[ODE] Rotation about Z-axis clockwise ?

[thomas.miconi@free.fr]

Quoting Antonio Tejada Lacaci <wildfred@teleline.es>:   
   
> On Tue, 26 Aug 2003 17:31:33 +0200, thomas.miconi@free.fr wrote:   
> >According to the Rule Thumb, this seems to correspond to an indirect   
> rotation    
> >about the z-axis (i.e. clockwise rotation if the z-axis points to you).    
>    
> If you are in a "right-handed coordinate system", i.e. a system which   
> holds the right-hand rule, rotating when the axis points towards you   
> (out of the computer screen) is counterclockwise, not clockwise.   
   
   (0.707107, -0.707107, 0.000000) (0.707107, 0.707107, 0.000000) (0.000000, 
0.000000, 1.000000) 
 
I agree wholeheartedly. This is exactly what I wrote (direct -> counterclock,   
indirect -> clock). And it seems to me that ODE does exactly the contrary !   
   
This seems highly improbable however, because somebody would probably have   
seen it already. So I just can't find the problem.   
   
Below is a minimum piece of code that shows the problem with quaternions. One  
can just copy/paste it and compile with "gcc -Wall -I../../include  
./Program.cpp ../../lib/libode.a -lm" (possibly changing the directories, of  
course).  
  
A much simpler way to see it is simply to call  dRFromAxisAndAngle(mymatrix, 
0, 0, 1, pi/4), and to have a look at the resulting matrix: It looks like it's   
been rotated *clockwise* (i.e. indirect direction - it gives the same coords 
as indicated below).   
 
Please, what am I doing wrong ? 
   
Amicalement,   
Thomas   
======   
#include <ode/ode.h> 
#include <drawstuff/drawstuff.h> 
#include <stdlib.h> 
#define MyPi 3.14159265 
 
int main (int argc, char **argv) 
{ 
    dWorldID world; 
    dBodyID limb1; 
    dReal * tmpmat; 
    dQuaternion q; 
 
    world = dWorldCreate(); 
 
    limb1 = dBodyCreate (world); 
 
    tmpmat = (double *) dBodyGetRotation (limb1); 
    printf(" (%f, %f, %f) (%f, %f, %f) (%f, %f, %f) \n", 
            tmpmat[0], tmpmat[1], tmpmat[2], 
            tmpmat[4], tmpmat[5], tmpmat[6], 
            tmpmat[8], tmpmat[9], tmpmat[10]); 
    // This prints the standard expected coords (100)(010)(001) 
 
    // Now, rotating Pi/4 around the Z axis... 
    // Expecting normal, direct, counterclockwise rotation 
    dQFromAxisAndAngle(q, 0, 0, 1, MyPi / 4.0); 
    dBodySetQuaternion (limb1, q); 
    tmpmat = (double *) dBodyGetRotation (limb1); 
    printf("\n (%f, %f, %f) (%f, %f, %f) (%f, %f, %f) \n", 
            tmpmat[0], tmpmat[1], tmpmat[2], 
            tmpmat[4], tmpmat[5], tmpmat[6], 
            tmpmat[8], tmpmat[9], tmpmat[10]); 
    // Resulting coords: 
    // (0.707107, -0.707107, 0.000000) 
    // (0.707107, 0.707107, 0.000000) 
    // (0.000000, 0.000000, 1.000000) 
    //  This looks like an indirect rotation ! 
    dWorldDestroy (world); 
    return 0; 
}