From 02db2d7ba911ab19ea98d55898a89061ba3fdacb Mon Sep 17 00:00:00 2001
From: Lukas <leisenhau@gmail.com>
Date: Sat, 1 May 2021 13:31:22 +0200
Subject: [PATCH] physics: add stepping

---
 .../minosoft/data/entities/entities/Entity.kt  | 18 +++++++++++++++---
 .../gui/rendering/chunk/models/AABB.kt         |  2 +-
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/src/main/java/de/bixilon/minosoft/data/entities/entities/Entity.kt b/src/main/java/de/bixilon/minosoft/data/entities/entities/Entity.kt
index 96e139e69..07c48ff68 100644
--- a/src/main/java/de/bixilon/minosoft/data/entities/entities/Entity.kt
+++ b/src/main/java/de/bixilon/minosoft/data/entities/entities/Entity.kt
@@ -227,13 +227,24 @@ abstract class Entity(
         val delta = Vec3(deltaPosition)
         if (delta.y != 0.0f) {
             delta.y = collisionsToCheck.computeOffset(aabb, deltaPosition.y, Axes.Y)
-            aabb.offsetAssign(0f, delta.y, 0f)
             if (delta.y != deltaPosition.y) {
                 onGround = false
                 velocity.y = 0.0f
                 if (deltaPosition.y < 0) {
                     onGround = true
                 }
+                aabb.offsetAssign(0f, delta.y, 0f)
+            } else if (delta.y < 0) {
+                onGround = false
+            }
+        }
+        if ((deltaPosition.x != 0f || deltaPosition.z != 0f)) {
+            val testDelta = Vec3(delta)
+            testDelta.y = STEP_HEIGHT
+            val stepMovementY = collisionsToCheck.computeOffset(aabb + testDelta, -STEP_HEIGHT, Axes.Y)
+            if (stepMovementY < 0 && stepMovementY >= -STEP_HEIGHT) {
+                delta.y = STEP_HEIGHT + stepMovementY
+                aabb.offsetAssign(0f, delta.y, 0f)
             }
         }
         val xPriority = delta.x > delta.z
@@ -264,7 +275,7 @@ abstract class Entity(
         val newVelocity = Vec3(velocity)
         val oldVelocity = Vec3(velocity)
         val deltaTime = deltaMillis.toFloat() / 1000.0f
-        if (!hasNoGravity && !isFlying) {
+        if (! hasNoGravity && !isFlying) {
             newVelocity.y -= ProtocolDefinition.GRAVITY * deltaTime
         }
         newVelocity *= 0.25f.pow(deltaTime) // apply
@@ -284,6 +295,7 @@ abstract class Entity(
         get() = defaultAABB + position
 
     companion object {
-        private const val HITBOX_MARGIN = 1e-5
+        private const val HITBOX_MARGIN = 1e-5f
+        private const val STEP_HEIGHT = 0.6f
     }
 }
diff --git a/src/main/java/de/bixilon/minosoft/gui/rendering/chunk/models/AABB.kt b/src/main/java/de/bixilon/minosoft/gui/rendering/chunk/models/AABB.kt
index fb0951b43..72a91f068 100644
--- a/src/main/java/de/bixilon/minosoft/gui/rendering/chunk/models/AABB.kt
+++ b/src/main/java/de/bixilon/minosoft/gui/rendering/chunk/models/AABB.kt
@@ -134,7 +134,7 @@ class AABB {
         offsetAssign(Vec3(x, y, z))
     }
 
-    fun offsetAssign(vec3: Vec3) {
+    private fun offsetAssign(vec3: Vec3) {
         min += vec3
         max += vec3
     }