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conetwist.go
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/
conetwist.go
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// Copyright 2016 The G3N Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package constraint
import (
"github.com/g3n/engine/math32"
"github.com/g3n/engine/experimental/physics/equation"
)
// ConeTwist constraint.
type ConeTwist struct {
PointToPoint
axisA *math32.Vector3 // Rotation axis, defined locally in bodyA.
axisB *math32.Vector3 // Rotation axis, defined locally in bodyB.
coneEq *equation.Cone
twistEq *equation.Rotational
angle float32
twistAngle float32
}
// NewConeTwist creates and returns a pointer to a new ConeTwist constraint object.
func NewConeTwist(bodyA, bodyB IBody, pivotA, pivotB, axisA, axisB *math32.Vector3, angle, twistAngle, maxForce float32) *ConeTwist {
ctc := new(ConeTwist)
// Default of pivots and axes should be vec3(0)
ctc.initialize(bodyA, bodyB, pivotA, pivotB, maxForce)
ctc.axisA = axisA
ctc.axisB = axisB
ctc.axisA.Normalize()
ctc.axisB.Normalize()
ctc.angle = angle
ctc.twistAngle = twistAngle
ctc.coneEq = equation.NewCone(bodyA, bodyB, ctc.axisA, ctc.axisB, ctc.angle, maxForce)
ctc.twistEq = equation.NewRotational(bodyA, bodyB, maxForce)
ctc.twistEq.SetAxisA(ctc.axisA)
ctc.twistEq.SetAxisB(ctc.axisB)
// Make the cone equation push the bodies toward the cone axis, not outward
ctc.coneEq.SetMaxForce(0)
ctc.coneEq.SetMinForce(-maxForce)
// Make the twist equation add torque toward the initial position
ctc.twistEq.SetMaxForce(0)
ctc.twistEq.SetMinForce(-maxForce)
ctc.AddEquation(ctc.coneEq)
ctc.AddEquation(ctc.twistEq)
return ctc
}
// Update updates the equations with data.
func (ctc *ConeTwist) Update() {
ctc.PointToPoint.Update()
// Update the axes to the cone constraint
worldAxisA := ctc.bodyA.VectorToWorld(ctc.axisA)
worldAxisB := ctc.bodyB.VectorToWorld(ctc.axisB)
ctc.coneEq.SetAxisA(&worldAxisA)
ctc.coneEq.SetAxisB(&worldAxisB)
// Update the world axes in the twist constraint
tA, _ := ctc.axisA.RandomTangents()
worldTA := ctc.bodyA.VectorToWorld(tA)
ctc.twistEq.SetAxisA(&worldTA)
tB, _ := ctc.axisB.RandomTangents()
worldTB := ctc.bodyB.VectorToWorld(tB)
ctc.twistEq.SetAxisB(&worldTB)
ctc.coneEq.SetAngle(ctc.angle)
ctc.twistEq.SetMaxAngle(ctc.twistAngle)
}