Class SoCSGShape

  • All Implemented Interfaces:

    public class SoCSGShape
    extends SoShape
    Shape defined by a binary boolean operation on two sub scene graphs. This shape represents the result of a Constructive Solid Geometry (CSG) operation applied on the two scene graphs leftOperand and rightOperand. Constructive solid geometry allows the application to create a (potentially) complex object by using Boolean operators to combine (relatively) simple objects.

    The left and right operands can be any scene graph, including other SoCSGShape nodes. You can define a complex CSG geometry by creating a tree using multiple SoCSGShape nodes. The specified scene graph's shapes must be closed (no holes) and CCW-orientated (all triangles composing shapes must be counter-clockwise).

    Each time an operand is modified, a CSG Operation is performed. Keep this in mind if you create a CSGTree (SoCSGShape which contains other SoCSGShapes), especially if you use associative and commutative operations (only additions or only intersections) because the result of such operations does not depend on the tree ( (A + B) + C = A + (B + C) ). In this case, try to build your tree by putting the most often modified nodes at the top of the tree.

    For example, a tree optimized for modification on first node ( N1 ) will look like this:

     |   __|__S
    N1  |   __|__S
       N2  |   __|__
          N3  |     |
             N4    N5

    Where S are SoCSGShape and N1, N2, ... are ordinary nodes. In this case, a modification on N1 will need only 1 csgOperation, whereas a modificaion on N5 will need 4 csgOperations to regenerate the resulting shape.

    A tree optimized for random modification will try to minimize its depth:

             |                  |
         ____S____          ____S____
        |         |        |         |
      __S__       N3       N4        N5
     |     |
     N1    N2

    In this case, any modification will require at most 3 CSG Operations.

    Open Inventor 8.6 File format/default:

    CSGShape {
      leftOperand NULL
      rightOperand NULL
      csgOperation ADD


    • CSG means Constructive Solid Geometry.
    • Some operations are not commutative (A - B) != (B - A).

    LIMITATIONS Only vertices are handled in the generated shape. None of the normal, color, or texCoord properties of the left or right operands are taken into account. Shaders are also not taken in account, even vertex shaders. But note that you can use a shader above SoCSGShape. The shader will be applied to the result of the CSG operation.

    See Also:
    • Field Detail

      • leftOperand

        public final SoSFNode leftOperand
        Geometry scene graph to be used as left operand for the Boolean operation.
      • rightOperand

        public final SoSFNode rightOperand
        Geometry scene graph to be used as right operand for the Boolean operation.
    • Constructor Detail

      • SoCSGShape

        public SoCSGShape()
    • Method Detail

      • setMaxAttempt

        public void setMaxAttempt​(int maxAttempt)
        If the CSG Operation failed for any reason, it will be retried by applying a small random transformation to the operand vertices. This can solve the problem if the geometries are well formed, but for example 2 faces are coplanar. This method sets the max number of times SoCSGShape will retry before giving up and using the rescueOperation (see setRescueOperation). A max attempt of 5 is enough. If CSG Operation fails after 5 attempts, it will probably fail all the time.

        Default is 5.

        Warning A value > 0 may change the coordinates of geometries as they will be transformed a little bit to apply the CSG operation. This transformation is normally not visible to the naked eye (it's about 0.01%), but may cause issues if you need precise values.

      • getStatus

        public SoCSGShape.CsgStatus getStatus()
        Returns status of csg operation.

        Note Status is updated only when the node is traversed. Initially returns CSG_NO_ERROR. .

      • setRescueOperation

        public static void setRescueOperation​(SoCSGShape.CsgOperationTypes op)
        Set operation to use if the CSG operation fails or CSGLib is not available. Default is NOTHING. Must be one of LEFT_ONLY, RIGHT_ONLY, NOTHING or ALL. .