Fixed to reset the simulation state properly.

Assets/Kvant/SprayMV/Shaders/Kernels.shader

@@ -45,12 +45,12 @@ Shader "Hidden/Kvant/SprayMV/Kernels"
     float3 _SpinParams;   // spin*2, speed-to-spin*2, randomness
     float2 _NoiseParams;  // freq, amp
     float3 _NoiseOffset;
-    float4 _Config;       // throttle, random seed, dT, time
+    float4 _Config;       // throttle, dT, time
 
     // Particle generator functions
     float4 NewParticlePosition(float2 uv)
     {
-        float t = _Config.w;
+        float t = _Config.z;
 
         // Random position
         float3 p = float3(UVRandom(uv, t), UVRandom(uv, t + 1), UVRandom(uv, t + 2));
@@ -130,7 +130,7 @@ Shader "Hidden/Kvant/SprayMV/Kernels"
         float3 v = tex2D(_VelocityBuffer, i.uv).xyz;
 
         // Decaying
-        float dt = _Config.z;
+        float dt = _Config.y;
         p.w -= lerp(_LifeParams.x, _LifeParams.y, UVRandom(i.uv, 12)) * dt;
 
         if (p.w > -0.5)
@@ -158,7 +158,7 @@ Shader "Hidden/Kvant/SprayMV/Kernels"
             v *= _Acceleration.w; // dt is pre-applied in script
 
             // Constant acceleration
-            float dt = _Config.z;
+            float dt = _Config.y;
             v += _Acceleration.xyz * dt;
 
             // Acceleration by turbulent noise
@@ -183,7 +183,7 @@ Shader "Hidden/Kvant/SprayMV/Kernels"
         float3 v = tex2D(_VelocityBuffer, i.uv).xyz;
 
         // Delta angle
-        float dt = _Config.z;
+        float dt = _Config.y;
         float theta = (_SpinParams.x + length(v) * _SpinParams.y) * dt;
 
         // Randomness

Assets/Kvant/SprayMV/SprayMV.cs

@@ -242,6 +242,7 @@ public void RequestReconfigurationFromEditor()
         RenderTexture _rotationBuffer2;
 
         // Variables for simulation
+        float _time;
         Vector3 _noiseOffset;
 
         // Custom properties applied to the mesh renderer.
@@ -282,8 +283,6 @@ void SetUpTemporaryObjects()
                 _material.hideFlags = HideFlags.HideAndDontSave;
             }
 
-            _material.SetFloat("_RandomSeed", _randomSeed);
-
             if (_positionBuffer1 == null) _positionBuffer1 = CreateSimulationBuffer();
             if (_positionBuffer2 == null) _positionBuffer2 = CreateSimulationBuffer();
             if (_velocityBuffer1 == null) _velocityBuffer1 = CreateSimulationBuffer();
@@ -307,6 +306,9 @@ void ReleaseTemporaryObjects()
         // Reset the simulation state.
         void ResetSimulationState()
         {
+            _time = 0;
+            _noiseOffset = Vector3.zero;
+
             UpdateSimulationParameters(0);
 
             Graphics.Blit(null, _positionBuffer2, _material, 0);
@@ -350,15 +352,15 @@ void UpdateSimulationParameters(float dt)
             m.SetVector("_NoiseParams", new Vector2(_noiseFrequency, _noiseAmplitude));
 
             // Move the noise field backward in the direction of the
-            // acceleration vector, or simply pull up when no acceleration.
-            if (_acceleration == Vector3.zero)
-                _noiseOffset += Vector3.up * _noiseMotion * dt;
-            else
-                _noiseOffset += _acceleration.normalized * _noiseMotion * dt;
-
+            // acceleration vector, or simply pull up if no acceleration is set.
+            var noiseDir = (_acceleration == Vector3.zero) ? Vector3.up : _acceleration.normalized;
+            _noiseOffset += noiseDir * _noiseMotion * dt;
             m.SetVector("_NoiseOffset", _noiseOffset);
 
-            m.SetVector("_Config", new Vector4(_throttle, _randomSeed, dt, Time.time));
+            _time += dt;
+            m.SetVector("_Config", new Vector3(_throttle, dt, _time));
+
+            m.SetFloat("_RandomSeed", _randomSeed);
         }
 
         // Invoke the simulation kernels.
@@ -451,24 +453,26 @@ void LateUpdate()
 
             if (_reconfigured)
             {
-                // - Initialize temporary objects at the first frame.
-                // - Re-initialize temporary objects on configuration changes.
+                // Initialize temporary objects at the first frame,
+                // and re-initialize them on configuration changes.
                 ReleaseTemporaryObjects();
                 SetUpTemporaryObjects();
-
-                // Reset the simulation state.
                 ResetSimulationState();
-
-                // Editor: do warmup before the first frame.
-                if (!Application.isPlaying)
-                    for (var i = 0; i < 24; i++) 
-                        InvokeSimulationKernels(1.0f / 24);
-
                 _reconfigured = false;
             }
 
-            // Advance simulation time.
-            if (Application.isPlaying) InvokeSimulationKernels(Time.deltaTime);
+            if (Application.isPlaying)
+            {
+                // Advance simulation time.
+                InvokeSimulationKernels(Time.deltaTime);
+            }
+            else
+            {
+                // Editor: Simulate 1 second from the initial state.
+                ResetSimulationState();
+                for (var i = 0; i < 24; i++) 
+                    InvokeSimulationKernels(1.0f / 24);
+            }
 
             // Update external components (mesh filter and renderer).
             UpdateMeshFilter();

ProjectSettings/EditorBuildSettings.asset

@@ -6,4 +6,4 @@ EditorBuildSettings:
   serializedVersion: 2
   m_Scenes:
   - enabled: 1
-    path: Assets/Test.unity
+    path: Assets/Test/Test.unity