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Doc comments added | everything.go #27

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Jan 4, 2024
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Doc comments added | everything.go #27

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215 changes: 128 additions & 87 deletions everything.go
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Original file line number Diff line number Diff line change
Expand Up @@ -15,9 +15,46 @@ const (
POOLED_BUFFER_SIZE = 1024
)

// Arbiter states
const (
// Arbiter is active and its the first collision.
CP_ARBITER_STATE_FIRST_COLLISION = iota
// Arbiter is active and its not the first collision.
CP_ARBITER_STATE_NORMAL
// Collision has been explicitly ignored.
// Either by returning false from a begin collision handler or calling cpArbiterIgnore().
CP_ARBITER_STATE_IGNORE
// Collison is no longer active. A space will cache an arbiter for up to cpSpace.collisionPersistence more steps.
CP_ARBITER_STATE_CACHED
// Collison arbiter is invalid because one of the shapes was removed.
CP_ARBITER_STATE_INVALIDATED
)

var (
NO_GROUP uint = 0 // Value for group signifying that a shape is in no group.
ALL_CATEGORIES uint = ^uint(0) // Value for Shape layers signifying that a shape is in every layer.
)

// SHAPE_FILTER_ALL is s collision filter value for a shape that will collide with anything except SHAPE_FILTER_NONE.
var SHAPE_FILTER_ALL = ShapeFilter{NO_GROUP, ALL_CATEGORIES, ALL_CATEGORIES}

// SHAPE_FILTER_NONE is a collision filter value for a shape that does not collide with anything.
var SHAPE_FILTER_NONE = ShapeFilter{NO_GROUP, ^ALL_CATEGORIES, ^ALL_CATEGORIES}

// CollisionBeginFunc is collision begin event function callback type.
//
// Returning false from a begin callback causes the collision to be ignored until the the separate callback is called when the objects stop colliding.
type CollisionBeginFunc func(arb *Arbiter, space *Space, userData interface{}) bool

// CollisionPreSolveFunc is collision pre-solve event function callback type.
//
// Returning false from a pre-step callback causes the collision to be ignored until the next step.
type CollisionPreSolveFunc func(arb *Arbiter, space *Space, userData interface{}) bool

// CollisionPostSolveFunc is collision post-solve event function callback type.
type CollisionPostSolveFunc func(arb *Arbiter, space *Space, userData interface{})

// CollisionSeparateFunc is collision separate event function callback type.
type CollisionSeparateFunc func(arb *Arbiter, space *Space, userData interface{})

type CollisionType uintptr
Expand Down Expand Up @@ -45,21 +82,6 @@ type CollisionHandler struct {
UserData interface{}
}

// Arbiter states
const (
// Arbiter is active and its the first collision.
CP_ARBITER_STATE_FIRST_COLLISION = iota
// Arbiter is active and its not the first collision.
CP_ARBITER_STATE_NORMAL
// Collision has been explicitly ignored.
// Either by returning false from a begin collision handler or calling cpArbiterIgnore().
CP_ARBITER_STATE_IGNORE
// Collison is no longer active. A space will cache an arbiter for up to cpSpace.collisionPersistence more steps.
CP_ARBITER_STATE_CACHED
// Collison arbiter is invalid because one of the shapes was removed.
CP_ARBITER_STATE_INVALIDATED
)

type Contact struct {
r1, r2 Vector

Expand Down Expand Up @@ -87,6 +109,7 @@ func (c *Contact) Clone() Contact {
}
}

// CollisionInfo collision info struct
type CollisionInfo struct {
a, b *Shape
collisionId uint32
Expand All @@ -107,11 +130,13 @@ func (info *CollisionInfo) PushContact(p1, p2 Vector, hash HashValue) {
info.count++
}

// ShapeMassInfo is mass info struct
type ShapeMassInfo struct {
m, i, area float64
cog Vector
}

// PointQueryInfo is point query info struct.
type PointQueryInfo struct {
// The nearest shape, NULL if no shape was within range.
Shape *Shape
Expand All @@ -124,6 +149,7 @@ type PointQueryInfo struct {
Gradient Vector
}

// SegmentQueryInfo is segment query info struct.
type SegmentQueryInfo struct {
// The shape that was hit, or NULL if no collision occurred.
Shape *Shape
Expand All @@ -139,14 +165,7 @@ type SplittingPlane struct {
v0, n Vector
}

var (
NO_GROUP uint = 0
ALL_CATEGORIES uint = ^uint(0)
)

var SHAPE_FILTER_ALL = ShapeFilter{NO_GROUP, ALL_CATEGORIES, ALL_CATEGORIES}
var SHAPE_FILTER_NONE = ShapeFilter{NO_GROUP, ^ALL_CATEGORIES, ^ALL_CATEGORIES}

// ShapeFilter is fast collision filtering type that is used to determine if two objects collide before calling collision or query callbacks.
type ShapeFilter struct {
// Two objects with the same non-zero group value do not collide.
// This is generally used to group objects in a composite object together to disable self collisions.
Expand All @@ -159,6 +178,7 @@ type ShapeFilter struct {
Mask uint
}

// NewShapeFilter creates a new collision filter.
func NewShapeFilter(group, categories, mask uint) ShapeFilter {
return ShapeFilter{group, categories, mask}
}
Expand All @@ -171,27 +191,52 @@ func (a ShapeFilter) Reject(b ShapeFilter) bool {
(b.Categories&a.Mask) == 0
}

func MomentForCircle(m, r1, r2 float64, offset Vector) float64 {
return m * (0.5*(r1*r1+r2*r2) + offset.LengthSq())
// Mat2x2 is a 2x2 matrix type used for tensors and such.
type Mat2x2 struct {
a, b, c, d float64
}

func AreaForCircle(r1, r2 float64) float64 {
return math.Pi * math.Abs(r1*r1-r2*r2)
// Transform transforms Vector v
func (m *Mat2x2) Transform(v Vector) Vector {
return Vector{v.X*m.a + v.Y*m.b, v.X*m.c + v.Y*m.d}
}

func MomentForSegment(m float64, a, b Vector, r float64) float64 {
offset := a.Lerp(b, 0.5)
length := b.Distance(a) + 2.0*r
return m * ((length*length+4.0*r*r)/12.0 + offset.LengthSq())
// MomentForBox calculates the moment of inertia for a solid box.
func MomentForBox(mass, width, height float64) float64 {
return mass * (width*width + height*height) / 12.0
}

func AreaForSegment(a, b Vector, r float64) float64 {
return r * (math.Pi*r + 2.0*a.Distance(b))
// MomentForBox2 calculates the moment of inertia for a solid box.
func MomentForBox2(mass float64, box BB) float64 {
width := box.R - box.L
height := box.T - box.B
offset := Vector{box.L + box.R, box.B + box.T}.Mult(0.5)

// TODO: NaN when offset is 0 and m is INFINITY
return MomentForBox(mass, width, height) + mass*offset.LengthSq()
}

// MomentForCircle calculates the moment of inertia for a circle.
//
// r1 and r2 are the inner and outer diameters. A solid circle has an inner diameter of 0.
func MomentForCircle(mass, r1, r2 float64, offset Vector) float64 {
return mass * (0.5*(r1*r1+r2*r2) + offset.LengthSq())
}

// MomentForSegment calculates the moment of inertia for a line segment.
//
// Beveling radius is not supported.
func MomentForSegment(mass float64, a, b Vector, r float64) float64 {
offset := a.Lerp(b, 0.5)
length := b.Distance(a) + 2.0*r
return mass * ((length*length+4.0*r*r)/12.0 + offset.LengthSq())
}

func MomentForPoly(m float64, count int, verts []Vector, offset Vector, r float64) float64 {
// MomentForPoly calculates the moment of inertia for a solid polygon shape assuming it's center of gravity is at it's centroid.
// The offset is added to each vertex.
func MomentForPoly(mass float64, count int, verts []Vector, offset Vector, r float64) float64 {
if count == 2 {
return MomentForSegment(m, verts[0], verts[1], 0)
return MomentForSegment(mass, verts[0], verts[1], 0)
}

var sum1 float64
Expand All @@ -207,9 +252,24 @@ func MomentForPoly(m float64, count int, verts []Vector, offset Vector, r float6
sum2 += a
}

return (m * sum1) / (6.0 * sum2)
return (mass * sum1) / (6.0 * sum2)
}

// AreaForCircle returns area of a hollow circle.
//
// r1 and r2 are the inner and outer diameters. A solid circle has an inner diameter of 0.
func AreaForCircle(r1, r2 float64) float64 {
return math.Pi * math.Abs(r1*r1-r2*r2)
}

// AreaForSegment calculates the area of a fattened (capsule shaped) line segment.
func AreaForSegment(a, b Vector, r float64) float64 {
return r * (math.Pi*r + 2.0*a.Distance(b))
}

// AreaForPoly calculates the signed area of a polygon.
//
// A Clockwise winding gives positive area. This is probably backwards from what you expect, but matches Chipmunk's the winding for poly shapes.
func AreaForPoly(count int, verts []Vector, r float64) float64 {
var area float64
var perimeter float64
Expand All @@ -224,6 +284,7 @@ func AreaForPoly(count int, verts []Vector, r float64) float64 {
return r*(math.Pi*math.Abs(r)+perimeter) + area/2.0
}

// CentroidForPoly calculates the natural centroid of a polygon.
func CentroidForPoly(count int, verts []Vector) Vector {
var sum float64
vsum := Vector{}
Expand All @@ -240,17 +301,39 @@ func CentroidForPoly(count int, verts []Vector) Vector {
return vsum.Mult(1.0 / (3.0 * sum))
}

func MomentForBox(m, width, height float64) float64 {
return m * (width*width + height*height) / 12.0
}
// DebugInfo returns info of space
func DebugInfo(space *Space) string {
arbiters := len(space.arbiters)
points := 0

func MomentForBox2(m float64, box BB) float64 {
width := box.R - box.L
height := box.T - box.B
offset := Vector{box.L + box.R, box.B + box.T}.Mult(0.5)
for i := 0; i < arbiters; i++ {
points += int(space.arbiters[i].count)
}

// TODO: NaN when offset is 0 and m is INFINITY
return MomentForBox(m, width, height) + m*offset.LengthSq()
constraints := len(space.constraints) + points*int(space.Iterations)
if arbiters > maxArbiters {
maxArbiters = arbiters
}
if points > maxPoints {
maxPoints = points
}
if constraints > maxConstraints {
maxConstraints = constraints
}

var ke float64
for _, body := range space.dynamicBodies {
if body.m == INFINITY || body.i == INFINITY {
continue
}
ke += body.m*body.v.Dot(body.v) + body.i*body.w*body.w
}

return fmt.Sprintf(`Arbiters: %d (%d) - Contact Points: %d (%d)
Other Constraints: %d, Iterations: %d
Constraints x Iterations: %d (%d)
KE: %e`, arbiters, maxArbiters,
points, maxPoints, len(space.constraints), space.Iterations, constraints, maxConstraints, ke)
}

func k_scalar_body(body *Body, r, n Vector) float64 {
Expand Down Expand Up @@ -310,46 +393,4 @@ func bias_coef(errorBias, dt float64) float64 {
return 1.0 - math.Pow(errorBias, dt)
}

type Mat2x2 struct {
a, b, c, d float64
}

func (m *Mat2x2) Transform(v Vector) Vector {
return Vector{v.X*m.a + v.Y*m.b, v.X*m.c + v.Y*m.d}
}

var maxArbiters, maxPoints, maxConstraints int

func DebugInfo(space *Space) string {
arbiters := len(space.arbiters)
points := 0

for i := 0; i < arbiters; i++ {
points += int(space.arbiters[i].count)
}

constraints := len(space.constraints) + points*int(space.Iterations)
if arbiters > maxArbiters {
maxArbiters = arbiters
}
if points > maxPoints {
maxPoints = points
}
if constraints > maxConstraints {
maxConstraints = constraints
}

var ke float64
for _, body := range space.dynamicBodies {
if body.m == INFINITY || body.i == INFINITY {
continue
}
ke += body.m*body.v.Dot(body.v) + body.i*body.w*body.w
}

return fmt.Sprintf(`Arbiters: %d (%d) - Contact Points: %d (%d)
Other Constraints: %d, Iterations: %d
Constraints x Iterations: %d (%d)
KE: %e`, arbiters, maxArbiters,
points, maxPoints, len(space.constraints), space.Iterations, constraints, maxConstraints, ke)
}
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