direction between points

On 11/11/2013 at 03:53, xxxxxxxx wrote:
User Information:
Cinema 4D Version: r14
Platform:
Language(s) : C++ ;
hm, i am still having problems to detect the direction between two points. i thought this would work, but it seems not:Vector angle = VectorToHPB(point_topoint_from);
how do i get the correct angle between two points?

On 11/11/2013 at 05:52, xxxxxxxx wrote:
Howdy,
Well, I think what you need is the Dot Product. The dot product of 2 normalized vectors gives you the cosine of the angle between them.
Adios,
Cactus Dan

On 11/11/2013 at 08:17, xxxxxxxx wrote:
There's also the VectorAngle() function in the SDK that you can use. If you want to test the angle of two splines. Using their points rather than their axis values.
//This example gets the angle between two splines //NOTE: This does NOT!! test the angle between the two spline objects axis values // You need to move the points of the splines to get a result from this code // It doesn't care how the two spline objects are oriented to eachother BaseObject *sp1 = doc>SearchObject("s1"); SplineObject *s1 = ToPoint(sp1); BaseObject *sp2 = doc>SearchObject("s2"); SplineObject *s2 = ToPoint(sp2); Vector *s1pnts = s1>GetPointW(); //Get all the points...We only have two points in the spline Vector *s2pnts = s2>GetPointW(); //Get all the points...We only have two points in the spline Vector vec1 = s1pnts[1]s1pnts[0]; //The first spline's vector Vector vec2 = s2pnts[1]s2pnts[0]; //The second spline's vector Real angle_rad = VectorAngle(vec1, vec2); //This gets the angle bewteen the two spline vectors in radians Real angle_deg = angle_rad*180.0/pi; //Converts radians to degrees GePrint(RealToString(angle_deg));
ScottA

On 11/11/2013 at 08:35, xxxxxxxx wrote:
Howdy,
Ah! I've never noticed the VectorAngle() function in the SDK.
I've always just done it myself like this:Real angle = ACos(!v1 * !v2);
Adios,
Cactus Dan

On 11/11/2013 at 09:08, xxxxxxxx wrote:
thank you for your inputs. i came across the VectorAngle today, too. but it seems it doesn't return what i want. because if i rotate an object by the retrieved value, it behaves wrong when the second point passes the axis of the first point. generally i am trying to rotate an object placed at point x so it points the direction from point x1 to point x+1. somehow i need to divide the result of VectorAngle by two, also.
btw, what would i need to do if i need 3dimensional rotation?

On 11/11/2013 at 22:54, xxxxxxxx wrote:
here is a shot of what is happening.
edit: ok, got it now. in my previous approach i missed using the normalized vectors. now it seems to work:
VectorToHPB(from.GetNormalized()  to.GetNormalized())

On 12/11/2013 at 11:10, xxxxxxxx wrote:
Howdy,
Yes, vectors need to be normalized to get a proper angle calculation.
Adios,
Cactus Dan