具有THREE.js ()能力的lookAt厚箭
具有THREE.js ()能力的lookAt厚箭
提问于 2020-12-03 12:09:06
我想做一个“厚箭”网格，也就是像标准箭手这样的箭头，但用的是cylinder而不是line制成的轴。
tldr;不复制Arrow设计；请参阅问题末尾的Epilogue部分。
因此，我根据自己的需要复制和修改了代码(不用构造函数和方法)并进行了更改，现在它可以工作了：-
// = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
//= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
//... 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
// = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
//= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = 这可以用于固定方向箭头，其中箭头方向可以在施工时提供。
但是现在我需要随着时间的推移改变箭头的方向(用于跟踪移动的目标)。目前，Object3D.lookAt()函数是不够的，因为箭头沿其Object3D y轴指向，而lookAt()则将Object3D z轴定向到给定的目标位置。
通过实验，我在那里得到了一些帮助：-
geometry.applyMatrix( new THREE.Matrix4().makeRotationX( Math.PI / 2 ) );在轴和头部几何图形上(在上面的代码摘录中注释掉了这两行)。这似乎使圆柱网格指向正确的方向。但问题是，网格是错误的形状和头部网格被移动远离轴网格。
通过反复尝试，我可能能够调整代码，使箭头适用于我现在的示例。但是(鉴于我对四元数理解不足)，我不相信它将(a)足够普遍地适用于所有情况，或(b)是充分未来的证据，以防止THREE.js的演变。
因此，对于如何实现“厚箭”的lookAt()功能，我将不胜感激。
结束语
我的主要目的是不遵循“帮助箭”的设计。
正如s 01和其他一些问题的答案所表明的那样，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(用于箭头和箭头)，这些网格在默认情况下将指向Y方向；使几何长度=1.0以协助将来的重新缩放。
(2)将网格添加到父Object3D对象中。
(3)用parent.rotateX(Math.PI/2)将母轴+90度绕X轴旋转.
(4)将父对象添加到祖父母对象中。
(5)随后使用grandparent.lookAt(target_point_as_World_position_Vec3_or_x_y_z)。
注:如果父母或祖父母的比例不是lookAt()，则(n,n,n) ()将不能正常工作。
父对象和祖父母对象类型可以是普通的THREE.Object3D，或者THREE.Group，或者THREE.Mesh (如果需要的话，可以是不可见的，例如通过设置小维度或.visibility=false)。
箭头助手可以动态使用，但前提是内部方向在使用lookAt()之前被设置为(0,0,1)。
回答 2
Stack Overflow用户
回答已采纳
发布于 2020-12-03 15:07:54
您可以将lookAt应用于任何Object3D。Object3D.lookAt( ... )
您已经发现lookAt会导致形状指向+Z方向，并且正在对此进行补偿。但是，随着Group的引入，它可以更进一步。Group也是从Object3D派生的，所以它们也支持lookAt方法。
let W = window.innerWidth;
let H = window.innerHeight;
const renderer = new THREE.WebGLRenderer({
antialias: true,
alpha: true
});
document.body.appendChild(renderer.domElement);
const scene = new THREE.Scene();
const camera = new THREE.PerspectiveCamera(28, 1, 1, 1000);
camera.position.set(10, 10, 50);
camera.lookAt(scene.position);
scene.add(camera);
const light = new THREE.DirectionalLight(0xffffff, 1);
light.position.set(0, 0, -1);
camera.add(light);
const group = new THREE.Group();
scene.add(group);
const arrowMat = new THREE.MeshLambertMaterial({color:"green"});
const arrowGeo = new THREE.ConeBufferGeometry(2, 5, 32);
const arrowMesh = new THREE.Mesh(arrowGeo, arrowMat);
arrowMesh.rotation.x = Math.PI / 2;
arrowMesh.position.z = 2.5;
group.add(arrowMesh);
const cylinderGeo = new THREE.CylinderBufferGeometry(1, 1, 5, 32);
const cylinderMesh = new THREE.Mesh(cylinderGeo, arrowMat);
cylinderMesh.rotation.x = Math.PI / 2;
cylinderMesh.position.z = -2.5;
group.add(cylinderMesh);
function render() {
renderer.render(scene, camera);
}
function resize() {
W = window.innerWidth;
H = window.innerHeight;
renderer.setSize(W, H);
camera.aspect = W / H;
camera.updateProjectionMatrix();
render();
}
window.addEventListener("resize", resize);
resize();
let rad = 0;
function animate() {
rad += 0.05;
group.lookAt(Math.sin(rad) * 100, Math.cos(rad) * 100, 100);
renderer.render(scene, camera);
requestAnimationFrame(animate);
}
requestAnimationFrame(animate);html,
body {
width: 100%;
height: 100%;
padding: 0;
margin: 0;
overflow: hidden;
background: skyblue;
}<script src="https://threejs.org/build/three.min.js"></script>
这里的关键是使锥/轴指向+Z方向，然后添加到Group中。这意味着他们的方向现在是本地的团体。当组的lookAt发生变化时，形状也随之变化。因为“箭头”形状指向小组的局部+Z方向，这意味着它们也指向给group.lookAt(...);的任何位置。
进一步工作
这只是一个起点。您将需要根据您希望它在正确位置上构造箭头、具有正确长度等方面进行调整。尽管如此，分组模式应该使lookAt更容易使用。
Stack Overflow用户
发布于 2020-12-03 17:37:56
你所需要的只是对嵌套有更多的了解，这样你就可以相对于他们的父母放置物体了。正如上面的答案所提到的，您可以使用Group或Object3D，但不必使用。你可以在你的圆柱体上嵌套你的箭头，把你的圆柱体指向z方向，然后使用内置的，不太复杂的方法lookAt。
不要在这样简单的事情上使用矩阵或四元数，因为这会使我们更难搞清楚事情。既然THREE.js允许嵌套帧，那么就利用它吧！
const renderer = new THREE.WebGLRenderer;
const camera = new THREE.PerspectiveCamera;
const scene = new THREE.Scene;
const mouse = new THREE.Vector2;
const raycaster = new THREE.Raycaster;
const quaternion = new THREE.Quaternion;
const sphere = new THREE.Mesh(
new THREE.SphereGeometry( 10, 10, 10 ),
new THREE.MeshBasicMaterial({ transparent: true, opacity: .1 })
);
const arrow = new THREE.Group;
const arrowShaft = new THREE.Mesh(
// We want to ensure our arrow is completely offset into one direction
// So the translation ensure every bit of it is in Y+
new THREE.CylinderGeometry( .1, .3, 3 ).translate( 0, 1.5, 0 ),
new THREE.MeshBasicMaterial({ color: 'blue' })
);
const arrowPoint = new THREE.Mesh(
// Same thing, translate to all vertices or +Y
new THREE.ConeGeometry( 1, 2, 10 ).translate( 0, 1, 0 ),
new THREE.MeshBasicMaterial({ color: 'red' })
);
const trackerPoint = new THREE.Mesh(
new THREE.SphereGeometry( .2 ),
new THREE.MeshBasicMaterial({ color: 'green' })
);
const clickerPoint = new THREE.Mesh(
trackerPoint.geometry,
new THREE.MeshBasicMaterial({ color: 'yellow' })
);
camera.position.set( 10, 10, 10 );
camera.lookAt( scene.position );
// Place the point at the top of the shaft
arrowPoint.position.y = 3;
// Point the shaft into the z-direction
arrowShaft.rotation.x = Math.PI / 2;
// Attach the point to the shaft
arrowShaft.add( arrowPoint );
// Add the shaft to the global arrow group
arrow.add( arrowShaft );
// Add the arrow to the scene
scene.add( arrow );
scene.add( sphere );
scene.add( trackerPoint );
scene.add( clickerPoint );
renderer.domElement.addEventListener( 'mousemove', mouseMove );
renderer.domElement.addEventListener( 'click', mouseClick );
renderer.domElement.addEventListener( 'wheel', mouseWheel );
render();
document.body.appendChild( renderer.domElement );
function render(){
renderer.setSize( innerWidth, innerHeight );
camera.aspect = innerWidth / innerHeight;
camera.updateProjectionMatrix();
renderer.render( scene, camera );
}
function mouseMove( event ){
mouse.set(
event.clientX / event.target.clientWidth * 2 - 1,
-event.clientY / event.target.clientHeight * 2 + 1
);
raycaster.setFromCamera( mouse, camera );
const hit = raycaster.intersectObject( sphere ).shift();
if( hit ){
trackerPoint.position.copy( hit.point );
render();
}
document.body.classList.toggle( 'tracking', !!hit );
}
function mouseClick( event ){
clickerPoint.position.copy( trackerPoint.position );
arrow.lookAt( trackerPoint.position );
render();
}
function mouseWheel( event ){
const angle = Math.PI * event.wheelDeltaX / innerWidth;
camera.position.applyQuaternion(
quaternion.setFromAxisAngle( scene.up, angle )
);
camera.lookAt( scene.position );
render();
}body { padding: 0; margin: 0; }
body.tracking { cursor: none; }<script src="https://cdnjs.cloudflare.com/ajax/libs/three.js/r123/three.min.js"></script>
你可以使用你的鼠标(如果它有水平滚动，应该在履带上)并点击指向箭头。我还添加了一些跟踪点，这样您就可以看到‘`lookAt’可以工作，而不会使其过于复杂，这就是指向您单击的包装球的点。
有了这个，我肯定把shaft这个词打得太频繁了。听起来有点奇怪。
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原文链接：
https://stackoverflow.com/questions/65125697
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