void Ball::AngularAcceleration(const Vertex3Ds& hitnormal)
{
const Vertex3Ds bccpd = -radius * hitnormal; // vector ball center to contact point displacement
const float bnv = vel.Dot(hitnormal); // ball normal velocity to hit face
const Vertex3Ds bvn = bnv * hitnormal; // project the normal velocity along normal
const Vertex3Ds bvt = vel - bvn; // calc the tangent velocity
Vertex3Ds bvT = bvt; // ball tangent velocity Unit Tangent
bvT.Normalize();
const Vertex3Ds bstv = // ball surface tangential velocity
CrossProduct(m_angularvelocity, bccpd); // velocity of ball surface at contact point
const float dot = bstv.Dot(bvT); // speed ball surface contact point tangential to contact surface point
const Vertex3Ds cpvt = dot * bvT; // contact point velocity tangential to hit face
const Vertex3Ds slideVel = bstv - cpvt; // contact point slide velocity with ball center velocity -- slide velocity
// If the point and the ball are travelling in opposite directions,
// and the point's velocity is at least the magnitude of the balls,
// then we have a natural roll
Vertex3Ds cpctrv = -slideVel; //contact point co-tangential reverse velocity
if (vel.LengthSquared() > (float)(0.7*0.7))
{
// Calculate the maximum amount the point velocity can change this
// time segment due to friction
Vertex3Ds FrictionForce = cpvt + bvt;
// If the point can change fast enough to go directly to a natural roll, then do it.
if (FrictionForce.LengthSquared() > (float)(ANGULARFORCE*ANGULARFORCE))
FrictionForce.Normalize(ANGULARFORCE);
cpctrv -= FrictionForce;
}
// Divide by the inertial tensor for a sphere in order to change
// linear force into angular momentum
cpctrv *= (float)(2.0/5.0); // Inertial tensor for a sphere
const Vertex3Ds vResult = CrossProduct(bccpd, cpctrv); // ball center contact point displacement X reverse contact point co-tan vel
m_angularmomentum *= 0.99f;
m_angularmomentum += vResult; // add delta
m_angularvelocity = m_inverseworldinertiatensor.MultiplyVector(m_angularmomentum);
}
HitLine3D::HitLine3D(const Vertex3Ds& v1, const Vertex3Ds& v2)
{
Vertex3Ds vLine = v2 - v1;
vLine.Normalize();
// Axis of rotation to make 3D cylinder a cylinder along the z-axis
Vertex3Ds transaxis;
/*const Vertex3Ds vup(0,0,1.0f);
CrossProduct(vLine, vup, &transaxis);*/
transaxis.x = vLine.y;
transaxis.y = -vLine.x;
transaxis.z = 0.0f;
if (transaxis.LengthSquared() <= 1e-6f) // line already points in z axis?
transaxis.Set(1, 0, 0); // choose arbitrary rotation vector
else
transaxis.Normalize();
// Angle to rotate the line into the z-axis
const float dot = vLine.z; //vLine.Dot(&vup);
const float transangle = acosf(dot);
matTrans.RotationAroundAxis(transaxis, -transangle);
const Vertex3Ds vtrans1 = matTrans * v1;
const Vertex3Ds vtrans2 = matTrans * v2;
// set up HitLineZ parameters
m_xy.x = vtrans1.x;
m_xy.y = vtrans1.y;
m_zlow = min(vtrans1.z, vtrans2.z);
m_zhigh = max(vtrans1.z, vtrans2.z);
m_rcHitRect.left = min(v1.x, v2.x);
m_rcHitRect.right = max(v1.x, v2.x);
m_rcHitRect.top = min(v1.y, v2.y);
m_rcHitRect.bottom = max(v1.y, v2.y);
m_rcHitRect.zlow = min(v1.z, v2.z);
m_rcHitRect.zhigh = max(v1.z, v2.z);
}
