stepjoint: fixed step_joint logic in physics, added Run button to Editor

docs/content/physics.md

@@ -157,7 +157,7 @@ addSlider(&dampStr, &damp, 1000)
 
 This simulation allows interactive control over the parameters of a `Prismatic` joint, which sets the linear position of a body along a given axis, in this case along the horizontal (`X`) axis.
 
-Click the `Step 10000` button and then start moving the sliders to see the effects interactively. Here's what you should observe:
+Click the `Run` button and then start moving the sliders to see the effects interactively (press `Stop` to stop when done). Here's what you should observe:
 
 * `Stiff` (stiffness) determines how quickly the joint responds to the position changes. You can make this variable even stronger in practice (e.g., 10,000).
 

physics/phyxyz/editor.go

@@ -215,6 +215,41 @@ func (pe *Editor) Step(n int) {
 	pe.AsyncUnlock()
 }
 
+// Run runs the physics until stopped
+func (pe *Editor) Run() {
+	if pe.isRunning {
+		return
+	}
+	pe.isRunning = true
+	pe.Model.SetAsCurrent()
+	pe.toolbar.AsyncLock()
+	pe.toolbar.UpdateRender()
+	pe.toolbar.AsyncUnlock()
+	for {
+		if pe.ControlFunc != nil {
+			pe.ControlFunc(physics.StepsToMsec(pe.TimeStep))
+		}
+		pe.Model.Step()
+		pe.TimeStep++
+		pe.Scene.Update()
+		pe.editor.AsyncLock()
+		pe.editor.NeedsRender()
+		pe.editor.AsyncUnlock()
+		if !pe.Model.GPU {
+			time.Sleep(time.Nanosecond) // this is essential for web (wasm) running to actually update
+			// if running in GPU mode, it works, but otherwise the thread never yields and it never updates.
+		}
+		if pe.stop {
+			pe.stop = false
+			break
+		}
+	}
+	pe.isRunning = false
+	pe.AsyncLock()
+	pe.Update()
+	pe.AsyncUnlock()
+}
+
 func (pe *Editor) MakeToolbar(p *tree.Plan) {
 	stepNButton := func(n int) {
 		nm := fmt.Sprintf("Step %d", n)
@@ -253,6 +288,14 @@ func (pe *Editor) MakeToolbar(p *tree.Plan) {
 	})
 	tree.Add(p, func(w *core.Separator) {})
 
+	tree.Add(p, func(w *core.Button) {
+		w.SetText("Run").SetIcon(icons.PlayArrow).
+			SetTooltip("Run physics until Stop is pressed.").
+			OnClick(func(e events.Event) {
+				go pe.Run()
+			})
+		w.FirstStyler(func(s *styles.Style) { s.SetEnabled(!pe.isRunning) })
+	})
 	stepNButton(1)
 	stepNButton(10)
 	stepNButton(100)

physics/step_joint.goal

@@ -74,12 +74,14 @@ func StepJointForces(i uint32) { //gosl:kernel
 	// child world transform
 	poseCR := DynamicPos(jCi, params.Cur)
 	poseCQ := DynamicQuat(jCi, params.Cur)
+	jCR := JointCPos(ji)
+	jCQ := JointCQuat(ji)
 	xwCR := jCR
 	xwCQ := jCQ
 	slmath.MulSpatialTransforms(poseCR, poseCQ, jCR, jCQ, &xwCR, &xwCQ)
 	// https://github.com/newton-physics/newton/issues/1261
 	comC := BodyCom(jCbi)
-	dC := poseCR.Sub(slmath.MulSpatialPoint(poseCR, poseCQ, comC)) // child moment arm
+	dC := xwCR.Sub(slmath.MulSpatialPoint(poseCR, poseCQ, comC)) // child moment arm
 
 	var f, t math32.Vector3
 	switch jt {