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.
Related
Theres 2 parts to my problem and they are related. I have a weird shape on my interface illustrated below, I am trying to randomly spawn MovieClips within its' boundaries but I am having some trouble finding a good way to do it.
Question 1: I can run an If condition to check with bitMapData.hitTest to see if the MovieClip has randomly spawn within this shape, if it doesn't simply retry with a new set of random coordinates. However, is there a better way? Like a way to only take into account coordinates within the shape? There will be plenty of MC spawned at one go so I am hoping to lessen the load, or at least find an efficient way to do this calculation.
Question 2: The MovieClips spawned within this shape will eventually have collision detection mechanics that will repel itself when interacted with. Is there a way to contain them within this shape via some kind of boundary detection?
If it was a square, we could easily have contained them with a quick check on all 4 edges, but not with this shape. Currently I am thinking of using bitMapData.hitTest again to detect for out-of-bounds after being repelled, but how do I know which Point() is the nearest 'edge' of this shape to return the MC to?
For question 1: I'm going to go on an assumption that you have some geometry data about the shape.
One method you can use to check if a point is within a shape is to take that point, then draw a line from that point to infinity (the edge of the screen) in one direction. Then count how many times that line intersects an edge of the shape. If it's odd, the point is within the shape (or on the edge) and if it's even, than that point is outside of the shape.
First link in google: https://www.geeksforgeeks.org/how-to-check-if-a-given-point-lies-inside-a-polygon/
Or can also try a more simple method (at the cost of doing more work): if the above shape is generated with all squares and rectangles and you know the point and size of all of those: can just do a check for the point vs all the squares and rectangles that make up the shape.
For question 2: As Organis mentioned, I'd go with a library like Box2D to do this. You'll most likely spend tons of time (that you may not want to) if you try to implement this alone.
The big issue is how much cpu or gpu the code uses. You're trying to avoid using any collision detection. Collision detection is having code do calculations to determine the edges of an object. It should be the last option.
Most of the time you know there's no need for collision detection. You know where everything is and how big it is. Everything has a centerpoint and comparing simple number coordinates is the lightweight way to check if there's a need to check further.
When things get near each other, you only need to do a collision detection on the immediate area around an object. See how your shape fits in a box that is easy to check for collisions? That box should get a collision check before the actual jagged shape inside it.
Yes that collision detection box has to be drawn or mapped but it's done when the object is defined, not when the game is playing. If you are using sprite sheets, keep an xml of the boxes or circles around the shapes.
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 new to programming games, so I'll make it short and sweet:
Is there any standard practice for Flash/AS3 for organizing sets of game Sprites, especially related to movement. For Example, if I am moving left, and then down, there should be a fill in animation...if we want that fill-in animation, do we need to create an animation for every permutation of all 8 directions our character can move? Also, if we want to have dynamic shadows for our 2d sprites, do we have to draw a light source for every one of those 8 directions for all 8 directions?
No, there is no practice like that.
However, here are some tips from my personal experience:
fill-ins:
if your sprite is small, just don't do any
other - SOME filling - for example, just from one direction to the one near it, and whenever the sprite rotates more than just on direction, play the fill-ins in a row
if you want to make ALL fill-ins, that would be a lot of work, I would say too much for something as small as a fill-in between two directions - better spend the time for something else
light sources:
again, matters HOW visible this sprite will be - if it is something very small, just mirror and / or don't make any lighting at all
other - I am used to always make one sprite (fully redrawn, or just light redrawn - does not mater) - for all directions - it adds a nice touch to visible things like player sprite that are always going to be on the screen
I'm brand new to Flash (and game programming, really), but want to learn a bit of it. My overall learning project is to create a Monopoly clone in Flash. Unfortunately, I'm struggling to get over even my first hurdle - how to create the board graphically, and how then to deal with it in the code. So far, my thoughts are to break the board down into the different sizes of tiles (the normal property ones, the corner 4 and a large one for the middle section), then somehow place these all in the correct position relative to each other and keep that positioning correct as the pieces (and thus the camera view) move about the board. (And, hopefully some day have a zooming ability too...)
Is this a good approach, or is there a better one? Does anyone know where I can find a tutorial specifically on creating board games in Flash (any sort really, wouldn't have to be Monopoly but just a game that has a board which tokens move across - and preferably which has to pan as well).
Also, as an aside, is there any way to have a dynamically coloured rectangle in a flash MovieClip (like you can have dynamic textboxs)? I ask because it would be useful if there was, as I could generate every property tile with just one MovieClip which took a name, a value and a colour...
everything you describe here you can do pretty easily once you get the hang of component sprites. personally i would make a single sprite that will then hold all of the "tiles" in the game, this would allow you to "zoom" the board while keeping all the pieces relative:
if you create this parent to have an addTile() and getTile(index:int):Sprite method then you can easily push the tiles and retrieve them from an array, so that Go is at index 0, old kent road is at 1 etc. that way you can use a single integer value to determine the position of the player piece as you can then use getTile(int).x etc.
the position of the tiles themselves can be worked out relative to the others. if you have a tile that is 20px wide and 40px high then you can position the tile as x = index * 20 for the first row, after the initial 11, you need to rotate them all and then use the y index instead (rotation = 90; x = 11*20; y = (index-11)*20) this will depend exactly on your origin point of your Sprite.
to draw coloured boxes you use the graphics of the Sprite, there are plenty of tuts on API drawing out there, but here is a basic box of 10x10px:
var drawing:Sprite = new Sprite();
drawing.graphics.beginFill(0x0000FF);
drawing.graphics.drawRect(0, 0, 10, 10);
drawing.graphics.endFill();
Another approach to your question could be to learn about Object Oriented Programming. That may not solve your representing the board graphically straight away, but it would definitely help you structure your game.
With OOP, you could define a "Property" Class with a set of properties such as streetName , color , price etc... I haven't played Monopoly in a while but you can get the general idea, i.e. to create a base object and make it specific by setting the object's properties. Your question about the colored rectangle can actually apply to other properties, a great way to avoid unnecessary repetition.
Broadly speaking OOP tends to emulate real life situations, so you could actually look at your Monopoly game, break it into its various parts, find common properties etc... I won't start a lesson here :) I'd be pretty bad at it, but there's plenty of resources out there . Look for OOP, Design Patterns & Actionscript3.
After a little research, you may find that your question about how to handle graphics may not be such a problem after all.
Your questions are way too general. I'm sure you don't want us to walk you through your whole project right?
Now to gain some experience, I suggest to you simply work through a few flash gaming tutorials. There are a LOT of those, I googled for 2-3 seconds and found this:
http://pelfusion.com/tutorials/35-flash-game-development-tutorials-fla-files/
I'm sure you feel disappointed by this answer, but this is the first step in solving your own problems. The internet has more than enough general game tutorials already. If you have specific problems, we might be of better help to you.
I assume with dynamically colored rectangles, you mean simply changing the color during runtime. Well you simply give the rectangle a name, and change the color property of it in code. Like this: rectangle.Color = Something.
You might want to start out with a simpler project just to learn some of the basics, maybe a little game where the player has to move a rectangle from one side of the screen to the other using the arrow keys or mouse, upon which a score is incremented or something. This will help teach you how the coordinate system works, among other things.
To draw stuff using code, you can create a new Sprite or MovieClip object and use its graphics property to draw primitive shapes (rectangles, etc.) to it at runtime.
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.