Fixed bug where reduced manifold would attempt to grab an invalid contact

Assets/Editor/Editor.SHConfig

@@ -1,4 +1,4 @@
 Start Maximized: true
-Working Scene ID: 92914350
+Working Scene ID: 97402985
 Window Size: {x: 2000, y: 1518}
 Style: 0

Assets/Scenes/PhysicsSandbox.shade

@@ -207,7 +207,7 @@
   Components:
     Transform Component:
       Translate: {x: -1, y: 7, z: 0}
-      Rotate: {x: 0, y: 0, z: 0.785398185}
+      Rotate: {x: 0, y: 0, z: 0}
       Scale: {x: 0.999999642, y: 0.999998569, z: 0.999999642}
       IsActive: true
     RigidBody Component:
@@ -223,9 +223,9 @@
       Freeze Position X: false
       Freeze Position Y: false
       Freeze Position Z: false
-      Freeze Rotation X: false
+      Freeze Rotation X: true
-      Freeze Rotation Y: false
+      Freeze Rotation Y: true
-      Freeze Rotation Z: false
+      Freeze Rotation Z: true
       IsActive: true
     Collider Component:
       DrawColliders: false

SHADE_Engine/src/Physics/Collision/Narrowphase/SHConvexVsConvex.cpp

@@ -542,13 +542,12 @@ namespace SHADE
     }
 
     // Reduce contact manifold if more than 4 points
-    if (numContacts > 4)
+    if (numContacts > SHPHYSICS_MAX_MANIFOLD_CONTACTS)
     {
-      const auto INDICES_TO_KEEP = reduceContacts(contacts, REF_NORMAL);
+      const auto INDICES_TO_KEEP = reduceContacts(contacts, LOCAL_REF_NORMAL);
       std::vector<SHContact> reducedContacts;
 
-      const int32_t NUM_REDUCED = static_cast<int32_t>(INDICES_TO_KEEP.size());
+      for (int32_t i = 0; i < SHPHYSICS_MAX_MANIFOLD_CONTACTS; ++i)
-      for (int32_t i = 0; i < NUM_REDUCED; ++i)
         reducedContacts.emplace_back(contacts[INDICES_TO_KEEP[i]]);
 
       contacts.clear();
@@ -638,7 +637,7 @@ namespace SHADE
         // In case the edge is parallel, the intersection is just the end point
         const float   DOT           = SHVec3::Dot(v2Pos - v1Pos, PLANE_NORMAL);
         const bool    IS_PARALLEL   = SHMath::CompareFloat(DOT, 0.0f);
-        const float   ALPHA         = IS_PARALLEL ? 1.0f : (-plane.GetDistance() - SHVec3::Dot(v1Pos, PLANE_NORMAL)) / DOT;
+        const float   ALPHA         = IS_PARALLEL ? 0.0f : (-plane.GetDistance() - SHVec3::Dot(v1Pos, PLANE_NORMAL)) / DOT;
 
         intersection.position         = SHVec3::ClampedLerp(v1Pos, v2Pos, ALPHA);
         intersection.featurePair.inI  = 0;
@@ -670,12 +669,13 @@ namespace SHADE
 
     // Use a map to temporarily store and track the contacts we want
     std::unordered_map<int, const SHContact*> contactMap;
+
     const int32_t NUM_CONTACTS = static_cast<int32_t>(in.size());
     for (int32_t i = 0; i < NUM_CONTACTS; ++i)
       contactMap.emplace(i, &in[i]);
 
     // Find the furthest point in a given direction
-    int32_t indexToKeep = -1;
+    int32_t indexToKeep = 0;
     float bestDistance  = std::numeric_limits<float>::lowest();
 
     for (const auto& [index, contact] : contactMap)
@@ -691,8 +691,7 @@ namespace SHADE
     indicesToKeep.emplace_back(indexToKeep);
     contactMap.erase(indexToKeep);
 
-
+    indexToKeep   = 0;
-    indexToKeep   = -1;
     bestDistance  = std::numeric_limits<float>::lowest();
 
     // Find point furthest away from the first index
@@ -710,7 +709,7 @@ namespace SHADE
     indicesToKeep.emplace_back(indexToKeep);
     contactMap.erase(indexToKeep);
 
-    indexToKeep = -1;
+    indexToKeep = 0;
 
     // We compute the triangle with the largest area.
     // The area can be positive or negative depending on the winding order.
@@ -745,7 +744,7 @@ namespace SHADE
 
     // Compare which triangle creates the largest area
     bool isAreaPositive = false;
-    if (maxArea > (-minArea))
+    if (maxArea > std::fabs(minArea))
     {
       isAreaPositive  = true;
       indexToKeep     = maxAreaIndex;
@@ -759,7 +758,7 @@ namespace SHADE
     indicesToKeep.emplace_back(indexToKeep);
     contactMap.erase(indexToKeep);
 
-    indexToKeep = -1;
+    indexToKeep = 0;
 
     // For the last point, we want the point which forms the largest area that is winded opposite to the first triangle
     // The areas should be inverted: If area was -ve, we want a +ve. Otherwise, vice versa.

SHADE_Engine/src/Physics/SHPhysicsConstants.h

@@ -15,36 +15,42 @@
 
 namespace SHADE
 {
+  /**
+   * @brief
+   * The number of contacts required to build a stable manifold.
+  */
+  static constexpr int    SHPHYSICS_MAX_MANIFOLD_CONTACTS   = 4;
+
   /**
    * @brief
    * The number of simulations length for every real world unit meter. <br/>
    * Modify this to change the global scale of the simulation.
   */
-  static constexpr float SHPHYSICS_LENGTHS_PER_UNIT_METER   = 1.0f;
+  static constexpr float  SHPHYSICS_LENGTHS_PER_UNIT_METER  = 1.0f;
 
   /**
    * @brief
    * Linear Collision & Constraint tolerance.
   */
-  static constexpr float SHPHYSICS_LINEAR_SLOP              = 0.01f * SHPHYSICS_LENGTHS_PER_UNIT_METER;
+  static constexpr float  SHPHYSICS_LINEAR_SLOP             = 0.01f * SHPHYSICS_LENGTHS_PER_UNIT_METER;
 
   /**
    * @brief
    * Velocity threshold for restitution to be applied.
   */
-  static constexpr float SHPHYSICS_RESTITUTION_THRESHOLD    = 1.0f;
+  static constexpr float  SHPHYSICS_RESTITUTION_THRESHOLD   = 1.0f;
 
   /**
   * @brief
   * Scaling factor to control how fast overlaps are resolved.<br/>
   * 1 is ideal for instant correction, but values close to 1 can lead to overshoot.
   */
-  static constexpr float SHPHYSICS_BAUMGARTE                = 0.2f;
+  static constexpr float  SHPHYSICS_BAUMGARTE               = 0.2f;
 
   /**
    * @brief
    * Distance threshold to consider two contacts as the same.
   */
-  static constexpr float SHPHYSICS_SAME_CONTACT_DISTANCE    = 0.01;
+  static constexpr float  SHPHYSICS_SAME_CONTACT_DISTANCE    = 0.01;
 
 }