FarseerPhysics Forum Rss Feed

New Post: Feature Request: Query for Colliders

genbox — Thu, 19 Nov 2009 14:59:09 GMT

Farseer Physics Engine 3.0 includes the broad phase from Box2D and thus you will have the Query() functionality once it is released. The reason we don't have the Query functionality in the current version of FPE is that we have several broad phase algorithms and they all work in their own way. To implement something like a query would make the implementation a lot more complex (we strive for simplicity in 2.x) and I simple don't have the time to implement query in all the algorithms.

FPE 3.0 only have a single broad phase and thus it can be a lot more optimized (specialized) and I don't have to maintain 4-5 different implementations. If someone wants to take up the challenge of implementing query in the broad phase algorithms, I would be more than happy to take a look at it and include it in the 2.x source tree.

New Post: Feature Request: Query for Colliders

thehipgamer — Wed, 18 Nov 2009 20:16:57 GMT

Not to resurrect the dead or anything, but I've been working on implementing geometry-aware path finding nodes via FarSeer, and agree with fuzzybinary: having a Query() method would be significantly nicer than needing to drop all of the nodes into the simulator and then deal with the overhead they introduce to the collision code. While the situation is somewhat mitigated by setting IsSensor=true on those nodes and then overriding OnBroadphaseCollision() when dealing with static navigation grids, it would be really nice to have a way to query for broad phase collisions on objects not within the physics simulator list.

I realize it's on the edge of the "physics sim" part of the use case for FS, but I'm not sure that I can see an elegant alternative that would somehow allow for the efficient functionality of checking for blocked nodes outside of the FS classes themselves. I suspect that's why the Box2D guys went with the Query() method, and it's important enough that it seems like a natural fit within FarSeer.

New Post: New game using Farseer

jrommann — Mon, 16 Nov 2009 02:08:47 GMT

Ascii Dungeon Shooter by Rabid Design Studios

Ascii Dungeon Shooter was created for the XNA 7 Day Challenge - http://xna7day.com/
The game is a simple 2d top down shooter. You are in a dungeon full of monsters and turrets.
To escape you must find the exit. The exit is marked with a E.

Just thought I would share this since it is using Farseer. If this doesn't belong feel free to remove this post

Thanks,

Rabid Baboon

New Post: Geometries not colliding?

jamesbrauman — Sun, 15 Nov 2009 05:35:50 GMT

I'm fairly sure its something stupid I'm doing, but these geometries are not colliding.

I'm trying to use the border code from the advanced samples for some simple testing, that works fine. It draws fine and debug shows that its all good.

Then I create just any shaped geometry (I've chosen an ellipse).

Then the ellipse will fall through the border. I'm not sure what's causing it.

        public override void LoadContent()
        {
            simulator = new PhysicsSimulator(new Vector2(0, 200));
            simulatorView = new PhysicsSimulatorView(simulator);
            simulatorView.EnableEdgeView = true;

            levelBorder = new Border(800, 600, 20, new Vector2(400, 300));
            levelBorder.Load(ScreenManager.GraphicsDevice, simulator);

            Body b = Factories.BodyFactory.Instance.CreateEllipseBody(simulator, 30, 50, 30);
            Geom g = Factories.GeomFactory.Instance.CreateEllipseGeom(simulator, b, 30, 50, 50);
            b.Position = new Vector2(300, 300);

            simulatorView.LoadContent(ScreenManager.GraphicsDevice, ScreenManager.Game.Content);
            base.LoadContent();
        }

Do you know whats wrong?

Edit: Turns out the border was too thin? Even though it was 20px.

New Post: Geom vertices question

tdk08 — Sat, 14 Nov 2009 01:45:04 GMT

Exactly what I needed, thanks a lot, good luck with your game!

New Post: Geom vertices question

sterlingware — Fri, 13 Nov 2009 21:10:58 GMT

You can simply set Body.IsStatic = true, then subscribe to the OnCollision event and set Body.IsStatic = false in the event handler (and be sure to return true). That would cause the object to be static until it collided with an object. You could even go one step further and check which object it collided with (by observing the Geom.Tag property of the colliding geom) and respond accordingly; so you could make your object become un-static only when certain other objects collide with it.

I use this in a game I'm working on. Observe the red blocks, they're static until hit by the character.

New Post: Cutting peices out of Geometry

robertdodd — Fri, 13 Nov 2009 08:52:21 GMT

Hi James.

If the shapes are going to be simple like that you can easily write your own code to generate them, because Polygon clipping can be quite expensive. If you need to use clipping though the "Union", "Subtract" and "CutHoleInShape" functions from the Vertices class will do what you want, and if I remember correctly theres even an example on how to use them in AdvancedSamples.

Also have a look at the GPC Polygon Clipping Library, which I use in my game Boxycraft for both the clipping and triangulation.

But still, if they are going to be that simple (boxes and circles), you can write your own code to generate them, or even use the clipping functions and save the result.

New Post: Cutting peices out of Geometry

jamesbrauman — Fri, 13 Nov 2009 08:08:54 GMT

I'm trying to figure out the best way to create some geometry to represent my 'level'. What I basically want to do is to define a shape, then to define another shape to 'cut' out of the first shape.

Pictures of what I'd like to do:

http://img237.imageshack.us/img237/2687/85266134.png

Just imagine the game taking place inside those areas, boxes flying around etc. Basically, the gray area is the bounding area.

Whats the best way to achieve this? Thanks

New Post: Geom vertices question

tdk08 — Thu, 12 Nov 2009 22:02:47 GMT

I already posted this on the XNA forums so I'll just quote it:

"For anyone that has used Farseer before, you know you have to specify vertices to create the geom of a body if it isn't a basic shape. Besides the texture to vertices way of doing it that is talked about in the manual (it works but there are random holes in the geom with even very simple textures), is there any way of calculating the vertices for a geom from an image you have? Doing it manually isn't completely out of the question but that would be a last resort method. Also, is there any way to keep an object in a fixed position until something hits it? At that point it would move in response to the force of the other object hitting it and gravity would then act on it as well."

I just got directed to these forums over there so maybe someone can put me in the right direction. Also, I find it very odd that no one has asked this question before (I just did a ctrl-f in the forums while viewing all discussions at once). If they have then just post a link to the solution please. Thanks a lot.

New Post: Farseer Physics Engine 2.1.2 Released

thehipgamer — Thu, 12 Nov 2009 17:56:35 GMT

You guys rock. Thanks very much!

New Post: Mouse Spring/Joint ?

danthekilla — Thu, 12 Nov 2009 00:13:19 GMT

Im currently using a revolute joint but perhaps a weld would work better so ill give it a try.

New Post: Mouse Spring/Joint ?

rhythm86 — Wed, 11 Nov 2009 18:36:17 GMT

Ha! Good idea RogueCommander, the Weld Joint works nicely. I didn't play with it before because it's not described in the manual.

dan, try using the WeldJoint - be sure to give the mouse body a very large mass (I used float.MaxValue), and set the anchor to the common World Point you want to bind them at. This will lock the orientation of your bodies while they are being controlled by the mouse, you could use a different type of joint if this is not desired.

New Post: Farseer and XNA 3.1

Beringela — Wed, 11 Nov 2009 09:41:14 GMT

I had a similar problem, if I remember rightly the fix was this:

In the farseer project properties, under the build tab, you need to add the build parameter "XNA". You'll see lots of "#if XNA" scattered around the farseer code, that's why you need it.

New Post: Mouse Spring/Joint ?

RogueCommanderIX — Wed, 11 Nov 2009 08:12:33 GMT

Another idea is to add a body to the engine and manually set it's position to the moue's every update, then add a weld joint between that and the selected item.

New Post: Blob physics issues

RogueCommanderIX — Wed, 11 Nov 2009 08:00:53 GMT

Took a look at that article (Cool one BTW, thanks!), and it says to use a two layer skin to maintain a reasonable surface structure, try that and see if that helps.

New Post: Farseer and XNA 3.1

jsaade — Wed, 11 Nov 2009 05:34:25 GMT

Hello,

my game uses 3.1 features (such as video, ...)

I cannot natively build farseer in 3.1 (it gives around 2000 errors related to #defines and specially to Vector2 confusion).

Is there any guide to build it on 3.1 or should I have to wait for 2.2 version of Farseer?

New Post: Weird Bug when using Springs on Xbox360

jsaade — Tue, 10 Nov 2009 20:11:18 GMT

I got the latest release (2.1.3) and compiled the dll.

On windows in works fine, but on the xbox360, whenever I declare a variable

of type AngleSpring or any other type of Springs and try to run the game, I get a black

screen without any kind of errors and loose the connection to the console!

New Post: Mouse Spring/Joint ?

danthekilla — Tue, 10 Nov 2009 13:31:33 GMT

I have tried the 2nd approch you suggested but it is very hard to control and stuff and doesnt work that well.

However i have never used a slider joint, i will give that ago tommrow...
Thanks for the help.

New Post: Mouse Spring/Joint ?

AtomicInteger — Tue, 10 Nov 2009 13:12:01 GMT

If I understand you correctly, perhaps you could create a Slider Joint with one end tracking the position of the mouse, and the other end attached to the body you want to track.

Another approach may be to create a Linear Spring between the target body and a body tracking the Mouse position - (Spring RestLength set to the distance between the mouse and target body when the mouse is first pressed) You can tune the Springs DampningConstant & SpringConstant to create a very 'stiff' spring ?

New Post: Mouse Spring/Joint ?

danthekilla — Tue, 10 Nov 2009 10:24:55 GMT

Well it would just run into the static object... and not be able to pass though.

I will also write my own code however to prevent the mouse from traveling any further. So this way i can just drag around objects with no delay or springiness but still have them in the physics sim.
Imagine the mouse spring from the farseer samples but with no lag between moving the mouse and the object following, i belive there are quite a few people who have wanted/tried to get this.

Any ideas?