<!DOCTYPE html
  PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<!--
Copyright (c) 2006 UGS Corp.

All Rights Reserved.

This software and related documentation are proprietary to UGS Corp.
-->
<html>
   <head>
      <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
      <title>Sketch practices</title>
      <script language="javaScript">
        abridged="false";
        displayConditions=new Array();
      </script>
      <link type="text/css" href="../css/main_styles.css" rel="stylesheet">
   </head>
   <body class="bodydocs" onload="top.pageLoader()" bgcolor="#FFFFFF">
      <div class="title_topic3" id="xps10_pagetitle">Sketch practices</div>
      <hr noshade="true">
      <p class="para_topic"><img align="bottom" src="graphics/commandref/ideas_rule.gif" border="0"></p>
      <p class="para_topic">This article discusses some sketch differences between I-deas and NX.</p>
      <p class="para_topic"><img align="bottom" src="graphics/commandref/nx_rule.gif" border="0"></p>
      <p class="para_topic">Although the concepts of sketching are very similar in I-deas and NX, there are some subtle differences. These differences require some slight changes to your standard sketch practices.</p>
      <div class="title_division">Focus</div>
      <p class="para_division">In I-deas, the <b class="uiTerm">Focus</b> option is used to create constraints to part geometry that does not lie in the sketch plane. 
      </p>
      <p class="para_division">NX does not have a <b class="uiTerm">Focus</b> option because it does not need it. You can create dimensional or geometric constraints directly to geometry on other faces of the part or to other datums. Distance is measured as if the geometry was projected to the sketch plane.
      </p>
      <p class="para_division">This difference means that you will not get yellow out-of-date sketch edges in NX.</p>
      <table border="0">
         <tr>
            <td valign="top" align="left"><img align="left" src="../graphics/tip.gif" alt="Tip" title="Tip"></td>
            <td valign="bottom" align="left" width="100%">
               <div class="para_tip">
                  <p class="para_tip_body">This will change your sketching practice, because you no longer need to use the <b class="uiTerm">Focus</b> option.
                  </p>
               </div>
            </td>
         </tr>
      </table>
      <div class="title_division">Positioning sketches</div>
      <p class="para_division">In I-deas, sketches are positioned on a sketch plane using constraints between sketch curves and other part geometry, often using the <b class="uiTerm">Focus</b> option.
      </p>
      <p class="para_division">In NX, there are two different ways to position a sketch.</p>
      <ul>
         <li>
            <p class="para_item">The first method is to constrain the sketch to part geometry or datums. This is the same as the normal practice in I-deas except that the <b class="uiTerm">Focus</b> option is not required.
            </p>
         </li>
         <li>
            <p class="para_item">The second method is to create a sketch without any constraints to geometry or datums outside the sketch. Use positional constraints to position the sketch as a rigid body. These constraints are similar to the feature relations used in I-deas to position features. </p>
         </li>
      </ul>
      <table border="0">
         <tr>
            <td valign="top" align="left"><img align="left" src="../graphics/tip.gif" alt="Tip" title="Tip"></td>
            <td valign="bottom" align="left" width="100%">
               <div class="para_tip">
                  <p class="para_tip_body">The normal practice is to only use the second method when you intend to reuse a sketch by using <b class="uiTerm">Copy</b> and <b class="uiTerm">Paste</b> or to create a user defined feature (<b class="uiTerm">UDF</b>).
                  </p>
               </div>
            </td>
         </tr>
      </table>
      <div class="title_division">Grounding the 1st point</div>
      <p class="para_division">In I-deas, the starting point of a sketch is implicitly grounded. If you later explicitly ground (fix) some other point or fully constrain the sketch to part edges, the automatic implicit ground constraint will be removed. NX does not add this implicit ground constraint. This makes it easier to reuse sketches. </p>
      <p class="para_division">The sketch below may look fully dimensioned, but since no point is grounded, every point is shown free to move in two degrees of freedom.</p>
      <p align="center"><img align="bottom" src="graphics/parts/constraints3.gif"></p>
      <table border="0">
         <tr>
            <td valign="top" align="left"><img align="left" src="../graphics/tip.gif" alt="Tip" title="Tip"></td>
            <td valign="bottom" align="left" width="100%">
               <div class="para_tip">
                  <p class="para_tip_body">As a best practice, you should make sure that your sketch is properly constrained to the part. This will not change your sketching practice unless your normal work habits relied on the implicit ground constraint in I-deas.</p>
               </div>
            </td>
         </tr>
      </table>
      <div class="title_division">Horizontal constraints</div>
      <p class="para_division">In I-deas, overuse of horizontal and vertical constraints is discouraged. This is because these constraints lock the sketch in the sketch plane coordinates (the S and T coordinates that are not controlled by the user). Parallel and perpendicular constraints are recommended in I-deas instead of horizontal and vertical constraints for this reason. </p>
      <p class="para_division">Because NX prompts you to select an associative horizontal reference, horizontal and vertical constraints are no longer an issue. Horizontal and vertical constraints are actually constraints to the horizontal axis you selected. You can edit the sketch definition to change the horizontal reference at any time. Horizontal and vertical constraints can be seen in the sketch above.</p>
      <table border="0">
         <tr>
            <td valign="top" align="left"><img align="left" src="../graphics/tip.gif" alt="Tip" title="Tip"></td>
            <td valign="bottom" align="left" width="100%">
               <div class="para_tip">
                  <p class="para_tip_body">In NX, the use of horizontal and vertical constraints should not be considered bad practice.</p>
               </div>
            </td>
         </tr>
      </table>
      <div class="title_division">Midpoint</div>
      <p class="para_division">In I-deas, the <b class="uiTerm">Midpoint</b> constraint constrains a point to the midpoint of a line.
      </p>
      <p class="para_division">In NX, the <b class="uiTerm">Midpoint</b> constraint is separate from the <b class="uiTerm">Point on Curve</b> constraint. In the picture below, the circle is constrained to the center of the rectangle using two <b class="uiTerm">Midpoint</b> constraints. Notice that no extra sketch lines are needed to center the circle.
      </p>
      <p align="center"><img align="bottom" src="graphics/parts/midpoint1.gif"></p>
      <p class="para_division">To center a circle on a line as shown below, a <b class="uiTerm">Midpoint</b> and a <b class="uiTerm">Point on Curve</b> constraint are used.
      </p>
      <p align="center"><img align="bottom" src="graphics/parts/midpoint2.gif"></p>
      <table border="0">
         <tr>
            <td valign="top" align="left"><img align="left" src="../graphics/tip.gif" alt="Tip" title="Tip"></td>
            <td valign="bottom" align="left" width="100%">
               <div class="para_tip">
                  <p class="para_tip_body">This may change your sketch practices, since you do not need to sketch extra construction lines as you did in I-deas.</p>
               </div>
            </td>
         </tr>
      </table>
      <div class="title_division">Line-to-line dimensions</div>
      <p class="para_division">In I-deas, you can create point-to-point, line-to-point, or line-to-line dimensions in a sketch. When you create a line-to-line dimension, I-deas automatically adds the required parallel constraint to ensure that the lines remain parallel.</p>
      <p class="para_division">If you create a line-to-line dimension in an NX sketch, the software will substitute a line-to-point dimension using the closest point to where you select the second line.</p>
      <table border="0">
         <tr>
            <td valign="top" align="left"><img align="left" src="../graphics/tip.gif" alt="Tip" title="Tip"></td>
            <td valign="bottom" align="left" width="100%">
               <div class="para_tip">
                  <p class="para_tip_body">This may change your sketching practice in NX because the software does not automatically create a parallel constraint when creating line to line dimensions.</p>
               </div>
            </td>
         </tr>
      </table>
      <div class="title_division">Inferred constraints</div>
      <p class="para_division">As you sketch in both I-deas and NX, the cursor snaps to possible constraint conditions. In I-deas, every curve in the sketch is a candidate for constraint recognition. This can speed up constraining, but if you are not careful, it can lead to creating undesired constraints. </p>
      <p class="para_division">In NX, a &ldquo;short list&rdquo; of sketch objects is maintained, and the cursor only snaps to this list of candidates. To add a curve to the &ldquo;short list,&rdquo; just move the cursor over the curve.</p>
      <p align="center"><img align="bottom" src="graphics/parts/sketch_infer_anim.gif"></p>
      <table border="0">
         <tr>
            <td valign="top" align="left"><img align="left" src="../graphics/tip.gif" alt="Tip" title="Tip"></td>
            <td valign="bottom" align="left" width="100%">
               <div class="para_tip">
                  <p class="para_tip_body">Momentarily move the cursor over sketch curves you want the software to use to create inferred constraints.</p>
               </div>
            </td>
         </tr>
      </table>
      <p class="para_division">See also:</p>
      <ul class="unmarkedList">
         <li>
            <p class="para_item">Help: <img align="bottom" src="graphics/widgets/book_closed.gif" border="0"> Design &rarr; Sketcher &rarr; Tutorials
            </p>
         </li>
         <li>
            <p class="para_item">Help: <img align="bottom" src="graphics/widgets/book_closed.gif" border="0"> Design &rarr; Sketcher &rarr; Constraints Overview
            </p>
         </li>
      </ul>
   </body>
</html>