Graphics Programming in 3D - Essentials of Interactive Computer Graphics - page 465

void CModel::UpdateSimulation() {
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UWB _ XformInfo pxf = m _ Plane->GetXformInfo(); // M t : parent (Trophy) transform
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UWB _ XformInfo cxf = child->GetXformInfo();

A:

// M s :child (shusui) transform

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B:

// P o , P y , P z : initial positions of the ref frame

vec3 pos(0,0,0), yPos(0,1,0), zPos(0,0,1);

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pxf.SetUpModelStack(drawHelper); // Top of stack is now: M t

cxf.SetUpModelStack(drawHelper); // Top of stack is now: M s M t

// Compute: P o M s M t drawHelper.TransformPoint(pos);

// Compute: P y M s M t drawHelper.TransformPoint(yPos);

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// Compute: V y = P y − P o

C:

vec3 Vy = yPos - pos;

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vec3 nVz = pos - zPos; // Forward direction: this is negative z
vec3 Vx = cross(Vy, -nVz); // This is the side vector
Vy = cross(-nVz, Vx); // Ensure all vectors are perpendicular

normalize(Vy); ... // Ensure all vectors are noramlized

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D: R[0][0]=Vx.x; R[0][1]=Vx.y; R[0][2]=Vx.z; // The computed orthonomal basis is

R[1][0]=Vy.x; R[1][1]=Vy.y; R[1][2]=Vy.z; // is the rotation matrix

R[2][0]=-nVz.x;R[2][1]=-nVz.y;R[2][2]=-nVz.z;
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UWB _ XformInfo rxf=m _ RefNode->GetXformInfo(); // Axis Frame objects XformInfo
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rxf.SetTranslation(pos);

E:

// Set the position to draw the axis frame

rxf.SetRotation(R); // Orthonormal basis is the rotation matrix

m _ RefNode->SetXformInfo(rxf);
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UWB _ XformInfo bxf=m _ BallNode.GetXformInfo(); // The traveling sphere's XformInfo
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bxf.SetTranslation(pos);

F:

// Sphere starts at the axis frame position

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m _ BallNode.SetVelocity(nVz); // Sphere velocity is negative-Z direction

Listing 16.22. Computing the orthonormal basis of a scene node.