From b4d97fc42e7f81056db9daa28a9cf44a6416fc11 Mon Sep 17 00:00:00 2001
From: minjaesong <alswo9628@gmail.com>
Date: Sun, 20 Jan 2019 07:03:23 +0900
Subject: [PATCH] issue #16: jump height is "close enough", friction and
 walk/stop needs fix

---
 .../terrarum/gameactors/ActorWBMovable.kt     | 21 +++++++++++--------
 .../gameactors/ActorHumanoid.kt               |  2 +-
 2 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/src/net/torvald/terrarum/gameactors/ActorWBMovable.kt b/src/net/torvald/terrarum/gameactors/ActorWBMovable.kt
index 6a441437a..ce057a2e4 100644
--- a/src/net/torvald/terrarum/gameactors/ActorWBMovable.kt
+++ b/src/net/torvald/terrarum/gameactors/ActorWBMovable.kt
@@ -358,7 +358,7 @@ open class ActorWBMovable(renderOrder: RenderOrder, val immobileBody: Boolean =
     override fun update(delta: Float) {
         if (isUpdate && !flagDespawn) {
 
-            val ddelta = delta.toFloat()
+            val ddelta = delta.toDouble()
 
             if (!assertPrinted) assertInit()
 
@@ -388,7 +388,7 @@ open class ActorWBMovable(renderOrder: RenderOrder, val immobileBody: Boolean =
                 // Actors are subject to the gravity and the buoyancy if they are not levitating
 
                 if (!isNoSubjectToGrav) {
-                    applyGravitation()
+                    applyGravitation(ddelta)
                 }
 
                 //applyBuoyancy()
@@ -409,7 +409,7 @@ open class ActorWBMovable(renderOrder: RenderOrder, val immobileBody: Boolean =
                  *     This body is NON-STATIC and the other body is STATIC
                  */
                 if (!isNoCollideWorld) {
-                    displaceHitbox()
+                    displaceHitbox(ddelta)
                 }
                 else {
                     val vecSum = externalForce + (controllerMoveDelta ?: Vector2(0.0, 0.0))
@@ -495,7 +495,7 @@ open class ActorWBMovable(renderOrder: RenderOrder, val immobileBody: Boolean =
         }
     }*/
 
-    fun getDrag(externalForce: Vector2): Vector2 {
+    fun getDrag(delta: Double, externalForce: Vector2): Vector2 {
         /**
          * weight; gravitational force in action
          * W = mass * G (9.8 [m/s^2])
@@ -513,7 +513,10 @@ open class ActorWBMovable(renderOrder: RenderOrder, val immobileBody: Boolean =
 
         val V: Vector2 = (W - D) / Terrarum.PHYS_TIME_FRAME * SI_TO_GAME_ACC
 
-        return V
+        return V * (Terrarum.PHYS_REF_FPS * delta).sqrt()
+
+        // FIXME v * const, where const = 1.0 for FPS=60, sqrt(2.0) for FPS=30, etc.
+        //       this is "close enough" solution and not perfect.
     }
 
     /**
@@ -531,11 +534,11 @@ open class ActorWBMovable(renderOrder: RenderOrder, val immobileBody: Boolean =
      *
      * Apply only if not grounded; normal force is precessed separately.
      */
-    private fun applyGravitation() {
+    private fun applyGravitation(delta: Double) {
 
         if (!isNoSubjectToGrav && !(gravitation.y > 0 && walledBottom || gravitation.y < 0 && walledTop)) {
             //if (!isWalled(hitbox, COLLIDING_BOTTOM)) {
-            applyForce(getDrag(externalForce))
+            applyForce(getDrag(delta, externalForce))
             //}
         }
     }
@@ -567,7 +570,7 @@ open class ActorWBMovable(renderOrder: RenderOrder, val immobileBody: Boolean =
         }
     }*/
 
-    private fun displaceHitbox() {
+    private fun displaceHitbox(delta: Double) {
         // // HOW IT SHOULD WORK // //
         // ////////////////////////
         // combineVeloToMoveDelta now
@@ -633,7 +636,7 @@ open class ActorWBMovable(renderOrder: RenderOrder, val immobileBody: Boolean =
             fun Double.modTileDelta() = this - this.modTile()
 
 
-            val vectorSum = externalForce + controllerMoveDelta
+            val vectorSum = (externalForce + controllerMoveDelta) * (Terrarum.PHYS_REF_FPS * delta)
             val ccdSteps = minOf(16, (vectorSum.magnitudeSquared / TILE_SIZE.sqr()).floorInt() + 1) // adaptive
 
 
diff --git a/src/net/torvald/terrarum/modulebasegame/gameactors/ActorHumanoid.kt b/src/net/torvald/terrarum/modulebasegame/gameactors/ActorHumanoid.kt
index afc170f4c..fca0dfb97 100644
--- a/src/net/torvald/terrarum/modulebasegame/gameactors/ActorHumanoid.kt
+++ b/src/net/torvald/terrarum/modulebasegame/gameactors/ActorHumanoid.kt
@@ -519,7 +519,7 @@ open class ActorHumanoid(
 
                     val timedJumpCharge = jumpFunc(MAX_JUMP_LENGTH, jmpCtr)
                     forceVec.y -= getJumpAcc(jumpPower, timedJumpCharge)
-                    forceVec.y += getDrag(forceVec).y
+                    forceVec.y += getDrag(1.0 / Terrarum.PHYS_REF_FPS, forceVec).y
 
                     simYPos += forceVec.y // ignoring all the fluid drag OTHER THAN THE AIR