remedios79

04-15-2004, 03:49 AM

Hi all,

I'm trying to implement a direction constraint between two objects.

So, I have a series of translation vector for the object constraining the other, and I want to get the rotation along the three axis for the constrained object.

what I do now is the following:

find the projection of the center of my constraining object on the constrained object coordinates, then calculate the arctan of the variation.

Here is the code:

c is the position vector for the constraining object,

o is the position vector for the constrained object

rot is the rotation vector (I apply the three components separately)

double radian = 180.0 / 3.141592654;

double dizx;

float dx, dy, dz;

// calculate distances along axes

dx = o[0] - c[0];

dy = o[1] - c[1];

dz = o[2] - c[2];

if ((dx == 0) && (dy == 0) && (dz == 0))

exit(printf("Distance is 0 (%d)\n", i));

// calculate the length of the projection on xz plane

dizx = sqrt((dx * dx) + (dz * dz));

rot[0] = 0.0f;

rot[1] = - radian * atan2(dz, dx);

rot[2] = radian * atan2(dy, dizx);My constraining object is moving along x direction, y and z are fixed to 0.

x is in the range [-4, +4]

Until the value of x is < 0 my algorithm works fine, then the rotation invert his way, and so the constraint is not working at all.

I'm not very expert with trigonometry, can you tell me what am I doing wrong?

Thank you

Remedios

I'm trying to implement a direction constraint between two objects.

So, I have a series of translation vector for the object constraining the other, and I want to get the rotation along the three axis for the constrained object.

what I do now is the following:

find the projection of the center of my constraining object on the constrained object coordinates, then calculate the arctan of the variation.

Here is the code:

c is the position vector for the constraining object,

o is the position vector for the constrained object

rot is the rotation vector (I apply the three components separately)

double radian = 180.0 / 3.141592654;

double dizx;

float dx, dy, dz;

// calculate distances along axes

dx = o[0] - c[0];

dy = o[1] - c[1];

dz = o[2] - c[2];

if ((dx == 0) && (dy == 0) && (dz == 0))

exit(printf("Distance is 0 (%d)\n", i));

// calculate the length of the projection on xz plane

dizx = sqrt((dx * dx) + (dz * dz));

rot[0] = 0.0f;

rot[1] = - radian * atan2(dz, dx);

rot[2] = radian * atan2(dy, dizx);My constraining object is moving along x direction, y and z are fixed to 0.

x is in the range [-4, +4]

Until the value of x is < 0 my algorithm works fine, then the rotation invert his way, and so the constraint is not working at all.

I'm not very expert with trigonometry, can you tell me what am I doing wrong?

Thank you

Remedios