protected void TryToAdd(Collidable a, Collidable b, Material materialA, Material materialB) { CollisionRule rule; if ((rule = CollisionRules.collisionRuleCalculator(a.collisionRules, b.collisionRules)) < CollisionRule.NoNarrowPhasePair) { //Clamp the rule to the parent's rule. Always use the more restrictive option. //Don't have to test for NoNarrowPhasePair rule on the parent's rule because then the parent wouldn't exist! if (rule < CollisionRule) { rule = CollisionRule; } var pair = new CollidablePair(a, b); if (!subPairs.ContainsKey(pair)) { CollidablePairHandler newPair = NarrowPhaseHelper.GetPairHandler(ref pair, rule); if (newPair != null) { newPair.UpdateMaterialProperties(materialA, materialB); //Override the materials, if necessary. newPair.Parent = this; subPairs.Add(pair, newPair); } } containedPairs.Add(pair); } }