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API: Physics (AB) (r2)

API Uses canvas Graphics libraries AB framework Worlds using this API Starter Worlds
Physics (AB) (r2) Yes Three.js, Ammo Yes 1 World Starter Worlds


This API is for Three.js Worlds with physics using ammo.js. It comes with an Ancient Brain framework to make writing Worlds easier.

This API has the following features:

  • Includes Three.js release 127.

  • Includes the following libraries for loading 3D models:

  • Includes Physics support with the ammo.js library. Build of Apr 4, 2021 .

  • Includes jQuery 3.6.0.
  • Loads up minimal CSS that should not conflict with user CSS.

  • 3D and 2D graphics.
  • Built-in mouse (and touch screen) control of camera. Scroll and drag the mouse (or touch pinch and touch drag) to see camera control in both 3D and 2D Worlds.

Global variables

This API defines the following global variables:
 

 ABWorld;       // instance of class ABWorldClass - basic functionality for this API
 ABHandler;     // instance of class ABHandlerClass - mouse and touch handling for this API
 

The "ABWorld" object

The "ABWorld" object has the following public data, shown with default values where possible:

 
 
   ABWorld.camera;       // Three.js camera: THREE.PerspectiveCamera                 
   ABWorld.renderer;     // Three.js renderer: THREE.WebGLRenderer
   ABWorld.scene;        // Three.js scene: THREE.Scene 
	
	
 // draw camera control buttons (Track/Move/Normal) or not 
 
   ABWorld.drawCameraControls = true; 	 
		
		
 // change these points to control camera movement:
  
   ABWorld.follow;               // THREE.Vector3          
   ABWorld.lookat;               // THREE.Vector3        

	  // when camera is in "Track" mode, it will look at ABWorld.follow
	  // when camera is in "Move" mode, it will position at ABWorld.follow,
	  //   and look at ABWorld.lookat
	 


The "ABWorld" object has the following public methods:

 
	
// start a 3D or 2D scene with camera on the canvas:		

   ABWorld.init3d ( startRadius, maxRadius, color );   
   ABWorld.init2d ( startRadius, maxRadius, color );  

     // startRadius = start position of camera  
     // maxRadius = camera frustum far plane  
  
 
// change the mode of the camera to Track/Move With/Normal
 
   ABWorld.cameraTrack(); 
   ABWorld.cameraMove();
   ABWorld.cameraFixed();

   
// Useful functions for finding size of loaded 3D objects.
// Size of object along each dimension.

   ABWorld.objectXsize ( theobject );
   ABWorld.objectYsize ( theobject );
   ABWorld.objectZsize ( theobject );

   
// Useful "ray casting" function for mouse/touch control of objects.
// Returns if click/tap on that x,y screen position hits object in 3D World.

   ABWorld.hitsObject ( x, y, theobject );		 // boolean 

// Returns (3D co-ordinates) x,y,z point at which click/tap hits object:

   ABWorld.hitsObjectPoint ( x, y, theobject );  // returns null if no hit
   

The "ABHandler" object

The "ABHandler" object implements mouse and touch event handling. The default is that mouse and touch control the camera, but this can be overridden.

The "ABHandler" object has the following public data. Default values are shown. These can be changed.

 
   
// multiply mouse scroll by some factor to increase/decrease how much camera zooms:

   ABHandler.SCROLLFACTOR = 1;          	 

// multiply touch pinch by some factor to increase/decrease how much camera zooms:

   ABHandler.PINCHFACTOR  = 1;           	 	
	
// for 2D worlds, multiply mouse (or touch) drag by some factor to increase/decrease how much camera moves:
 
   ABHandler.DRAGFACTOR   = 1;            	 

   
// maximum position of camera:

   ABHandler.MAXCAMERAPOS;    // given some sensible default depending on World   

   
// does a "ground" exist at altitude zero (that camera should not zoom below):

   ABHandler.GROUNDZERO = false;
	


The "ABHandler" object defines the following functions for mouse and touch events.

 

  ABHandler.initMouseDrag = function ( x, y )  { ... };    
    // start drag now, at screen position x,y   

  ABHandler.mouseDrag     = function ( x, y )  { ... };   
    // drag went to new screen position x, y  
 
  ABHandler.mouseZoom     = function ( delta ) { ... };
    // zoom in or out by some amount 
    // the amount is set up for camera zoom 
    // for other usage of zoom, maybe just ignore delta, or only look at its sign  

	
  ABHandler.initTouchDrag = function ( x, y )  { ... };
  ABHandler.touchDrag     = function ( x, y )  { ... };
  ABHandler.touchZoom     = function ( delta ) { ... };
  
The above functions move the camera by default. To override this, and do your own mouse and touch event handling, simply redefine these functions.

To restore the default mouse/touch camera control, use:

 
	
  ABHandler.defaultMouse();   // Restore default mouse camera control 
  ABHandler.defaultTouch();   // Restore default touch camera control 
  

Optional: Customising scene, camera, renderer

The functions init3d and init2d create default forms of scene, camera and renderer. If you want a customised form of these, define the variable before calling init3d or init2d, and then your version will be used, not the default. Example:
 
ABWorld.renderer = new THREE.WebGLRenderer ( { antialias: true } );
ABWorld.init3d ( startRadius, maxRadius, color ); 

Optional: With custom renderer, set preserveDrawingBuffer for performance

If you are not customising renderer, but rather using init3d and init2d, then ignore this section.

This API uses an edited version of Three.js with the THREE.WebGLRenderer property "preserveDrawingBuffer" set to true. This is needed to allow the site generate a World image screenshot from the canvas. This may lead to lower performance, though.

If you are not customising renderer, but rather using init3d and init2d, this issue is taken care of automatically - preserveDrawingBuffer is true on "generate image" runs and false on normal runs.

If you are customising renderer, you will need to manage preserveDrawingBuffer yourself. It will be true by default. You can set it to false:

 
ABWorld.renderer = new THREE.WebGLRenderer ( { preserveDrawingBuffer: false } );
But then your World cannot have a screenshot. So a better approach is to set it to true for "generate image" runs and false for normal runs, which can be done as follows:
 
if ( AB.isScreenshotRun() ) ABWorld.renderer = new THREE.WebGLRenderer ( { preserveDrawingBuffer : true } );
else                        ABWorld.renderer = new THREE.WebGLRenderer ( { preserveDrawingBuffer : false } );

Templates


Examples

Examples of Worlds that use this API:


Ammo for AB
61 runs ♦ 0 likes
By Starter user  
Created: 19 Apr 2021
Modified: 19 Apr 2021
Ammo world for AB API

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