cylinder
而不是line
构成。
tldr; 不要复制箭头助手设计,请参见问题末尾的结论部分。
因此,我复制并修改了代码以满足我的需求(放弃了构造函数和方法),并进行了更改,现在它可以正常工作:
// = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
//= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
//... START of ARROWMAKER SET of FUNCTIONS
// adapted from https://github.com/mrdoob/three.js/blob/master/src/helpers/ArrowHelper.js
//====================================
function F_Arrow_Fat_noDoesLookAt_Make ( dir, origin, length, shaftBaseWidth, shaftTopWidth, color, headLength, headBaseWidth, headTopWidth )
{
//... dir is assumed to be normalized
var thisArrow = new THREE.Object3D();////SW
if ( dir === undefined ) dir = new THREE.Vector3( 0, 0, 1 );
if ( origin === undefined ) origin = new THREE.Vector3( 0, 0, 0 );
if ( length === undefined ) length = 1;
if ( shaftBaseWidth === undefined ) shaftBaseWidth = 0.02 * length;
if ( shaftTopWidth === undefined ) shaftTopWidth = 0.02 * length;
if ( color === undefined ) color = 0xffff00;
if ( headLength === undefined ) headLength = 0.2 * length;
if ( headBaseWidth === undefined ) headBaseWidth = 0.4 * headLength;
if ( headTopWidth === undefined ) headTopWidth = 0.2 * headLength;//... 0.0 for a point.
/* CylinderBufferGeometry parameters from:-
// https://threejs.org/docs/index.html#api/en/geometries/CylinderBufferGeometry
* radiusTop — Radius of the cylinder at the top. Default is 1.
* radiusBottom — Radius of the cylinder at the bottom. Default is 1.
* height — Height of the cylinder. Default is 1.
* radialSegments — Number of segmented faces around the circumference of the cylinder. Default is 8
* heightSegments — Number of rows of faces along the height of the cylinder. Default is 1.
* openEnded — A Boolean indicating whether the ends of the cylinder are open or capped. Default is false, meaning capped.
* thetaStart — Start angle for first segment, default = 0 (three o'clock position).
* thetaLength — The central angle, often called theta, of the circular sector. The default is 2*Pi, which makes for a complete cylinder.
*/
//var shaftGeometry = new THREE.CylinderBufferGeometry( 0.0, 0.5, 1, 8, 1 );//for strongly tapering, pointed shaft
var shaftGeometry = new THREE.CylinderBufferGeometry( 0.1, 0.1, 1, 8, 1 );//shaft is cylindrical
//shaftGeometry.translate( 0, - 0.5, 0 );
shaftGeometry.translate( 0, + 0.5, 0 );
//... for partial doesLookAt capability
//shaftGeometry.applyMatrix( new THREE.Matrix4().makeRotationX( Math.PI / 2 ) );
var headGeometry = new THREE.CylinderBufferGeometry( 0, 0.5, 1, 5, 1 ); //for strongly tapering, pointed head
headGeometry.translate( 0, - 0.5, 0 );
//... for partial doesLookAt capability
//headGeometry.applyMatrix( new THREE.Matrix4().makeRotationX( Math.PI / 2 ) );
thisArrow.position.copy( origin );
/*thisArrow.line = new Line( _lineGeometry, new LineBasicMaterial( { color: color, toneMapped: false } ) );
thisArrow.line.matrixAutoUpdate = false;
thisArrow.add( thisArrow.line ); */
thisArrow.shaft = new THREE.Mesh( shaftGeometry, new THREE.MeshLambertMaterial( { color: color } ) );
thisArrow.shaft.matrixAutoUpdate = false;
thisArrow.add( thisArrow.shaft );
thisArrow.head = new THREE.Mesh( headGeometry, new THREE.MeshLambertMaterial( { color: color } ) );
thisArrow.head.matrixAutoUpdate = false;
thisArrow.add( thisArrow.head );
//thisArrow.setDirection( dir );
//thisArrow.setLength( length, headLength, headTopWidth );
var arkle = new THREE.AxesHelper (2 * length);
thisArrow.add (arkle);
F_Arrow_Fat_noDoesLookAt_setDirection( thisArrow, dir ) ;////SW
F_Arrow_Fat_noDoesLookAt_setLength ( thisArrow, length, headLength, headBaseWidth ) ;////SW
F_Arrow_Fat_noDoesLookAt_setColor ( thisArrow, color ) ;////SW
scene.add ( thisArrow );
//... this screws up for the F_Arrow_Fat_noDoesLookAt kind of Arrow
//thisArrow.lookAt(0,0,0);//...makes the arrow's blue Z axis lookAt Point(x,y,z).
}
//... EOFn F_Arrow_Fat_noDoesLookAt_Make().
//=============================================
function F_Arrow_Fat_noDoesLookAt_setDirection( thisArrow, dir )
{
// dir is assumed to be normalized
if ( dir.y > 0.99999 )
{
thisArrow.quaternion.set( 0, 0, 0, 1 );
} else if ( dir.y < - 0.99999 )
{
thisArrow.quaternion.set( 1, 0, 0, 0 );
} else
{
const _axis = /*@__PURE__*/ new THREE.Vector3();
_axis.set( dir.z, 0, - dir.x ).normalize();
const radians = Math.acos( dir.y );
thisArrow.quaternion.setFromAxisAngle( _axis, radians );
}
}
//... EOFn F_Arrow_Fat_noDoesLookAt_setDirection().
//=========================================
function F_Arrow_Fat_noDoesLookAt_setLength( thisArrow, length, headLength, headBaseWidth )
{
if ( headLength === undefined ) headLength = 0.2 * length;
if ( headBaseWidth === undefined ) headBaseWidth = 0.2 * headLength;
thisArrow.shaft.scale.set( 1, Math.max( 0.0001, length - headLength ), 1 ); // see #17458
//x&z the same, y as per length-headLength
//thisArrow.shaft.position.y = length;//SW ???????
thisArrow.shaft.updateMatrix();
thisArrow.head.scale.set( headBaseWidth, headLength, headBaseWidth ); //x&z the same, y as per length
thisArrow.head.position.y = length;
thisArrow.head.updateMatrix();
}
//...EOFn F_Arrow_Fat_noDoesLookAt_setLength().
//========================================
function F_Arrow_Fat_noDoesLookAt_setColor( thisArrow, color )
{
thisArrow.shaft.material.color.set( color );
thisArrow.head.material.color.set( color );
}
//...EOFn F_Arrow_Fat_noDoesLookAt_setColor().
//... END of ARROWMAKER SET of FUNCTIONS
// = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
//= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
对于固定方向的箭头,在构建时可以提供箭头方向,这样可以正常工作。
但现在我需要随着时间改变箭头的方向(以跟踪移动目标)。目前,Object3D.lookAt()函数不够用,因为箭头沿着其Object3D y轴指向,而lookAt()将Object3D z轴定向到给定的目标位置。
通过尝试,我已经实现了部分功能:
geometry.applyMatrix( new THREE.Matrix4().makeRotationX( Math.PI / 2 ) );
在轴和头部几何形状上(以上代码提取中的两行被注释掉),这似乎可以使圆柱网格指向正确的方向。但问题是网格形状不正确,头部网格与轴网格分离。
通过试错,我可能能够调整代码以使箭头适用于我的当前示例。但是(考虑到我对四元数的理解很弱),我不确定它是否(a)足够通用以适用于所有情况或(b)是否足够未来证明其针对THREE.js的演变具备可靠性。
因此,我将感激任何关于如何实现“粗箭头”的lookAt()功能的解决方案/建议。
结语
我的主要收获不是遵循Helper Arrow的设计。
正如TheJim01和somethinghere的答案所示,使用Object3D.add()“嵌套”函数有一种更简单的方法。
例如:
(1) 创建两个圆柱网格(用于箭杆和箭头),默认情况下将指向Y方向;将几何长度设置为1.0以帮助将来重新缩放。
(2) 将网格添加到父Object3D对象中。
(3) 使用parent.rotateX(Math.PI/2)
将父对象沿X轴旋转+90度。
(4) 将父对象添加到祖父对象中。
(5) 随后使用grandparent.lookAt(target_point_as_World_position_Vec3_or_x_y_z)
。
N.B.如果父级或祖先具有除(n,n,n)
之外的缩放,则lookAt()将无法正常工作。
父对象和祖先对象类型可以是普通的THREE.Object3D
,也可以是THREE.Group
或THREE.Mesh
(如果需要可以设置为不可见,例如通过设置小尺寸或.visibility=false
)
Arrow Helper可以动态使用,但仅在使用lookAt()之前将内部方向设置为(0,0,1)时才能使用。
ArrowHelper
来看看如何构建和使用它。这个辅助工具也使用lookAt
而没有任何问题。 - somethinghere