From 6444ba1933a8e8ec098a25e31dc8dfc590fd7543 Mon Sep 17 00:00:00 2001
From: Joshua Barretto <joshua.s.barretto@gmail.com>
Date: Thu, 27 Jun 2019 15:21:41 +0100
Subject: [PATCH] Made collision detection cheaper, fixed snapping bug,
 somewhat nerfed rolling

---
 common/src/state.rs    |  2 +-
 common/src/sys/phys.rs | 20 +++++++-------------
 2 files changed, 8 insertions(+), 14 deletions(-)

diff --git a/common/src/state.rs b/common/src/state.rs
index d04e814fe7..7b7f0bd46a 100644
--- a/common/src/state.rs
+++ b/common/src/state.rs
@@ -38,7 +38,7 @@ pub struct DeltaTime(pub f32);
 /// too fast, we'd skip important physics events like collisions. This constant determines the
 /// upper limit. If delta time exceeds this value, the game's physics will begin to produce time
 /// lag. Ideally, we'd avoid such a situation.
-const MAX_DELTA_TIME: f32 = 0.1;
+const MAX_DELTA_TIME: f32 = 1.0;
 
 pub struct Changes {
     pub new_chunks: HashSet<Vec2<i32>>,
diff --git a/common/src/sys/phys.rs b/common/src/sys/phys.rs
index fb03a430bf..cd51d6ae32 100644
--- a/common/src/sys/phys.rs
+++ b/common/src/sys/phys.rs
@@ -15,7 +15,7 @@ const HUMANOID_SPEED: f32 = 120.0;
 const HUMANOID_AIR_ACCEL: f32 = 10.0;
 const HUMANOID_AIR_SPEED: f32 = 100.0;
 const HUMANOID_JUMP_ACCEL: f32 = 16.0;
-const ROLL_ACCEL: f32 = 160.0;
+const ROLL_ACCEL: f32 = 120.0;
 const ROLL_SPEED: f32 = 550.0;
 const GLIDE_ACCEL: f32 = 15.0;
 const GLIDE_SPEED: f32 = 45.0;
@@ -28,19 +28,11 @@ const GLIDE_ANTIGRAV: f32 = 9.81 * 3.95;
 // damp = linear damping
 // Friction is a type of damping.
 fn integrate_forces(dt: f32, mut lv: Vec3<f32>, damp: f32) -> Vec3<f32> {
-    lv.z -= (GRAVITY * dt).max(-50.0);
+    lv.z = (lv.z - GRAVITY * dt).max(-50.0);
 
-    let mut linear_damp = 1.0 - dt * damp;
+    let linear_damp = (1.0 - dt * damp).max(0.0);
 
-    if linear_damp < 0.0
-    // reached zero in the given time
-    {
-        linear_damp = 0.0;
-    }
-
-    lv *= linear_damp;
-
-    lv
+    lv * linear_damp
 }
 
 /// This system applies forces and calculates new positions and velocities.
@@ -189,6 +181,7 @@ impl<'a> System<'a> for Sys {
                 false
             };
 
+            let was_on_ground = on_grounds.get(entity).is_some();
             on_grounds.remove(entity); // Assume we're in the air - unless we can prove otherwise
             pos.0.z -= 0.0001; // To force collision with the floor
 
@@ -251,7 +244,7 @@ impl<'a> System<'a> for Sys {
                     let resolve_dir = -dir.map(|e| if e.abs() == max_axis { e } else { 0.0 });
 
                     // When the resolution direction is pointing upwards, we must be on the ground
-                    if resolve_dir.z > 0.0 {
+                    if resolve_dir.z > 0.0 && vel.0.z <= 0.0 {
                         on_ground = true;
                     }
 
@@ -282,6 +275,7 @@ impl<'a> System<'a> for Sys {
             } else if collision_with(pos.0 - Vec3::unit_z() * 1.0, near_iter.clone())
                 && vel.0.z < 0.0
                 && vel.0.z > -1.0
+                && was_on_ground
             {
                 pos.0.z = (pos.0.z - 0.05).floor();
                 on_grounds.insert(entity, OnGround);