yair reshef

hi, i am trying to make a plane always keep its orientation facing the

center. after some digging i have found i need to use " direction cosines"

to extract the angles. but something is wrong.

hi, i am trying to make a plane always keep its orientation facing the
center. after some digging i have found i need to use " direction cosines"
to extract the angles. but something is wrong.

direction-cosines-math-problem

this is better, but its 2d, how do i convert Cartesian to polar in 3d?(!)

the equation at the bottom of this page makes no sense, i need three radians

to correctly Orient the cube, this gives me 2 and a length. pls good ppl of

http://electron9.phys.utk.edu/vectors/3dcoordinates.htm

> hi, i am trying to make a plane always keep its orientation facing the

> center. after some digging i have found i need to use " direction cosines"

> to extract the angles. but something is wrong.

> #P message 82 525 86 9109513 rotatexyz $1 $2 $3;

> #P comment 22 453 55 9109513 rad to deg;

> #P newex 82 475 103 9109513 jit.op @op * @val 180.;

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> #P newex 82 372 56 9109513 jit.op @op /;

> #P comment 16 374 53 9109513 unit vector;

> #P newex 128 343 311 9109513 jit.expr @expr

> sqrt(pow(in[0].p[0]\,2)+pow(in[0].p[1]\,2)+pow(in[0].p[2]\,2));

> #P newex 263 186 55 9109513 jit.multiplex;

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> #P newex 18 232 132 9109513 jit.gl.videoplane quadr @texture grid @color 1

this is better, but its 2d, how do i convert Cartesian to polar in 3d?(!)
the equation at the bottom of this page makes no sense, i need three radians
to correctly Orient the cube, this gives me 2 and a length. pls good ppl of
intranet...
http://electron9.phys.utk.edu/vectors/3dcoordinates.htm

On 9/29/07, yair reshef  wrote:
>
> hi, i am trying to make a plane always keep its orientation facing the
> center. after some digging i have found i need to use " direction cosines"
> to extract the angles. but something is wrong.
>
> #P window setfont "Sans Serif" 9.;
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>
>

> this is better, but its 2d, how do i convert Cartesian to polar in 3d?(!)

http://local.wasp.uwa.edu.au/~pbourke/geometry/coords/

On 9/30/07, yair reshef  wrote:
> this is better, but its 2d, how do i convert Cartesian to polar in 3d?(!)

thanks wes, the page you directed me is missing a formula to find the

zenith(?) angle (probably me missing the point).

i followed wikipedia on this, also switched from arctang to atan2. bu still

no good, i still thnk i am missing an angle.

http://en.wikipedia.org/wiki/Spherical_coordinates

> > this is better, but its 2d, how do i convert Cartesian to polar in

thanks wes, the page you directed me is missing a formula to find the
zenith(?) angle (probably me missing the point).
i followed wikipedia on this, also switched from arctang to atan2. bu still
no good, i still thnk  i am missing an angle.
http://en.wikipedia.org/wiki/Spherical_coordinates

On 9/30/07, Wesley Smith  wrote:
>
> On 9/30/07, yair reshef  wrote:
> > this is better, but its 2d, how do i convert Cartesian to polar in
> 3d?(!)
>
> http://local.wasp.uwa.edu.au/~pbourke/geometry/coords/
>
>
> wes
>

i switched the x and y at the atan2 formula,

i understand now there are only two values as roll is not given. i'll find

another way to retrieve it. the working patch for posterity.

> thanks wes, the page you directed me is missing a formula to find the

> zenith(?) angle (probably me missing the point).

> i followed wikipedia on this, also switched from arctang to atan2. bu

> still no good, i still thnk i am missing an angle.

> #P message 224 466 45 9109513 $1 $2 0.;

> #P newex 194 493 101 9109513 pak rotatexyz 0. 0. 0.;

> #P newex 224 403 222 9109518 jit.expr @expr "(in[0]*180.)/ 3.141";

> #P message 453 561 154 9109513 81.863235 80.227272 1.677804;

> #P newex 453 538 57 9109513 prepend set;

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> #P newex 224 354 374 9109518 jit.expr @expr

> "atan2((pow(in[0].p[0]\,2)+pow(in[0].p[1]\,2)) \, in[0].p[2])"

> "atan2(in[0].p[0]\, in[0].p[1])" in[0].p[2];

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i switched the x and y at the atan2 formula,
 i understand now there are only two values as roll is not given. i'll find
another way to retrieve it. the working patch for posterity.

On 9/30/07, yair reshef  wrote:
>
> thanks wes, the page you directed me is missing a formula to find the
> zenith(?) angle (probably me missing the point).
> i followed wikipedia on this, also switched from arctang to atan2. bu
> still no good, i still thnk  i am missing an angle.
> http://en.wikipedia.org/wiki/Spherical_coordinates
>
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> "atan2((pow(in[0].p[0]\,2)+pow(in[0].p[1]\,2)) \, in[0].p[2])"
> "atan2(in[0].p[0]\, in[0].p[1])" in[0].p[2];
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>
> On 9/30/07, Wesley Smith  wrote:
> >
> > On 9/30/07, yair reshef  wrote:
> > > this is better, but its 2d, how do i convert Cartesian to polar in
> > 3d?(!)
> >
> > http://local.wasp.uwa.edu.au/~pbourke/geometry/coords/
> >
> >
> > wes
> >
>
>

What are you after, Euler angles or "3D polar coordinates" which are

What are you after, Euler angles or "3D polar coordinates" which are
called Spherical coordinates?

basically i am after rotating a number of planes around a center. keeping

them looking in the same direction. if i need math to do it, so be it.

i would now lke to apply this to the formulas supplied by andrew b. in my

shatter experiments, were i cannot use the rotatexyz (which is Euler if im

here is an example of the effect with jit.gl.multiple

> What are you after, Euler angles or "3D polar coordinates" which are

basically i am after rotating a number of planes around a center. keeping
them looking in the same direction. if i need math to do it, so be it.
i would now lke to apply this to the formulas supplied by andrew b. in my
shatter experiments, were i cannot use the rotatexyz (which is Euler if im
not wrong).

On 9/30/07, Wesley Smith  wrote:
>
> What are you after, Euler angles or "3D polar coordinates" which are
> called Spherical coordinates?
>
> wes
>

Euler angles don't give you a unique orientation. Sometimes the

result can be ambiguous. For unambigues 3D orientations, you have to

That said, given a location and vector direction (velocity for

instance), you can derive an axis angle orientation. You take the

vector from the point you want to face to yor location. This forms a

triangle with your vector orientation. You then normalize both of

those vectors. Next, make a vector halfway between them by

subtracting one form the other and dividing in half. This will be

your axis. To find the angle, take the arcsine of the distance from

your orientation to your halfvector. I forget if you have to multiply

by 2 here or not, but that is the basic procedure.

> basically i am after rotating a number of planes around a center. keeping

> them looking in the same direction. if i need math to do it, so be it.

> i would now lke to apply this to the formulas supplied by andrew b. in my

> shatter experiments, were i cannot use the rotatexyz (which is Euler if im

> #P newex 50 113 469 9109513 jit.expr @expr in[0]

> "in[0].p[1]*cos(in[1])-in[0].p[2]*sin(in[1])"

> "in[0].p[2]*cos(in[1])+in[0].p[1]*sin(in[1])" in[0] in[0];

> #P newex 50 91 469 9109513 jit.expr @expr

> "in[0].p[0]*cos(in[1])+in[0].p[2]*sin(in[1])" in[0]

> "in[0].p[2]*cos(in[1])-in[0].p[0]*sin(in[1])" in[0] in[0];

> #P newex 50 69 480 9109513 jit.expr @expr "in[0].p[0]*cos(in[1]) -

> in[0].p[1]*sin(in[1])" "in[0].p[1]*cos(in[1]) + in[0].p[0]*sin(in[1])" in[0]

> here is an example of the effect with jit.gl.multiple

> #P message 67 75 68 9109513 fullscreen $1;

> #P number 441 76 35 9 0 0 0 139 0 0 0 221 221 221 222 222 222 0 0 0;

> #P message 50 50 109 9109513 setall 0.2 0.2 0.05 , bang;

> #P newex 50 73 92 9109513 jit.matrix 3 float32 3;

Euler angles don't give you a unique orientation.  Sometimes the
result can be ambiguous.  For unambigues 3D orientations, you have to
use either axis-angle or quaternions.

That said, given a location and vector direction (velocity for
instance), you can derive an axis angle orientation.  You take the
vector from the point you want to face to yor location.  This forms a
triangle with your vector orientation.  You then normalize both of
those vectors.  Next, make a vector halfway between them by
subtracting one form the other and dividing in half.  This will be
your axis.  To find the angle, take the arcsine of the distance from
your orientation to your halfvector.  I forget if you have to multiply
by 2 here or not, but that is the basic procedure.

On 9/30/07, yair reshef  wrote:
> basically i am after rotating a number of planes around a center. keeping
> them looking in the same direction. if i need math to do it, so be it.
> i would now lke to apply this to the formulas supplied by andrew b. in my
> shatter experiments, were i cannot use the rotatexyz (which is Euler if im
> not wrong).
>
> #P window setfont "Sans Serif" 9.;
> #P window linecount 1;
> #P newex 50 113 469 9109513 jit.expr @expr in[0]
> "in[0].p[1]*cos(in[1])-in[0].p[2]*sin(in[1])"
> "in[0].p[2]*cos(in[1])+in[0].p[1]*sin(in[1])" in[0] in[0];
> #P newex 50 91 469 9109513 jit.expr @expr
> "in[0].p[0]*cos(in[1])+in[0].p[2]*sin(in[1])" in[0]
> "in[0].p[2]*cos(in[1])-in[0].p[0]*sin(in[1])" in[0] in[0];
> #P newex 50 69 480 9109513 jit.expr @expr "in[0].p[0]*cos(in[1]) -
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> in[0] in[0];
> #P connect 1 0 2 0;
> #P connect 0 0 1 0;
> #P window clipboard copycount 3;
>
> here is an example of the effect with jit.gl.multiple
>
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> #P newex 307 67 30 9109513 t b b;
> #P newex 307 177 44 9109513 jit.matrix;
> #P newex 307 203 172 9109513 jit.slide @slide_up 15. @slide_down 15.;
> #P newex 327 110 88 9109513 jit.noise 3 float32 3;
> #P newex 13 28 45 9109513 loadbang;
> #B color 4;
> #P message 13 49 81 9109513 texture grid 64 64;
> #P message 103 97 29 9109513 reset;
> #P window linecount 2;
> #P newex 103 116 95 9109513 jit.gl.handle quadr @inherit_transform 1;
> #P newex 185 339 273 9109513 jit.gl.gridshape quadr @texture grid @color 1 1
> 1 0.2 @blend_enable 1 @shape cube @name fatPlane @automatic 0;
> #P toggle 29 71 15 0;
> #P window linecount 1;
> #P newex 29 92 50 9109513 qmetro 5;
> #P newex 58 137 33 9109513 s draz;
> #P newex 29 115 71 9109513 t b b erase;
> #P newex 29 184 124 9109513 jit.window quadr @floating 1;
> #P newex 29 162 147 9109513 jit.gl.render quadr @camera 0 0 5;
> #P comment 463 273 82 9109513 radians 2 degrees;
> #P window linecount 2;
> #P newex 13 230 130 9109513 jit.gl.gridshape quadr @shape sphere @scale 0.1
> 0.1 0.1;
> #P connect 28 0 26 2;
> #P connect 29 0 20 0;
> #P connect 29 0 13 0;
> #P connect 29 0 28 0;
> #P connect 30 0 29 0;
> #P connect 32 0 30 0;
> #P connect 12 0 11 0;
> #P connect 12 0 7 0;
> #P fasten 12 0 32 0 18 51 445 51;
> #P fasten 25 0 26 1 331 308 386 308;
> #P connect 22 0 23 0;
> #P connect 13 0 22 0;
> #P connect 17 0 13 0;
> #P connect 16 1 17 0;
> #P connect 24 0 25 0;
> #P fasten 14 0 26 0 312 308 190 308;
> #P fasten 14 0 21 1 312 223 251 223;
> #P fasten 14 0 24 0 312 229 331 229;
> #P connect 15 0 14 0;
> #P fasten 23 0 15 0 332 174 312 174;
> #P fasten 16 0 20 0 312 151 206 151;
> #P connect 16 0 15 0;
> #P connect 18 0 16 0;
> #P connect 21 0 19 0;
> #P connect 20 0 21 0;
> #P connect 27 0 8 0;
> #P connect 10 0 9 0;
> #P connect 4 1 5 0;
> #P connect 31 0 3 0;
> #P fasten 11 0 2 0 18 150 34 150;
> #P fasten 4 2 2 0 94 158 34 158;
> #P connect 4 0 2 0;
> #P fasten 9 0 2 0 108 160 34 160;
> #P connect 6 0 4 0;
> #P connect 7 0 6 0;
> #P window clipboard copycount 33;
>
>
> On 9/30/07, Wesley Smith  wrote:
> >
> > What are you after, Euler angles or "3D polar coordinates" which are
> > called Spherical coordinates?
> >
> > wes
> >
>
>
>
>


> Euler angles don't give you a unique orientation. Sometimes the

> result can be ambiguous. For unambigues 3D orientations, you have to

> That said, given a location and vector direction (velocity for

> instance), you can derive an axis angle orientation. You take the

> vector from the point you want to face to yor location. This forms a

> triangle with your vector orientation. You then normalize both of

> those vectors. Next, make a vector halfway between them by

> subtracting one form the other and dividing in half. This will be

> your axis. To find the angle, take the arcsine of the distance from

> your orientation to your halfvector. I forget if you have to multiply

> by 2 here or not, but that is the basic procedure.

> > basically i am after rotating a number of planes around a center.

> > them looking in the same direction. if i need math to do it, so be it.

> > i would now lke to apply this to the formulas supplied by andrew b. in

> > shatter experiments, were i cannot use the rotatexyz (which is Euler if

> > #P newex 50 113 469 9109513 jit.expr @expr in[0]

> > "in[0].p[1]*cos(in[1])-in[0].p[2]*sin(in[1])"

> > "in[0].p[2]*cos(in[1])+in[0].p[1]*sin(in[1])" in[0] in[0];

> > #P newex 50 91 469 9109513 jit.expr @expr

> > "in[0].p[0]*cos(in[1])+in[0].p[2]*sin(in[1])" in[0]

> > "in[0].p[2]*cos(in[1])-in[0].p[0]*sin(in[1])" in[0] in[0];

> > #P newex 50 69 480 9109513 jit.expr @expr "in[0].p[0]*cos(in[1]) -

> > in[0].p[1]*sin(in[1])" "in[0].p[1]*cos(in[1]) + in[0].p[0]*sin(in[1])"

> > here is an example of the effect with jit.gl.multiple

On 9/30/07, Wesley Smith  wrote:
>
> Euler angles don't give you a unique orientation.  Sometimes the
> result can be ambiguous.  For unambigues 3D orientations, you have to
> use either axis-angle or quaternions.
>
> That said, given a location and vector direction (velocity for
> instance), you can derive an axis angle orientation.  You take the
> vector from the point you want to face to yor location.  This forms a
> triangle with your vector orientation.  You then normalize both of
> those vectors.  Next, make a vector halfway between them by
> subtracting one form the other and dividing in half.  This will be
> your axis.  To find the angle, take the arcsine of the distance from
> your orientation to your halfvector.  I forget if you have to multiply
> by 2 here or not, but that is the basic procedure.
>
> wes
>
>
>
> On 9/30/07, yair reshef  wrote:
> > basically i am after rotating a number of planes around a center.
> keeping
> > them looking in the same direction. if i need math to do it, so be it.
> > i would now lke to apply this to the formulas supplied by andrew b. in
> my
> > shatter experiments, were i cannot use the rotatexyz (which is Euler if
> im
> > not wrong).
> >
> > #P window setfont "Sans Serif" 9.;
> > #P window linecount 1;
> > #P newex 50 113 469 9109513 jit.expr @expr in[0]
> > "in[0].p[1]*cos(in[1])-in[0].p[2]*sin(in[1])"
> > "in[0].p[2]*cos(in[1])+in[0].p[1]*sin(in[1])" in[0] in[0];
> > #P newex 50 91 469 9109513 jit.expr @expr
> > "in[0].p[0]*cos(in[1])+in[0].p[2]*sin(in[1])" in[0]
> > "in[0].p[2]*cos(in[1])-in[0].p[0]*sin(in[1])" in[0] in[0];
> > #P newex 50 69 480 9109513 jit.expr @expr "in[0].p[0]*cos(in[1]) -
> > in[0].p[1]*sin(in[1])" "in[0].p[1]*cos(in[1]) + in[0].p[0]*sin(in[1])"
> in[0]
> > in[0] in[0];
> > #P connect 1 0 2 0;
> > #P connect 0 0 1 0;
> > #P window clipboard copycount 3;
> >
> > here is an example of the effect with jit.gl.multiple
> >
> > #P window setfont "Sans Serif" 9.;
> > #P window linecount 1;
> > #P message 440 55 18 9109513 22;
> > #N vpatcher 15 55 184 207;
> > #P outlet 67 100 15 0;
> > #P window setfont "Sans Serif" 9.;
> > #P message 67 75 68 9109513 fullscreen $1;
> > #P toggle 50 75 15 0;
> > #P newex 92 50 35 9109513 sel 27;
> > #P newex 50 50 40 9109513 key;
> > #P fasten 1 0 2 0 97 72 55 72;
> > #P fasten 2 0 3 0 66 90 66 75;
> > #P connect 3 0 4 0;
> > #P fasten 0 0 1 0 91 67 91 52;
> > #P pop;
> > #P newobj 0 184 25 9109513 p fs;
> > #P number 441 76 35 9 0 0 0 139 0 0 0 221 221 221 222 222 222 0 0 0;
> > #P message 441 96 36 9109513 dim $1;
> > #N vpatcher 15 55 209 203;
> > #P button 4 53 15 0;
> > #P inlet 3 26 15 0;
> > #P window setfont "Sans Serif" 9.;
> > #P window linecount 1;
> > #P newex 50 29 45 9109513 loadbang;
> > #P message 50 50 109 9109513 setall 0.2 0.2 0.05 , bang;
> > #P newex 50 73 92 9109513 jit.matrix 3 float32 3;
> > #P outlet 50 97 15 0;
> > #P connect 4 0 5 0;
> > #P connect 3 0 2 0;
> > #P connect 5 0 2 0;
> > #P connect 2 0 1 0;
> > #P connect 4 0 1 0;
> > #P connect 1 0 0 0;
> > #P pop 1;
> > #P newobj 577 273 38 9109513 p scale;
> > #P button 167 342 15 0;
> > #P newex 185 314 402 9109513 jit.gl.multiple quadr 3 @targetname
> fatPlane
> > @glparams position rotatexyz scale @texture grid;
> > #B color 5;
> > #P newex 326 273 135 9109513 jit.expr @expr in[0]*(57.29578);
> > #P window linecount 2;
> > #P newex 326 236 277 9109513 jit.expr @expr 0.
> > "atan(sqrt((pow(in[0].p[0]\,2)+pow(in[0].p[1]\,2))) /
> > in[0].p[2])" "atan2(in[0].p[1] \, in[0].p[0])";
> > #P window linecount 1;
> > #P newex 327 153 97 9109513 jit.op @op - @val 1.5;
> > #P newex 327 132 93 9109513 jit.op @op * @val 3.;
> > #P newex 201 229 55 9109513 jit.multiplex;
> > #P newex 201 198 92 9109513 jit.matrix 3 float32 3;
> > #P window linecount 3;
> > #P newex 201 256 87 9109513 jit.gl.mesh quadr @draw_mode lines
> @blend_enable
> > 1;
> > #P window linecount 1;
> > #P newex 307 46 31 9109513 r draz;
> > #P newex 327 89 68 9109513 speedlim 1500;
> > #P newex 307 67 30 9109513 t b b;
> > #P newex 307 177 44 9109513 jit.matrix;
> > #P newex 307 203 172 9109513 jit.slide @slide_up 15. @slide_down 15.;
> > #P newex 327 110 88 9109513 jit.noise 3 float32 3;
> > #P newex 13 28 45 9109513 loadbang;
> > #B color 4;
> > #P message 13 49 81 9109513 texture grid 64 64;
> > #P message 103 97 29 9109513 reset;
> > #P window linecount 2;
> > #P newex 103 116 95 9109513 jit.gl.handle quadr @inherit_transform 1;
> > #P newex 185 339 273 9109513 jit.gl.gridshape quadr @texture grid @color
> 1 1
> > 1 0.2 @blend_enable 1 @shape cube @name fatPlane @automatic 0;
> > #P toggle 29 71 15 0;
> > #P window linecount 1;
> > #P newex 29 92 50 9109513 qmetro 5;
> > #P newex 58 137 33 9109513 s draz;
> > #P newex 29 115 71 9109513 t b b erase;
> > #P newex 29 184 124 9109513 jit.window quadr @floating 1;
> > #P newex 29 162 147 9109513 jit.gl.render quadr @camera 0 0 5;
> > #P comment 463 273 82 9109513 radians 2 degrees;
> > #P window linecount 2;
> > #P newex 13 230 130 9109513 jit.gl.gridshape quadr @shape sphere @scale
> 0.1
> > 0.1 0.1;
> > #P connect 28 0 26 2;
> > #P connect 29 0 20 0;
> > #P connect 29 0 13 0;
> > #P connect 29 0 28 0;
> > #P connect 30 0 29 0;
> > #P connect 32 0 30 0;
> > #P connect 12 0 11 0;
> > #P connect 12 0 7 0;
> > #P fasten 12 0 32 0 18 51 445 51;
> > #P fasten 25 0 26 1 331 308 386 308;
> > #P connect 22 0 23 0;
> > #P connect 13 0 22 0;
> > #P connect 17 0 13 0;
> > #P connect 16 1 17 0;
> > #P connect 24 0 25 0;
> > #P fasten 14 0 26 0 312 308 190 308;
> > #P fasten 14 0 21 1 312 223 251 223;
> > #P fasten 14 0 24 0 312 229 331 229;
> > #P connect 15 0 14 0;
> > #P fasten 23 0 15 0 332 174 312 174;
> > #P fasten 16 0 20 0 312 151 206 151;
> > #P connect 16 0 15 0;
> > #P connect 18 0 16 0;
> > #P connect 21 0 19 0;
> > #P connect 20 0 21 0;
> > #P connect 27 0 8 0;
> > #P connect 10 0 9 0;
> > #P connect 4 1 5 0;
> > #P connect 31 0 3 0;
> > #P fasten 11 0 2 0 18 150 34 150;
> > #P fasten 4 2 2 0 94 158 34 158;
> > #P connect 4 0 2 0;
> > #P fasten 9 0 2 0 108 160 34 160;
> > #P connect 6 0 4 0;
> > #P connect 7 0 6 0;
> > #P window clipboard copycount 33;
> >
> >
> > On 9/30/07, Wesley Smith  wrote:
> > >
> > > What are you after, Euler angles or "3D polar coordinates" which are
> > > called Spherical coordinates?
> > >
> > > wes
> > >
> >
> >
> >
> >
>

This is an old thread - but in case anyone's interested, here's a solution that keeps the gridshapes perpetually oriented to the world origin.

direction cosines, math problem