Three.js mesh based on BufferGeometry not appearing

问题

I'm working on a WebGL game using Three.js & I've decided to switch to a THREE.BufferGeometry implementation from my (working) regular THREE.Geometry solution. I'm messing something up, because the mesh does not draw. I've given the relevant parts of my code below. If I switch to a regular geometry, everything works fine.

It's a voxel based game and I've pre-created each face of each cube as a regular THREE.Geometry. The positionVertices function takes the vertices and faces from each face geometry, positions them so that they correspond to the voxel, and generates the buffer data for the THREE.BufferGeometry. There are no errors or warnings, the final mesh just doesn't appear. I suspect my problem has less to do with Three.js and more with my limited understanding of 3D graphics programming. My best guess right now is that it has something to do with the indexes not being correct. If I remove the indexes, the object appears, but half of the triangles have their normals in the opposite direction.

Chunk.prototype.positionVertices = function( position, vertices, faces, vertexBuffer, indexBuffer, normalBuffer, colorBuffer ) {
    var vertexOffset = vertexBuffer.length / 3;
    for( var i = 0; i < faces.length; ++i ) {
        indexBuffer.push( faces[i].a + vertexOffset );
        indexBuffer.push( faces[i].b + vertexOffset );
        indexBuffer.push( faces[i].c + vertexOffset );

        normalBuffer.push( faces[i].vertexNormals[0].x );
        normalBuffer.push( faces[i].vertexNormals[0].y );
        normalBuffer.push( faces[i].vertexNormals[0].z );

        normalBuffer.push( faces[i].vertexNormals[1].x );
        normalBuffer.push( faces[i].vertexNormals[1].y );
        normalBuffer.push( faces[i].vertexNormals[1].z );

        normalBuffer.push( faces[i].vertexNormals[2].x );
        normalBuffer.push( faces[i].vertexNormals[2].y );
        normalBuffer.push( faces[i].vertexNormals[2].z );
    }

    var color = new THREE.Color();
    color.setRGB( 0, 0, 1 );
    for( var i = 0; i < vertices.length; ++i ) {
        vertexBuffer.push( vertices[i].x + position.x );
        vertexBuffer.push( vertices[i].y + position.y );
        vertexBuffer.push( vertices[i].z + position.z );

        colorBuffer.push( color.r );
        colorBuffer.push( color.g );
        colorBuffer.push( color.b );
    }
};

// This will need to change when more than one type of block exists.
Chunk.prototype.buildMesh = function() {

    var cube = new THREE.Mesh();
    var vertexBuffer = []; // [0] = v.x, [1] = v.y, etc
    var faceBuffer = [];
    var normalBuffer = [];
    var colorBuffer = [];
    for( var k = 0; k < this.size; ++k )
    for( var j = 0; j < this.size; ++j )
    for( var i = 0; i < this.size; ++i ) {
        // Iterates over all of the voxels in this chunk and calls
        // positionVertices( position, vertices, faces, vertexBuffer, indexBuffer, normalBuffer, colorBuffer ) for each face in the chunk
    }

    var bGeo = new THREE.BufferGeometry();

    bGeo.attributes = {

        index: {
            itemSize: 1,
            array: new Uint16Array( faceBuffer ),
            numItems: faceBuffer.length
        },
        position: {
            itemSize: 3,
            array: new Float32Array( vertexBuffer ),
            numItems: vertexBuffer.length
        },
        normal: {
            itemSize: 3,
            array: new Float32Array( normalBuffer ),
            numItems: normalBuffer.length
        },
        color: {
            itemSize: 3,
            array: new Float32Array( colorBuffer ),
            numItems: colorBuffer.length
        }
    }


    var mesh = new THREE.Mesh( bGeo, VOXEL_MATERIALS["ROCK"]);

    return mesh;
}

回答1:

I needed to set a single offset on the geometry.

    bGeo.offsets = [
        {
            start: 0,
            index: 0,
            count: faceBuffer.length
        }
    ];

Fixed it. The triangles are still displaying wrong, so I guess the faces are messed up, but I can figure that out easily enough.

来源：https://stackoverflow.com/questions/19613281/three-js-mesh-based-on-buffergeometry-not-appearing