111 lines
4.2 KiB
HTML
111 lines
4.2 KiB
HTML
<head>
|
|
<title>qball(3) - Plan 9 from User Space</title>
|
|
<meta content="text/html; charset=utf-8" http-equiv=Content-Type>
|
|
</head>
|
|
<body bgcolor=#ffffff>
|
|
<table border=0 cellpadding=0 cellspacing=0 width=100%>
|
|
<tr height=10><td>
|
|
<tr><td width=20><td>
|
|
<tr><td width=20><td><b>QBALL(3)</b><td align=right><b>QBALL(3)</b>
|
|
<tr><td width=20><td colspan=2>
|
|
<br>
|
|
<p><font size=+1><b>NAME </b></font><br>
|
|
|
|
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
|
|
|
|
qball – 3-d rotation controller<br>
|
|
|
|
</table>
|
|
<p><font size=+1><b>SYNOPSIS </b></font><br>
|
|
|
|
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
|
|
|
|
|
|
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
|
|
|
|
<tt><font size=+1>#include <draw.h>
|
|
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
|
|
</font></tt>
|
|
<tt><font size=+1>#include <geometry.h>
|
|
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
|
|
</font></tt>
|
|
<tt><font size=+1>void qball(Rectangle r, Mouse *mousep,<br>
|
|
|
|
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
|
|
|
|
Quaternion *orientation,<br>
|
|
void (*redraw)(void), Quaternion *ap)<br>
|
|
|
|
</table>
|
|
</font></tt>
|
|
</table>
|
|
<p><font size=+1><b>DESCRIPTION </b></font><br>
|
|
|
|
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
|
|
|
|
<i>Qball</i> is an interactive controller that allows arbitrary 3-space
|
|
rotations to be specified with the mouse. Imagine a sphere with
|
|
its center at the midpoint of rectangle <i>r</i>, and diameter the smaller
|
|
of <i>r</i>’s dimensions. Dragging from one point on the sphere to another
|
|
specifies the endpoints of a great-circle arc. (Mouse
|
|
points outside the sphere are projected to the nearest point on
|
|
the sphere.) The axis of rotation is normal to the plane of the
|
|
arc, and the angle of rotation is twice the angle of the arc.
|
|
|
|
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
|
|
|
|
Argument <i>mousep</i> is a pointer to the mouse event that triggered
|
|
the interaction. It should have some button set. <i>Qball</i> will read
|
|
more events into <i>mousep</i>, and return when no buttons are down.
|
|
|
|
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
|
|
|
|
While <i>qball</i> is reading mouse events, it calls out to the caller-supplied
|
|
routine <i>redraw</i>, which is expected to update the screen to reflect
|
|
the changing orientation. Argument <i>orientation</i> is the orientation
|
|
that <i>redraw</i> should examine, represented as a unit Quaternion (see
|
|
<i>quaternion(9.2)).</i> The caller may set it to any
|
|
orientation. It will be updated before each call to <i>redraw</i> (and
|
|
on return) by multiplying by the rotation specified with the mouse.
|
|
|
|
<table border=0 cellpadding=0 cellspacing=0><tr height=5><td></table>
|
|
|
|
It is possible to restrict <i>qball’s</i> attention to rotations about
|
|
a particular axis. If <i>ap</i> is null, the rotation is unconstrained.
|
|
Otherwise, the rotation will be about the same axis as <i>*ap</i>. This
|
|
is accomplished by projecting points on the sphere to the nearest
|
|
point also on the plane through the sphere’s center and normal
|
|
to
|
|
the axis.<br>
|
|
|
|
</table>
|
|
<p><font size=+1><b>SOURCE </b></font><br>
|
|
|
|
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
|
|
|
|
<tt><font size=+1>/usr/local/plan9/src/libgeometry/qball.c<br>
|
|
</font></tt>
|
|
</table>
|
|
<p><font size=+1><b>SEE ALSO </b></font><br>
|
|
|
|
<table border=0 cellpadding=0 cellspacing=0><tr height=2><td><tr><td width=20><td>
|
|
|
|
<a href="../man3/quaternion.html"><i>quaternion</i>(3)</a><br>
|
|
Ken Shoemake, “Animating Rotation with Quaternion Curves”, <i>SIGGRAPH
|
|
’85 Conference Proceedings.<br>
|
|
</i>
|
|
</table>
|
|
|
|
<td width=20>
|
|
<tr height=20><td>
|
|
</table>
|
|
<!-- TRAILER -->
|
|
<table border=0 cellpadding=0 cellspacing=0 width=100%>
|
|
<tr height=15><td width=10><td><td width=10>
|
|
<tr><td><td>
|
|
<center>
|
|
<a href="../../"><img src="../../dist/spaceglenda100.png" alt="Space Glenda" border=1></a>
|
|
</center>
|
|
</table>
|
|
<!-- TRAILER -->
|
|
</body></html>
|