Graphics Programming in 3D - Essentials of Interactive Computer Graphics - page 444

class UWB _ XformInfo {
public :

Source file.
uwbgl _ XformInfo5.h/cpp
file in the Common Files/
XformInfo subfolder

// New methods for supporting rotation with Quaternion

of the

A:

void InitializeRotation();
void SetUpModelStack(UWB _ DrawHelper&);
void UpdateRotationXByDegree( float );
void SetRotation( const mat3 &);
mat3 GetRotation();
protected :
.

UWBGL _ D3D _ Lib17 project.

quat m _ rotation; // axis and rotation angle
.

B:

void UWB _ XformInfo::InitializeRotation() {
.
m _ rotation[0]=...[1]=...[2]=0.0f; // initial axis of rotation
m _ rotation[3] = 1.0f;

C:

// initial angle of rotation

void UWB _ XformInfo::SetUpModelStack(UWB _ DrawHelper& dh) const {
.
mat3 m = GetRotation(); // Convert quaternion to matrix
dh.AccumulateModelTransform(... , m, ...); // Set matrix rotation to matrix stack

D:

void UWB _ XformInfo::UpdateRotationXByDegree( float dx) {
quat q = quatFromAA( vec3 (1,0,0), dx); // construct Quarternion for R x

E:

( dx )

m _ rotation = m _ rotation * q; // concatenate the rotation (post-multiplication)

void UWB _ XformInfo::SetRotation( const mat3 &m) {
mat3 r(m); // ready to compute transpose
makeTranspose(r); // transpose of m is post-multiplication
m _ rotation = mat2quat(r); // Convert matrix rotation to Quaternion

F:

mat3 UWB _ XformInfo::GetRotation() {
mat3 r = mat2quat(m _ rotation); // convert from quaternion to matrix representation
makeTranspose(r);

G:

// transpose converts from post to pre-multiplication

return r; // r is pre-multiplication rotation matrix

Listing 16.12. Supporting 3D rotation with a quaternion.

concatenating the corresponding quaternion. With the more compact representa-
tion, it is computationally more efficient to concatenate quaternions. The major
shortcoming of the quaternion representation is that at this point, there is no hard-
ware support for transforming vertices by a quaternion. As programmers, we