Quaternion lookat

[{MSX}]

Hi! Anybody here knows about an algorithm for quaternion that orients it to look to a given vector ? (eventually with the up vector too)
Something like:

lookAt( target, up:TVector):TQuaternion

Thanks

[Paulius]

If no one gets a better idea and you?¢_Tre not too lazy you could snap matrix to quaternion conversion code onto gluLookAt.
Mesa?¢_~s gluLookAt looks likes this:

void GLAPIENTRY
gluLookAt(GLdouble eyex, GLdouble eyey, GLdouble eyez,
	  GLdouble centerx, GLdouble centery, GLdouble centerz,
	  GLdouble upx, GLdouble upy, GLdouble upz)
{
   GLdouble m[16];
   GLdouble x[3], y[3], z[3];
   GLdouble mag;

   /* Make rotation matrix */

   /* Z vector */
   z[0] = eyex - centerx;
   z[1] = eyey - centery;
   z[2] = eyez - centerz;
   mag = sqrt(z[0] * z[0] + z[1] * z[1] + z[2] * z[2]);
   if (mag) {			/* mpichler, 19950515 */
      z[0] /= mag;
      z[1] /= mag;
      z[2] /= mag;
   }

   /* Y vector */
   y[0] = upx;
   y[1] = upy;
   y[2] = upz;

   /* X vector = Y cross Z */
   x[0] = y[1] * z[2] - y[2] * z[1];
   x[1] = -y[0] * z[2] + y[2] * z[0];
   x[2] = y[0] * z[1] - y[1] * z[0];

   /* Recompute Y = Z cross X */
   y[0] = z[1] * x[2] - z[2] * x[1];
   y[1] = -z[0] * x[2] + z[2] * x[0];
   y[2] = z[0] * x[1] - z[1] * x[0];

   /* mpichler, 19950515 */
   /* cross product gives area of parallelogram, which is < 1.0 for
    * non-perpendicular unit-length vectors; so normalize x, y here
    */

   mag = sqrt&#40;x&#91;0&#93; * x&#91;0&#93; + x&#91;1&#93; * x&#91;1&#93; + x&#91;2&#93; * x&#91;2&#93;&#41;;
   if &#40;mag&#41; &#123;
      x&#91;0&#93; /= mag;
      x&#91;1&#93; /= mag;
      x&#91;2&#93; /= mag;
   &#125;

   mag = sqrt&#40;y&#91;0&#93; * y&#91;0&#93; + y&#91;1&#93; * y&#91;1&#93; + y&#91;2&#93; * y&#91;2&#93;&#41;;
   if &#40;mag&#41; &#123;
      y&#91;0&#93; /= mag;
      y&#91;1&#93; /= mag;
      y&#91;2&#93; /= mag;
   &#125;

#define M&#40;row,col&#41;  m&#91;col*4+row&#93;
   M&#40;0, 0&#41; = x&#91;0&#93;;
   M&#40;0, 1&#41; = x&#91;1&#93;;
   M&#40;0, 2&#41; = x&#91;2&#93;;

   M&#40;0, 3&#41; = 0.0;
   M&#40;1, 0&#41; = y&#91;0&#93;;
   M&#40;1, 1&#41; = y&#91;1&#93;;
   M&#40;1, 2&#41; = y&#91;2&#93;;
   M&#40;1, 3&#41; = 0.0;
   M&#40;2, 0&#41; = z&#91;0&#93;;
   M&#40;2, 1&#41; = z&#91;1&#93;;
   M&#40;2, 2&#41; = z&#91;2&#93;;
   M&#40;2, 3&#41; = 0.0;
   M&#40;3, 0&#41; = 0.0;
   M&#40;3, 1&#41; = 0.0;
   M&#40;3, 2&#41; = 0.0;
   M&#40;3, 3&#41; = 1.0;
#undef M
   glMultMatrixd&#40;m&#41;;

   /* Translate Eye to Origin */
   glTranslated&#40;-eyex, -eyey, -eyez&#41;;

&#125;

[Sly]

Sssh... if we give him the answer he might win the dog fight competition. :lol:

[{MSX}]

Sssh... if we give him the answer he might win the dog fight competition. :lol:

:lol: :lol:
Just becouse i ask about quaternions, that are expecially useful with airplane models, that doesn't mean it's about the dog fight compo..
Well, in this case, it is :mrgreen:

Btw my entry is going on greatly.. just wait and see

[{MSX}]

If no one gets a better idea and you?¢_Tre not too lazy you could snap matrix to quaternion conversion code onto gluLookAt.
Mesa?¢_~s gluLookAt looks likes this:

Umm that could be an idea.. but i'm way too lazy Also i'm not that good with matrices and i could make some bug..

[WILL]

:lol:

[{MSX}]

ok.. apart from jokes :mrgreen:
Any clue ? I need it quite a lot..

Thanks

[savage]

Nicola,
If you are using JEDI-SDL, in the OpenGL directory you should find Mike Lischke's excellent Geometry.pas file which has all sorts of 3D functions including Quaternions.

IHTH.

[{MSX}]

Nicola,
If you are using JEDI-SDL, in the OpenGL directory you should find Mike Lischke's excellent Geometry.pas file which has all sorts of 3D functions including Quaternions.

IHTH.

I've already looked there, but there is not a big support for quaternions. There are only basic functions.

I'm assembling a unit that is more complete, so btw if you want to use it on JEDI-SDL just ask. It's based on FastGEO for vectors and the like (but it can easily be changed)

[{MSX}]

I've spotted this article.
It tells something about how to obtain axis angle representation of the rotation of a given vector to another. It doesn't uses the up vector, but it can still be useful..

I tryed and implemented this:
[pascal]
v:=mul(a.position, b.position); // cross product
b.orientation.x:=v.x;
b.orientation.y:=v.y;
b.orientation.z:=v.z;
b.orientation.w:= magnitude(a.position) * magnitude(b.position) + dotproduct( unitvector(b.position), unitvector(a.position));
Q_normed(b.orientation);
[/pascal]
It should orient b to a but it doesn't work..
Anyone interested in helping ?
Thanks