View source for User:Lum Pfohl/LSL Goodies/Snippet/Align Prim Between Two Points

{| width="100%"
|-
|valign="top"|
<div id="box">
==Align Prim Between Two Points==
<div style="padding: 0.5em">
Occasionally, I have a need to rez a prim such as a cylinder, between two points, lined up in that direction.  The math for it is ridiculously easy, but maddeningly difficult to get right.  So I've documented it below (the text coloring is not standard LSL - rather it is the coloring applied by my UltraEdit text editor.  For a link to a sample 'wordfile' file UltraEdit, [[User:Lum Pfohl/LSL_Syntax_Highlighting_For_UltraEdit|follow this link]].

<font face='courier'>rez (<font color='blue'>vector</font> v1, <font color='blue'>vector</font> v2) {<br/>
&nbsp;&nbsp;<br/>
&nbsp;&nbsp;<font color='orange'>// Determine the midpoint between the two vectors to rez the prim</font><br/>
&nbsp;&nbsp;<font color='blue'>vector</font> rezPos = (v1 + v2) / <font color='red'>2.0</font> + <font color='red'>llGetPos</font>();<br/>
&nbsp;&nbsp;<br/>
&nbsp;&nbsp;<font color='orange'>// Setup for determining the rotation at which the prim will be rezzed<br/>
&nbsp;&nbsp;<br/>
&nbsp;&nbsp;// First, apply any constant transformations to the prim.  In the example<br/>
&nbsp;&nbsp;// below, the rezzed prim is a cylinder (shaped into a 'stick').  Tilt<br/>
&nbsp;&nbsp;// the 'stick' which is aligned vertically by default - sideways by<br/>
&nbsp;&nbsp;// 90 degrees (or PI/2)</font><br/>
&nbsp;&nbsp;<font color='blue'>rotation</font> rezRot = <font color='red'>llEuler2Rot</font>(<<font color='red'>0.0</font>, <font color='green'>PI_BY_TWO</font>, <font color='red'>0.0</font>>)<br/>
&nbsp;&nbsp;<br/>
&nbsp;&nbsp;<font color='orange'>// Get a Unit Vector that points along the space   v1 -> v2</font><br/>
&nbsp;&nbsp;<font color='blue'>vector</font> difference = <font color='red'>llVecNorm</font>(v2 - v1);<br/>
&nbsp;&nbsp;<br/>
&nbsp;&nbsp;<font color='orange'>// Now calculate the new prim rotation by the 'angle' made between<br/>
&nbsp;&nbsp;// an Unit Vector in the X-axis, and the one calculated above.  This value<br/>
&nbsp;&nbsp;// will be multiplied (we multiply rotations values to rotate the previous<br/>
&nbsp;&nbsp;// value).  This aligns the prim lengthwise between the two points, v1 v2</font><br/>
&nbsp;&nbsp;rezRot *= <font color='red'>llRotBetween</font>(<<font color='red'>1.0</font>, <font color='red'>0.0</font>, <font color='red'>0.0</font>>, difference);<br/>
&nbsp;&nbsp;<br/>
&nbsp;&nbsp;<font color='orange'>// Optionally, we will calculate the distance between the two points and<br/>
&nbsp;&nbsp;// send it to the rezzed object as a value.  Unfortunately, we can only<br/>
&nbsp;&nbsp;// send integer values, but by multiplying the float value by 1000, we<br/>
&nbsp;&nbsp;// can capture sufficient significant digits to be passed as an integer<br/>
&nbsp;&nbsp;// The rezzed prim will have an 'on_rez(integer param)' event, which<br/>
&nbsp;&nbsp;// can take the incoming param value and cast it to a float then divide<br/>
&nbsp;&nbsp;// by 1000.0 to get the length.</font><br/>
&nbsp;&nbsp;<font color='blue'>integer</font> resLength = (<font color='blue'>integer</font>)(<font color='red'>llVecMag</font>(v2 - v1) * <font color='red'>1000.0</font>);<br/>
&nbsp;&nbsp;<br/>
&nbsp;&nbsp;<font color='orange'>// All this setup - now we finally rez the prim.  The ZERO_VECTOR value<br/>
&nbsp;&nbsp;// is provided as the rezzed speed.  We don't want our prim to fly away.<br/>
&nbsp;&nbsp;// The rezzed object is called 'pentaedge' in my example.</font><br/>
&nbsp;&nbsp;<font color='red'>llRezObject</font>("<font color='gray'>pentaedge</font>", rezPos, <font color='green'>ZERO_VECTOR</font>, rezRot, resLength);<br/>
}<br/></font>

</div>
</div>
[[User:Lum Pfohl|Lum Pfohl]] 13:53, 21 September 2009 (UTC)
|valign="top" width="200 px"|
{{Lum's Quick Links}}
|}