DF-21 Forums

[Darth Oosha]

I imagine there'd be little actual use for this; for one thing, a lot of players would probably just be frustrated to start a new level and suddenly find that standard DF physics don't apply. But it'd be moderately fun to play with (maybe as a cheat code?), and furthermore I don't actually know how hard it'd be to write (or to allow room for someone to write it), so I'm throwing it out there.

[klasodeth]

I don't think that's a bad idea. It might even make the gameplay more interesting if explosives can send powerups flying. There would probably also be a lot of modding possibilies too. I think it would be a great addition to the extended feature set.

[lucius]

While this would be an interesting feature, there are many issues to solve. For example, automatically making volumes out of sprites so we can give them volume, mass, center of mass, intertia tensor (helps to determine how an object rotates about it's center of mass), etc. How to show orientation and motion properly with sprites. How to make the physics match DF physics well enough to make existing levels beatable - assuming we worry about this.

Of course there are some cases where limited physics may make sense, though. For example if I ever implement real vehicles, they can be made more believable using physics.

So I'm not saying no... but this isn't something I'd think about for a while. Many other features would go in first.

Anyway thanks for the suggestions, it's certainly not a bad idea - just an idea for much later

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[The MAZZTer]

Havok has recently been or will be soon release free-to-use for anyone to incorporate into their engines.

Might be worth a look, though I imagine being commercial-grade it won't be too simple or easy (or it might be very simple).

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[lucius]

There are other options as well such as Newton Game Dynamics and PhysX. I could easily use a free physics engine. The only reason that this is a feature for later is that the "hard" part is the integration with DF gameplay and DF style sprites. These engines tend to want you to format data the way they are setup and use them for collision detection and response. This means making character/NPC controllers and all that. Not to mention special handling so the physics engine sees a coherent view of the world - which isn't always the case with DF (rooms can be on top of each other for example). This stuff is clearly possible, like Portal, but a fair amount of work to get robust.

Certainly something I can explore down the road though

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[The MAZZTer]

You don't need to use them all the time... for example for best compatibility any extra physics would be disabled.

I imagine you could invoke the physics engine to act on only specific events, for example, an explosion scattering powerup items.

Although you shouldn't be able to blow around "mission critical" items because that would allow you to easily screw up some of the existing levels by blowing away keys to some inaccessible ledge.

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[Darth Oosha]

[Emon]

[klasodeth]

I don't think he meant that portal used overlapping areas, but rather that Portal required physics calculations that would never occur in a normal simulation of the real world. Courtesy of the portal gun, a moving object can suddenly find the direction of gravity changing several times versus its own orientation. Plus you can't make assumptions about distance based solely on start and end points. The distance could change depending on how the portals are placed.

Dark Forces wouldn't suffer from those exact same issues, but with the ability of sectors to overlap, a point in worldspace could refer to two or more points in the level, depending on how sectors are arranged.

[lucius]

Standard rigid body physics relies on the notion that space is a continous volume of 3D space. In order to simulate portals, physics objects must be duplicated and interactions of one duplicate must be replicated to the other one. Or you must implement "bubble" physics where you treat both sides of the portal as a continuous space but then must handle physical reactions between the continuous 3D world and this "bubble." My point is that portals are more then just a graphical affect because it must interact with the physics. This is an obviously solvable but non-trivial problem - atleast to make it robust.

Now we consider Dark Forces with overlapping sectors: assume you have two overlapping rooms (in x, y and z) with an adjoin in the middle of the room that allows you to "move" between rooms - even though you exist at the exact same physical position all the time. See the Perplexion level as an example of this. Now to handle this with physics you'd have to treat each room as a seperate continuous space and the adjoin as the portal between those spaces. This is where the comparison to the portal game comes in - it's the same idea and some of the same problems (not all of them since your momentum or orientation doesn't change direction).

Now as I said before, this is a solvable problem. In fact I could use similar solutions as Portal. However it is non-trivial and certainly more then just plugging in a physics engine which was my point

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[The MAZZTer]

Portal uses the first solution you described (duplicating physics objects) FYI.

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