[2hr] added verlet integration gravity and collision

JudahDoupe · Oct 11, 2023 · 26231e9 · 26231e9
1 parent 008bc43
commit 26231e9
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Showing 7 changed files with 34 additions and 15 deletions.
diff --git a/Assets/Plants/ECS/Components/Physics/PhysicsComponent.cs b/Assets/Plants/ECS/Components/Physics/PhysicsComponent.cs
@@ -6,10 +6,17 @@ public struct PhysicsBody : IComponentData
 {
     public float Mass;
 
-    // Force and Velocity ar in world space
-    public float3 Force;
-    public float3 Velocity;
-    public float3 PreviousPosition;
+    // All in world space
+    public float PrevTimeStep;
+    public float3 PrevPosition;
+    public float3 Position;
+    public float3 Acceleration;
+    public float3 Displacement => Position - PrevPosition;
+    public float3 Velocity => Displacement / PrevTimeStep;
+    public void AddAcceleration(float3 acceleration) => Acceleration += acceleration;
+    public void AddForce(float3 force) => Acceleration += force * Mass;
+    public void AddVelocity(float3 velocity) => PrevPosition -= velocity * PrevTimeStep;
+    public void SetVelocity(float3 velocity) => PrevPosition = Position - velocity * PrevTimeStep;
 }
 
 public class PhysicsComponent : MonoBehaviour
@@ -22,9 +29,14 @@ public class PhysicsComponentBaker : Baker<PhysicsComponent>
     public override void Bake(PhysicsComponent authoring)
     {
         var e = GetEntity(TransformUsageFlags.Dynamic);
+        var position = authoring.transform.position;
         AddComponent(e, new PhysicsBody
         {
             Mass = authoring.Mass,
+            Position = position,
+            PrevPosition = position,
+            Acceleration = float3.zero,
+            PrevTimeStep = 1,
         });
     }
 }
diff --git a/Assets/Plants/ECS/Components/Physics/SphereColliderComponent.cs b/Assets/Plants/ECS/Components/Physics/SphereColliderComponent.cs
@@ -4,8 +4,8 @@
 
 public struct CollisionResponse : IComponentData
 {
-    public float3 VelocityAdjustment;
     public float3 PositionAdjustment;
+    public float3 VelocityAdjustment;
 }
 
 public struct SphereCollider : IComponentData

diff --git a/Assets/Plants/ECS/Systems/Physics/CollisionSystem.cs b/Assets/Plants/ECS/Systems/Physics/CollisionSystem.cs
@@ -258,7 +258,9 @@ private void Execute(RefRW<PhysicsBody> physics,
                          CollisionAspect collision)
     {
         transform.ValueRW.TranslateWorld(worldTransform, collision.PositionAdjustment);
-        physics.ValueRW.Velocity += collision.VelocityAdjustment;
+        physics.ValueRW.Position += collision.PositionAdjustment;
+        physics.ValueRW.PrevPosition += collision.PositionAdjustment;
+        physics.ValueRW.AddVelocity(collision.VelocityAdjustment);
 
         collision.Clear();
     }

diff --git a/Assets/Plants/ECS/Systems/Physics/ContraintSystem.cs b/Assets/Plants/ECS/Systems/Physics/ContraintSystem.cs
@@ -40,6 +40,7 @@ public void OnDestroy(ref SystemState state) { }
     [BurstCompile]
     public void OnUpdate(ref SystemState state)
     {
+        return;
         if (!_haveTransformsInitialized)
         {
             _haveTransformsInitialized = true;
@@ -119,7 +120,7 @@ private void Execute(RefRW<ConstraintResponse> constraint,
                          LocalToWorld worldTransform)
     {
         localTransform.ValueRW.TranslateWorld(worldTransform, constraint.ValueRO.PositionAdjustment);
-        physics.ValueRW.Velocity += constraint.ValueRO.PositionAdjustment / TimeStep;
+        physics.ValueRW.Position += constraint.ValueRO.PositionAdjustment;
 
         constraint.ValueRW.PositionAdjustment = float3.zero;
     }

diff --git a/Assets/Plants/ECS/Systems/Physics/GravitySystem.cs b/Assets/Plants/ECS/Systems/Physics/GravitySystem.cs
@@ -23,6 +23,6 @@ public partial struct AddGravity : IJobEntity
     [BurstCompile]
     private void Execute(RefRW<PhysicsBody> physics)
     {
-        physics.ValueRW.Force += new float3(0, -9.8f, 0) * physics.ValueRO.Mass;
+        physics.ValueRW.AddAcceleration(new float3(0, -9.8f, 0));
     }
 }
diff --git a/Assets/Plants/ECS/Systems/Physics/SpringSystem.cs b/Assets/Plants/ECS/Systems/Physics/SpringSystem.cs
@@ -22,6 +22,7 @@ public void OnCreate(ref SystemState state)
     [BurstCompile]
     public void OnUpdate(ref SystemState state)
     {
+        return;
         if (!_haveTransformsInitialized)
         {
             _haveTransformsInitialized = true;
@@ -42,8 +43,8 @@ private void Execute(RefRW<PhysicsBody> physics,
                          LocalToWorld worldTransform,
                          SpringJoint spring)
     {
-        var springForce = -spring.Stiffness * worldTransform.LocalToWorldVector(localTransform.Position - spring.EquilibriumPosition);
-        var dampingForce = -spring.Dampening * physics.ValueRO.Velocity;
-        physics.ValueRW.Force += springForce + dampingForce;
+        //var springForce = -spring.Stiffness * worldTransform.LocalToWorldVector(localTransform.Position - spring.EquilibriumPosition);
+        //var dampingForce = -spring.Dampening * physics.ValueRO.Velocity;
+        //physics.ValueRW.Acceleration += springForce + dampingForce;
     }
 }
diff --git a/Assets/Plants/ECS/Systems/Physics/VelocityIntegrationSystem.cs b/Assets/Plants/ECS/Systems/Physics/VelocityIntegrationSystem.cs
@@ -58,9 +58,12 @@ private void Execute(RefRW<PhysicsBody> physics,
                          RefRW<LocalTransform> localTransform,
                          LocalToWorld worldTransform)
     {
-        physics.ValueRW.PreviousPosition = worldTransform.Position;
-        physics.ValueRW.Velocity += physics.ValueRO.Force / physics.ValueRO.Mass * TimeStep;
-        localTransform.ValueRW.TranslateWorld(worldTransform, physics.ValueRO.Velocity * TimeStep);
-        physics.ValueRW.Force = 0;
+        var totalDisplacement = physics.ValueRO.Displacement + physics.ValueRO.Acceleration * (TimeStep * TimeStep);
+        physics.ValueRW.PrevPosition = physics.ValueRO.Position;
+        physics.ValueRW.Position += totalDisplacement;
+        physics.ValueRW.Acceleration = 0;
+        physics.ValueRW.PrevTimeStep = TimeStep;
+
+        localTransform.ValueRW.TranslateWorld(worldTransform, totalDisplacement);
     }
 }