# Angle Between two 3d vectors and object's direction.

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Hi, I need to adjust object's direction in 3d. I have current point vector , and destination point vector. When current point == destination point, destination point gets a new random position. The poblem that i can't torn and adjust object to a new direction. i need to use function: glRotatef (XAngle, 1.0f, 0.0f, 0.0f); glRotatef (YAngle, 0.0f, 1.0f, 0.0f); glRotatef (ZAngle, 0.0f, 0.0f, 1.0f); but i can't calculate XAngle,YAngle,ZAngle. Please help. P.S. function don't work void DCreature::MobilisInMobile() { if(StepSize>=1) { InitPoint=DestPoint; float x1 = (rand()%2==0?-1:1)*(rand()%(-10))+((float)rand()/RAND_MAX ); float y1 = (rand()%2==0?-1:1)*(rand()%(-10))+((float)rand()/RAND_MAX ); float z1 = (rand()%2==0?-1:1)*(rand()%(-10))+((float)rand()/RAND_MAX ); DestPoint=Dpoint(x1,y1,z1); StepSize=0; } Dpoint DeltaXYZ(DestPoint-InitPoint); CurrPoint=InitPoint; CurrPoint+=DeltaXYZ*StepSize; //Angle Between two 3d vectors and object's direction /* Dpoint D; D.GetDistance(CurrPoint,DestPoint); if( D.z!=0) YAngle = atan( D.x / D.z ); else YAngle=0; YAngle = TODEG(YAngle); float len = sqrt( D.x * D.x + D.z * D.z ); if(len!=0) XAngle = atan(D.y / len ); else XAngle = 0; XAngle = TODEG(XAngle); */ //normal1 = Cross( WORLD_UP, CAMERA_DIR ) //normal2 = Cross( CAMERA_UP, CAMERA_DIR ) //roll = angle_between( normal1, normal2 ) // ComputeRPY(); glPushMatrix(); glTranslatef(InitPoint.x+DeltaXYZ.x*StepSize, InitPoint.y+DeltaXYZ.y*StepSize,InitPoint.z+DeltaXYZ.z*StepSize); DrawCreature(); glPopMatrix(); // StepSize+=Speed; }

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Hi,
did you consider using gluLookAt() function? It has 9 parameters. First 3 are point you are now at. Next 3 are point you are looking to. And the last 3 are Camera's Up vector (u can use 0,1,0). This way you can always look in the direction you specify directly, without need of computing the angles.

Hope this helps a little :)
Y.

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thank you yanco for a reply.
the point is that i don't need to change the camera view.
the objects must move in 3d space and the head of the objects
have to look at the direction point.

here is the function:

void DCreature::MobilisInMobile()
{
Dpoint DeltaXYZ(DestPoint-InitPoint);

CurrPoint=InitPoint;
CurrPoint+=DeltaXYZ*StepSize;

glPushMatrix();
glTranslatef(InitPoint.x+DeltaXYZ.x*StepSize, InitPoint.y+DeltaXYZ.y*StepSize,InitPoint.z+DeltaXYZ.z*StepSize);

//how to rotate?
// glRotatef (XAngle, 1.0f, 0.0f, 0.0f);
// glRotatef (YAngle, 0.0f, 1.0f, 0.0f);
// glRotatef (ZAngle, 0.0f, 0.0f, 1.0f);

DrawCreature();
glPopMatrix();

StepSize+=Speed;
}

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Quote:
 Original post by alicaman1the point is that i don't need to change the camera view.the objects must move in 3d space and the head of the objects have to look at the direction point.

gluLookAt() post-multiplies the currently 'active' matrix. Note, this matrix doesn't have to be the matrix for your _camera_, so you should be able to use it instead of the glTranslate/glRotate calls to simultaneously place your object in desired spot (eyex, y, z) and have it look in desired direction (centerx, y, z) ^^;;

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but how to apply it?

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sorry, i use 'manual' lookAt function so didn't really play with glu version of it >.<; if it helps any, simple code to build look-at matrix goes somewhat like:
matrix4&matrix4::set_lookAt( const vector3& Eye, const vector3& Target ) {	vector3 direction = Target - Eye; direction.normalize();	vector3 right;	if( math::is_zero( direction.x ) && math::is_zero( direction.z ) )		right = cross( direction, vector3::unit_x );	else	right = cross( direction, vector3::unit_y );	right.normalize();	vector3 up = cross( right, direction );	set_identity();	// x, y, z and t are 1st, 2nd, 3rd and 4th matrix column, respectively	x = right;	y = up;	z = -direction;	t = Eye;	return *this;}

then in the draw call for your creature you'd use it somewhat like this:
// pseudocode// eye is location where the creature should currently be// target is the spot to look atglPushMatrix();matrix4 transformation; transformation.set_lookAt( eye, target );glMultMatrixf( transformation );drawCreature();glPopMatrix();

Great!!!
Thank you.

Great!!!
Thank you.

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