如何从多个 Graphics3D 对象中选择一个并在 Mathematica 中更改其坐标？

Question

在问题“Mathematica and MouseListener - developing interactive graphics with Mma”的公认答案中，Sjoerd C de Vries 演示了可以选择 3D 图形中的对象并更改其颜色。

我想知道是否有可能（以与上述类似的方式）在具有两个或多个对象（例如两个长方体）的 Graphics3D 中选择一个并更改其坐标（通过移动或其他方式）？

Answer 1

我在这里部分重用了 Sjoerd 的代码，但可能是这样的

DynamicModule[{pos10, pos11 = {0, 0, 0}, 
  pos12 = {0, 0, 0}, pos20, pos21 = {0, 0, 0}, pos22 = {0, 0, 0}}, 
 Graphics3D[{EventHandler[
    Dynamic[{Translate[Cuboid[], pos11]}, ImageSize -> Tiny], 
   {"MouseDown" :> (pos10 = Mean@MousePosition["Graphics3DBoxIntercepts"]),
    "MouseDragged" :> (pos11 = 
      pos12 + Mean@MousePosition["Graphics3DBoxIntercepts"] - pos10),
    "MouseUp" :> (pos12 = pos11)}], 
  EventHandler[
   Dynamic[{Translate[Cuboid[{1, 1, 1}], pos21]}, ImageSize -> Tiny], 
   {"MouseDown" :> (pos20 = Mean@MousePosition["Graphics3DBoxIntercepts"]),
    "MouseDragged" :> (pos21 = 
       pos22 + Mean@MousePosition["Graphics3DBoxIntercepts"] - pos20),
    "MouseUp" :> (pos22 = pos21)}]},
  PlotRange -> {{-3, 3}, {-3, 3}, {-3, 3}}]]

请注意，这只是在平面中移动长方体，因此您必须旋转边界框以将它们垂直于该平面移动，但通过添加修饰键来引入第三维度应该不会太难。

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编辑

感谢 cmets。这是上面代码的更新版本。在这个版本中，如果立方体碰巧移到外面，立方体会跳回到边界框内，这样应该可以解决立方体消失的问题。

DynamicModule[{init, cube, bb, restrict, generate},
 init = {{0, 0, 0}, {2, 1, 0}};
 bb = {{-3, 3}, {-3, 3}, {-3, 3}};
 cube[pt_, scale_] := 
  Translate[Scale[Cuboid[{-1/2, -1/2, -1/2}, {1/2, 1/2, 1/2}], scale], pt];
 restrict[pt_] := MapThread[Min[Max[#1[[1]], #2], #1[[2]]] &, {bb, pt}];
 generate[pos_, scale_] := Module[{mp, pos0, pos1, pos2},
   mp := MousePosition["Graphics3DBoxIntercepts"];
   pos1 = pos;
   EventHandler[
    Dynamic[{cube[pos1, scale]}, ImageSize -> Tiny], 
    {"MouseDown" :> (pos0 = LeastSquares[Transpose[mp], pos1].mp), 
     "MouseDragged" :> 
       ((pos1 = #[[2]] + Projection[pos0 - #[[2]], #[[1]] - #[[2]]]) &@mp),
     "MouseUp" :> (pos1 = restrict[pos1])}]];

 Graphics3D[generate[#, 1] & /@ init, PlotRange -> bb, PlotRangePadding -> .5]
]