我需要一些帮助来处理 THREE.Frustum 对象。
我的问题:
我需要计算近/远平面顶点;我已经看过这些教程
- http://www.lighthouse3d.com/tutorials/view-frustum-culling/view-frustums-shape/
- http://www.lighthouse3d.com/tutorials/view-frustum-culling/geometric-approach-extracting-the-planes/
我已经草绘了这个函数,它准确地实现了(我希望如此)所解释的过程(只是为了获得左上/右上顶点,假设相机只能向左和向右看):
// Near Plane dimensions
hNear = 2 * Math.tan(camera.fov / 2) * camera.near; // height
wNear = hNear * camera.aspect; // width
// Far Plane dimensions
hFar = 2 * Math.tan(camera.fov / 2) * camera.far; // height
wFar = hFar * camera.aspect; // width
getVertices : function() {
var p = camera.position.clone();
var l = getCurrentTarget(); // see below
var u = new THREE.Vector3(0, 1, 0);
var d = new THREE.Vector3();
d.sub(l, p);
d.normalize();
var r = new THREE.Vector3();
r.cross(u, d);
r.normalize();
// Near Plane center
var dTmp = d.clone();
var nc = new THREE.Vector3();
nc.add(p, dTmp.multiplyScalar(camera.near));
// Near Plane top-right and top-left vertices
var uTmp = u.clone();
var rTmp = r.clone();
var ntr = new THREE.Vector3();
ntr.add(nc, uTmp.multiplyScalar(hNear / 2));
ntr.subSelf(rTmp.multiplyScalar(wNear / 2));
uTmp.copy(u);
rTmp.copy(r);
var ntl = new THREE.Vector3();
ntl.add(nc, uTmp.multiplyScalar(hNear / 2));
ntl.addSelf(rTmp.multiplyScalar(wNear / 2));
// Far Plane center
dTmp.copy(d);
var fc = new THREE.Vector3();
fc.add(p, dTmp.multiplyScalar(camera.far));
// Far Plane top-right and top-left vertices
uTmp.copy(u);
rTmp.copy(r);
var ftr = new THREE.Vector3();
ftr.add(fc, uTmp.multiplyScalar(hFar / 2));
ftr.subSelf(rTmp.multiplyScalar(wFar / 2));
uTmp.copy(u);
rTmp.copy(r);
var ftl = new THREE.Vector3();
ftl.add(fc, uTmp.multiplyScalar(hFar / 2));
ftl.addSelf(rTmp.multiplyScalar(wFar / 2));
getCurrentTarget : function() {
var l = new THREE.Vector3(0, 0, -100);
this.camera.updateMatrixWorld();
this.camera.matrixWorld.multiplyVector3(l);
return l;
}
这似乎有效,但是...
我的问题:
我可以使用 THREE.Frustum 对象以更优雅(也许更正确)的方式获得相同的结果吗?
Three.Frustum
并不会真正帮助你——它只是一组飞机。好消息是您的解决方案看起来是正确的,但有一种更简单的方法来考虑这个问题。
近平面的右上角是相机空间中的一个点,其坐标如下:
var ntr = new THREE.Vector3( wNear / 2, hNear / 2, -camera.near );
使用你的定义wNear
and hNear
,这是正确的。
现在,确保camera.matrixWorld
更新后,您可以将该点转换为世界坐标,如下所示:
camera.updateMatrixWorld();
ntr.applyMatrix4( camera.matrixWorld );
现在,翻转符号以获得其他三个角,然后对远平面重复计算。
看,你说得对;你只是走了一条更复杂的路线。 :-)
编辑:更新到 Three.js r.66
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