（2）计算AcDbBlockReference准确的包围盒

XDSoft · 发表于 2014-12-5 00:14:16

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Question
AcDbBlockReference::geomExtents() doesn't return an accurate value for a rotated
AcDbBlockReference. Is there a function that does?
Answer
The following function calculates the extents of an AcDbBlockReference. The
following restrictions apply:
-- Non uniformly scaled blocks containing solids are not supported.
-- Blocks containing AcDb3dPolylines are not supported.
-- Blocks containing AcDb2dPolylines other than of type k2dSimplePoly are not
supported.

Here's the code:

游客，如果您要查看本帖隐藏内容请回复

QiaoCheng · 发表于 2014-12-5 00:21:35

呵呵，这么快又有好码

Highflybird · 发表于 2014-12-5 09:33:25

为何不用:AcDbBlockReference::geomExtentsBestFit呢？

Lisphk · 发表于 2014-12-5 09:37:43

虽然不懂ARX，回复看看。

st788796 · 发表于 2014-12-5 09:39:24

Highflybird 发表于 2014-12-5 09:33
为何不用:AcDbBlockReference::geomExtentsBestFit呢？

geomExtents是与轴平行的，这个BestFit是什么情况？

st788796 · 发表于 2014-12-5 09:52:12

很吃力的看了看代码，除了加入属性，polyline没必要explode，对insert也是直接geomExtents

Highflybird · 发表于 2014-12-5 10:07:09

When working in non-WCS coordinate systems, the extents returned from AcDbBlockReference::geomExtents() can be somewhat larger that the actual geometry because AcDbBlockReference::geomExtents() transforms the contained entities' precomputed extents by the block reference's transformation matrix rather than transforming the entities and computing a new box for the transformed entity set. This results in non-world aligned extent boxes for the entities. This is fast, but will provide an "exaggerated" enclosing extents box.
This method works recursively for nested block references. When this method is called on the outermost block reference (the normal case for ARX applications), parentXform should be the identity matrix. For calls on nested block references, parentXform should be the cumulative transformation from the outermost block reference down to the block reference that is referencing the block table record that owns the block reference on which this method is being called.

st788796 · 发表于 2014-12-5 10:39:37

Highflybird 发表于 2014-12-5 10:07
When working in non-WCS coordinate systems, the extents returned from AcDbBlockReference::geomExtent ...

意思就是BlockReference 自个儿的平行轴(WCS)geomExtents吧

守仁格竹GM · 发表于 2014-12-5 11:20:54

虽然不懂ARX，回复看看

maker_lv · 发表于 2014-12-5 11:23:55

全英文全英文全英文全英文

Highflybird · 发表于 2014-12-5 11:40:25

st788796 发表于 2014-12-5 10:39
意思就是BlockReference 自个儿的平行轴(WCS)geomExtents吧

等下我测试一下。

牢固 · 发表于 2014-12-5 13:19:55

这个包围盒的生成限制有点多!

zytyd · 发表于 2014-12-5 14:02:13

好好学习---

Highflybird · 发表于 2014-12-5 15:54:57

本帖最后由 Highflybird 于 2014-12-5 16:31 编辑

测试了一下，geomExtents的确存在问题，得不到真实的box.
QQ图片20141205163040.png

st788796 · 发表于 2014-12-5 16:15:39

Highflybird 发表于 2014-12-5 15:54
测试了一下，geomExtents的确存在问题，得不到真实的box.

哪些实体有影响？

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[每日一码] （2）计算AcDbBlockReference准确的包围盒

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