This way, a bridge could enable units to pass through a part of deep water, while it could disable boats to pass there. As such, influencing the pathfinder (that shouldn't know about heights). While the virtual terrain could be used to lift units at those position up to the bridge level.

It could also make stairs possible, where the passability of mountains can be edited by the stair. This wouldn't need a virtual terrain though.

[wowgetoffyourcellphone]

Bridge Feature Work points

Here's a tentative list of things I thought might be worth considering from features perspective. It would be good if we can develop it further, prioritised from community perspective and commented by the developers as to their feasibility.

Must-have Features

• Ability to build bridges across waterways.
• The bridges may be traversed by most units.

In-game prerequisites?:

• Restricted to specific civilisations?
• Town or city level should be a basic requirement?
• Engineering tech development may also be a prerequisite?
• Perhaps longer lengths ought to be dependent on tech dev?
• Introduce engineer units (pros/cons?)
• Certain bridges (pontoon and smaller stone bridges) may not allow siege engine movement?

Types

Perhaps it would be best to start with the simplest and the most basic bridge type first to test the concept and its impact on the game as well as facilitating quicker implementation.

1. Wooden bridges (degradeable)
2. Pontoon bridges (degradeable)
3. Short stone bridges (permanent)
4. Long-span stone bridges (permanent)

Here's a good cross section of Roman bridges that have survived to the present day. That they've lasted means that they're all stone bridges and many have later modifications which would not be suitable for 0AD.

Nice-to-haves:

1. Degradation
2. Destruction through enemy action
3. Between different elevations
4. Overlapping movement
5. Integration with roads

I think KISS principle should be place in effect in this instance.

[Stan`]

I was wondering if we can set obstruction can ´t we set passability ?.

[FeXoR]

sanderd17: Though this wouldn't allow units passing over each other on different heights (It would be cool but I wouldn't givi it high priority) That sounds like the best way to to it by now.

[rmhibbs]

Could you allow the "bridges" to be build over land gaps, like large gullies or small canyons, as long as they did not exceed the same distance limitations as for spanning rivers?

The thread "Enlarge maximum map height" is discussing increasing the verticle map height by a factor of 8 that would increase the height from the current max of 89.5 m to a max of 712 m. If implemented, this would allow for a lot of interesting terrain features that could benefit from being able to build bridges over dry land "gaps".

Bob

[Ptolemy]

Could bridges not function like walls? You have to send men up on top to get them across via two access points. They could be built pretty much anywhere then, to bridge the gap between ravines and rivers. Any length and any height

[Loki1950]

Could bridges not function like walls? You have to send men up on top to get them across via two access points. They could be built pretty much anywhere then, to bridge the gap between ravines and rivers. Any length and any height

The game still does not allow units to walk on walls yet so that's not an option ATM.

Enjoy the Choice