<div dir="ltr"><div><div><br></div>If your terrain surface uses a GLSL fragment shader, you could add a 2D point in polygon test on the x/y coordinate and add or blend a highlighting color to the generated fragment when it passes the PIP test. It might get kind of slow when your enclosing polygons has a lot of vertices.<br><br></div>For a decent PIP test algorithm, look here: <a href="http://stackoverflow.com/questions/11716268/point-in-polygon-algorithm">http://stackoverflow.com/questions/11716268/point-in-polygon-algorithm</a><br><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">2015-11-18 12:58 GMT+01:00 Sebastian Messerschmidt <span dir="ltr"><<a href="mailto:sebastian.messerschmidt@gmx.de" target="_blank">sebastian.messerschmidt@gmx.de</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
  
    
  
  <div bgcolor="#FFFFFF" text="#000000">
    <div>Hello Bean?<br>
      <br>
      You can use the polytop intersector to get all primitives inside
      and draw them with an polygon offset applied on top of the
      original geometry.<br>
      <br>
      Cheers<br>
      Sebastian <br>
    </div>
    <blockquote type="cite"><div><div class="h5">
      <div dir="ltr">
        <div><span style="float:left;margin:0px;padding:0px;max-height:40px;overflow:hidden"><a href="https://groups.google.com/forum/#%21searchin/osg-users/how$20to$20draw$20a$20Curved$20Surface$20on$20the$20top$20of$20terrain$3F/osg-users/q0fcYqNZ84E/LqfRH3rBrTUJ" target="_blank"><font color="#50799b" face="Microsoft YaHei"><span style="font-size:12px;line-height:19.2px">primitive
                  problem</span></font><br>
            </a></span><span style="float:left;margin:0px;padding:0px;max-height:40px;overflow:hidden"><a href="https://groups.google.com/forum/#%21searchin/osg-users/how$20to$20draw$20a$20Curved$20Surface$20on$20the$20top$20of$20terrain$3F/osg-users/q0fcYqNZ84E/LqfRH3rBrTUJ" target="_blank"><br>
              <br>
            </a></span></div>
        <div><br>
        </div>
        <span style="color:rgb(0,0,0);font-family:Verdana,Arial,Helvetica,sans-serif;font-size:12px;line-height:18px;background-color:rgb(239,239,239)">
          <div><span style="color:rgb(0,0,0);font-family:Verdana,Arial,Helvetica,sans-serif;font-size:12px;line-height:18px;background-color:rgb(239,239,239)"><br>
            </span></div>
          1、how to draw a Curved Surface on the top of terrain? like the
          fig. </span><br style="color:rgb(0,0,0);font-family:Verdana,Arial,Helvetica,sans-serif;font-size:12px;line-height:18px;background-color:rgb(239,239,239)">
        <span style="color:rgb(0,0,0);font-family:Verdana,Arial,Helvetica,sans-serif;font-size:12px;line-height:18px;background-color:rgb(239,239,239)">2、
          how to compute the surface area of the Curved Surface? </span><br>
        <div><span style="color:rgb(0,0,0);font-family:Verdana,Arial,Helvetica,sans-serif;font-size:12px;line-height:18px;background-color:rgb(239,239,239)"><img src="cid:part3.00070806.01070505@gmx.de" alt="内嵌图片 1" height="187" width="196"><br>
          </span></div>
        <div><span style="background-color:rgb(239,239,239)"><font color="#000000" face="Verdana, Arial, Helvetica,
              sans-serif"><span style="font-size:12px;line-height:18px">I
                 want to use  polytope intersector, but I don't
                have  inspiration. So can you give me some advise?</span></font></span></div>
        <div><span style="background-color:rgb(239,239,239)"><font color="#000000" face="Verdana, Arial, Helvetica,
              sans-serif"><span style="font-size:12px;line-height:18px">thank
                you a lot.</span></font></span></div>
      </div>
      <br>
      <fieldset></fieldset>
      <br>
      </div></div><pre>_______________________________________________
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