[CONNECT C++] Basis Range vs. Element Range

Question

What's the difference between an element range and a basis range? 
 DisplayHandler::GetBasisRange() Returns false (and the standard element range) if no basis range/transform is available . 
 In my experience, the method returns true and sets the range to zero. mdlElement_extractRange() continues to behave as one would expect. 
 There's also DisplayHandler::SetBasisRange() . I don't understand what that function does.

Brien Bastings · Accepted Answer

The idea was to allow elements (i.e. extended elements created by applications) to store/return an element aligned vs. axis aligned box that fits their geometry. Similar to the range diagonal for cells/shared cells. A basis range would typically be centered around 0, the basis transform denotes the local to world transform. 
 In practice I haven't found it "generally" useful as it wasn't required to be implemented, meaning you need a fallback for dealing with elements that don't store/return a valid basis range anyway. So, it mostly ends up being useful to applications when dealing with their own elements. 
 -B

Robert Hook · Answer

Hi Jon, 
 The Get/Set BasisRange and BasisTransform methods provide a convenient means to store/persist a "basis/home" element range/transform via XAttributes. If no "basis" is present the range/transform returned will be that directly obtained from the current ElementHandle range/transform. 
 Please let me know if this helps, if so I will ensure we add to the documentation. HTH, Bob 
 [20200224-RH: Please see the Get/Set Basis Range/Transform topic to provide some background information on the Basis methods.]

[CONNECT C++] Basis Range vs. Element Range

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