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Clipping Planes

Clipping planes allow cutting off some part of the current object. They are helpful in many situations. One of usages is joining objects. Example of that is the Pipes.glm model from the installation folder. 

Clipping plane is defined by the point where the plane passes through and unitary vector of its normal. Semi space where the normal points to is called positive side of the plane. When enabled, clipping plane cuts off all parts of the object which are located on the negative side.

Every object has a fixed set of six clipping planes. A clipping plane has to be enabled to have effect on the appearance of the object.  By default all clipping planes are disabled and located at the origin of the local frame with normal directed along the local x axis.

In 3D Debugger clipping planes are managed by Clip Editor dialog, which is available from the Current Object > Clipping Planes menu option. In KernelCAD control clipping planes are managed by IClipArray interface, which can be queried from ISection, and IClipPlane interface, which can be be obtained using GetClipPlane method of the IClipArray.

Clipping plane can be drawn for debugging or other purposes. To enable drawing use IClipPlane.Show method.

Direction of normal vector of the clipping plane is controlled via IAxis, queried from the correspondent  IClipPlane Location of clipping plane can be controlled with ILocation interface queried from IClipPlane or previously obtained IAxis.

A clipping plane can be shared by different objects. This way it is easy to synchronize modifications of the plane. When a clipping plane is not shared it is called local clipping plane. Local clipping plane can have effect only on its object and it belongs to the object. When object is moved or exported, its local planes move with local frame of the object. Local clipping plane can be converted to shared clipping planes. 

Shared clipping planes belong to the model. When a local clipping plane is shared it is transferred to the model, so that it can be used by several other sections of the model. Shared planes are global. This mean that when  a object, which uses the plane is moved, global position and orientation of the plane remains unchanged.

An object can stop sharing a clipping plane, in which case a copy of the plane is created and made local to the object.

All clipping planes and their sharing properties are stored with the model, when saved.