Method internalStep

experimental/physics/simulation.go:381–500

TODO read https://gafferongames.com/post/fix_your_timestep/

(dt float32)

// TODO read https://gafferongames.com/post/fix_your_timestep/
func (s *Simulation) internalStep(dt float32) {

	s.dt = dt

	// Apply force fields (only to dynamic bodies
	for _, b := range s.bodies {
		if b.BodyType() == object.Dynamic {
			for _, ff := range s.forceFields {
				pos := b.Position()
				force := ff.ForceAt(&pos)
				b.ApplyForceField(&force)
			}
		}
	}

    // Find pairs of bodies that are potentially colliding (broadphase)
	pairs := s.broadphase.FindCollisionPairs(s.bodies)

	// Remove some pairs before proceeding to narrowphase based on constraints' colConn property
	// which specifies if constrained bodies should collide with one another
    s.prunePairs(pairs) // TODO review/implement

	// Precompute world normals/edges only for convex bodies that will undergo narrowphase
	for _, body := range s.uniqueBodiesFromPairs(pairs) {
		if ch, ok := body.Shape().(*shape.ConvexHull); ok{
			ch.ComputeWorldFaceNormalsAndUniqueEdges(body.Quaternion())
		}
	}

	// Switch collision matrices (to keep track of which collisions started/ended)
    s.collisionMatrixTick()

    // Resolve collisions and generate contact and friction equations
	contactEqs, frictionEqs := s.narrowphase.GenerateEquations(pairs)

	// Add all friction equations to solver
	for i := 0; i < len(frictionEqs); i++ {
		s.solver.AddEquation(frictionEqs[i])
	}

	// Add all contact equations to solver (and update some things)
	for i := 0; i < len(contactEqs); i++ {
		s.solver.AddEquation(contactEqs[i])
		s.updateSleepAndCollisionMatrix(contactEqs[i])
	}

    // Add all equations from user-added constraints to the solver
	userAddedEquations := 0
    for i := 0; i < len(s.constraints); i++ {
		s.constraints[i].Update()
        eqs := s.constraints[i].Equations()
        for j := 0; j < len(eqs); j++ {
			userAddedEquations++
            s.solver.AddEquation(eqs[j])
        }
    }

	// Emit events TODO implement