When I create two dynamic bodies in box2d(cocos2dx), they repels each other and start to move in opposite directions. Which property I have to set to avoid this.
Don't create them on top of each other. It seems like you are not using the debug draw display to see what is really happening. I strongly recommend you use it.
Related
My problem is that I have some objects I want to create a highlight around. Currently I am using glowfilter to do this, it works perfectly fine most of the time. But when I have partly transparent objects I get a problem, for example, a window, since the glass in the window is transparent the glowfilter will be visible through it.
Is there a solution on how to make a nice outline, without having to worry about transparency?
Thank you in advance!
OK there are two answers, one is easy and non-coding based, and the other requires the first answer plus coding and is non-trivial.
Easy answer: Don't use transparency. Flatten the source image, copy your part, and put a GlowFilter on it. Simple, and probably the way you should go.
Not easy answer: What you're seeing is the normal behavior for Bitmap filters. Instead, you will need to use a combination of at least two bitmaps, one without any interior transparency (same image part as in the Easy answer) that uses a GlowFilter with the knockout parameter set to true, and the other identical bitmap, without a filter, placed directly over it if you are intending to slide things between the device and the highlight. Doing this is way beyond the scope of a simple question, and you should research it if the Easy Answer doesn't do it.
What the best way to make this kind of transformation: I have 4 pairs of coordinates, and I need to put the corners of my image exactly to them?
Like in photoshop, when you in free transform mode and moving corners of the image while holding ctrl.
Something like that.
If you can use the Flash 10 drawTriangles() method, then this link will provide you with a great explanation of what you are trying to do, with some well documented functioning code. The code is very similar to the solution that romamik provided, however, you will need to calculate the correct t value of the uvtData to get it to render correctly:
To summarize from that link:
Calculate the center point of the rectangle you are trying to draw
Get the distance between each point and the center
Calculate the ratio between the diagonals
use the formula (1/point_distance)*ratio to calculate perspective distortion for each point -- project into a faux 3d space (aka "magic" as the author of the post calls it)
That should produce the effect you are looking for.
If you can't use drawTriangles() then this link provides an alternative, however it wont produce as good of results as the drawTriangles() method.
You can use graphics.drawTriangles.
http://help.adobe.com/en_US/as3/dev/WS84753F1C-5ABE-40b1-A2E4-07D7349976C4.html
This code should do what you need (untested)
graphics.beginBitmapFill(bitmapData);
graphics.drawTriangles(
Vector.<Number>([10,10, 100,10, 10,100, 100,100]),
Vector.<int>([0,1,2, 1,3,2]),
Vector.<Number>([0,0, 1,0, 0,1, 1,1])
);
You can use the DistortImage class ported from the old 3D engine Sandy. A cleaner way would be the make use of rotateX and rotateY but it would require some mathematical pain!
I am trying to create an animation for lemon juice and baking soda experiment, and I was wondering how can I create a foaming effect such as the one shown in this image:
The idea I have in mind is to simply draw a foam in photoshop and then use motion tween to change the size. I was hoping I could find a better solution to this.
I have something somewhat similar that you can probably use as a springboard for doing your own thing.
http://www.shaunhusain.com/SteamEffect/
http://www.shaunhusain.com/SteamEffect/srcview/index.html
Currently I'm just drawing some circles with this and then setting a blur on them (not very efficient I know but it served the purposed as I didn't need it to create a bajillion particles to still be effective as "steam" which was the intended goal). You could swap out the shapes/filter I'm using for your own drawing and use the same basic structure.
EDIT
Perhaps this requires at least a little explanation:
Basically you'd want to look at the two files SteamCanvas.mxml and BitOfSteam.as. To be honest I have no idea why I decided to write SteamCanvas as an mxml file. I chose to use Canvas as the base class so I could just wrap it around any other component as a container and be able to detect mouse clicks anywhere within a region. If this is being used in a pure Flash environment, that is one not using the Flex libraries (or mxmlc compiler) it could be changed to extend from Sprite and be written purely in AS3, essentially just the creationComplete code should be moved to the constructor. How this works is the SteamCanvas is a wrapper for whatever controls or components you want to put in it (just like a normal canvas uses absolute positioning, but could have containers that define layout nested within it if need be). The SteamCanvas sets up a timer and if the mouse is down when the timer ticks, it creates instances of BitOfSteam and sets the properties for the steam based on the SteamCanvases own currently set properties. In the project you'll also see a SteamEffectTest.mxml which is just the file you see running that has the sliders on it to change the properties of the SteamCanvas, I used these to come up with what I thought were good values to make somewhat realistic steam. If I remember I'll revisit this component tomorrow and try to take Marty's suggestions to get it updated.
I'm trying to check if two objects (e.g. a rectangle and a triangle) on a HTML5 canvas are overlapping each other.
Currently I can only check that by looking at the screen (having set globalCompositeOperation='lighter').
My first idea would have been to scan all over the canvas if the "lighter" (compare code snippet above) color exists in the canvas. But therefor I would have to look at every single pixel which was rather costly for what I need.
Is there a (better) alternative to automatically check if they are overlapping?
Best regards.
The site below explains how to use the Separating Axis Theorem to determine if two convex shapes overlap.
http://www.codezealot.org/archives/55
To use this you will need to know the coordinate data used in contstructing the shapes.
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.