From 1799a9a9096b945d9354000234a517e9b41790fb Mon Sep 17 00:00:00 2001
From: Alexander Nozik <altavir@gmail.com>
Date: Mon, 3 Jun 2024 18:34:08 +0300
Subject: [PATCH] Fix ball on springs demo

---
 .../controls/constructor/models/MaterialPoint.kt       | 10 ++++++++--
 .../kscience/controls/constructor/units/coordinates.kt |  8 ++++++++
 demo/constructor/src/jvmMain/kotlin/BodyOnSprings.kt   |  6 ++----
 3 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/controls-constructor/src/commonMain/kotlin/space/kscience/controls/constructor/models/MaterialPoint.kt b/controls-constructor/src/commonMain/kotlin/space/kscience/controls/constructor/models/MaterialPoint.kt
index c03841c..cc44a85 100644
--- a/controls-constructor/src/commonMain/kotlin/space/kscience/controls/constructor/models/MaterialPoint.kt
+++ b/controls-constructor/src/commonMain/kotlin/space/kscience/controls/constructor/models/MaterialPoint.kt
@@ -26,17 +26,23 @@ public class MaterialPoint(
     private var currentForce = force.value
 
     private val movement = onTimer(
+        DefaultTimer.REALTIME,
         reads = setOf(velocity, position),
         writes = setOf(velocity, position)
     ) { prev, next ->
         val dtSeconds = (next - prev).toDouble(DurationUnit.SECONDS)
 
         // compute new value based on velocity and acceleration from the previous step
-        position.value += (velocity.value * dtSeconds).cast(Meters) +
+        val deltaR = (velocity.value * dtSeconds).cast(Meters) +
                 (currentForce / mass.value * dtSeconds.pow(2) / 2).cast(Meters)
+        position.value += deltaR
 
         // compute new velocity based on acceleration on the previous step
-        velocity.value += (currentForce / mass.value * dtSeconds).cast(MetersPerSecond)
+        val deltaV = (currentForce / mass.value * dtSeconds).cast(MetersPerSecond)
+        //TODO apply energy correction
+        //val work = deltaR.length.value * currentForce.length.value
+        velocity.value += deltaV
+
         currentForce = force.value
     }
 }
\ No newline at end of file
diff --git a/controls-constructor/src/commonMain/kotlin/space/kscience/controls/constructor/units/coordinates.kt b/controls-constructor/src/commonMain/kotlin/space/kscience/controls/constructor/units/coordinates.kt
index 88d7bd6..027dbbb 100644
--- a/controls-constructor/src/commonMain/kotlin/space/kscience/controls/constructor/units/coordinates.kt
+++ b/controls-constructor/src/commonMain/kotlin/space/kscience/controls/constructor/units/coordinates.kt
@@ -1,5 +1,8 @@
 package space.kscience.controls.constructor.units
 
+import kotlin.math.pow
+import kotlin.math.sqrt
+
 public data class XY<U : UnitsOfMeasurement>(val x: NumericalValue<U>, val y: NumericalValue<U>)
 
 public fun <U : UnitsOfMeasurement> XY(x: Number, y: Number): XY<U> = XY(NumericalValue(x), NumericalValue((y)))
@@ -18,6 +21,11 @@ public data class XYZ<U : UnitsOfMeasurement>(
     val z: NumericalValue<U>,
 )
 
+public val <U : UnitsOfMeasurement> XYZ<U>.length: NumericalValue<U>
+    get() = NumericalValue(
+        sqrt(x.value.pow(2) + y.value.pow(2) + z.value.pow(2))
+    )
+
 public fun <U : UnitsOfMeasurement> XYZ(x: Number, y: Number, z: Number): XYZ<U> =
     XYZ(NumericalValue(x), NumericalValue((y)), NumericalValue(z))
 
diff --git a/demo/constructor/src/jvmMain/kotlin/BodyOnSprings.kt b/demo/constructor/src/jvmMain/kotlin/BodyOnSprings.kt
index e937d1b..57bc426 100644
--- a/demo/constructor/src/jvmMain/kotlin/BodyOnSprings.kt
+++ b/demo/constructor/src/jvmMain/kotlin/BodyOnSprings.kt
@@ -16,8 +16,6 @@ import space.kscience.controls.constructor.models.MaterialPoint
 import space.kscience.controls.constructor.units.*
 import space.kscience.dataforge.context.Context
 import java.awt.Dimension
-import kotlin.math.pow
-import kotlin.math.sqrt
 
 
 private class Spring(
@@ -33,7 +31,7 @@ private class Spring(
      */
     val tension: DeviceState<XYZ<Newtons>> = combineState(begin, end) { begin: XYZ<Meters>, end: XYZ<Meters> ->
         val delta = end - begin
-        val l = sqrt(delta.x.value.pow(2) + delta.y.value.pow(2) + delta.z.value.pow(2))
+        val l = delta.length.value
         ((delta / l) * k * (l - l0.value)).cast(Newtons)
     }
 }
@@ -87,7 +85,7 @@ private class BodyOnSprings(
 }
 
 fun main() = application {
-    val initialState = XYZ<Meters>(0.01, 0.1, 0)
+    val initialState = XYZ<Meters>(0, 0.4, 0)
 
     Window(title = "Ball on springs", onCloseRequest = ::exitApplication) {
         window.minimumSize = Dimension(400, 400)