Graphics Programming in 3D - Essentials of Interactive Computer Graphics - page 456

void CModel::ComputeTeapotRotation( float sec) {
.
// Compute dirToTiger ( V f ) : direction from teapot to tiger
// (1) : compute teapot position in WC: details are similar to Listing 16.14
// (2) : compute V f by subtracting teapot from tiger position:
// details are similar to Listing 16.15
// dirToTiger ( V f ) is computed and initialized
.
if (m _ RotateWithMatrix)
// Compute teapot aiming with rotation matrix:
// details are similar to Listing 16.16
.

Source file.
Model _ AimTeapot.cpp

file

else

in the Model folder of the

D3D _ Orientation project.

// V oc
t

- teapot spout direction in OC

A: vec3 teapotFront(1.0f,0.0f,0.0f);

// the R a rotation ( q a )
mat3 tm = teapotXf.GetRotation();
// V w t = V oc t R a
teapotFront = teapotFront * tm;
//

V wc
t

V f )
float cosTheta=dot(teapotFront,dirToTiger);
// convert from radians to degree
float theta = UWB _ ToDegrees(acosf(cosTheta));
.
vec3 rotAxis = cross(teapotFront, dirToTiger); // V b =

θ b = acos ( ,

V wc
t

V f

×

// normalize V b to get V b

normalize(rotAxis);

V b , θ b )

// q b =( quat qb = quatFromAA(rotAxis, theta);

// keep a copy of q a (or R a ) B: quat qa = teapotXf.GetRotationQuat();

teapotXf.UpdateRotationByQuat(qb); // concat. to the XformInfo:

// q c = q a q b

// q c

quat qc = teapotXf.GetRotationQuat();

C:

quat newQ = slerp(qa, qc, 0.05f); // newQ= q new 5 % from q a to q c
teapotXf.SetRotationQuat(newQ); // sets the new rotation q new
m _ TeapotNode->SetXformInfo(teapotXf); // to the XformInfo node

Listing 16.18. Slerp: Working with spherical linear interpolation.

spherical arc, or spherical linear interpolation, or simply slerp. Listing 16.18

shows implementation with spherical linear interpolation (slerp). At label A,

we compute the q b rotation that aligns the current V wc with V f (this computa-

t