Question

我基于平面几何为Three.js创建了一个自定义几何函数。一切都很好，除了我不知道如何正确地进行UV显示。我每平方使用4个三角形，而THREE.PlaneGeometry每平方仅使用2个三角形。

PlaneGeometry UV的代码如下所示：

var uva = new THREE.Vector2( ix / gridX, 1 - iz / gridZ );
var uvb = new THREE.Vector2( ix / gridX, 1 - ( iz + 1 ) / gridZ );
var uvc = new THREE.Vector2( ( ix + 1 ) / gridX, 1 - ( iz + 1 ) / gridZ );
var uvd = new THREE.Vector2( ( ix + 1 ) / gridX, 1 - iz / gridZ );

源代码中的代码：

var uva = new THREE.Vector2( a );
var uvb = new THREE.Vector2( b );
var uvc = new THREE.Vector2( c );
var uvd = new THREE.Vector2( d );
var uve = new THREE.Vector2( e );

显然这是错误的。但我试图使用PlaneGeometry代码，我得到奇怪的扭曲，我不知道如何计算正确的位置。这个：

var uva = new THREE.Vector2( ix / gridX, 1 - iz / gridZ );
var uvb = new THREE.Vector2( ix / gridX, 1 - ( iz + 1 ) / gridZ );
var uvc = new THREE.Vector2( ( ix + 1 ) / gridX, 1 - ( iz + 1 ) / gridZ );
var uvd = new THREE.Vector2( (( ix ) / gridX) + gridX, 1 - iz / gridZ );
var uve = new THREE.Vector2( ( ix + 1 ) / gridX, 1 - iz / gridZ );

给我这个：BAD UV

我在THREE.JS ChatRoom中得到了某种答案，但我不理解，而且这个人没有详细说明......

（Q）那么...... UV的Vector2不应该与verticies的位置相同吗？

（A）没有UV是一个映射到纹理的矢量   具有512x512纹理，并且具有[0.25,0.75]的UV，它将映射到   纹理中的像素为256,768每个顶点都有一个uv   这意味着这个顶点映射到纹理，如上所述    这是针对顶点的每个面，以及顶点中的所有片段完成的   然后使用这三个uvs插入面

所以这并没有消除我的困惑..我不理解[0.25,0.75]部分。或者每个顶点都有一个纹理。点如何具有纹理。

有人能指出我正确的方向吗？我只需知道紫外线是如何定位的。但是一个例子会很棒。

如果您想查看以下内容：

THREE.DiamondGeometry = function ( width, height, widthSegments, heightSegments ) {

    THREE.Geometry.call( this );

    this.width = width;
    this.height = height;

    this.widthSegments = widthSegments || 1;
    this.heightSegments = heightSegments || 2;

    var long_row = this.widthSegments + 1;
    var short_row = this.widthSegments;
    // First Row is the long_row, the ternary statement will toggle this.
    var current_row = short_row;
    var gridY = 0;
    var vX = width / 2, vY = height / 2;

    var ix, iz;
    var width_half = width / 2;
    var height_half = height / 2;

    var gridX = this.widthSegments;
    var gridZ = this.heightSegments;

    var gridX1 = gridX + 1;
    var gridZ1 = gridZ + ( gridZ - 2) + 1;

    var segment_width = this.width / gridX;
    var segment_height = this.height / gridZ;

    var normal = new THREE.Vector3( 0, 0, 1 );
                     // Height Segments Verticies
    for ( iz = 0; iz < (gridZ1 + 1) * 2; iz ++ ) {
        // Ternary Operator:
        current_row === long_row ? (current_row = short_row, vX = width_half - (segment_width / 2) ) : (current_row = long_row, vX = width_half );
                        // Width Segment Verticies
        for ( ix = 0; ix < current_row; ix ++ ) {

            var x = ix * segment_width - vX ;
            var y = (iz * segment_height - vY) / 2 - (vY / 2);

            this.vertices.push( new THREE.Vector3( x, - y, 0 ) );
        }
    }

    for ( iz = 0; iz < gridZ ; iz ++ ) {

            for ( ix = 0; ix < gridX; ix ++ ) {
                var a = ix + gridX * iz + (iz * gridX1) ;
                var b = a + 1;
                var c = a  + gridX1;
                var d = c + gridX;
                var e = d + 1;

                // THIS IS THE BAD PART THAT I NEED TO CALCULATE THE UV POSITIONS FOR:
                var uva = new THREE.Vector2( a );
                var uvb = new THREE.Vector2( b );
                var uvc = new THREE.Vector2( c );
                var uvd = new THREE.Vector2( d );
                var uve = new THREE.Vector2( e );



                // UP
                var face = new THREE.Face3( c, b, a );
                face.normal.copy( normal );
                face.vertexNormals.push( normal.clone(), normal.clone(), normal.clone() );

                this.faces.push( face );
                this.faceVertexUvs[ 0 ].push( [ uva, uvb, uvc ] );

                // DOWN
                face = new THREE.Face3( e, c, d );
                face.normal.copy( normal );
                face.vertexNormals.push( normal.clone(), normal.clone(), normal.clone() );

                this.faces.push( face );
                this.faceVertexUvs[ 0 ].push( [ uvd, uvc.clone(), uve ] );

                // LEFT
                face = new THREE.Face3( d, c, a );
                face.normal.copy( normal );
                face.vertexNormals.push( normal.clone(), normal.clone(), normal.clone() );

                this.faces.push( face );
                this.faceVertexUvs[ 0 ].push( [ uva.clone(), uvc.clone(), uvd.clone() ] );

                // RIGHT
                face = new THREE.Face3( e, b, c );
                face.normal.copy( normal );
                face.vertexNormals.push( normal.clone(), normal.clone(), normal.clone() );

                this.faces.push( face );
                this.faceVertexUvs[ 0 ].push( [ uvc.clone(), uvb.clone(), uve.clone() ] );

            }

    }

    this.computeCentroids();

};

THREE.DiamondGeometry.prototype = Object.create( THREE.Geometry.prototype );

Answer 1

看到这张图片： http://cgkit.sourceforge.net/tutorials/_images/uvmap.png 如上所述，对于没有纹理重复的1个纹理，UV坐标在（0,0）到（1,1）的范围内。如果您有一个四边形平面并将UV指定给顶点，就像在图像中一样，整个纹理将显示在四边形上。如果您在四个较小的四边形中添加边缘循环/细分四边形但仍希望在不重复的情况下强制显示纹理，则需要计算顶点在UV空间中的位置之间的值。例如，中间的顶点（由你的细分产生）现在是UV（0.5,0.5）而middl顶部的那个是（0,0.5）。看看PlaneGeometry如何做到这一点并尝试从中学习^^

（Three.js）自定义网格UV显示纹理正确

1 个答案: