func (arb *Arbiter) preStep2(inv_dt, slop, bias vect.Float) {
a := arb.ShapeA.Body
b := arb.ShapeB.Body
for i := 0; i < arb.NumContacts; i++ {
con := arb.Contacts[i]
// Calculate the offsets.
con.r1 = vect.Sub(con.p, a.p)
con.r2 = vect.Sub(con.p, b.p)
//con.Normal = vect.Vect{-1,0}
// Calculate the mass normal and mass tangent.
con.nMass = 1.0 / k_scalar(a, b, con.r1, con.r2, con.n)
con.tMass = 1.0 / k_scalar(a, b, con.r1, con.r2, vect.Perp(con.n))
// Calculate the target bias velocity.
con.bias = -bias * inv_dt * vect.FMin(0.0, con.dist+slop)
con.jBias = 0.0
//con.jtAcc = 0
//con.jnAcc = 0
//fmt.Println("con.dist", con.dist)
// Calculate the target bounce velocity.
con.bounce = normal_relative_velocity(a, b, con.r1, con.r2, con.n) * arb.e
}
}
func (arb *Arbiter) applyImpulse3() {
a := arb.ShapeA.Body
b := arb.ShapeB.Body
for i := 0; i < arb.NumContacts; i++ {
con := arb.Contacts[i]
n := con.n
r1 := con.r1
r2 := con.r2
// Calculate the relative bias velocities.
vb1 := vect.Add(a.v_bias, vect.Mult(vect.Perp(r1), a.w_bias))
vb2 := vect.Add(b.v_bias, vect.Mult(vect.Perp(r2), b.w_bias))
vbn := vect.Dot(vect.Sub(vb2, vb1), n)
// Calculate the relative velocity.
vr := relative_velocity(a, b, r1, r2)
vrn := vect.Dot(vr, n)
// Calculate the relative tangent velocity.
vrt := vect.Dot(vect.Add(vr, arb.Surface_vr), vect.Perp(n))
// Calculate and clamp the bias impulse.
jbn := (con.bias - vbn) * con.nMass
jbnOld := con.jBias
con.jBias = vect.FMax(jbnOld+jbn, 0.0)
// Calculate and clamp the normal impulse.
jn := -(con.bounce + vrn) * con.nMass
jnOld := con.jnAcc
con.jnAcc = vect.FMax(jnOld+jn, 0.0)
// Calculate and clamp the friction impulse.
jtMax := arb.u * con.jnAcc
jt := -vrt * con.tMass
jtOld := con.jtAcc
con.jtAcc = vect.FClamp(jtOld+jt, -jtMax, jtMax)
// Apply the bias impulse.
apply_bias_impulses(a, b, r1, r2, vect.Mult(n, con.jBias-jbnOld))
// Apply the final impulse.
apply_impulses(a, b, r1, r2, transform.RotateVect(n, transform.Rotation{con.jnAcc - jnOld, con.jtAcc - jtOld}))
}
}
func (arb *Arbiter) preStep(inv_dt, slop, bias vect.Float) {
a := arb.ShapeA.Body
b := arb.ShapeB.Body
for _, con := range arb.Contacts {
// Calculate the offsets.
x, y := con.p.X, con.p.Y
r1 := vect.Vect{x - a.p.X, y - a.p.Y}
r2 := vect.Vect{x - b.p.X, y - b.p.Y}
//con.Normal = vect.Vect{-1,0}
// Calculate the mass normal and mass tangent.
n := con.n
rcn := (r1.X * n.Y) - (r1.Y * n.X)
rcn = a.m_inv + (a.i_inv * rcn * rcn)
rcn2 := (r2.X * n.Y) - (r2.Y * n.X)
rcn2 = b.m_inv + (b.i_inv * rcn2 * rcn2)
value := rcn + rcn2
if value == 0.0 {
fmt.Printf("Warning: Unsolvable collision or constraint.")
}
con.nMass = 1.0 / value
n = vect.Perp(con.n)
rcn = (r1.X * n.Y) - (r1.Y * n.X)
rcn = a.m_inv + (a.i_inv * rcn * rcn)
rcn2 = (r2.X * n.Y) - (r2.Y * n.X)
rcn2 = b.m_inv + (b.i_inv * rcn2 * rcn2)
value = rcn + rcn2
if value == 0.0 {
fmt.Printf("Warning: Unsolvable collision or constraint.")
}
con.tMass = 1.0 / value
// Calculate the target bias velocity.
ds := con.dist + slop
if 0 > ds {
con.bias = -bias * inv_dt * (con.dist + slop)
} else {
con.bias = 0
}
con.jBias = 0.0
con.bounce = vect.Dot(vect.Vect{(-r2.Y*b.w + b.v.X) - (-r1.Y*a.w + a.v.X), (r2.X*b.w + b.v.Y) - (r1.X*a.w + a.v.Y)}, con.n) * arb.e
con.r1 = r1
con.r2 = r2
}
}
//Called to update N, Tn, Ta, Tb and the the bounding box.
func (segment *SegmentShape) update(xf transform.Transform) AABB {
a := xf.TransformVect(segment.A)
b := xf.TransformVect(segment.B)
segment.Ta = a
segment.Tb = b
segment.N = vect.Perp(vect.Normalize(vect.Sub(segment.B, segment.A)))
segment.Tn = xf.RotateVect(segment.N)
rv := vect.Vect{segment.Radius, segment.Radius}
min := vect.Min(a, b)
min.Sub(rv)
max := vect.Max(a, b)
max.Add(rv)
return AABB{
min,
max,
}
}
// Sets the vertices offset by the offset and calculates the PolygonAxes.
func (poly *PolygonShape) SetVerts(verts Vertices, offset vect.Vect) {
if verts == nil {
log.Printf("Error: no vertices passed!")
return
}
if verts.ValidatePolygon() == false {
log.Printf("Warning: vertices not valid")
}
numVerts := len(verts)
oldnumVerts := len(poly.Verts)
poly.NumVerts = numVerts
if oldnumVerts < numVerts {
//create new slices
poly.Verts = make(Vertices, numVerts)
poly.TVerts = make(Vertices, numVerts)
poly.Axes = make([]PolygonAxis, numVerts)
poly.TAxes = make([]PolygonAxis, numVerts)
} else {
//reuse old slices
poly.Verts = poly.Verts[:numVerts]
poly.TVerts = poly.TVerts[:numVerts]
poly.Axes = poly.Axes[:numVerts]
poly.TAxes = poly.TAxes[:numVerts]
}
for i := 0; i < numVerts; i++ {
a := vect.Add(offset, verts[i])
b := vect.Add(offset, verts[(i+1)%numVerts])
n := vect.Normalize(vect.Perp(vect.Sub(b, a)))
poly.Verts[i] = a
poly.Axes[i].N = n
poly.Axes[i].D = vect.Dot(n, a)
}
}
func relative_velocity2(a, b *Body, r1, r2 vect.Vect) vect.Vect {
v1 := vect.Add(b.v, vect.Mult(vect.Perp(r2), b.w))
v2 := vect.Add(a.v, vect.Mult(vect.Perp(r1), a.w))
return vect.Sub(v1, v2)
}