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    <title>tema Change in arc start angle and end angle on 3DRotate. en AutoCAD Forum</title>
    <link>https://forums.autodesk.com/t5/autocad-forum/change-in-arc-start-angle-and-end-angle-on-3drotate/m-p/9857800#M1035387</link>
    <description>&lt;P&gt;I created an ARC, start angle 0, and end angle 90 degrees. Please refer to the below screenshot&lt;/P&gt;&lt;P&gt;&lt;span class="lia-inline-image-display-wrapper lia-image-align-inline" image-alt="yashchauhan281_0-1604989351888.png" style="width: 400px;"&gt;&lt;img src="https://forums.autodesk.com/t5/image/serverpage/image-id/842355i0D4B3214A2CA983D/image-size/medium?v=v2&amp;amp;px=400" role="button" title="yashchauhan281_0-1604989351888.png" alt="yashchauhan281_0-1604989351888.png" /&gt;&lt;/span&gt;&lt;/P&gt;&lt;P&gt;Then I did a 3DRotate, from the start point of arc, about X-axis 30 degrees. I check the start and end angle it remains the same. i.e. 0 and 90 respectively. Please refer to the screenshot below.&lt;/P&gt;&lt;P&gt;&lt;span class="lia-inline-image-display-wrapper lia-image-align-inline" image-alt="yashchauhan281_1-1604989506380.png" style="width: 400px;"&gt;&lt;img src="https://forums.autodesk.com/t5/image/serverpage/image-id/842356iEB26FF7D27D21B55/image-size/medium?v=v2&amp;amp;px=400" role="button" title="yashchauhan281_1-1604989506380.png" alt="yashchauhan281_1-1604989506380.png" /&gt;&lt;/span&gt;&lt;/P&gt;&lt;P&gt;Next I again did a 3DRotate from the start point of Arc but this time about Y axis, 30 degrees. On checking the start and end angle this time, it got changed to 49 and 139 degrees respectively. Please refer to the below screenshot.&lt;/P&gt;&lt;P&gt;&lt;span class="lia-inline-image-display-wrapper lia-image-align-inline" image-alt="yashchauhan281_2-1604989590017.png" style="width: 400px;"&gt;&lt;img src="https://forums.autodesk.com/t5/image/serverpage/image-id/842357i9BE39D22121E32C6/image-size/medium?v=v2&amp;amp;px=400" role="button" title="yashchauhan281_2-1604989590017.png" alt="yashchauhan281_2-1604989590017.png" /&gt;&lt;/span&gt;&lt;/P&gt;&lt;P&gt;So my question is, how come the start &amp;amp; end angle changed upon rotating it to Y axis, but not changed when rotating it about X axis.&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;P&gt;I understand that there will be some mathematics behind this calculation, if someone can refer the behind the scene calculation it would be really great.&lt;/P&gt;&lt;P&gt;Please help me to understand this.&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;P&gt;Thanks,&lt;/P&gt;&lt;P&gt;Yash&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;</description>
    <pubDate>Tue, 10 Nov 2020 06:35:35 GMT</pubDate>
    <dc:creator>Anonymous</dc:creator>
    <dc:date>2020-11-10T06:35:35Z</dc:date>
    <item>
      <title>Change in arc start angle and end angle on 3DRotate.</title>
      <link>https://forums.autodesk.com/t5/autocad-forum/change-in-arc-start-angle-and-end-angle-on-3drotate/m-p/9857800#M1035387</link>
      <description>&lt;P&gt;I created an ARC, start angle 0, and end angle 90 degrees. Please refer to the below screenshot&lt;/P&gt;&lt;P&gt;&lt;span class="lia-inline-image-display-wrapper lia-image-align-inline" image-alt="yashchauhan281_0-1604989351888.png" style="width: 400px;"&gt;&lt;img src="https://forums.autodesk.com/t5/image/serverpage/image-id/842355i0D4B3214A2CA983D/image-size/medium?v=v2&amp;amp;px=400" role="button" title="yashchauhan281_0-1604989351888.png" alt="yashchauhan281_0-1604989351888.png" /&gt;&lt;/span&gt;&lt;/P&gt;&lt;P&gt;Then I did a 3DRotate, from the start point of arc, about X-axis 30 degrees. I check the start and end angle it remains the same. i.e. 0 and 90 respectively. Please refer to the screenshot below.&lt;/P&gt;&lt;P&gt;&lt;span class="lia-inline-image-display-wrapper lia-image-align-inline" image-alt="yashchauhan281_1-1604989506380.png" style="width: 400px;"&gt;&lt;img src="https://forums.autodesk.com/t5/image/serverpage/image-id/842356iEB26FF7D27D21B55/image-size/medium?v=v2&amp;amp;px=400" role="button" title="yashchauhan281_1-1604989506380.png" alt="yashchauhan281_1-1604989506380.png" /&gt;&lt;/span&gt;&lt;/P&gt;&lt;P&gt;Next I again did a 3DRotate from the start point of Arc but this time about Y axis, 30 degrees. On checking the start and end angle this time, it got changed to 49 and 139 degrees respectively. Please refer to the below screenshot.&lt;/P&gt;&lt;P&gt;&lt;span class="lia-inline-image-display-wrapper lia-image-align-inline" image-alt="yashchauhan281_2-1604989590017.png" style="width: 400px;"&gt;&lt;img src="https://forums.autodesk.com/t5/image/serverpage/image-id/842357i9BE39D22121E32C6/image-size/medium?v=v2&amp;amp;px=400" role="button" title="yashchauhan281_2-1604989590017.png" alt="yashchauhan281_2-1604989590017.png" /&gt;&lt;/span&gt;&lt;/P&gt;&lt;P&gt;So my question is, how come the start &amp;amp; end angle changed upon rotating it to Y axis, but not changed when rotating it about X axis.&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;P&gt;I understand that there will be some mathematics behind this calculation, if someone can refer the behind the scene calculation it would be really great.&lt;/P&gt;&lt;P&gt;Please help me to understand this.&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;P&gt;Thanks,&lt;/P&gt;&lt;P&gt;Yash&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;</description>
      <pubDate>Tue, 10 Nov 2020 06:35:35 GMT</pubDate>
      <guid>https://forums.autodesk.com/t5/autocad-forum/change-in-arc-start-angle-and-end-angle-on-3drotate/m-p/9857800#M1035387</guid>
      <dc:creator>Anonymous</dc:creator>
      <dc:date>2020-11-10T06:35:35Z</dc:date>
    </item>
    <item>
      <title>Re: Change in arc start angle and end angle on 3DRotate.</title>
      <link>https://forums.autodesk.com/t5/autocad-forum/change-in-arc-start-angle-and-end-angle-on-3drotate/m-p/9857909#M1035388</link>
      <description>&lt;P&gt;For an explanation see:&lt;/P&gt;&lt;P&gt;Object Coordinate Systems (OCS) in DXF&lt;/P&gt;&lt;P&gt;&lt;A href="http://help.autodesk.com/cloudhelp/2016/ENU/AutoCAD-DXF/files/GUID-D99F1509-E4E4-47A3-8691-92EA07DC88F5.htm" target="_blank"&gt;http://help.autodesk.com/cloudhelp/2016/ENU/AutoCAD-DXF/files/GUID-D99F1509-E4E4-47A3-8691-92EA07DC88F5.htm&lt;/A&gt;&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;P&gt;and:&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;P&gt;About Arbitrary Axis Algorithm (DXF)&lt;/P&gt;&lt;P&gt;&lt;A href="http://help.autodesk.com/cloudhelp/2016/ENU/AutoCAD-DXF/files/GUID-E19E5B42-0CC7-4EBA-B29F-5E1D595149EE.htm" target="_blank"&gt;http://help.autodesk.com/cloudhelp/2016/ENU/AutoCAD-DXF/files/GUID-E19E5B42-0CC7-4EBA-B29F-5E1D595149EE.htm&lt;/A&gt;&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;</description>
      <pubDate>Tue, 10 Nov 2020 07:34:51 GMT</pubDate>
      <guid>https://forums.autodesk.com/t5/autocad-forum/change-in-arc-start-angle-and-end-angle-on-3drotate/m-p/9857909#M1035388</guid>
      <dc:creator>SEANT61</dc:creator>
      <dc:date>2020-11-10T07:34:51Z</dc:date>
    </item>
    <item>
      <title>Re: Change in arc start angle and end angle on 3DRotate.</title>
      <link>https://forums.autodesk.com/t5/autocad-forum/change-in-arc-start-angle-and-end-angle-on-3drotate/m-p/9858138#M1035392</link>
      <description>&lt;P&gt;Thanks for the reply, but still I am not able to figure out this problem. I wanted to know the calculation for obtaining the start angle and end angle when the arc is rotated in 3D space.&amp;nbsp;&lt;/P&gt;</description>
      <pubDate>Tue, 10 Nov 2020 09:34:23 GMT</pubDate>
      <guid>https://forums.autodesk.com/t5/autocad-forum/change-in-arc-start-angle-and-end-angle-on-3drotate/m-p/9858138#M1035392</guid>
      <dc:creator>Anonymous</dc:creator>
      <dc:date>2020-11-10T09:34:23Z</dc:date>
    </item>
    <item>
      <title>Re: Change in arc start angle and end angle on 3DRotate.</title>
      <link>https://forums.autodesk.com/t5/autocad-forum/change-in-arc-start-angle-and-end-angle-on-3drotate/m-p/9858258#M1035395</link>
      <description>&lt;P&gt;The Object Coordinate System methodology is somewhat unintuitive.&amp;nbsp; It was originally designed for computers with far less resources.&amp;nbsp; That notwithstanding, it is a well thought out and makes better sense when fully understood.&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;P&gt;From your other post we can see that you are automating a task – what language/approach are you employing?&amp;nbsp; All the AutoCAD programming APIs have functions to assist the translation process.&amp;nbsp; If you are working outside of AutoCAD, you will need to write those yourself.&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;P&gt;Clarification on the issue above will assist the effort to present good advice.&lt;/P&gt;</description>
      <pubDate>Tue, 10 Nov 2020 10:37:15 GMT</pubDate>
      <guid>https://forums.autodesk.com/t5/autocad-forum/change-in-arc-start-angle-and-end-angle-on-3drotate/m-p/9858258#M1035395</guid>
      <dc:creator>SEANT61</dc:creator>
      <dc:date>2020-11-10T10:37:15Z</dc:date>
    </item>
    <item>
      <title>Re: Change in arc start angle and end angle on 3DRotate.</title>
      <link>https://forums.autodesk.com/t5/autocad-forum/change-in-arc-start-angle-and-end-angle-on-3drotate/m-p/9858420#M1035396</link>
      <description>&lt;P&gt;I am using JavaScript for this development, and I am working completely outside of CAD environment. Project is 90% JavaScript and 10% Java, but help from any programming language is good with me. So far i was able to calculate extrusion vector, below is the python code, hope it might help someone.&lt;/P&gt;&lt;DIV&gt;&lt;DIV&gt;&amp;nbsp;&lt;/DIV&gt;&lt;/DIV&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;LI-CODE lang="python"&gt;#rotList = normal vector to the plane from three points
extrution_vector = np.array(rotList)
if abs(extrution_vector[0]) &amp;lt; 1/64 and abs(extrution_vector[1]) &amp;lt; 1/64:
    ax = np.cross((0,1,0), extrution_vector)
else:
    ax = np.cross((0,0,1), extrution_vector)

mx = sum([i**2 for i in ax])**.5   #calculate magnitude of ax
ax = ax * 1/mx   #scale ax to have magnitude 1

ay = np.cross(extrution_vector, ax)
az = extrution_vector&lt;/LI-CODE&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;&lt;P&gt;&amp;nbsp;&lt;/P&gt;</description>
      <pubDate>Tue, 10 Nov 2020 11:59:03 GMT</pubDate>
      <guid>https://forums.autodesk.com/t5/autocad-forum/change-in-arc-start-angle-and-end-angle-on-3drotate/m-p/9858420#M1035396</guid>
      <dc:creator>Anonymous</dc:creator>
      <dc:date>2020-11-10T11:59:03Z</dc:date>
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