我正在使用Java 3D API编写一个小游戏，并且使用javax.media.j3d.BoundingBox对象存储模型的边界。
BoundingBox的构造函数如下：
public BoundingBox(Point3d lower, Point3d upper) {
boundId = BOUNDING_BOX;
this.lower = new Point3d(lower);
this.upper = new Point3d(upper);
updateBoundsStates();
}
现在，我想平移和旋转BoundingBox，因为模型本身可以，并且我使用以下BoundingBox方法：
/**
* Transforms this bounding box by the given matrix.
* @param matrix a transformation matrix
*/
public void transform(Transform3D matrix) {
if(boundsIsInfinite)
return;
if (tmpP3d == null)
tmpP3d = new Point3d();
double ux, uy, uz, lx, ly, lz;
ux = upper.x;
uy = upper.y;
uz = upper.z;
lx = lower.x;
ly = lower.y;
lz = lower.z;
tmpP3d.set(ux, uy, uz);
matrix.transform( tmpP3d );
upper.x = tmpP3d.x;
upper.y = tmpP3d.y;
upper.z = tmpP3d.z;
lower.x = tmpP3d.x;
lower.y = tmpP3d.y;
lower.z = tmpP3d.z;
tmpP3d.set(lx, uy, uz);
matrix.transform( tmpP3d );
if ( tmpP3d.x > upper.x ) upper.x = tmpP3d.x;
if ( tmpP3d.y > upper.y ) upper.y = tmpP3d.y;
if ( tmpP3d.z > upper.z ) upper.z = tmpP3d.z;
if ( tmpP3d.x < lower.x ) lower.x = tmpP3d.x;
if ( tmpP3d.y < lower.y ) lower.y = tmpP3d.y;
if ( tmpP3d.z < lower.z ) lower.z = tmpP3d.z;
tmpP3d.set(lx, ly, uz);
matrix.transform( tmpP3d );
if ( tmpP3d.x > upper.x ) upper.x = tmpP3d.x;
if ( tmpP3d.y > upper.y ) upper.y = tmpP3d.y;
if ( tmpP3d.z > upper.z ) upper.z = tmpP3d.z;
if ( tmpP3d.x < lower.x ) lower.x = tmpP3d.x;
if ( tmpP3d.y < lower.y ) lower.y = tmpP3d.y;
if ( tmpP3d.z < lower.z ) lower.z = tmpP3d.z;
tmpP3d.set(ux, ly, uz);
matrix.transform( tmpP3d );
if ( tmpP3d.x > upper.x ) upper.x = tmpP3d.x;
if ( tmpP3d.y > upper.y ) upper.y = tmpP3d.y;
if ( tmpP3d.z > upper.z ) upper.z = tmpP3d.z;
if ( tmpP3d.x < lower.x ) lower.x = tmpP3d.x;
if ( tmpP3d.y < lower.y ) lower.y = tmpP3d.y;
if ( tmpP3d.z < lower.z ) lower.z = tmpP3d.z;
tmpP3d.set(lx, uy, lz);
matrix.transform( tmpP3d );
if ( tmpP3d.x > upper.x ) upper.x = tmpP3d.x;
if ( tmpP3d.y > upper.y ) upper.y = tmpP3d.y;
if ( tmpP3d.z > upper.z ) upper.z = tmpP3d.z;
if ( tmpP3d.x < lower.x ) lower.x = tmpP3d.x;
if ( tmpP3d.y < lower.y ) lower.y = tmpP3d.y;
if ( tmpP3d.z < lower.z ) lower.z = tmpP3d.z;
tmpP3d.set(ux, uy, lz);
matrix.transform( tmpP3d );
if ( tmpP3d.x > upper.x ) upper.x = tmpP3d.x;
if ( tmpP3d.y > upper.y ) upper.y = tmpP3d.y;
if ( tmpP3d.z > upper.z ) upper.z = tmpP3d.z;
if ( tmpP3d.x < lower.x ) lower.x = tmpP3d.x;
if ( tmpP3d.y < lower.y ) lower.y = tmpP3d.y;
if ( tmpP3d.z < lower.z ) lower.z = tmpP3d.z;
tmpP3d.set(lx, ly, lz);
matrix.transform( tmpP3d );
if ( tmpP3d.x > upper.x ) upper.x = tmpP3d.x;
if ( tmpP3d.y > upper.y ) upper.y = tmpP3d.y;
if ( tmpP3d.z > upper.z ) upper.z = tmpP3d.z;
if ( tmpP3d.x < lower.x ) lower.x = tmpP3d.x;
if ( tmpP3d.y < lower.y ) lower.y = tmpP3d.y;
if ( tmpP3d.z < lower.z ) lower.z = tmpP3d.z;
tmpP3d.set(ux, ly, lz);
matrix.transform( tmpP3d );
if ( tmpP3d.x > upper.x ) upper.x = tmpP3d.x;
if ( tmpP3d.y > upper.y ) upper.y = tmpP3d.y;
if ( tmpP3d.z > upper.z ) upper.z = tmpP3d.z;
if ( tmpP3d.x < lower.x ) lower.x = tmpP3d.x;
if ( tmpP3d.y < lower.y ) lower.y = tmpP3d.y;
if ( tmpP3d.z < lower.z ) lower.z = tmpP3d.z;
if (VirtualUniverse.mc.releaseBoundingBoxMemory) {
// Free memory
tmpP3d = null;
}
}
但是：如果使用此方法旋转BoundingBox，它将生成一个新的BoundingBox，其体积可能大于旧的BoundingBox。仅当您精确旋转90、180、270或360度时，它才会提供相同的音量。
附加信息：我必须手动计算BoundingBox，因为我通过在模型上调用setAutoComputeBounds（false）和setBounds（XYZ）使用手动边界（而不是太大的自动计算的边界）（在这种情况下，它实际上是javax的一个实例）。 media.j3d指向javax.media.j3d.SharedGroup），并且在转换/旋转相应模型的情况下，Java 3d Engine（至少在这种情况下）似乎不会自动重新计算手动边界。
我的问题是：我应该如何（重新）实现上面显示的方法transform（）以获得始终具有相同体积的BoundingBoxes？
最佳答案
实际上，无论BoundingBox的两个点在哪里，它都始终与轴对齐。两点不能定义任意立方体。无论您如何重写转换函数，它都将无法工作。
您可以考虑BoundingPolytope类。尽管它确实具有接受另一个Bounds对象的构造函数，但它提供了由平面形成的更一般的边界，因此您实际上不必自己定义平面。