// Recalculates the global center of the circle and the the bounding box.
func (circle *CircleShape) update(xf transform.Transform) aabb.AABB {
//global center of the circle
center := xf.TransformVect(circle.Position)
circle.Tc = center
rv := vect.Vect{circle.Radius, circle.Radius}
return aabb.AABB{
vect.Sub(center, rv),
vect.Add(center, rv),
}
}
//Called to update N, Tn, Ta, Tb and the the bounding box.
func (segment *SegmentShape) update(xf transform.Transform) aabb.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.AABB{
min,
max,
}
}
// Calculates the transformed vertices and axes and the bounding box.
func (poly *PolygonShape) update(xf transform.Transform) aabb.AABB {
//transform axes
{
src := poly.Axes
dst := poly.TAxes
for i := 0; i < poly.NumVerts; i++ {
n := xf.RotateVect(src[i].N)
dst[i].N = n
dst[i].D = vect.Dot(xf.Position, n) + src[i].D
}
}
//transform verts
{
inf := math.Inf(1)
aabb := aabb.AABB{
Lower: vect.Vect{inf, inf},
Upper: vect.Vect{-inf, -inf},
}
src := poly.Verts
dst := poly.TVerts
for i := 0; i < poly.NumVerts; i++ {
v := xf.TransformVect(src[i])
dst[i] = v
aabb.Lower.X = math.Min(aabb.Lower.X, v.X)
aabb.Upper.X = math.Max(aabb.Upper.X, v.X)
aabb.Lower.Y = math.Min(aabb.Lower.Y, v.Y)
aabb.Upper.Y = math.Max(aabb.Upper.Y, v.Y)
}
return aabb
}
}
func DrawTransform(xf *transform.Transform, radius float64) {
DrawCircle(xf.Position, radius, false)
p := xf.RotateVect(vect.Vect{0, -radius})
p.Add(xf.Position)
DrawLine(xf.Position, p)
}