Whenever I connect two bodies with btGeneric6DofConstraint, bullet doesn't detect collisions between them anymore and lets them freely penetrate into each other. How do I force it to detect collisions?
You can specify if you want the two objects to collide with a flag when you call to addConstraint() to the world.
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Good evening/ morning.
I am creating a game in As3 where the enemies are added not added dynamically.
if(hero attacks enemy)
{ then parent.removeChild(enemy) }
When the hero attacks the enemy the enemy removes it self from the display list I presume.
but when you reset the level, i.e go back to the start menu and go back to the level you will see the enemies are not in the level, since they've been removed.
My question is, is there a way I can reset the display object in that frame, in As2 I refreshed the flash movie. But that's not good in terms of coding as it shows you are not developing or learning.
IF there is no way, will you suggest adding the objects that will be removed, dynamically?
another question is that my level is in a container.
//on the stage, there is a movieclip called container.
//In this container mc(movie clip) it contains the whole level, including platforms,
//enemies and props
IF I remove a prop from that container, in order to reset the game will I do this
container.addChild(prop)
//the question is that how do I set it's x and y position?
Thank you, I will appreciate every ones feedback and advice.
Yes, as you remove them dynamically, you need to add them dynamically again in order to reset them. You either predefine their positions and set them again, or you can just hide those enemies and make them visible once again the game resets. Depends on your code and structure.
Ideally, instead of removing them from the display list, your best bet is to hide then and put them and reset their position back to their original point.
A good practice to get into is to avoid the chance of runaway instantiation if at all possible; this means, if you're going to instantiate and remove enemies every time they're spawned and killed, the garbage collector has to work very hard to keep up. A better approach would be to have a pool of enemies that is as large enough to support as many enemies as you would ever need at one time.
I have a problem with a game that I'm doing. I basically have objects that are in a map and I have to check for each of them if they collide with the walls (and then do something). Since was working with AS2, I thought about doing the same way: I drew a picture with only the walls, so with only rectangles and everything else in between is transparent (does not exist, then the floor for example). In AS2 I put the image to the screen, let's call it wall, and then I did a hitTest to wall with every object. That is for instance, the object was actually on the image, since that the transparent parts were part of it, but the function was testing only on the visible parts, and so with the walls. So it worked.
Now in AS3 there is no HitTest but hitTestObject, which I used, and I do for example wall.hitTestObject(object). The problem is that this function is as if it doens't see the transparencies, and the objects while not touching the walls collide with them!
I found the PixelPerfectCollisionDetection that actually solves the problem but it is huge and heavy so in my case, with so many objects to be tested (at least 60) at each frame, the game slows down a lot!
What I need is a function like hitTestObject (i don't need a lot of accuracy!) that take care of the transparent parts of an image.
How can I do?
As mentioned in the comments, physics/game libraries will have this code built-in for you and should work out of the box.
But if you want to build it yourself, or even introduce your own optimizations, the first step (which is very inexpensive) is checking for bounds collision using entirely built-in functionality of DisplayObject.getBounds and Rectangle.intersects (though you must do so in a consistent coordinate space, i.e. the stage):
if (obj1.getBounds(stage).intersects(obj2.getBounds(stage)) {
// Cheap bounds intersection is true, now do pixel-perfect detection...
}
Then if the bounds check is true, perform the pixel-perfect collision detection.
It seems that BitmapData.hitTest is your best bet - see a blog post by Mike Chambers.
Prior to this method, if you're interested in neat techniques, there was a method outlined by Grant Skinner in his blog. It's quite a clever algorithm using built-in bitmap routines (aka, fairly fast), creating a BitmapData only as large as the overlapping region (or even scaling that down), and drawing the two objects into specific channels of the bitmapdata, then using BitmapData.getColorBoundsRect() to determine if there are any pixels touch. I'm guessing BitmapData.hitTest is faster, but it'd be fun to compare.
I ran into the same problem and to be honest i found the easy way to get rid of that is just generating a "mask" layer for the collisions. You can always place this under your background so it doesn't show, or change the transparencies and whatsoever. Do this in Flash, and after "covering" with rectangles (or whatever) the collisions, just select them all and make that a movie clip.
I'm guessing since you made the symbol in Flash, it obviously knows that even if the symbol consists of several individual drawings or whatever, it's not just an image.
For me this worked fine .
I'm currently trying to implement a "crouch" function in my game. I'm using WCK with Box2D.
I have something rather basic, I generate my main character as an extension of a shape. This means that collision is automatically generated from the getgo. This is wonderful for a lot of things, but not everything.
I have a crouch/roll function. The problem is that the hitbox for crouching and standing are the same, so if a box drops onto you while crouching it "levitates" ontop of you since the hitbox is still the standing hitbox.
How would I go about "refreshing" the shape collision? Is there a way to delete the collision and make Box2D recalculate?
It's possible to filter contacts and prevent them from happening (using a contact listener or iterating the world's contact list) but I think there are better ways to do what you want.
You could split the body in two parts, and connect them with a prismatic joint (limits and motor enabled, collideConnected disabled). Standing up you'd have the motor push the parts apart to the upper limit and when crouching you'd pull them together to the lower limit thus reducing the height.
If you need really different shapes (e.g. a rectangle when standing and a circle for rolling around metroid style) this might work: Add both shape's fixtures to the body and use mask filtering to prevent the one you don't need from colliding with anything.
I'm creating a space game in actionscript/flex 3 (flash). The world is infinitely big, because there are no maps. For this to work I need to dynamically (programatically) render the background, which has to look like open space.
To make the world feel real and to make certain places look different than others, I must be able to add filters such as colour differences and maybe even a misty kind of transformation - these would then be randomly added and changed.
The player is able to "scroll" the "map" by flying to the sides of the screen, so that a certain part of the world is only visible at once but the player is able to go anywhere. The scrolling works by moving all objects except for the player in the opposite direction, making it look like it was the player that moved into that direction. The background also needs to be moved, but has to be different on the new discovered terrain (dynamically created).
Now my question is how I would do something like this, what kind of things do I need to use and how do I implement them? Performance also needs to be taken into account, as many more objects will be in the game.
You should only have views for objects that are within the visible area. You might want to use a quad tree for that.
The background should maybe be composed of a set of tiles, that you can repeat more or less randomly (do you really need a background, actually? wouldn't having some particles be enough?). Use the same technique here you use for the objects.
So in the end, you wind up having a model for objects and tiles or particles (that you would generate in the beginning). This way, you will only add a few floats (you can achieve additional performance, if you do not calculate positions of objects, that are FAR away. The quad tree should help you with that, but I think this shouldn't be necessary) If an object having a view leaves the stage, free the view, and use the quad tree to check, if new objects appear.
If you use a lot of objects/particles, consider using an object pool. If objects only move, and are not rotated/scaled, consider using DisplayObject::cacheAsBitmap.
Currently I'm writing an app. If I want to avoid Singletons, do I have to simply pass references of everything around?
For example,
I have a "main" class.
Class: Main
+---- Screen
+---- Camera
+---- Terrain
+---- Vehicle
+---- PhysicsWorld
It contains my Camera, Terrain, and Vehicle,etc classes. Now, I have issues when I'm creating say, the Terrain object. Terrain wants to access Main classes Screen object so it can add its Terrain Graphics to the screen. It also wants to know about the Camera object for when it is drawing so it knows what scale to draw it. It also wants to know about my PhysicsWorld object so it can add itself to the physics engine.
Do I have to always lug these objects back and forth between constructors? I mean, when I create a Terrain object, do I simply have to pass around my screen object, my physicsWorld, camera, etc?
Another random scenario I have, is now.. inside my Vehicle class I need to call a Restart() method on my Main class. Does this mean I have to pass an instance of main to Vehicle? Really??
It feels cumbersome to constantly have to pass 4-5 things to my classes, especially in my scenario now where almost every in-game object I have needs a screen, physics, camera info, etc.
Any suggestions?
It feels cumbersome to constantly have
to pass 4-5 things to my classes,
especially in my scenario now where
almost every in-game object I have
needs a screen, physics, camera info,
etc.
Then the correct question to ask is "why do I need all 5 objects in all my classes?"
Why on Earth does every in-gmae object need any of the mentioned things? An in-game object needs a position and whatever it needs to process its behavior. Then a separate renderer can, you know, render, the object. Which means that only the renderer needs the camera info and screen.
The physics could go either way. You could have a separate physics entity which updates the game object, or you could pass that physics object to every game object. But even if you do pass that around, we're down to one out of the three objects listed. :)
That's why globals and singletons are often best avoided. They disguise your dependencies so you end up with far more dependencies between your objects than you actually need. And then it becomes almost impossible to remove the globals.
However, if you do stick with globals, do yourself a favor, and at least avoid singletons. You don't need the additional constraints enforced by a singleton.
Terrain wants to access Main classes
Screen object so it can add its
Terrain Graphics to the screen. It
also wants to know about the Camera
object for when it is drawing so it
knows what scale to draw it. It also
wants to know about my PhysicsWorld
object so it can add itself to the
physics engine.
The terrain object needs to know one thing: What is the terrain like. Someone else can take responsibility for rendering it. That someone will need to know about the camera, screen and terrain graphics, sure, which suggests that the same object might plausibly be able to do other tasks involving these objects (such as other rendering tasks).
Why should the terrain care about what scale it's drawn in? It needs to know the scale ingame, but not the scale in camera-space. And why can't someone else add the terrain to the physics engine? The main function might be able to do that, even. Create terrain, create physics engine, register terrain with physics engine, start game.
I don't know ActionScript, but assuming variables are passed by reference, the least you could do is construct a 'Environment' class holding Camera, Screen, Terrain, PhysicsWorld which you pass to the instances.
I have the exact same problem (also in actionscript 3, coincidentally).
I have been working on an RTS for flash and had found myself needing to pass around large numbers of references to each new class (e.g., gameGrid, currentSelection, visibleUnits, etc.).
I eventually realised that what I really should be doing is to have every class maintain it's own properties, and instead pass around references to these classes, (well objects).
But anyway, now what I'm doing is having static variables containing references to commonly used objects such as the main stage, interface, engine and display area inside a class called RTSGlobals. I'm also putting constants such as the screen size in there.
I know this doesn't really answer your question, but I figure sometimes it is worth ignoring a bit of OOP good practice in favour of an efficient solution.
If someone has a does have a good practice solution though, please tell :)
I suggest you take a look at XNA's samples projects (google it). They're well designed and might give you some hints.
Also, since you're using AS3, you could use the event system to dispatch message to other entities. For example, instead of passing your Main to your Vehicle class, make your Main (or whatever else interested) a listener of your Vehicle class. Then, let's say the car crash and you want to restart the game, dispatch an event, for example CAR_CRASHED. The listeners of your car should do something based on this message. If you want to understand the event system, type EventDispatcher, highlight it and hit F1 in your Flash IDE.