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////////////////////////////////////////////////////////////////////////////////
//
// (C) 2012, Alexander Grahn
//
// asylabels.js
//
// version 20120301
//
////////////////////////////////////////////////////////////////////////////////
//
// 3D JavaScript to be used with media9.sty (option `add3Djscript') for
// Asymptote generated PRC files
//
// adds billboard behaviour to text labels in Asymptote PRC files for improved
// visibility, they always face the camera while dragging the 3d object with the
// mouse.
//
//
// This work may be distributed and/or modified under the
// conditions of the LaTeX Project Public License, either version 1.3
// of this license or (at your option) any later version.
// The latest version of this license is in
// http://www.latex-project.org/lppl.txt
// and version 1.3 or later is part of all distributions of LaTeX
// version 2005/12/01 or later.
//
// This work has the LPPL maintenance status `maintained'.
//
// The Current Maintainer of this work is A. Grahn.
//
////////////////////////////////////////////////////////////////////////////////
//recursive function which computes the lower left BBox corner of a text
//label; it marches through all sibling mesh nodes the label is composed of;
//the returned Vector3 object will become the pivot point of the label
function nextCenter(msh){
//compute local-to-world transf. matrix of current mesh node
var trans=new Matrix4x4(msh.transform);
var parent=msh.parent;
while(parent.transform){
trans.multiplyInPlace(parent.transform);
parent=parent.parent;
}
//min BBox corner of current mesh node
var min=new Vector3();
min.set(msh.computeBoundingBox().min);
min.set(trans.transformPosition(min));
//get min BBox corner closest to origin (0,0,0)
if(msh.nextSibling){
var nextmin=nextCenter(msh.nextSibling);
return(min.length < nextmin.length ? min : nextmin);
}else{
return(min);
}
}
//find all text labels in the scene and determine pivoting points
var zero=new Vector3(0,0,0);
var nodes=scene.nodes;
var center=new Array();
var index=new Array();
for(var i=0; i<nodes.count; i++){
var node=nodes.getByIndex(i);
var name=node.name;
var end=name.lastIndexOf(".")-1;
if(end > 0){
if(name.charAt(end) == "\001"){
var start=name.lastIndexOf("-")+1;
if(end-start > 0) {
index.push(i);
center.push(nextCenter(node.firstChild));
node.name=name.substr(0,start-1);
}
}
}
}
var camera=scene.cameras.getByIndex(0);
//event handler to maintain upright position of text labels
billboardHandler=new RenderEventHandler();
billboardHandler.onEvent=function(event)
{
var position=camera.position;
var direction=position.subtract(camera.targetPosition);
var up=camera.up.subtract(position);
for(var i=0; i<index.length; i++){
var node=nodes.getByIndex(index[i]);
var R=Matrix4x4();
R.setView(zero,direction,up);
var c=center[i];
var T=node.transform;
T.setIdentity();
T.translateInPlace(c.scale(-1));
T.multiplyInPlace(R);
T.translateInPlace(c);
}
runtime.refresh();
}
runtime.addEventHandler(billboardHandler);
runtime.refresh();
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