INSERT entity with xClip: copied instances have identical xClip data (except handle), how to compute actual clipping box coordinates?

[xp345902274]

Thank you Dom, the new version has added support for the xClip data (SpatialFilter) of INSERT entities. However, I have a few questions when using it:

I created an INSERT entity with xClip data in AutoCAD, and then copied it. When reading the drawing, I noticed that the xClip data of the two INSERTs is almost identical — the only difference is the handle. Other properties such as Origin, BoundaryPoints, InsertTransform, and InverseInsertTransform are the same.

How can I calculate the actual coordinates of the clipping box from this data?

[xp345902274]

I've done some further research and found that the format of SpatialFilter.InverseInsertTransformseems incorrect.

​​First​​, the offset components offXand offY appear to be misplaced:

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offX should normally be in ​​M30​​ (X translation), and offY in ​​M31​​ (Y translation), but based on the data I observed, they are actually in ​​M03​​ and ​​M13​​, which are part of the linear (rotation/scale) part of the matrix, not the translation vector.

​​Second​​, it seems the offset should be ​​stored as two separate variables​​, rather than being mixed into the transform matrix.

Based on my testing, the correct approach appears to be:

Apply the ​​inverse matrix of the spatialFilter.InverseInsertTransform(without the offset)​​ to the xClipBoundarypoints.

Then, ​​apply the offset separately​​ to get the position relative to the BlockRecord.

Finally, apply the ​​INSERT entity's transform​​ to get the final world coordinates of the clipping boundary.

I wrote the following code based on this logic:

The code works as expected and displays the correct clipping area.

​​@DomCR​​ Could you please review this and let me know if my understanding is correct?

[DomCR]

Hi @xp345902274,

I'll have to check with the dwg and dxf documentation and see how the matrix is really formed, for what you say it makes sense so I'll need to take a closer look at this issue.

Regarding XClip, I'll have to implement the methods GetBoundingBox and ApplyTransform to make it easier to manage with the Inserts.

Thanks for the report!