Simple Quickbox2d Sensors
Hey, wouldn’t be nice if you could make sensors easily in quickbox2d (which is already fantastic and easy). Well, you can, and here’s how, really easily. I’d post the source code, but if you haven’t figured it out by yourself, you might need the practice tinkering (besides Zevan will add it soon, I’m sure). This is painless, I promise.
If you don’t know what a sensor is, or why you’d want one – think of it as a physics object that detects collision but doesn’t actually affect the movement of anything its collides with – like passing through a ghost. No category or mask bits needed here, just a simple “true” or ”false”.
here’s how to add it to quickbox2d:
OVERVIEW:
you are going to open and add one tiny line of code to 3 files.
Step 1) open com.actionsnippet.QuickObject.as
Step) find the function “defineDefaults” should look something like this:
196 197 198 199 200 201 202 203 204 205 206 207 208 209 | private function defineDefaults():void{ defaults = {x:3, y:3, linearDamping:0, angularDamping:0, isBullet:false, fixedRotation:false, allowSleep: true, isSleeping:false, scaleSkin:true, density:1.0, friction:0.5, restitution:0.2, angle:0.0, maskBits:0xFFFF, categoryBits:1, groupIndex:0, draggable: true, lineColor:0x000000, lineAlpha:1, lineThickness:0, fillColor:0xCCCCCC, fillAlpha:1 } |
When you create an object, you pass parameters. these are the default parameters and we need to do as add “, isSensor:false” at the end so it looks like this
196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 | private function defineDefaults():void{ defaults = {x:3, y:3, linearDamping:0, angularDamping:0, isBullet:false, fixedRotation:false, allowSleep: true, isSleeping:false, scaleSkin:true, density:1.0, friction:0.5, restitution:0.2, angle:0.0, maskBits:0xFFFF, categoryBits:1, groupIndex:0, draggable: true, lineColor:0x000000, lineAlpha:1, lineThickness:0, fillColor:0xCCCCCC, fillAlpha:1, isSenor:false } |
1 of 3 completed. Now lets add a couple of tiny bits of code to the “BoxObject.as” and “CircleObject.as” files as well
BoxObject code: “boxDef.isSensor = p.isSensor;” see example below
33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 | override protected function build():void{ var p:Object = params; if(p.skin is DisplayObject){ bodyDef.userData = p.skin; var t:Number = p.skin.rotation; p.skin.rotation = 0; if (!p.width){ p.width = p.skin.width / 30; } if (!p.height){ p.height = p.skin.height / 30; } p.skin.rotation = t; } if (!p.width) p.width = 1; if (!p.height) p.height = 1; var boxDef:b2PolygonDef = new b2PolygonDef(); shapeDef = boxDef; var hw:Number = p.width / 2; var hh:Number = p.height / 2; boxDef.SetAsBox(hw, hh); boxDef.density = p.density; boxDef.friction = p.friction; boxDef.restitution = p.restitution; boxDef.filter.maskBits = p.maskBits; boxDef.filter.categoryBits = p.categoryBits; boxDef.filter.groupIndex = p.groupIndex; boxDef.isSensor = p.isSensor; // <------ HERE IT IS! |
CircleObject code: “circDef.isSensor = p.isSensor;” see example below
31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 | protected override function build():void{ var p:Object = params; var circDef:b2CircleDef = new b2CircleDef(); shapeDef = circDef; if (p.skin is DisplayObject){ bodyDef.userData = p.skin; if (!p.radius){ p.radius = p.skin.width/60; } } if (!p.radius) p.radius = .5; circDef.radius = p.radius; circDef.density = p.density; circDef.friction = p.friction; circDef.restitution = p.restitution; circDef.filter.maskBits = p.maskBits; circDef.filter.categoryBits = p.categoryBits; circDef.filter.groupIndex = p.groupIndex; circDef.isSensor = p.isSensor; // HERE IT IS!!! |
so, now, anytime you want an object to be a sensor, just tell it so on creation.
Examples:
1 2 3 | sim.addBox({x:someNumber, y:someNumber, width: x:someNumber, height: x:someNumber, density:0, isSensor:true}); sim.addCircle({x: x:someNumber, y: x:someNumber, radius: x:someNumber, density: 0, isSensor:true}); |