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Assets/Obi/Scripts/Common/Backends/Burst/Solver/PredictPositionsJob.cs

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+#if (OBI_BURST && OBI_MATHEMATICS && OBI_COLLECTIONS)
+using UnityEngine;
+using Unity.Jobs;
+using Unity.Collections;
+using Unity.Mathematics;
+using Unity.Burst;
+using System;
+using System.Collections;
+
+namespace Obi
+{
+    [BurstCompile]
+    struct PredictPositionsJob : IJobParallelFor
+    {
+        [ReadOnly] public NativeArray<int> activeParticles;
+        [ReadOnly] public NativeArray<int> phases;
+        [ReadOnly] public NativeArray<float4> buoyancies;
+
+        // linear/position properties:
+        [ReadOnly] public NativeArray<float4> externalForces;
+        [ReadOnly] public NativeArray<float> inverseMasses;
+        [NativeDisableParallelForRestriction] public NativeArray<float4> previousPositions;
+        [NativeDisableParallelForRestriction] public NativeArray<float4> positions;
+        [NativeDisableParallelForRestriction] public NativeArray<float4> velocities;
+
+        // angular/orientation properties:
+        [ReadOnly] public NativeArray<float4> externalTorques;
+        [ReadOnly] public NativeArray<float> inverseRotationalMasses;
+        [NativeDisableParallelForRestriction] public NativeArray<quaternion> previousOrientations;
+        [NativeDisableParallelForRestriction] public NativeArray<quaternion> orientations;
+        [NativeDisableParallelForRestriction] public NativeArray<float4> angularVelocities;
+
+        [ReadOnly] public float4 gravity;
+        [ReadOnly] public float deltaTime;
+        [ReadOnly] public bool is2D;
+
+        public void Execute(int index)
+        {
+            int i = activeParticles[index];
+
+            // the previous position/orientation is the current position/orientation at the start of the step.
+            previousPositions[i] = positions[i];
+            previousOrientations[i] = orientations[i];
+
+            if (inverseMasses[i] > 0)
+            {
+                float4 effectiveGravity = gravity;
+
+                // Adjust gravity for buoyant fluid particles:
+                if ((phases[i] & (int)ObiUtils.ParticleFlags.Fluid) != 0)
+                    effectiveGravity *= -buoyancies[i].z;
+
+                // apply external forces and gravity:
+                float4 vel = velocities[i] + (inverseMasses[i] * externalForces[i] + effectiveGravity) * deltaTime; 
+
+                // project velocity to 2D plane if needed:
+                if (is2D)
+                    vel[3] = 0;
+
+                velocities[i] = vel;
+            }
+
+            if (inverseRotationalMasses[i] > 0)
+            {
+                // apply external torques (simplification: we don't use full inertia tensor here)
+                float3 angularVel = angularVelocities[i].xyz + inverseRotationalMasses[i] * externalTorques[i].xyz * deltaTime;
+
+                // project angular velocity to 2D plane normal if needed:
+                if (is2D)
+                    angularVel = angularVel.project(new float3(0, 0, 1));
+
+                angularVelocities[i] = new float4(angularVel, angularVelocities[i].w);
+            }
+
+            // integrate velocities:
+            positions[i]    = BurstIntegration.IntegrateLinear(positions[i], velocities[i], deltaTime);
+            orientations[i] = BurstIntegration.IntegrateAngular(orientations[i], angularVelocities[i], deltaTime);
+
+        }
+    }
+}
+#endif