July 5, 2019

Dump Geometries of 2D Curve

Follow @Xiaodong Liang

A few posts have introduced how to dump the geometries of the model in Forge Viewer. The basic workflow is to dump fragments of the object, get renderProxy of each fragment. renderProxy.geometry contains the vertex buffer of the geometry, by which we can sort it out with the data of mesh.

However when applying the same workflow with 2D drawing, you would be stuck because the fragment id for almost all objects (with different dbId) is same. And it does not work to get render proxy. This is because one fragment = one mesh/vertex buffer. In the 3D case, one element (one dbId) can be split across multiple fragments when the mesh is too big or it uses different materials. In the 2D case, multiple "grass clippings" (line dashes) from several elements get consolidated into single fragments.

 

So, how to get corresponding geometry of a specific curve in 2D? The answer is to Autodesk.Viewing.Private.VertexBufferReader

 

The class is defined in VertexBufferReader.js.  If checking source map in the browser, you would find it at LMV/./wgs/scene/VertexBufferReader.js.  This class manages all curves with their types, relationship with dbId, vertex, and also provides method to dump the geometry of specific dbId by VertexBufferReader .enumGeomsForObject.

 

My colleagues have demoed some codes at:

 

I am sorting them out and make an independent extension. thought it might be useful for some cases.

 

The definition of enumGeomsForObject is:

VertexBufferReader.prototype.enumGeomsForObject = function(dbId, callback)

The callback object needs these optional functions:

•              onLineSegment(x0, y0, x1, y1, viewport_id)

•              onCircularArc(centerX, centerY, startAngle, endAngle, radius, viewport_id)

•              onEllipticalArccenterX, centerY, startAngle, endAngle, major, minor, tilt, viewport_id)

•              onTriangleVertex(x, y, viewport_id)

The extension below will get the geometry of selected curve, and make a copy by Three.js object. This is a love demo:

https://forge-viewer-unit-test.herokuapp.com/ent-2d/showcurve.html

To play with it, after the model is loaded, click key ‘S’, then select any curve, the copy object will be created. Click key ‘Q’, all copied objects will be removed and select event is removed.

 


function GeometryCallback(viewer,copiedGeometryName,curveMaterial) {

  this.viewer = viewer;   
  this.opiedGeometryName = copiedGeometryName;

  // linewidth does not take effect in Chrome and Firefox 
  // It is a known issue with OpenGL core
  // try with Safari
  this.curveMaterial = curveMaterial;
  this.is2PITimes = function(angle1,angle2){
    return Math.abs(angle1-angle2)/Math.PI % 2 == 0
  }

}

GeometryCallback.prototype.onLineSegment = function(x1, y1, x2, y2, vpId) {

  var vpXform = this.viewer.model.getPageToModelTransform(vpId);
  //if in CAD coordinate system, applyMatrix4 with vpXform
  var pt1 = new THREE.Vector3().set(x1, y1, 0)//.applyMatrix4(vpXform);
  var pt2 = new THREE.Vector3().set(x2, y2, 0)//.applyMatrix4(vpXform); 

  console.log('Line segment vertices coordinates: ', {
      pointX1: pt1.x,
      pointY1: pt1.y,
      pointX2: pt2.x,
      pointY2: pt2.y
  }); 
  
  //add overlay geometry 
  var geometry = new THREE.Geometry () 
  geometry.vertices.push (new THREE.Vector3 ( pt1.x,  pt1.y, 0))
  geometry.vertices.push (new THREE.Vector3 ( pt2.x,  pt2.y, 0))

  var lines = new THREE.Line (geometry,
                              this.curveMaterial,
                              THREE.LinePieces)
  this.viewer.impl.addOverlay (this.opiedGeometryName, lines) 
  this.viewer.impl.invalidate (false,false,true)   
}

GeometryCallback.prototype.onCircularArc = function(cx, cy, start, end, radius, vpId) {

  var vpXform = this.viewer.model.getPageToModelTransform(vpId);
  //if in CAD coordinate system, applyMatrix4 with vpXform
  var center = new THREE.Vector3().set(cx, cy, 0)//.applyMatrix4(vpXform);

  console.log('CircleArc segment: ', {
    centerX: center.x,
    centerY: center.y,
    radius: radius,
    startAngle: start,
    endAngle: end
  }); 

  //add overlay geometry
  var curve = new THREE.EllipseCurve(
    center.x, center.y,            
    radius, radius,     
    start, end,  
    false            
  );
  var path = new THREE.Path(curve.getPoints(50));
  var geometry = path.createPointsGeometry(50);
  //remove last vertex if it an arc
  if(!this.is2PITimes(start,end))
    geometry.vertices.pop();
  var circularArc = new THREE.Line(geometry, this.curveMaterial);
  this.viewer.impl.addOverlay (this.opiedGeometryName, circularArc) 
  this.viewer.impl.invalidate (false,false,true)  
};

GeometryCallback.prototype.onEllipticalArc = function(cx, cy, start, end, major, minor, tilt, vpId) {
  var vpXform = this.viewer.model.getPageToModelTransform(vpId);
  //if in CAD coordinate system, applyMatrix4 with vpXform
  var center = new THREE.Vector3().set(cx, cy, 0)//.applyMatrix4(vpXform);

  console.log('EllipticalArc segment: ', {
    centerX: center.x,
    centerY: center.y,
    radius: radius,
    startAngle: start,
    endAngle: end
  }); 

  //add overlay geometry
  var curve = new THREE.EllipseCurve(
    center.x, center.y,            
    major, minor,     
    start, end,  
    false            
  );
  var path = new THREE.Path(curve.getPoints(50));
  var geometry = path.createPointsGeometry(50);
  //remove last vertex if it an arc
  if(!this.is2PITimes(start,end))
    geometry.vertices.pop();
  var ellipticalArc = new THREE.Line(geometry, this.curveMaterial);
  this.viewer.impl.addOverlay (this.opiedGeometryName, ellipticalArc) 
  this.viewer.impl.invalidate (false,false,true)  
};
GeometryCallback.prototype.onOneTriangle = function(x1, y1, x2, y2, x3, y3, vpId){
  //Similar logic as above
};
GeometryCallback.prototype.onTexQuad = function(centerX, centerY, width, height, rotation, vpId){
  //from VertexBufferReader.js:
  //Currently this case does not actually come up
};

//extension of MyShow2dCurve
function MyShow2dCurve(viewer, options) {

    Autodesk.Viewing.Extension.call(this, viewer, options)

    var _viewer = this.viewer 
    var _copiedGeometryName = 'copiedGeometryName'

    // linewidth does not take effect in Chrome and Firefox 
    // It is a known issue with OpenGL core
    // try with Safari
    var _curveMaterial = new THREE.LineBasicMaterial ({
      color: new THREE.Color (0xFF0000),
      transparent: true,
      depthWrite: false,
      depthTest: false,
      linewidth: 5,
      opacity: 1.0
      }) 

    //when extension is loaded
    this.load = function() {
        console.log('MyShow2dCurve is loaded!'); 
        //bind keyup event
        $(document).bind('keyup', onKeyUp); 
        _viewer.impl.invalidate(true);  
        return true;
    };

    //when extension is unloaded 
    this.unload = function() {
        console.log('MyShow2dCurve is now unloaded!');
        //unbind keyup event
        $(document).unbind('keyup', this.onKeyUp);
        return true;
    }; 

    //when key up
    function onKeyUp(evt) {  
        console.log('onKeyUp:' + evt.keyCode); 
  
        //when key 'S' is pressed
        if(evt.keyCode == 83){   
          //create overlay
          _viewer.impl.createOverlayScene (_copiedGeometryName, _curveMaterial)   
           //start to monitor select event 
          _viewer.addEventListener(Autodesk.Viewing.SELECTION_CHANGED_EVENT, onSelectObj) 
        }
      
        //when key 'Q' is pressed
        if(evt.keyCode == 81){ 
          //undelegate selection event
          _viewer.removeEventListener(Autodesk.Viewing.SELECTION_CHANGED_EVENT, onSelectObj) 
          //remove overlay
          _viewer.impl.removeOverlayScene(_copiedGeometryName);
          _viewer.impl.invalidate(false, false, true);  
          }
      
        return true;
      } 

      //when selecting object
      function onSelectObj(evt){ 
            console.log(evt) 
            //selected object id
            var dbId = evt.dbIdArray[0] 
            //get instance tree
            var it = _viewer.model.getData().instanceTree;
            //dump fragments of the object
            it.enumNodeFragments( dbId, function( fragId ) {
                //get each fragment
                var m = _viewer.impl.getRenderProxy(_viewer.model, fragId);
                //initialize VertexBufferReader
                var vbr = new Autodesk.Viewing.Private.VertexBufferReader(m.geometry, _viewer.impl.use2dInstancing);
                //dump geometry of this fragment
                vbr.enumGeomsForObject(dbId, new GeometryCallback(_viewer,_copiedGeometryName, _curveMaterial));
            }); 
      }    
}

MyShow2dCurve.prototype = Object.create(Autodesk.Viewing.Extension.prototype);
MyShow2dCurve.prototype.varructor = MyShow2dCurve; 
  
Autodesk.Viewing.theExtensionManager.registerExtension('MyShow2dCurve', MyShow2dCurve);  

 

Note:

  • linewidth of material does not take effect in Chrome and Firefox. It is a known issue with OpenGL core. If you want to see width, please try with Safari.

 

 

 

 

 

 

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