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Diffstat (limited to 'progs/demos/trackball.c')
| -rw-r--r-- | progs/demos/trackball.c | 338 |
1 files changed, 338 insertions, 0 deletions
diff --git a/progs/demos/trackball.c b/progs/demos/trackball.c new file mode 100644 index 00000000000..a6c4c60d06b --- /dev/null +++ b/progs/demos/trackball.c @@ -0,0 +1,338 @@ +#include <stdio.h> +/* + * (c) Copyright 1993, 1994, Silicon Graphics, Inc. + * ALL RIGHTS RESERVED + * Permission to use, copy, modify, and distribute this software for + * any purpose and without fee is hereby granted, provided that the above + * copyright notice appear in all copies and that both the copyright notice + * and this permission notice appear in supporting documentation, and that + * the name of Silicon Graphics, Inc. not be used in advertising + * or publicity pertaining to distribution of the software without specific, + * written prior permission. + * + * THE MATERIAL EMBODIED ON THIS SOFTWARE IS PROVIDED TO YOU "AS-IS" + * AND WITHOUT WARRANTY OF ANY KIND, EXPRESS, IMPLIED OR OTHERWISE, + * INCLUDING WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY OR + * FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL SILICON + * GRAPHICS, INC. BE LIABLE TO YOU OR ANYONE ELSE FOR ANY DIRECT, + * SPECIAL, INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY + * KIND, OR ANY DAMAGES WHATSOEVER, INCLUDING WITHOUT LIMITATION, + * LOSS OF PROFIT, LOSS OF USE, SAVINGS OR REVENUE, OR THE CLAIMS OF + * THIRD PARTIES, WHETHER OR NOT SILICON GRAPHICS, INC. HAS BEEN + * ADVISED OF THE POSSIBILITY OF SUCH LOSS, HOWEVER CAUSED AND ON + * ANY THEORY OF LIABILITY, ARISING OUT OF OR IN CONNECTION WITH THE + * POSSESSION, USE OR PERFORMANCE OF THIS SOFTWARE. + * + * US Government Users Restricted Rights + * Use, duplication, or disclosure by the Government is subject to + * restrictions set forth in FAR 52.227.19(c)(2) or subparagraph + * (c)(1)(ii) of the Rights in Technical Data and Computer Software + * clause at DFARS 252.227-7013 and/or in similar or successor + * clauses in the FAR or the DOD or NASA FAR Supplement. + * Unpublished-- rights reserved under the copyright laws of the + * United States. Contractor/manufacturer is Silicon Graphics, + * Inc., 2011 N. Shoreline Blvd., Mountain View, CA 94039-7311. + * + * OpenGL(TM) is a trademark of Silicon Graphics, Inc. + */ +/* + * Trackball code: + * + * Implementation of a virtual trackball. + * Implemented by Gavin Bell, lots of ideas from Thant Tessman and + * the August '88 issue of Siggraph's "Computer Graphics," pp. 121-129. + * + * Vector manip code: + * + * Original code from: + * David M. Ciemiewicz, Mark Grossman, Henry Moreton, and Paul Haeberli + * + * Much mucking with by: + * Gavin Bell + */ +#if defined(_WIN32) +#pragma warning (disable:4244) /* disable bogus conversion warnings */ +#endif +#include <math.h> +#include "trackball.h" + +/* + * This size should really be based on the distance from the center of + * rotation to the point on the object underneath the mouse. That + * point would then track the mouse as closely as possible. This is a + * simple example, though, so that is left as an Exercise for the + * Programmer. + */ +#define TRACKBALLSIZE (0.8f) + +/* + * Local function prototypes (not defined in trackball.h) + */ +static float tb_project_to_sphere(float, float, float); +static void normalize_quat(float [4]); + +static void +vzero(float v[3]) +{ + v[0] = 0.0; + v[1] = 0.0; + v[2] = 0.0; +} + +static void +vset(float v[3], float x, float y, float z) +{ + v[0] = x; + v[1] = y; + v[2] = z; +} + +static void +vsub(const float src1[3], const float src2[3], float dst[3]) +{ + dst[0] = src1[0] - src2[0]; + dst[1] = src1[1] - src2[1]; + dst[2] = src1[2] - src2[2]; +} + +static void +vcopy(const float v1[3], float v2[3]) +{ + register int i; + for (i = 0 ; i < 3 ; i++) + v2[i] = v1[i]; +} + +static void +vcross(const float v1[3], const float v2[3], float cross[3]) +{ + float temp[3]; + + temp[0] = (v1[1] * v2[2]) - (v1[2] * v2[1]); + temp[1] = (v1[2] * v2[0]) - (v1[0] * v2[2]); + temp[2] = (v1[0] * v2[1]) - (v1[1] * v2[0]); + vcopy(temp, cross); +} + +static float +vlength(const float v[3]) +{ + return sqrt(v[0] * v[0] + v[1] * v[1] + v[2] * v[2]); +} + +static void +vscale(float v[3], float div) +{ + v[0] *= div; + v[1] *= div; + v[2] *= div; +} + +static void +vnormal(float v[3]) +{ + vscale(v,1.0/vlength(v)); +} + +static float +vdot(const float v1[3], const float v2[3]) +{ + return v1[0]*v2[0] + v1[1]*v2[1] + v1[2]*v2[2]; +} + +static void +vadd(const float src1[3], const float src2[3], float dst[3]) +{ + dst[0] = src1[0] + src2[0]; + dst[1] = src1[1] + src2[1]; + dst[2] = src1[2] + src2[2]; +} + +/* + * Ok, simulate a track-ball. Project the points onto the virtual + * trackball, then figure out the axis of rotation, which is the cross + * product of P1 P2 and O P1 (O is the center of the ball, 0,0,0) + * Note: This is a deformed trackball-- is a trackball in the center, + * but is deformed into a hyperbolic sheet of rotation away from the + * center. This particular function was chosen after trying out + * several variations. + * + * It is assumed that the arguments to this routine are in the range + * (-1.0 ... 1.0) + */ +void +trackball(float q[4], float p1x, float p1y, float p2x, float p2y) +{ + float a[3]; /* Axis of rotation */ + float phi; /* how much to rotate about axis */ + float p1[3], p2[3], d[3]; + float t; + + if (p1x == p2x && p1y == p2y) { + /* Zero rotation */ + vzero(q); + q[3] = 1.0; + return; + } + + /* + * First, figure out z-coordinates for projection of P1 and P2 to + * deformed sphere + */ + vset(p1,p1x,p1y,tb_project_to_sphere(TRACKBALLSIZE,p1x,p1y)); + vset(p2,p2x,p2y,tb_project_to_sphere(TRACKBALLSIZE,p2x,p2y)); + + /* + * Now, we want the cross product of P1 and P2 + */ + vcross(p2,p1,a); + + /* + * Figure out how much to rotate around that axis. + */ + vsub(p1,p2,d); + t = vlength(d) / (2.0*TRACKBALLSIZE); + + /* + * Avoid problems with out-of-control values... + */ + if (t > 1.0) t = 1.0; + if (t < -1.0) t = -1.0; + phi = 2.0 * asin(t); + + axis_to_quat(a,phi,q); +} + +/* + * Given an axis and angle, compute quaternion. + */ +void +axis_to_quat(const float a[3], float phi, float q[4]) +{ + vcopy(a,q); + vnormal(q); + vscale(q, sin(phi/2.0)); + q[3] = cos(phi/2.0); +} + +/* + * Project an x,y pair onto a sphere of radius r OR a hyperbolic sheet + * if we are away from the center of the sphere. + */ +static float +tb_project_to_sphere(float r, float x, float y) +{ + float d, t, z; + + d = sqrt(x*x + y*y); + if (d < r * 0.70710678118654752440) { /* Inside sphere */ + z = sqrt(r*r - d*d); + } else { /* On hyperbola */ + t = r / 1.41421356237309504880; + z = t*t / d; + } + return z; +} + +/* + * Given two rotations, e1 and e2, expressed as quaternion rotations, + * figure out the equivalent single rotation and stuff it into dest. + * + * This routine also normalizes the result every RENORMCOUNT times it is + * called, to keep error from creeping in. + * + * NOTE: This routine is written so that q1 or q2 may be the same + * as dest (or each other). + */ + +#define RENORMCOUNT 97 + +void +add_quats(const float q1[4], const float q2[4], float dest[4]) +{ + static int count=0; + float t1[4], t2[4], t3[4]; + float tf[4]; + +#if 0 +printf("q1 = %f %f %f %f\n", q1[0], q1[1], q1[2], q1[3]); +printf("q2 = %f %f %f %f\n", q2[0], q2[1], q2[2], q2[3]); +#endif + + vcopy(q1,t1); + vscale(t1,q2[3]); + + vcopy(q2,t2); + vscale(t2,q1[3]); + + vcross(q2,q1,t3); + vadd(t1,t2,tf); + vadd(t3,tf,tf); + tf[3] = q1[3] * q2[3] - vdot(q1,q2); + +#if 0 +printf("tf = %f %f %f %f\n", tf[0], tf[1], tf[2], tf[3]); +#endif + + dest[0] = tf[0]; + dest[1] = tf[1]; + dest[2] = tf[2]; + dest[3] = tf[3]; + + if (++count > RENORMCOUNT) { + count = 0; + normalize_quat(dest); + } +} + +/* + * Quaternions always obey: a^2 + b^2 + c^2 + d^2 = 1.0 + * If they don't add up to 1.0, dividing by their magnitued will + * renormalize them. + * + * Note: See the following for more information on quaternions: + * + * - Shoemake, K., Animating rotation with quaternion curves, Computer + * Graphics 19, No 3 (Proc. SIGGRAPH'85), 245-254, 1985. + * - Pletinckx, D., Quaternion calculus as a basic tool in computer + * graphics, The Visual Computer 5, 2-13, 1989. + */ +static void +normalize_quat(float q[4]) +{ + int i; + float mag; + + mag = sqrt(q[0]*q[0] + q[1]*q[1] + q[2]*q[2] + q[3]*q[3]); + for (i = 0; i < 4; i++) + q[i] /= mag; +} + +/* + * Build a rotation matrix, given a quaternion rotation. + * + */ +void +build_rotmatrix(float m[4][4], const float q[4]) +{ + m[0][0] = 1.0 - 2.0 * (q[1] * q[1] + q[2] * q[2]); + m[0][1] = 2.0 * (q[0] * q[1] - q[2] * q[3]); + m[0][2] = 2.0 * (q[2] * q[0] + q[1] * q[3]); + m[0][3] = 0.0; + + m[1][0] = 2.0 * (q[0] * q[1] + q[2] * q[3]); + m[1][1]= 1.0 - 2.0 * (q[2] * q[2] + q[0] * q[0]); + m[1][2] = 2.0 * (q[1] * q[2] - q[0] * q[3]); + m[1][3] = 0.0; + + m[2][0] = 2.0 * (q[2] * q[0] - q[1] * q[3]); + m[2][1] = 2.0 * (q[1] * q[2] + q[0] * q[3]); + m[2][2] = 1.0 - 2.0 * (q[1] * q[1] + q[0] * q[0]); + m[2][3] = 0.0; + + m[3][0] = 0.0; + m[3][1] = 0.0; + m[3][2] = 0.0; + m[3][3] = 1.0; +} + |