Initial commit

physics/physics.go

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+// 2D Physics library for videogames
+//
+// A port of Victor Fisac's physac engine (https://github.com/raysan5/raylib/blob/master/src/physac.h)
+package physics
+
+import (
+	"github.com/gen2brain/raylib-go/raylib"
+)
+
+// Defines
+const (
+	PhysacMaxBodies      = 64
+	PhysacMaxManifolds   = 4096
+	PhysacMaxVertices    = 24
+	PhysacCircleVertices = 24
+
+	PhysacDesiredDeltatime      = 1.0 / 60.0
+	PhysacMaxTimestep           = 0.02
+	PhysacCollisionIterations   = 100
+	PhysacPenetrationAllowance  = 0.05
+	PhysacPenetrationCorrection = 0.4
+)
+
+// Physics shape type
+const (
+	PhysicsCircle = iota
+	PhysicsPolygon
+)
+
+// Mat2 type (used for polygon shape rotation matrix)
+type Mat2 struct {
+	M00 float32
+	M01 float32
+	M10 float32
+	M11 float32
+}
+
+type PolygonData struct {
+	// Current used vertex and normals count
+	VertexCount uint32
+	// Polygon vertex positions vectors
+	Vertices [24]raylib.Vector2
+	// Polygon vertex normals vectors
+	Normals [24]raylib.Vector2
+	// Vertices transform matrix 2x2
+	Transform Mat2
+}
+
+type PhysicsShape struct {
+	// Physics shape type (circle or polygon)
+	Type uint32
+	// Padding
+	_ [4]byte
+	// Shape physics body reference
+	Body *PhysicsBodyData
+	// Circle shape radius (used for circle shapes)
+	Radius float32
+	// Polygon shape vertices position and normals data (just used for polygon shapes)
+	VertexData PolygonData
+}
+
+type PhysicsBodyData struct {
+	// Reference unique identifier
+	Id uint32
+	// Enabled dynamics state (collisions are calculated anyway)
+	Enabled uint32
+	// Physics body shape pivot
+	Position raylib.Vector2
+	// Current linear velocity applied to position
+	Velocity raylib.Vector2
+	// Current linear force (reset to 0 every step)
+	Force raylib.Vector2
+	// Current angular velocity applied to orient
+	AngularVelocity float32
+	// Current angular force (reset to 0 every step)
+	Torque float32
+	// Rotation in radians
+	Orient float32
+	// Moment of inertia
+	Inertia float32
+	// Inverse value of inertia
+	InverseInertia float32
+	// Physics body mass
+	Mass float32
+	// Inverse value of mass
+	InverseMass float32
+	// Friction when the body has not movement (0 to 1)
+	StaticFriction float32
+	// Friction when the body has movement (0 to 1)
+	DynamicFriction float32
+	// Restitution coefficient of the body (0 to 1)
+	Restitution float32
+	// Apply gravity force to dynamics
+	UseGravity uint32
+	// Physics grounded on other body state
+	IsGrounded uint32
+	// Physics rotation constraint
+	FreezeOrient uint32
+	// Padding
+	_ [4]byte
+	// Physics body shape information (type, radius, vertices, normals)
+	Shape PhysicsShape
+}
+
+type PhysicsManifoldData struct {
+	// Reference unique identifier
+	Id uint32
+	// Paddin
+	_ [4]byte
+	// Manifold first physics body reference
+	BodyA *PhysicsBodyData
+	// Manifold second physics body reference
+	BodyB *PhysicsBodyData
+	// Depth of penetration from collision
+	Penetration float32
+	// Normal direction vector from 'a' to 'b'
+	Normal raylib.Vector2
+	// Points of contact during collision
+	Contacts [2]raylib.Vector2
+	// Current collision number of contacts
+	ContactsCount uint32
+	// Mixed restitution during collision
+	Restitution float32
+	// Mixed dynamic friction during collision
+	DynamicFriction float32
+	// Mixed static friction during collision
+	StaticFriction float32
+	// Padding
+	_ [4]byte
+}