use enum variants rather than casting to u8 for comparisons (#781)

Author: ThierryBerger

src/dynamics/coefficient_combine_rule.rs

@@ -7,29 +7,34 @@ use crate::math::Real;
 /// Each collider has its combination rule of type
 /// `CoefficientCombineRule`. And the rule
 /// actually used is given by `max(first_combine_rule as usize, second_combine_rule as usize)`.
-#[derive(Default, Copy, Clone, Debug, PartialEq, Eq)]
+#[derive(Default, Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
 #[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
 pub enum CoefficientCombineRule {
     /// The two coefficients are averaged.
     #[default]
     Average = 0,
     /// The smallest coefficient is chosen.
-    Min,
+    Min = 1,
     /// The two coefficients are multiplied.
-    Multiply,
+    Multiply = 2,
     /// The greatest coefficient is chosen.
-    Max,
+    Max = 3,
 }
 
 impl CoefficientCombineRule {
-    pub(crate) fn combine(coeff1: Real, coeff2: Real, rule_value1: u8, rule_value2: u8) -> Real {
+    pub(crate) fn combine(
+        coeff1: Real,
+        coeff2: Real,
+        rule_value1: CoefficientCombineRule,
+        rule_value2: CoefficientCombineRule,
+    ) -> Real {
         let effective_rule = rule_value1.max(rule_value2);
 
         match effective_rule {
-            0 => (coeff1 + coeff2) / 2.0,
-            1 => coeff1.min(coeff2),
-            2 => coeff1 * coeff2,
-            _ => coeff1.max(coeff2),
+            CoefficientCombineRule::Average => (coeff1 + coeff2) / 2.0,
+            CoefficientCombineRule::Min => coeff1.min(coeff2),
+            CoefficientCombineRule::Multiply => coeff1 * coeff2,
+            CoefficientCombineRule::Max => coeff1.max(coeff2),
         }
     }
 }

src/geometry/narrow_phase.rs

@@ -969,14 +969,14 @@ impl NarrowPhase {
                 let friction = CoefficientCombineRule::combine(
                     co1.material.friction,
                     co2.material.friction,
-                    co1.material.friction_combine_rule as u8,
-                    co2.material.friction_combine_rule as u8,
+                    co1.material.friction_combine_rule,
+                    co2.material.friction_combine_rule,
                 );
                 let restitution = CoefficientCombineRule::combine(
                     co1.material.restitution,
                     co2.material.restitution,
-                    co1.material.restitution_combine_rule as u8,
-                    co2.material.restitution_combine_rule as u8,
+                    co1.material.restitution_combine_rule,
+                    co2.material.restitution_combine_rule,
                 );
 
                 let zero = RigidBodyDominance(0); // The value doesn't matter, it will be MAX because of the effective groups.