Particle system improvements:

- particles can collide with the outer walls of the sub
- drag + waterdrag parameters
- fixed particles "twitching" when the submarine is moving fast
- submarine velocity only affects the initial velocity of the particles (i.e. accelerating the sub doesn't automatically accelerate them)

Subsurface/Source/Map/Gap.cs

@@ -163,6 +163,8 @@ namespace Barotrauma
                 hulls[1] = temp;
             }
 
+            flowTargetHull = hulls[0];
+
             for (int i = 0 ; i <2; i++)
             {
                 if (hulls[i]==null) continue;

Subsurface/Source/Map/Structure.cs

@@ -537,8 +537,22 @@ namespace Barotrauma
 
             if (sectionIndex < 0 || sectionIndex > sections.Length - 1) return;
 
-            if (GameMain.Client == null) SetDamage(sectionIndex, sections[sectionIndex].damage + damage);
+            var section = sections[sectionIndex];
 
+            int particleAmount = (int)(Math.Min(Health - section.damage, damage) * Rand.Range(0.1f, 1.0f));
+            for (int i = 0; i < particleAmount; i++)
+            {
+                Vector2 particlePos = new Vector2(
+                    Rand.Range(section.rect.X, section.rect.Right),
+                    Rand.Range(section.rect.Y - section.rect.Height, section.rect.Y));
+
+                if (Submarine != null) particlePos += Submarine.DrawPosition;
+
+                var particle = GameMain.ParticleManager.CreateParticle("shrapnel", particlePos, Rand.Vector(Rand.Range(1.0f, 50.0f)));
+                if (particle == null) break;
+            }
+
+            if (GameMain.Client == null) SetDamage(sectionIndex, section.damage + damage);
         }
 
         public int FindSectionIndex(Vector2 displayPos)

Subsurface/Source/Map/SubmarineBody.cs

@@ -444,6 +444,18 @@ namespace Barotrauma
                 float wallImpact = Vector2.Dot(Velocity, -collisionNormal);
 
                 ApplyImpact(wallImpact, -collisionNormal, contact);
+
+                Vector2 n;
+                FixedArray2<Vector2> particlePos;
+                contact.GetWorldManifold(out n, out particlePos);
+                
+                int particleAmount = (int)(wallImpact*10.0f);
+                for (int i = 0; i < particleAmount; i++)
+                {
+                    var particle = GameMain.ParticleManager.CreateParticle("iceshards",
+                        ConvertUnits.ToDisplayUnits(particlePos[0]) + Rand.Vector(Rand.Range(1.0f, 50.0f)), 
+                        Rand.Vector(Rand.Range(50.0f,500.0f)) + Velocity);
+                }
             
                 return true;
             }