使用AxisHelper帮助理解View and Data API中的坐标系统

大家使用View and Data API做三维模型开发,必然首先要理解View and Data API的坐标系统,即XYZ三个轴向分别是怎么定义的。Three.js里面提供了一个AxisHelper,但如果你直接运用的话,你会发现在viewer中并不显示,并且控制台中会有这样的错误信息:"Only THREE.Mesh can be rendered by the Firefly renderer. Use THREE.Mesh to draw lines."  原因是因为View and Data API采用的是Three.js上定制的render,有些three.js中可以使用的功能在viewer中并不能用。所以我重写了一个这样的AxisHelper,希望对你有帮助。

 

使用非常简单,只需要加载这个扩展即可。建议在GEOMETRY_LOADED_EVENT事件中加载:

// It is recommended to load the extension when geometry is loaded
viewer.addEventListener(Autodesk.Viewing.GEOMETRY_LOADED_EVENT,
function(){ viewer.loadExtension('Autodesk.ADN.Viewing.Extension.AxisHelper'); });

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下面是截图,你可以看到红线是X轴,绿线是Y轴,蓝线是Z轴。请注意和右上角的view cube的对应关系。

使用AxisHelper帮助理解View and Data API中的坐标系统

下面是这个扩展的源代码,不过最好到 github 上下载,因为我可能会时不时的做更新,github上的才是最新的。

///////////////////////////////////////////////////////////////////////////////
AutodeskNamespace("Autodesk.ADN.Viewing.Extension"); Autodesk.ADN.Viewing.Extension.AxisHelper = function (viewer, options) { Autodesk.Viewing.Extension.call(this, viewer, options); var _self = this; var _axisLines = []; _self.load = function () { console.log('Autodesk.ADN.Viewing.Extension.AxisHelper loaded'); addAixsHelper(); //workaround
//have to call this to show up the axis
viewer.restoreState(viewer.getState()); return true;
}; _self.unload = function () { removeAixsHelper(); console.log('Autodesk.ADN.Viewing.Extension.AxisHelper unloaded');
return true;
}; var addAixsHelper = function() { _axisLines = []; //get bounding box of the model
var boundingBox = viewer.model.getBoundingBox();
var maxpt = boundingBox.max;
var minpt = boundingBox.min; var xdiff = maxpt.x - minpt.x;
var ydiff = maxpt.y - minpt.y;
var zdiff = maxpt.z - minpt.z; //make the size is bigger than the max bounding box
//so that it is visible
var size = Math.max(xdiff,ydiff,zdiff) * 1.2;
//console.log('axix size :' + size); // x-axis is red
var material_X_Axis = new THREE.LineBasicMaterial({
color: 0xff0000, //red
linewidth: 2
});
viewer.impl.matman().addMaterial('material_X_Axis',material_X_Axis,true);
//draw the x-axix line
var xLine = drawLine(
{x : 0, y : 0, z : 0} ,
{x : size, y : 0, z : 0} ,
material_X_Axis); _axisLines.push(xLine); // y-axis is green
var material_Y_Axis = new THREE.LineBasicMaterial({
color: 0x00ff00, //green
linewidth: 2
});
viewer.impl.matman().addMaterial('material_Y_Axis',material_Y_Axis,true);
//draw the y-axix line
var yLine = drawLine(
{x : 0, y : 0, z : 0} ,
{x : 0, y : size, z : 0} ,
material_Y_Axis); _axisLines.push(yLine); // z-axis is blue
var material_Z_Axis = new THREE.LineBasicMaterial({
color: 0x0000ff, //blue
linewidth: 2
});
viewer.impl.matman().addMaterial('material_Z_Axis',material_Z_Axis,true);
//draw the z-axix line
var zLine = drawLine(
{x : 0, y : 0, z : 0} ,
{x : 0, y : 0, z : size} ,
material_Z_Axis); _axisLines.push(zLine); } var drawLine = function(start, end, material) { var geometry = new THREE.Geometry(); geometry.vertices.push(new THREE.Vector3(
start.x, start.y, start.z)); geometry.vertices.push(new THREE.Vector3(
end.x, end.y, end.z)); var line = new THREE.Line(geometry, material); viewer.impl.scene.add(line);
//refresh viewer
viewer.impl.invalidate(true); return line;
} var removeAixsHelper = function() { _axisLines = []; _axisLines.forEach(function(line){ viewer.impl.scene.remove(line);
}); //remove materials
delete viewer.impl.matman().materials.material_X_Axis;
delete viewer.impl.matman().materials.material_Y_Axis;
delete viewer.impl.matman().materials.material_Z_Axis; } }; Autodesk.ADN.Viewing.Extension.AxisHelper.prototype =
Object.create(Autodesk.Viewing.Extension.prototype); Autodesk.ADN.Viewing.Extension.AxisHelper.prototype.constructor =
Autodesk.ADN.Viewing.Extension.AxisHelper; Autodesk.Viewing.theExtensionManager.registerExtension(
'Autodesk.ADN.Viewing.Extension.AxisHelper',
Autodesk.ADN.Viewing.Extension.AxisHelper);

Hope it helps.

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