DXF 解析器:椭圆角度方向 [英] DXF Parser : Ellipses angle direction
问题描述
我编写了自己的 ASCII DXF 文件解析器，但在某些特定文档中遇到了省略号的问题.
I wrote my own ASCII DXF file parser and I encounter a problem with ellipses in some particular documents.
似乎没有定义开始和结束参数的角度方向(顺时针或逆时针)的组代码".在大多数情况下，它是逆时针的，但并非在所有情况下...
It seems that there is no "Group Code" defining the angle direction (Clockwise or Counterclockwise) for Start and End Parameters. In most case, it's counterclockwise, but not in ALL cases...
为了简化，这里有一个直观的例子:
To simplify, here is a visual exemple:
如您所见，第一个的起始角为 135，第二个的起始角为 45...但是，椭圆似乎是相同的(半圆，在左边)...这是因为第一个的角度是顺时针的，第二个的角度是逆时针的...
As you can see, the first one has a start angle of 135, and the second one a start angle of 45... But, the ellipses seems to be identical (half-circle, on the left)... This is because the first one's angles are clockwise, and the second one's are counter-clockwise...
显然，它们在 AutoCAD 中正确显示，但使用我的解析器，它们显示如下:
Obviously, they appear correctly in AutoCAD, but with my parser, they appear like that:
只是因为我不知道角度是用顺时针还是逆时针表示...
Simply because I don't know if angles are represented CW or CCW...
我是不是遗漏了群号之类的东西?
Did I miss a group code or something ?
信息:在 AutoCAD 中，我可以看到第一个椭圆Minor Axis Endpoint"是 [200, -200, 0]，而第二个是 [-200, 200, 0]，我想这就是 AutoCAD知道角度是 CW 还是 CCW ......但我在 DXF 文件中只有长轴端点"和长短轴比"(一个数字)
Info: In AutoCAD, I can see that the first ellipse "Minor Axis Endpoint" is [200, -200, 0], while the second one's is [-200, 200, 0], I suppose this is how AutoCAD knows if the angles are CW or CCW... But all I have in the DXF file is the "Major Axis Endpoint" and the "Major to Minor Axis Ratio" (a number)
这是与此示例对应的 DXF 文件:http://www.woofiles.com/dl-279966-ZvoMjamr-c.dxf
Here is the DXF file corresponding to this example: http://www.woofiles.com/dl-279966-ZvoMjamr-c.dxf
推荐答案
已解决:忘记考虑挤压向量
Solved: I forgot to take in account the extrusion vector
当它为负数 (0,0,-1) 时，角度必须被视为 CCW 而不是 CW(反之亦然)
When it is negative (0,0,-1), the angles must be treated as CCW instead of CW (and vice-versa)
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