Finding the Quad Snap Points of Nurbs Curves - Grasshopper2024-03-29T12:27:32Zhttps://www.grasshopper3d.com/forum/topics/finding-the-turning-points-of-nurbs-curves?commentId=2985220%3AComment%3A1487376&feed=yes&xn_auth=noSomehow I thought using the E…tag:www.grasshopper3d.com,2016-03-18:2985220:Comment:14878132016-03-18T15:02:12.396ZPieter Segerenhttps://www.grasshopper3d.com/profile/Pieter
<p>Somehow I thought using the Extremes (X-tremez) component (from Curve > Analysis tab) could be part of a solution, but I clearly misunderstood the component... and maybe the question aswell... or? <br/><a target="_self" href="http://storage.ning.com/topology/rest/1.0/file/get/2769124909?profile=original"><img class="align-full" src="http://storage.ning.com/topology/rest/1.0/file/get/2769124909?profile=original" width="555"/></a></p>
<p>Somehow I thought using the Extremes (X-tremez) component (from Curve > Analysis tab) could be part of a solution, but I clearly misunderstood the component... and maybe the question aswell... or? <br/><a target="_self" href="http://storage.ning.com/topology/rest/1.0/file/get/2769124909?profile=original"><img class="align-full" src="http://storage.ning.com/topology/rest/1.0/file/get/2769124909?profile=original" width="555"/></a></p> It's an interesting problem a…tag:www.grasshopper3d.com,2016-03-18:2985220:Comment:14876142016-03-18T11:04:06.765ZDavid Ruttenhttps://www.grasshopper3d.com/profile/DavidRutten
<p>It's an interesting problem and I don't know how to solve it analytically, or even with extreme accuracy while using pure GH, but you can get to any desired accuracy by sampling more points in my attached solution.</p>
<p></p>
<p>The idea is this:</p>
<ol>
<li>Sample the tangent of the curve at N locations (I picked 1000).</li>
<li>Get the X and Y components of all these tangent vectors.</li>
<li>Create two new curves, where the X component comes from the original curve parameters and the Y…</li>
</ol>
<p>It's an interesting problem and I don't know how to solve it analytically, or even with extreme accuracy while using pure GH, but you can get to any desired accuracy by sampling more points in my attached solution.</p>
<p></p>
<p>The idea is this:</p>
<ol>
<li>Sample the tangent of the curve at N locations (I picked 1000).</li>
<li>Get the X and Y components of all these tangent vectors.</li>
<li>Create two new curves, where the X component comes from the original curve parameters and the Y component comes from the tangent x and y values.</li>
<li>Intersect these two curves with the world X-axis to find all the roots.</li>
<li>The x-coordinate of all root points will tell you at what curve parameters the quad points are.</li>
</ol>
<p></p>
<p><a href="http://storage.ning.com/topology/rest/1.0/file/get/2769124855?profile=original" target="_self"><img width="721" src="http://storage.ning.com/topology/rest/1.0/file/get/2769124855?profile=RESIZE_1024x1024" width="721" class="align-full"/></a></p> You mean those points where t…tag:www.grasshopper3d.com,2016-03-18:2985220:Comment:14872022016-03-18T09:15:13.821ZDavid Ruttenhttps://www.grasshopper3d.com/profile/DavidRutten
You mean those points where the curve goes vertical or horizontal, as with the Quad snap?
You mean those points where the curve goes vertical or horizontal, as with the Quad snap? ouch!tag:www.grasshopper3d.com,2016-03-18:2985220:Comment:14873762016-03-18T08:47:49.701ZAditya Tognattahttps://www.grasshopper3d.com/profile/AdityaTognatta
<p>ouch!</p>
<p>ouch!</p> Olaudah:
WTF is a turning po…tag:www.grasshopper3d.com,2016-03-17:2985220:Comment:14872422016-03-17T23:25:02.066ZNik Willmorehttps://www.grasshopper3d.com/profile/NikFromNYC
<p>Olaudah:</p>
<p></p>
<p>WTF is a turning point? Inflection points, sure, but those points you show don't seem meaningful.</p>
<p></p>
<p>And you are invoking within your script via Rhinocommon one of the most obscure command of all, Greville parameters:…</p>
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<p>Olaudah:</p>
<p></p>
<p>WTF is a turning point? Inflection points, sure, but those points you show don't seem meaningful.</p>
<p></p>
<p>And you are invoking within your script via Rhinocommon one of the most obscure command of all, Greville parameters:</p>
<p></p>
<p><a rel="nofollow" href="http://4.rhino3d.com/5/rhinocommon/?topic=html/M_Rhino_Geometry_NurbsCurve_GrevilleParameter.htm" target="_blank">http://4.rhino3d.com/5/rhinocommon/?topic=html/M_Rhino_Geometry_Nur...</a></p>
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<p>I believe that in plain English this means finding the most boring curve points possible? Where the lease variation in curvature occurs? That's like a derivative in calculus, or the reverse Fourier transform of it. And isn't there a threshold effect where many more points can be included as most boring?</p>
<p></p>
<p>And why are you rebuilding the left curve, you didn't show, with 50 control points?</p>
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<p>And there's all these boxes:</p>
<p><a href="http://storage.ning.com/topology/rest/1.0/file/get/2769121651?profile=original" target="_self"><img src="http://storage.ning.com/topology/rest/1.0/file/get/2769121651?profile=original" width="548" class="align-full"/></a></p>
<p>Why?</p>