From 78e51a8c6678b6e3dff3d619aa786669f531f4bc Mon Sep 17 00:00:00 2001 From: rsc Date: Fri, 14 Jan 2005 03:45:44 +0000 Subject: checkpoint --- man/man3/qball.html | 111 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 111 insertions(+) create mode 100644 man/man3/qball.html (limited to 'man/man3/qball.html') diff --git a/man/man3/qball.html b/man/man3/qball.html new file mode 100644 index 00000000..b1403336 --- /dev/null +++ b/man/man3/qball.html @@ -0,0 +1,111 @@ + +qball(3) - Plan 9 from User Space + + + + +
+
+
QBALL(3)QBALL(3) +
+
+

NAME
+ +
+ + qball – 3-d rotation controller
+ +
+

SYNOPSIS
+ +
+ + +
+ + #include <draw.h> +
+ + #include <geometry.h> +
+ + void qball(Rectangle r, Mouse *mousep,
+ +
+ + Quaternion *orientation,
+ void (*redraw)(void), Quaternion *ap)
+ +
+ +
+

DESCRIPTION
+ +
+ + Qball 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 r, and diameter the smaller + of r’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. + +
+ + Argument mousep is a pointer to the mouse event that triggered + the interaction. It should have some button set. Qball will read + more events into mousep, and return when no buttons are down. + +
+ + While qball is reading mouse events, it calls out to the caller-supplied + routine redraw, which is expected to update the screen to reflect + the changing orientation. Argument orientation is the orientation + that redraw should examine, represented as a unit Quaternion (see + quaternion(9.2)). The caller may set it to any + orientation. It will be updated before each call to redraw (and + on return) by multiplying by the rotation specified with the mouse. + +
+ + It is possible to restrict qball’s attention to rotations about + a particular axis. If ap is null, the rotation is unconstrained. + Otherwise, the rotation will be about the same axis as *ap. 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.
+ +
+

SOURCE
+ +
+ + /usr/local/plan9/src/libgeometry/qball.c
+ +
+

SEE ALSO
+ +
+ + quaternion(3)
+ Ken Shoemake, “Animating Rotation with Quaternion Curves”, SIGGRAPH + ’85 Conference Proceedings.
+ +
+ +

 +
+
+ + +
+
+
+Space Glenda +
+
+ + -- cgit v1.2.3