Workaround for lack of line width on Windows when

问题:

I'm trying to draw a rotating 3D coordinate system using Three.js. I want the axes to have some thickness, which so far I have accomplished using LineBasicMaterial's linewidth parameter.

The following code works for me since I am not on Windows:

    var scene = new THREE.Scene();                                              
    var camera = new THREE.PerspectiveCamera( 75, window.innerWidth / window.   innerHeight, 0.1, 1000 );                                                           

    var renderer = new THREE.WebGLRenderer();
    renderer.setSize( window.innerWidth, window.innerHeight );
    document.body.appendChild( renderer.domElement );

    var triad = new THREE.Geometry();
    triad.vertices.push( new THREE.Vector3(  0,  0,  0 ) ); 
    triad.vertices.push( new THREE.Vector3( 10,  0,  0 ) );
    triad.vertices.push( new THREE.Vector3(  0,  0,  0 ) );
    triad.vertices.push( new THREE.Vector3(  0, 10,  0 ) );
    triad.vertices.push( new THREE.Vector3(  0,  0,  0 ) );
    triad.vertices.push( new THREE.Vector3(  0,  0, 10 ) );

    var line_mat = new THREE.LineBasicMaterial({'linewidth': 3});

    var frame = new THREE.Line(triad, line_mat, THREE.LinePieces);
    scene.add( frame );                       
    camera.position.z = 40;                        

    function render() {                    
        requestAnimationFrame(render);             
        frame.rotation.x += 0.1;            
        frame.rotation.y += 0.02;             
        renderer.render(scene, camera);                            
    }                                                                           
    render();

Unfortunately, there is a limitation on linewidth on Windows due to the ANGLE library, see this question: Thickness of lines using THREE.LineBasicMaterial

What can I use as a workaround so that this displays correctly on Windows?

回答1:

I got workaround for the width of the line. I created a new method and passed the coordinates where line is to be drawn. Then in your method , draw multiple lines around the coordinates. Here is the code :

function drawLine(lineMaterial, x1, y1 , z1, x2, y2, z2, thickness){
    for (i = 0; i < thickness * 2; i++) {  // multiplied it by 2 to be more granule pixels
        var routerLine1Geometry = new THREE.Geometry();
        routerLine1Geometry.vertices.push( new THREE.Vector3(x1, y1+i/4, z1));//divided it by 4 to be more granule pixels 

        routerLine1Geometry.vertices.push( new THREE.Vector3(x2, y2+i/4, z2)  );
        var routerLine1 = new THREE.Line( routerLine1Geometry, lineMaterial );
        scene.add(routerLine1);
    }
    for (i = 0; i < thickness * 2; i++) { 
        var routerLine1Geometry = new THREE.Geometry();
        routerLine1Geometry.vertices.push( new THREE.Vector3(x1, y1-i/4, z1)  );  // 
        routerLine1Geometry.vertices.push( new THREE.Vector3(x2, y2-i/4, z2)  );
        var routerLine1 = new THREE.Line( routerLine1Geometry, lineMaterial );
        scene.add(routerLine1);
    }
}

Let me know if this doesnt work.

回答2:

To run WebGL with native gl you have to install the OpenGL in your windows machine.

You have these options below:

1. Google Chrome "solution": "run chrome with the --use-gl=desktop command-line argument. As you can see in http://nuclear.mutantstargoat.com/webgl/
2. Firefox "solution": "Just type in navigation bar about:config and search for preference webgl.prefer-native-gl and set to true. As you can see in "http://forums.mozillazine.org/viewtopic.php?f=23&t=2090351&start=15

回答3:

By using Angle the rendering is actually handled by DirectX. Switching to native gl can even lead to performance increase (depending on the OpenGL performance of your graphics card).

You can check the current "under the hood" WebGL settings of your browser using this website here . It also shows you if your browser is currently using angle for WebGL.

You can also check this website for detailed explanation of how to switch to native gl.