From 17e7879777226212f00e898d2aa3ada21c3a2e00 Mon Sep 17 00:00:00 2001
From: Joshua Barretto <joshua.s.barretto@gmail.com>
Date: Thu, 9 Dec 2021 15:16:16 +0000
Subject: [PATCH] Added surface traction factor

---
 common/src/states/utils.rs  |  4 ++--
 common/src/terrain/block.rs | 16 +++++++++++++++-
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/common/src/states/utils.rs b/common/src/states/utils.rs
index 0470964555..c567d46769 100644
--- a/common/src/states/utils.rs
+++ b/common/src/states/utils.rs
@@ -307,7 +307,7 @@ fn basic_move(data: &JoinData<'_>, update: &mut StateUpdate, efficiency: f32) {
 
     let accel = if let Some(block) = data.physics.on_ground {
         // FRIC_GROUND temporarily used to normalize things around expected values
-        data.body.base_accel() * block.get_friction() / FRIC_GROUND
+        data.body.base_accel() * block.get_traction() * block.get_friction() / FRIC_GROUND
     } else {
         data.body.air_accel()
     } * efficiency;
@@ -354,7 +354,7 @@ pub fn handle_forced_movement(
             let strength = strength * data.stats.move_speed_modifier * data.stats.friction_modifier;
             if let Some(accel) = data.physics.on_ground.map(|block| {
                 // FRIC_GROUND temporarily used to normalize things around expected values
-                data.body.base_accel() * block.get_friction() / FRIC_GROUND
+                data.body.base_accel() * block.get_traction() * block.get_friction() / FRIC_GROUND
             }) {
                 update.vel.0 += Vec2::broadcast(data.dt.0)
                     * accel
diff --git a/common/src/terrain/block.rs b/common/src/terrain/block.rs
index 9eb1049535..1bad97490a 100644
--- a/common/src/terrain/block.rs
+++ b/common/src/terrain/block.rs
@@ -312,7 +312,8 @@ impl Block {
             .unwrap_or(1.0)
     }
 
-    // Used to calculate surface friction when walking. Currently has no units.
+    /// Get the friction constant used to calculate surface friction when
+    /// walking/climbing. Currently has no units.
     #[inline]
     pub fn get_friction(&self) -> f32 {
         match self.kind() {
@@ -321,6 +322,19 @@ impl Block {
         }
     }
 
+    /// Get the traction permitted by this block as a proportion of the friction
+    /// applied.
+    ///
+    /// 1.0 = default, 0.0 = completely inhibits movement, > 1.0 = potential for
+    /// infinite acceleration (in a vacuum).
+    #[inline]
+    pub fn get_traction(&self) -> f32 {
+        match self.kind() {
+            BlockKind::Snow => 0.8,
+            _ => 1.0,
+        }
+    }
+
     #[inline]
     pub fn kind(&self) -> BlockKind { self.kind }