Sign in to follow this  
Silex

OpenGL anyone using SGI's trackball code?

Recommended Posts

I've been using SGI's trackball code to rotate the view around objects with the mouse but I haven't been able to get it to work around an arbitrary center of rotation. Did they hard-code their trackball stuff so it only works around the origin? (if you don't know what I'm talking about the source is below) Can anyone point me to a good resource on how to achieve this effect? I don't care if it means moving away from SGI's code as long its easy (1-2 hours max) to implement. header
/*

 * (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 * Unpublished-- rights reserved under the copyright laws of the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.h

 * A virtual trackball implementation

 * Written by Gavin Bell for Silicon Graphics, November 1988.

 */



/*

 * Pass the x and y coordinates of the last and current positions of

 * the mouse, scaled so they are from (-1.0 ... 1.0).

 *

 * The resulting rotation is returned as a quaternion rotation in the

 * first paramater.

 */

void

trackball(float q[4], float p1x, float p1y, float p2x, float p2y);



/*

 * Given two quaternions, add them together to get a third quaternion.

 * Adding quaternions to get a compound rotation is analagous to adding

 * translations to get a compound translation.  When incrementally

 * adding rotations, the first argument here should be the new

 * rotation, the second and third the total rotation (which will be

 * over-written with the resulting new total rotation).

 */

void

add_quats(float *q1, float *q2, float *dest);



/*

 * A useful function, builds a rotation matrix in Matrix based on

 * given quaternion.

 */

void

build_rotmatrix(float m[4][4], float q[4]);



/*

 * This function computes a quaternion based on an axis (defined by

 * the given vector) and an angle about which to rotate.  The angle is

 * expressed in radians.  The result is put into the third argument.

 */

void

axis_to_quat(float a[3], float phi, float q[4]);

source
/*

 * (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

 */

#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  (0.8)



/*

 * Local function prototypes (not defined in trackball.h)

 */

static float tb_project_to_sphere(float, float, float);

static void normalize_quat(float [4]);



void

vzero(float *v)

{

    v[0] = 0.0;

    v[1] = 0.0;

    v[2] = 0.0;

}



void

vset(float *v, float x, float y, float z)

{

    v[0] = x;

    v[1] = y;

    v[2] = z;

}



void

vsub(const float *src1, const float *src2, float *dst)

{

    dst[0] = src1[0] - src2[0];

    dst[1] = src1[1] - src2[1];

    dst[2] = src1[2] - src2[2];

}



void

vcopy(const float *v1, float *v2)

{

    register int i;

    for (i = 0 ; i < 3 ; i++)

        v2[i] = v1[i];

}



void

vcross(const float *v1, const float *v2, float *cross)

{

    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);

}



float

vlength(const float *v)

{

    return sqrt(v[0] * v[0] + v[1] * v[1] + v[2] * v[2]);

}



void

vscale(float *v, float div)

{

    v[0] *= div;

    v[1] *= div;

    v[2] *= div;

}



void

vnormal(float *v)

{

    vscale(v,1.0/vlength(v));

}



float

vdot(const float *v1, const float *v2)

{

    return v1[0]*v2[0] + v1[1]*v2[1] + v1[2]*v2[2];

}



void

vadd(const float *src1, const float *src2, float *dst)

{

    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(float a[3], float phi, float q[4])

{

    vnormal(a);

    vcopy(a,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(float q1[4], float q2[4], float dest[4])

{

    static int count=0;

    float t1[4], t2[4], t3[4];

    float tf[4];



    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);



    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 = (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], 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;

}





Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Forum Statistics

    • Total Topics
      627749
    • Total Posts
      2978913
  • Similar Content

    • By DelicateTreeFrog
      Hello! As an exercise for delving into modern OpenGL, I'm creating a simple .obj renderer. I want to support things like varying degrees of specularity, geometry opacity, things like that, on a per-material basis. Different materials can also have different textures. Basic .obj necessities. I've done this in old school OpenGL, but modern OpenGL has its own thing going on, and I'd like to conform as closely to the standards as possible so as to keep the program running correctly, and I'm hoping to avoid picking up bad habits this early on.
      Reading around on the OpenGL Wiki, one tip in particular really stands out to me on this page:
      For something like a renderer for .obj files, this sort of thing seems almost ideal, but according to the wiki, it's a bad idea. Interesting to note!
      So, here's what the plan is so far as far as loading goes:
      Set up a type for materials so that materials can be created and destroyed. They will contain things like diffuse color, diffuse texture, geometry opacity, and so on, for each material in the .mtl file. Since .obj files are conveniently split up by material, I can load different groups of vertices/normals/UVs and triangles into different blocks of data for different models. When it comes to the rendering, I get a bit lost. I can either:
      Between drawing triangle groups, call glUseProgram to use a different shader for that particular geometry (so a unique shader just for the material that is shared by this triangle group). or
      Between drawing triangle groups, call glUniform a few times to adjust different parameters within the "master shader", such as specularity, diffuse color, and geometry opacity. In both cases, I still have to call glBindTexture between drawing triangle groups in order to bind the diffuse texture used by the material, so there doesn't seem to be a way around having the CPU do *something* during the rendering process instead of letting the GPU do everything all at once.
      The second option here seems less cluttered, however. There are less shaders to keep up with while one "master shader" handles it all. I don't have to duplicate any code or compile multiple shaders. Arguably, I could always have the shader program for each material be embedded in the material itself, and be auto-generated upon loading the material from the .mtl file. But this still leads to constantly calling glUseProgram, much more than is probably necessary in order to properly render the .obj. There seem to be a number of differing opinions on if it's okay to use hundreds of shaders or if it's best to just use tens of shaders.
      So, ultimately, what is the "right" way to do this? Does using a "master shader" (or a few variants of one) bog down the system compared to using hundreds of shader programs each dedicated to their own corresponding materials? Keeping in mind that the "master shaders" would have to track these additional uniforms and potentially have numerous branches of ifs, it may be possible that the ifs will lead to additional and unnecessary processing. But would that more expensive than constantly calling glUseProgram to switch shaders, or storing the shaders to begin with?
      With all these angles to consider, it's difficult to come to a conclusion. Both possible methods work, and both seem rather convenient for their own reasons, but which is the most performant? Please help this beginner/dummy understand. Thank you!
    • By JJCDeveloper
      I want to make professional java 3d game with server program and database,packet handling for multiplayer and client-server communicating,maps rendering,models,and stuffs Which aspect of java can I learn and where can I learn java Lwjgl OpenGL rendering Like minecraft and world of tanks
    • By AyeRonTarpas
      A friend of mine and I are making a 2D game engine as a learning experience and to hopefully build upon the experience in the long run.

      -What I'm using:
          C++;. Since im learning this language while in college and its one of the popular language to make games with why not.     Visual Studios; Im using a windows so yea.     SDL or GLFW; was thinking about SDL since i do some research on it where it is catching my interest but i hear SDL is a huge package compared to GLFW, so i may do GLFW to start with as learning since i may get overwhelmed with SDL.  
      -Questions
      Knowing what we want in the engine what should our main focus be in terms of learning. File managements, with headers, functions ect. How can i properly manage files with out confusing myself and my friend when sharing code. Alternative to Visual studios: My friend has a mac and cant properly use Vis studios, is there another alternative to it?  
    • By ferreiradaselva
      Both functions are available since 3.0, and I'm currently using `glMapBuffer()`, which works fine.
      But, I was wondering if anyone has experienced advantage in using `glMapBufferRange()`, which allows to specify the range of the mapped buffer. Could this be only a safety measure or does it improve performance?
      Note: I'm not asking about glBufferSubData()/glBufferData. Those two are irrelevant in this case.
    • By xhcao
      Before using void glBindImageTexture(    GLuint unit, GLuint texture, GLint level, GLboolean layered, GLint layer, GLenum access, GLenum format), does need to make sure that texture is completeness. 
  • Popular Now