在将组添加到 Locale 或 SimpleUniverse 后，将对象添加到 BranchGroup

Question

考虑一个简单的代码：

import java.awt.*;
import javax.media.j3d.*;
import javax.vecmath.Color3f;
import javax.vecmath.*;
import com.sun.j3d.utils.universe.*;
import com.sun.j3d.utils.geometry.*;

public class Main {
  public static void main(final String[] args) {
    final SimpleUniverse universe = new SimpleUniverse();
    final BranchGroup group = new BranchGroup();

    TriangleArray triangle = new TriangleArray(3, TriangleArray.COORDINATES);
    triangle.setCoordinates(0, new Point3f[]{
        new Point3f(-0.3f,     0, -1),
        new Point3f(    0, -0.3f, -1),
        new Point3f(    0,     0, -1),
    });
    group.addChild(new Shape3D(triangle));

    universe.addBranchGraph(group);

    TriangleArray triangle1 = new TriangleArray(3, TriangleArray.COORDINATES);
    triangle1.setCoordinates(0, new Point3f[]{
        new Point3f(0.3f,    0, -1),
        new Point3f(   0, 0.3f, -1),
        new Point3f(   0,    0, -1),
    });
    group.addChild(new Shape3D(triangle1));
  }
}

在将 group 添加到 universe 之前，我添加了一个三角形 triangle，它工作正常。

将组添加到宇宙后，我想再添加一个三角形triangle1。但是，我收到错误

Exception in thread "main" javax.media.j3d.RestrictedAccessException: Group: only a BranchGroup node may be added
        at javax.media.j3d.Group.addChild(Group.java:284)
        at Main.<init>(Main.java:34)
        at Main.main(Main.java:11)

所以我设置了 BranchGroup 的 ALLOW_DETACH 功能，将其从语言环境中删除，添加对象，然后将组重新添加到宇宙中：

// On initialization
group.setCapability(BranchGroup.ALLOW_DETACH);

// ...

// Adding another triangle
group.detach();
group.addChild(new Shape3D(triangle1));
universe.addBranchGraph(group);

但是，这似乎不必要地复杂。还有其他更好的方法来添加对象吗？

Answer 1

只需尽早调用 BranchGroup.setCapability(Group.ALLOW_CHILDREN_EXTEND)，即使在添加 BranchGroup 之后，您也应该被允许添加新的子项。

在将组添加到 Locale 或 SimpleUniverse 后，将对象添加到 BranchGroup

Add a Object to a BranchGroup after the group is added to a Locale or a SimpleUniverse

java

java-3d