如何向 THREE.BufferGeometry 添加面？

我以编程方式创建了一个简单的网格：

var CreateSimpleMesh = new function () {
    var xy = [],
        maxX = 7,
        maxY = 10,
        river = [[0, 5], [0, 4], [1, 3], [2, 2], [3, 2], [4, 1], [5, 1], [6, 0]],
        grassGeometry = new THREE.BufferGeometry(),
        grassVertexPositions = []

    this.init = function () {
        for (i = 0; i < maxX; i++) {
            for (j = 0; j < maxY; j++) {
                xy.push([i, j])
            }
        }

        for (var i = 0; i < xy.length; i++) {
            grassVertexPositions.push([xy[i][0], xy[i][1], 0])
            grassVertexPositions.push([xy[i][0] + 1, xy[i][1], 0])
            grassVertexPositions.push([xy[i][0], xy[i][1] + 1, 0])

            grassVertexPositions.push([xy[i][0] + 1, xy[i][1] + 1, 0])
            grassVertexPositions.push([xy[i][0], xy[i][1] + 1, 0])
            grassVertexPositions.push([xy[i][0] + 1, xy[i][1], 0])
        }

        for (var i = 0; i < grassVertexPositions.length; i++) {
            for (var j = 0; j < river.length; j++) {
                if (river[j][0] == grassVertexPositions[i][0] && river[j][1] == grassVertexPositions[i][1]) {
                    grassVertexPositions[i][2] = -0.5
                }
            }
        }

        var grassVertices = new Float32Array(grassVertexPositions.length * 3)

        for (var i = 0; i < grassVertexPositions.length; i++) {
            grassVertices[i * 3 + 0] = grassVertexPositions[i][0];
            grassVertices[i * 3 + 1] = grassVertexPositions[i][1];
            grassVertices[i * 3 + 2] = grassVertexPositions[i][2];
        }

        grassGeometry.addAttribute('position', new THREE.BufferAttribute(grassVertices, 3))

    var grassMaterial = new THREE.MeshLambertMaterial({color: 0x00ff00}),
        grassMesh = new THREE.Mesh(grassGeometry, grassMaterial)

        grassMesh.rotation.x = -Math.PI / 2
        Test.getScene().add(grassMesh);
    }
}

问题是这个网格只有顶点。我尝试添加像这样的面孔this https://stackoverflow.com/questions/15795348/generate-mesh-faces-for-vertices-in-three-js使用 THREE.Shape.Utils.triangulateShape 的问题，但 BufferGeometry 与普通几何体不同，并且它不起作用。是否可以向 BufferGeometry 添加面？

EDIT: 工作小提琴 http://jsfiddle.net/grz671u9/

以下是如何创建一个网格BufferGeometry。这是更简单的“非索引”BufferGeometry其中顶点不共享。

// non-indexed buffer geometry
var geometry = new THREE.BufferGeometry();

// number of triangles
var NUM_TRIANGLES = 10;

// attributes
var positions = new Float32Array( NUM_TRIANGLES * 3 * 3 );
var normals   = new Float32Array( NUM_TRIANGLES * 3 * 3 );
var colors    = new Float32Array( NUM_TRIANGLES * 3 * 3 );
var uvs       = new Float32Array( NUM_TRIANGLES * 3 * 2 );

var color = new THREE.Color();
var scale = 15;
var size = 5;
var x, y, z;

for ( var i = 0, l = NUM_TRIANGLES * 3; i < l; i ++ ) {

    if ( i % 3 === 0 ) {

        x = ( Math.random() - 0.5 ) * scale;
        y = ( Math.random() - 0.5 ) * scale;
        z = ( Math.random() - 0.5 ) * scale;

    } else {

        x = x + size * ( Math.random() - 0.5 );
        y = y + size * ( Math.random() - 0.5 );
        z = z + size * ( Math.random() - 0.5 );

    }

    var index = 3 * i;

    // positions
    positions[ index     ] = x;
    positions[ index + 1 ] = y;
    positions[ index + 2 ] = z;

    //normals -- we will set normals later

    // colors
    color.setHSL( i / l, 1.0, 0.5 );
    colors[ index     ] = color.r;
    colors[ index + 1 ] = color.g;
    colors[ index + 2 ] = color.b;

    // uvs
    uvs[ index     ] = Math.random(); // just something...
    uvs[ index + 1 ] = Math.random();

}

geometry.addAttribute( 'position', new THREE.BufferAttribute( positions, 3 ) );
geometry.addAttribute( 'normal', new THREE.BufferAttribute( normals, 3 ) );
geometry.addAttribute( 'color', new THREE.BufferAttribute( colors, 3 ) );
geometry.addAttribute( 'uv', new THREE.BufferAttribute( uvs, 2 ) );

// optional
geometry.computeBoundingBox();
geometry.computeBoundingSphere();

// set the normals
geometry.computeVertexNormals(); // computed vertex normals are orthogonal to the face for non-indexed BufferGeometry

有关创建的许多其他示例，请参阅 Three.js 示例BufferGeometry。另请查看源代码PlaneGeometry and SphereGeometry，这相当容易理解。

三.js r.143