{"id":9966,"date":"2018-07-20T11:50:59","date_gmt":"2018-07-20T18:50:59","guid":{"rendered":"http:\/\/www.autodesk.com\/products\/fusion-360\/blog\/?p=9966"},"modified":"2018-07-20T11:50:59","modified_gmt":"2018-07-20T18:50:59","slug":"sketch-control-point-splines-faq","status":"publish","type":"post","link":"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/sketch-control-point-splines-faq\/","title":{"rendered":"Control Point Splines: Create complex Sketch curves with precision and ease"},"content":{"rendered":"<p>For the upcoming July update, we&#8217;re extremely excited to introduce a brand new way to create curves in Fusion 360&#8217;s sketching environment &#8211; the <strong>Control Point Spline<\/strong> tool. This new tool promises to provide:<\/p>\n<p>&nbsp;<\/p>\n<ul>\n<li>More precise shape control over your spline curves<\/li>\n<li>More flexibility in how you create splines<\/li>\n<li>The ability to constrain splines more easily, reliably and repeatably<\/li>\n<li>Visibility and control of the underlying degree of your splines<\/li>\n<\/ul>\n<p>We know that many of you have been anxiously waiting for this tool to arrive, and we really hope this satisfies your hunger for added power and more control in creating complex shapes in Fusion 360.<\/p>\n<p>&nbsp;<\/p>\n<p>We also know that this type of spline will be brand new to a lot of people, so we&#8217;ve put together together this in-depth FAQ to answer some of the most common questions concerning control point splines: what they are, where they are most useful, and some best practices for designing with them. Note that some of these tips and techniques make use of the unique capabilities and workflows inside Fusion 360, so be sure to check these out even if you&#8217;re a seasoned spline pro!<\/p>\n<p>&nbsp;<\/p>\n<p>[toc]<\/p>\n<p>&nbsp;<\/p>\n<h1><strong><span style=\"font-size: 16pt;\">What are control point splines?<\/span><\/strong><\/h1>\n<p>&nbsp;<\/p>\n<p>Control point splines &#8211; also known as CV splines, NURBS curves or style splines &#8211; provide a way for defining complex curves in a Sketch.<\/p>\n<p>&nbsp;<\/p>\n<p>Until now, this requirement has been met by the existing Spline command. With this tool, you select a series of points, and\u00a0Fusion\u00a0will create a smooth curve that passes through them.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10022 size-full\" title=\"In the Spline tool (now called Fit Point Spline), you select a series of fit points, and a smooth spline is generated through them\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/fpspline1.gif\" alt=\"Fit Point Spline creation\" width=\"571\" height=\"191\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>Control point splines offer an alternative\u00a0approach for achieving the same result. You select a\u00a0series\u00a0of points, and these points will define a &#8216;control frame&#8217; from which a smooth curve is derived.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10021 size-full\" title=\"In the Control Point Spline tool, you select points to represent a control frame; a smooth curve is then calculated based on this control frame\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/cpspline1.gif\" alt=\"Control Point Spline creation\" width=\"571\" height=\"191\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>If you&#8217;ve ever used Box Display or Control Frame Display in\u00a0the\u00a0Sculpt workspace, you&#8217;re\u00a0essentially seeing the same concept there: you manipulate a simple polygonal control frame, and this drives the resultant smooth shape of the surface.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10020\" title=\"Box Display and Control Frame Display in the Sculpt workspace work in the same way as a control point spline; you manipulate a frame that controls the smooth result\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/tspline1.gif\" alt=\"Editing a Sculpt surface using Control Frame Display mode\" width=\"500\" height=\"267\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>Since we&#8217;ll now have two spline commands, we&#8217;re renaming the previous Spline tool to &#8220;Fit Point Spline&#8221; (i.e. the spline &#8216;fits&#8217; to the specified points). These are now presented in a Spline flyout in the Sketch tool menu.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10019\" title=\"Spline has been renamed to Fit Point Spline, and both spline creation tools now live in a Spline flyout in the Sketch menu\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/newmenu.png\" alt=\"Spline flyout menu\" width=\"500\" height=\"97\" srcset=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/newmenu.png 750w, https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/newmenu-300x58.png 300w\" sizes=\"auto, (max-width: 500px) 100vw, 500px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>As you start to use these two tools together, there are two key differences to keep in mind between fit point splines and control point splines:<\/p>\n<p>&nbsp;<\/p>\n<p><strong>1.<\/strong> As shown above, <strong>a control point spline will (usually) not pass through the selected points<\/strong>\u00a0besides the first and last points. Unlike fit points, which define points that the spline must pass through, control points just define the\u00a0underlying frame used to calculate the curve. You can think of a control point as applying &#8216;tension&#8217; to the spline in a given direction: pulling a point further away increases the tension on the curve in that area, and pushing it closer relaxes that tension.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10014 size-full\" title=\"Moving a control point applies 'tension' to the curve in that localized area\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/cptension.gif\" alt=\"Dragging a control point\" width=\"538\" height=\"329\" \/><\/p>\n<p><strong>2.<\/strong> In most cases, <strong>you\u00a0will need more control points than fit points to define a given shape<\/strong>. This is because\u00a0each individual control point has less\u00a0influence\u00a0on the overall curve than a fit point does. What&#8217;s more, control point splines do not offer tangent\/curvature handles; to apply more refined shape control, you&#8217;ll need to add more points (you can do this by right-clicking the spline and selecting Insert Spline Control Point).<\/p>\n<p>&nbsp;<\/p>\n<p>For an example of this, see the two curves below. A fit point spline with three points will feel very flexible, and can be easily manipulated into a variety of shapes. A\u00a0control point\u00a0spline with three points will feel much more rigid, and the lack of tangent\/curvature handles limits the types of shape change possible. In such cases, adding more\u00a0control points as needed is the required approach to achieving more flexible shape control.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10006 size-full\" title=\"A fit point spline with three points (left) can be manipulated into a variety of shapes; a control point spline with three points (right) is more limited, and requires additional points for more drastic shape changes\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/fpcp3points3.gif\" alt=\"Modifying a three-point fit point spline and a three-point control point spline\" width=\"717\" height=\"276\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<h1><strong><span style=\"font-size: 16pt;\">Why add a new spline tool to Fusion 360?<\/span><\/strong><\/h1>\n<p>&nbsp;<\/p>\n<p>Fit points are a very intuitive way to define a spline &#8211; the points you create will directly constrain the curve. However,\u00a0behind the scenes Fusion is taking most of the responsibility for deciding\u00a0how the spline shape flows\u00a0as it passes from one fit point to the next.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10040 size-full\" title=\"In the Fit Point Spline tool, you define the point locations, but (by default) Fusion 360 takes responsibility for the shape of the curve between those points\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/pointsflow2.png\" alt=\"How a fit point spline shape is determined\" width=\"510\" height=\"324\" srcset=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/pointsflow2.png 510w, https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/pointsflow2-300x191.png 300w\" sizes=\"auto, (max-width: 510px) 100vw, 510px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>As a product designer, sometimes you need to have very precise control of that intermediate shape flow. Fit point splines provide tangent &amp; curvature handles to apply additional control if needed; but occasionally these don&#8217;t provide fine-enough control, and manipulating these handles can affect other areas of the spline in unexpected ways.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10010 size-full\" title=\"Tangent and curvature handles give you more control over fit point spline shapes, but they can impact the entire curve shape in unexpected ways (see highlighted area, top right)\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/fphandle.gif\" alt=\"Fit point spline tangent handle manipulation having impact elsewhere on the spline\" width=\"472\" height=\"319\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>Control point splines give you\u00a0direct access to the underlying control points\u00a0that define the full shape of the curve. This offers you extremely precise control over specific areas of its shape.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10011 size-full\" title=\"Control points have a more localized impact on the spline shape, so you can adjust these while keeping other areas of your curve intact\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/cphandle.gif\" alt=\"Control point manipulation having localized impact on the spline\" width=\"472\" height=\"319\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>We heard from many of you with professional design backgrounds that this fine-tuned control is a must-have for your work. Whether you prefer the interaction of creating fit point splines or control point splines is really down to your previous experience and personal taste &#8211; but control point splines offer a clear advantage in the level of shape control they provide.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<h1><strong><span style=\"font-size: 16pt;\">When should I use control point splines?<\/span><\/strong><\/h1>\n<p>&nbsp;<\/p>\n<p>The classic school of thought is that control point splines are better than fit point splines for defining the primary surfaces of your model. They provide you the ability to very explicitly control the math of the surface; and by following the best practices discussed below, you can ensure that surfaces created from these splines will be both aesthetically and\u00a0technically smooth.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10009 size-full\" title=\"Control point splines allow you to control your curve math and produce surfaces with extremely high quality; this surface was created by sweeping one simple control point spline along another\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/cpsurface.png\" alt=\"Surface created using Sweep with two control point splines as inputs\" width=\"609\" height=\"373\" srcset=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/cpsurface.png 609w, https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/cpsurface-300x184.png 300w\" sizes=\"auto, (max-width: 609px) 100vw, 609px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>However, since a control point spline will require more points than a fit point spline to define a given shape, complex shapes with lots of curvature changes may be simpler to draw with the Fit Point Spline tool. An example of this would be a traced logo: for a small &amp; detailed design task like this, the high degree of mathematical smoothness provided by control point splines is probably less important, and the shape can be created and edited with much less work using a fit point spline.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10044\" title=\"For a logo with complex curve forms, you may need a control point spline with 10s of control points to fully define the shape, whereas the Fit Point Spline tool might be able to achieve the same shape with fewer points and less effort\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/fitpointlogo3b.gif\" alt=\"Tracing a logo with a fit point spline\" width=\"500\" height=\"359\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>However,\u00a0for many tasks the choice of spline tool is really a personal preference &#8211; while control point splines offer more flexibility for certain scenarios, the two tools fundamentally create the same type of geometry, so you may just gravitate towards one particular tool that suits you best!<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<h1><strong><span style=\"font-size: 16pt;\">What are best practices for using control point splines?<\/span><\/strong><\/h1>\n<p>&nbsp;<\/p>\n<p>There are a few core rules of thumb to follow in order to create high-quality curves with the Control Point Spline tool.<\/p>\n<p>&nbsp;<\/p>\n<p><strong>1. Use the fewest points possible to describe the shape you need<\/strong><br \/>\nSplines will naturally form the smoothest transition possible between two points. Creating unnecessary intermediate points means you are &#8216;overriding&#8217; that natural smoothness, which increases the potential for undesired bumps or wobbles in the curve.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10038\" title=\"When you have a large number of control points (left) it can be difficult to maintain a smooth curvature profile; minimizing the number of control points (right) allows the curve math to take over, and gives you a high-quality curvature profile for free\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/toomanypoints.png\" alt=\"Too many control points vs. reduced number of control points\" width=\"700\" height=\"196\" srcset=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/toomanypoints.png 884w, https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/toomanypoints-300x84.png 300w, https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/toomanypoints-768x215.png 768w\" sizes=\"auto, (max-width: 700px) 100vw, 700px\" \/><\/p>\n<p>The general rule here is &#8220;less is more&#8221;. Keep this within\u00a0balance though &#8211; if you&#8217;re finding yourself stretching control points a long way from the curve in order to get the shape you want, you may be trying to do too much work with too few control points. In this case, adding one or two more control points can provide a more suitable level of shape control.<\/p>\n<p>&nbsp;<\/p>\n<p><strong>2. Try to keep points evenly-spaced\u00a0where possible<\/strong><br \/>\nUneven control point distribution is another factor that can cause smoothness problems in a spline, so wherever possible keep the spacing between adjacent control points even. There are scenarios where you need to have control points more bunched-together in certain areas &#8211; namely, in areas where you want a higher-curvature shape. But keep in mind that, where you have transitions from spread-out control points to bunched-together control points, make sure those transitions are smooth and natural to maintain a high-quality curve.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10036\" title=\"Uneven control point spacing (left) leads to bumps and poor curvature transitions; try to even-out point spacing for maximum curve smoothness (right)\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/pointplacement2.png\" alt=\"Uneven control point spacing vs. even control point spacing\" width=\"700\" height=\"199\" srcset=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/pointplacement2.png 975w, https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/pointplacement2-300x85.png 300w, https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/pointplacement2-768x218.png 768w\" sizes=\"auto, (max-width: 700px) 100vw, 700px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p><strong>3. Keep adjacent points relatively close to each other<\/strong><br \/>\nAvoid having drastic distances or direction changes from one control point to the next &#8211; this results in splines that will be difficult to work with or adjust later on. If you find you need drastic distances between points in order to achieve a given shape, it might be better to insert a few additional control points so that all points lie relatively close to the curve and to one another.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10035 size-full\" title=\"If your control points are a long way from the curve, or a long way from each other (left), your curve shape will be difficult to edit later on; insert more control points for a more controllable shape (right)\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/pointspacing.png\" alt=\"Widely-spaced control points vs. closely-spaced control points\" width=\"577\" height=\"367\" srcset=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/pointspacing.png 577w, https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/pointspacing-300x191.png 300w\" sizes=\"auto, (max-width: 577px) 100vw, 577px\" \/><\/p>\n<p>In fact, the three rules above apply to all spline-based geometry, including fit point splines and Sculpt geometry &#8211; so live by these rules whenever you can.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<h1><strong><span style=\"font-size: 16pt;\">How do I constrain a control point spline?<\/span><\/strong><\/h1>\n<p>&nbsp;<\/p>\n<p>A unique characteristic of control point splines is that they are always paired with a visible control frame. To make the most of this, <strong>Fusion 360 allows you to apply constraints on both the control frame and the curve itself<\/strong>.\u00a0Combining these two methods can\u00a0open up\u00a0some unique and powerful constraint workflows.<\/p>\n<p>&nbsp;<\/p>\n<p>Since the control frame consists of straight lines, and the curve itself is a shape with complex curvature, different constraint types will be more meaningful on the two different object types. As a general rule:<\/p>\n<p>&nbsp;<\/p>\n<ul>\n<li>Constraints used to <strong>control the overall size and shape of the spline<\/strong> are best applied on the<strong> control frame<\/strong><\/li>\n<li>Constraints used to <strong>describe a relationship between the spline to other geometry<\/strong> are best applied on the <strong>curve itself<\/strong><\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<p>The most frequently-used constraints for describing a relationship to other geometry will be Tangent and Curvature constraints: these will build a smooth connection between a control point spline and another curve or edge on the model.<\/p>\n<p>&nbsp;<\/p>\n<p>One important rule for applying tangent or curvature constraints on control point splines is that you will need enough &#8216;free&#8217; control points for the constraint to succeed. For a Tangent constraint, you must have at least one free control point next to the tangent connection. This is because, when you apply the constraint, Fusion will need to shift that control point to a new aligned position that enforces the tangent relationship. For a Curvature constraint, you&#8217;ll need two free control points, for the same reason.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10057\" title=\"Applying a tangent constraint will cause one control point to snap into alignment to enforce the constraint; for a curvature constraint, two points will snap into alignment\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/tangentapply5.gif\" alt=\"Control point alignment when applying tangent and curvature constraints\" width=\"475\" height=\"288\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>After you have created a tangent or curvature constraint like this, those shifted control points will have their degrees of freedom limited in order to maintain the constraint. However, you should still be able to slide the affected control points in a way that adjusts the &#8216;weight&#8217; of the tangent\/curvature\u00a0relationship. This is a powerful technique for fine-tuning the character of a curve or surface transition.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10024\" title=\"With a tangent or curvature constraint applied, you can still slide control point in an aligned direction - this can be used to adjust the 'weight' of the tangent\/curvature constraint\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/adjustG2c.gif\" alt=\"Moving control points to adjust the weight of a curvature transition\" width=\"550\" height=\"307\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>In order to fully define the shape of a control point spline, you&#8217;ll need to constrain all control points locations as well &#8211; this is where control frame constraints are necessary.\u00a0You can constrain control frame edges in the same way as any other straight lines in a sketch. For example, apply distance and angle dimensions to the control frame edges to control the spline shape in those areas. Keep adding these until the control frame is fully-constrained, at which point the spline curve shape will &#8211; by definition &#8211; also be fully-constrained.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10023\" title=\"Dimensions can be added to the control frame to constrain the size and shape of the spline curve\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/cfconstrained.png\" alt=\"Control point spline with dimensioned control frame\" width=\"500\" height=\"235\" srcset=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/cfconstrained.png 1202w, https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/cfconstrained-300x141.png 300w, https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/cfconstrained-1024x480.png 1024w, https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/cfconstrained-768x360.png 768w\" sizes=\"auto, (max-width: 500px) 100vw, 500px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>Note that control point spline shapes are &#8220;repeatable&#8221; using matching constraints: i.e. once a control point spline is fully-constrained,\u00a0if you apply the same set of constraints to a second spline (of the same degree; see more about spline degree below), you&#8217;ll get an identical resultant shape.<\/p>\n<p>&nbsp;<\/p>\n<p>You can also use constraints on the control frame to describe specific characteristics of the spline shape. For example, adding a horizontal\/vertical constraint at one end of the control frame will ensure the spline runs perfectly horizontally\/vertically at that end. This can be very useful when creating a spline that will eventually be mirrored.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10033 size-full\" title=\"Applying a horizontal\/vertical constraint on the last edge of a control frame forces the spline to finish in a horizontal\/vertical direction; if the spline is then mirrored, you will automatically have tangent continuity across the mirror line\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/horizvert.png\" alt=\"Control point spline with horizontal and vertical constraints on control frame\" width=\"447\" height=\"273\" srcset=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/horizvert.png 447w, https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/horizvert-300x183.png 300w\" sizes=\"auto, (max-width: 447px) 100vw, 447px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>If your part requires a draft angle for manufacturing, you can specify an angle between the control frame and a horizontal\/vertical\u00a0datum line to enforce that draft angle on geometry created from the spline.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10031\" title=\"To apply a draft angle to a control frame spline, add an angle dimension between the end of its control frame and a vertical datum line; a surface extruded or revolved from this spline will now obey the draft angle\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/draftangle.png\" alt=\"Control point spline with draft angle applied\" width=\"400\" height=\"359\" srcset=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/draftangle.png 850w, https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/draftangle-300x269.png 300w, https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/draftangle-768x688.png 768w\" sizes=\"auto, (max-width: 400px) 100vw, 400px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>To create a symmetric control point spline, rather than relying on Symmetry constraints, you can also apply Equal constraints between matching pairs of control frame edges. This sometimes requires less work and offers more flexibility than standard symmetry constraints. For example, you can create a spline with rotational symmetry by applying a combination of Equal and Parallel constraints, which isn&#8217;t otherwise possible using Symmetry constraints.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10030\" title=\"By applying Equal and Parallel constraints between 'mirrored pairs' of control frame edges, you can add unique symmetry behavior to your control point splines\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/rotatesymm.gif\" alt=\"Control point spline with rotation symmetry using Equal and Parallel constraints \" width=\"500\" height=\"313\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>There are many more techniques made possible through combinations of spline curve and control frame constraints &#8211; be sure to experiment with these!<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<h1><strong><span style=\"font-size: 16pt;\">What does the Spline Degree control do?<\/span><\/strong><\/h1>\n<p>&nbsp;<\/p>\n<p>For experienced users of control point splines, we&#8217;ve also provided some control over the degree of your splines.<\/p>\n<p>&nbsp;<\/p>\n<p>At a technical level, the degree of a spline describes the complexity of the equation used to describe its shape. A high-degree spline is defined by a high-degree\u00a0equation, which results in a spline that is technically smoother than a lower-degree spline. The downside of high-degree splines is that more points are required to define a given shape, so lower-degree splines tend to be easier to work with.<\/p>\n<p>&nbsp;<\/p>\n<p>In Fusion, we&#8217;ve provided a choice from the two most commonly used spline degrees &#8211; degree 5 and degree 3. You can choose this from the Spline Degree option in the sketch palette while the Control Point Spline tool is active.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10041\" title=\"The Spline Degree option can be seen and chosen from the sketch palette while the Control Point Spline tool is active\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/splinedegreeoption.png\" alt=\"Spline Degree access point\" width=\"400\" height=\"166\" srcset=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/splinedegreeoption.png 516w, https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/splinedegreeoption-300x124.png 300w\" sizes=\"auto, (max-width: 400px) 100vw, 400px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p><strong>Degree 5<\/strong> is the default option, and will give the best results for most scenarios. This provides an optimal balance of geometry smoothness and ease-of-use. Their high degree of smoothness makes degree 5 splines perfect for defining primary surfaces on your model, and building transition surfaces between existing geometry.<\/p>\n<p>&nbsp;<\/p>\n<p><strong>Degree 3<\/strong> splines usually require fewer control points, so can be easier to work with. The biggest downside is that they are technically\u00a0less smooth than degree 5 splines &#8211; degree 5 splines ensure G4-continuity internal to the curve, while degree 3 splines only guarantee G2-continuity internally.<\/p>\n<p>&nbsp;<\/p>\n<p>If you create a degree 3 spline with a large number of control points, you may observe some sharp turns\/bumps in the curvature comb: these represent points on the curve that are not\u00a0G3-continuous (note that degree 3 splines are still guaranteed to be G2-continuous throughout &#8211; surfaces created from G2-continuous curves will still have visibly smooth highlights, so these are smooth enough for most use cases!)<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10032\" title=\"A degree 5 spline (left) is G4-continuous internally: this results in extremely high internal curvature regardless of how many points are used; degree 3 curves (right) are only G2-contunous, which means they may have G3 continuity breaks (seen as sharp turns in the curvature comb)\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/d5d3.png\" alt=\"Degree 5 spline vs. Degree 3 spline\" width=\"700\" height=\"175\" srcset=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/d5d3.png 978w, https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/d5d3-300x75.png 300w, https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/d5d3-768x192.png 768w\" sizes=\"auto, (max-width: 700px) 100vw, 700px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>One special behavior of note regarding Degree 3 splines is that they can give improved matching behavior when working with geometry in the Sculpt workspace.\u00a0This is because the Sculpt tools are based on T-Splines, a technology which fundamentally is built on degree 3 surfaces. Because of this, we&#8217;ll switch the default Spline Degree to Degree 3 when creating control point splines in the Sculpt workspace.<\/p>\n<p>&nbsp;<\/p>\n<p>Also note that the chosen Spline Degree setting actually determines the <em>maximum<\/em> degree of created spline. A spline&#8217;s degree will only ever be equal to or less than the <strong>number of control points minus 1<\/strong>: e.g. a spline with 4 control points can only be degree 3 or less. As you select points to build your control point spline, its degree with incrementally increase until it hits degree 5 or degree 3 (based on the Spline Degree setting), and will then stay at that degree. So, if your Spline Degree setting is Degree 5, but you finish the spline after selecting four points, the spline degree can only be as high as 3 regardless of the degree setting.<\/p>\n<p>&nbsp;<\/p>\n<p>The gif below shows how the spline degree increases as you add control points using both settings:<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10055\" title=\"When the Spline Degree setting is Degree 5, adding control points will continue increasing the curve degree until it reaches degree 5, at which point it stays there; the same thing occurs at degree 3 when the Degree 3 setting is enabled\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/degreeincrementing.gif\" alt=\"How spline degree increments when adding control points\" width=\"600\" height=\"220\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>You can check the\u00a0true\u00a0degree of a control point spline at any time by selecting it and observing the selection info at the bottom-right corner of the canvas.<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-10042\" title=\"By selecting a control point spline and looking at the selection feedback in the bottom-right corner of the canvas, you can see the spline's true underlying degree\" src=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/degreeselectfeedback.png\" alt=\"Selection feedback for control point spline\" width=\"500\" height=\"169\" srcset=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/degreeselectfeedback.png 944w, https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/degreeselectfeedback-300x102.png 300w, https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/degreeselectfeedback-768x260.png 768w\" sizes=\"auto, (max-width: 500px) 100vw, 500px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<h2><strong>Conclusion<\/strong><\/h2>\n<p>&nbsp;<\/p>\n<p>We hope this has provided a useful overview of the new Control Point Spline tool, and we really hope you enjoy using the new functionality. Be sure to leave any questions or comments below &#8211; we&#8217;d love to hear what you think, and we&#8217;ll continue to iterate and improve this technology based on your feedback!<\/p>\n<p>&nbsp;<\/p>\n<p>&#8211; Jake and the Fusion 360 team<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Your complete guide to this powerful new complex curve creation tool in Fusion 360&#8217;s Sketch toolset.<\/p>\n","protected":false},"author":239,"featured_media":10059,"menu_order":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"categories":[1],"tags":[159,122,158],"coauthors":[],"class_list":["post-9966","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-fusion","tag-control-point-spline","tag-sketch","tag-spline","dhig-theme--light"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.3 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Control Point Splines: Create complex Sketch curves with precision and ease - Fusion Blog<\/title>\n<meta name=\"description\" content=\"Your complete guide to this powerful new freeform curve creation tool in Fusion 360&#039;s Sketch toolset.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/sketch-control-point-splines-faq\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Control Point Splines: Create complex Sketch curves with precision and ease - Fusion Blog\" \/>\n<meta property=\"og:description\" content=\"Your complete guide to this powerful new freeform curve creation tool in Fusion 360&#039;s Sketch toolset.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.autodesk.com\/products\/fusion-360\/blog\/sketch-control-point-splines-faq\/\" \/>\n<meta property=\"og:site_name\" content=\"Fusion Blog\" \/>\n<meta property=\"article:published_time\" content=\"2018-07-20T18:50:59+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/i0.wp.com\/www.autodesk.com\/products\/fusion-360\/blog\/wp-content\/uploads\/2018\/07\/cpspline.png?fit=400%2C220&ssl=1\" \/>\n\t<meta property=\"og:image:width\" content=\"400\" \/>\n\t<meta property=\"og:image:height\" content=\"220\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\n<meta name=\"author\" content=\"jakefowler\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"jakefowler\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"13 minutes\" \/>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"Control Point Splines: Create complex Sketch curves with precision and ease - 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