Small improvements and refactorings.

Assets/DFVolume/VolumeData.cs

@@ -29,7 +29,7 @@ public void Initialize(VolumeSampler sampler)
             _texture.name = "Distance Field Texture";
             _texture.filterMode = FilterMode.Bilinear;
             _texture.wrapMode = TextureWrapMode.Clamp;
-            _texture.SetPixels(sampler.GenerateBitmap2());
+            _texture.SetPixels(sampler.GenerateBitmap());
             _texture.Apply();
         }
 

Assets/DFVolume/VolumeSampler.cs

@@ -34,7 +34,7 @@ void OnDrawGizmos()
             Gizmos.DrawWireCube(Vector3.zero, Vector3.one * _extent * 2);
         }
 
-        public Color[] GenerateBitmap2()
+        public Color[] GenerateBitmap()
         {
             // Generate a distance field.
             var df = new float[_resolution * _resolution * _resolution];

Assets/Swarm/CrawlerSwarm.cs

@@ -20,15 +20,15 @@ public int instanceCount {
 
         #endregion
 
-        #region Renderer settings
+        #region Render settings
 
         [SerializeField] TubeTemplate _template;
 
         public TubeTemplate template {
             get { return _template; }
         }
 
-        [SerializeField, Range(0, 0.1f)] float _radius = 0.01f;
+        [SerializeField] float _radius = 0.005f;
 
         public float radius {
             get { return _radius; }
@@ -52,7 +52,7 @@ public CosineGradient gradient {
 
         #region Dynamics settings
 
-        [SerializeField] float _speed = 0.5f;
+        [SerializeField] float _speed = 0.75f;
 
         public float speed {
             get { return _speed; }
@@ -65,20 +65,20 @@ public VolumeData volume {
             get { return _volume; }
         }
 
-        [SerializeField] float _constraint = 6;
-
-        public float constraint {
-            get { return _constraint; }
-            set { _constraint = value; }
-        }
-
-        [SerializeField] float _noiseFrequency = 2;
+        [SerializeField] float _noiseFrequency = 4;
 
         public float noiseFrequency {
             get { return _noiseFrequency; }
             set { _noiseFrequency = value; }
         }
 
+        [SerializeField] float _noiseSpread = 0.5f;
+
+        public float noiseSpread {
+            get { return _noiseSpread; }
+            set { _noiseSpread = value; }
+        }
+
         [SerializeField] float _noiseMotion = 0.1f;
 
         public float noiseMotion {
@@ -116,6 +116,11 @@ public float noiseMotion {
 
         #region MonoBehaviour functions
 
+        void OnValidate()
+        {
+            _instanceCount = Mathf.Max(kThreadCount, _instanceCount);
+        }
+
         void Start()
         {
             // Initialize the indirect draw args buffer.
@@ -135,12 +140,12 @@ void Start()
 
             // Initialize the position buffer.
             var kernel = _compute.FindKernel("CrawlerInit");
-            _compute.SetInt("InstanceCount", InstanceCount);
-            _compute.SetInt("HistoryLength", HistoryLength);
             _compute.SetBuffer(kernel, "PositionBuffer", _positionBuffer);
             _compute.SetBuffer(kernel, "TangentBuffer", _tangentBuffer);
             _compute.SetBuffer(kernel, "NormalBuffer", _normalBuffer);
             _compute.SetTexture(kernel, "DFVolume", _volume.texture);
+            _compute.SetInt("InstanceCount", InstanceCount);
+            _compute.SetInt("HistoryLength", HistoryLength);
             _compute.Dispatch(kernel, ThreadGroupCount, 1, 1);
 
             // Initialize the update kernel.
@@ -155,11 +160,11 @@ void Start()
             _compute.SetBuffer(kernel, "NormalBuffer", _normalBuffer);
 
             // Initialize the mateiral.
-            _material.SetInt("_InstanceCount", InstanceCount);
-            _material.SetInt("_HistoryLength", HistoryLength);
             _material.SetBuffer("_PositionBuffer", _positionBuffer);
             _material.SetBuffer("_TangentBuffer", _tangentBuffer);
             _material.SetBuffer("_NormalBuffer", _normalBuffer);
+            _material.SetInt("_InstanceCount", InstanceCount);
+            _material.SetInt("_HistoryLength", HistoryLength);
 
             // This property block is used only for avoiding an instancing bug.
             _props = new MaterialPropertyBlock();
@@ -176,31 +181,33 @@ void OnDestroy()
 
         void Update()
         {
-            var time = Time.time;
-            var delta = Mathf.Min(Time.deltaTime, 1.0f / 15);
-
-            // Index offset on the position buffer.
-            var offset0 = InstanceCount * ( _frameCount      % HistoryLength);
-            var offset1 = InstanceCount * ((_frameCount + 1) % HistoryLength);
-            var offset2 = InstanceCount * ((_frameCount + 2) % HistoryLength);
-
-            // Parameters for the compute kernels.
-            _compute.SetInt("IndexOffset0", offset0);
-            _compute.SetInt("IndexOffset1", offset1);
-            _compute.SetInt("IndexOffset2", offset2);
-            _compute.SetFloat("Time", time);
-            _compute.SetFloat("Speed", _speed * delta);
-            _compute.SetFloat("Constraint", _constraint);
-            _compute.SetFloat("NoiseFrequency", _noiseFrequency);
-            _compute.SetFloat("NoiseOffset", time * _noiseMotion);
-
-            // Update the position buffer.
-            var kernel = _compute.FindKernel("CrawlerUpdate");
-            _compute.Dispatch(kernel, ThreadGroupCount, 1, 1);
-
-            // Reconstruct tangent/normal vectors.
-            kernel = _compute.FindKernel("CrawlerReconstruct");
-            _compute.Dispatch(kernel, ThreadGroupCount, 1, 1);
+            var delta = Mathf.Min(Time.deltaTime, 1.0f / 30);
+
+            if (delta > 0)
+            {
+                // Index offset on the position buffer.
+                var offset0 = InstanceCount * ( _frameCount      % HistoryLength);
+                var offset1 = InstanceCount * ((_frameCount + 1) % HistoryLength);
+                var offset2 = InstanceCount * ((_frameCount + 2) % HistoryLength);
+
+                // Update the parameters for the compute kernels.
+                _compute.SetInt("IndexOffset0", offset0);
+                _compute.SetInt("IndexOffset1", offset1);
+                _compute.SetInt("IndexOffset2", offset2);
+                _compute.SetFloat("Speed", _speed * delta);
+                _compute.SetFloat("NoiseFrequency", _noiseFrequency);
+                _compute.SetFloat("NoiseSpread", _noiseSpread / InstanceCount);
+                _compute.SetFloat("NoiseOffset", Time.time * _noiseMotion);
+                _compute.SetFloat("Time", Time.time);
+
+                // Update the position buffer.
+                var kernel = _compute.FindKernel("CrawlerUpdate");
+                _compute.Dispatch(kernel, ThreadGroupCount, 1, 1);
+
+                // Reconstruct tangent/normal vectors.
+                kernel = _compute.FindKernel("CrawlerReconstruct");
+                _compute.Dispatch(kernel, ThreadGroupCount, 1, 1);
+            }
 
             // Draw the meshes with instancing.
             _material.SetInt("_IndexOffset", _frameCount + 3);
@@ -214,7 +221,7 @@ void Update()
 
             Graphics.DrawMeshInstancedIndirect(
                 _template.mesh, 0, _material,
-                new Bounds(Vector3.zero, Vector3.one * 10000),
+                new Bounds(Vector3.zero, Vector3.one * 1.5f),
                 _drawArgsBuffer, 0, _props
             );
 

Assets/Swarm/Editor/CrawlerSwarmEditor.cs

@@ -17,10 +17,10 @@ public class CrawlerSwarmEditor : Editor
         SerializedProperty _material;
         SerializedProperty _gradient;
 
-        SerializedProperty _speed;
         SerializedProperty _volume;
-        SerializedProperty _constraint;
+        SerializedProperty _speed;
         SerializedProperty _noiseFrequency;
+        SerializedProperty _noiseSpread;
         SerializedProperty _noiseMotion;
 
         void OnEnable()
@@ -32,10 +32,10 @@ void OnEnable()
             _material = serializedObject.FindProperty("_material");
             _gradient = serializedObject.FindProperty("_gradient");
 
-            _speed = serializedObject.FindProperty("_speed");
             _volume = serializedObject.FindProperty("_volume");
-            _constraint = serializedObject.FindProperty("_constraint");
+            _speed = serializedObject.FindProperty("_speed");
             _noiseFrequency = serializedObject.FindProperty("_noiseFrequency");
+            _noiseSpread = serializedObject.FindProperty("_noiseSpread");
             _noiseMotion = serializedObject.FindProperty("_noiseMotion");
         }
 
@@ -56,8 +56,8 @@ public override void OnInspectorGUI()
 
             EditorGUILayout.PropertyField(_speed);
             EditorGUILayout.PropertyField(_volume);
-            EditorGUILayout.PropertyField(_constraint);
             EditorGUILayout.PropertyField(_noiseFrequency);
+            EditorGUILayout.PropertyField(_noiseSpread);
             EditorGUILayout.PropertyField(_noiseMotion);
 
             serializedObject.ApplyModifiedProperties();

Assets/Swarm/Editor/Default Gradient.asset

@@ -0,0 +1,16 @@
+%YAML 1.1
+%TAG !u! tag:unity3d.com,2011:
+--- !u!114 &11400000
+MonoBehaviour:
+  m_ObjectHideFlags: 0
+  m_PrefabParentObject: {fileID: 0}
+  m_PrefabInternal: {fileID: 0}
+  m_GameObject: {fileID: 0}
+  m_Enabled: 1
+  m_EditorHideFlags: 0
+  m_Script: {fileID: 11500000, guid: 54276434dda9c694e85abaf98cdd981d, type: 3}
+  m_Name: Default Gradient
+  m_EditorClassIdentifier: 
+  _redCoeffs: {x: 0.5, y: 0.5, z: 1, w: 0}
+  _greenCoeffs: {x: 0.5, y: 0.5, z: 1, w: 0.333}
+  _blueCoeffs: {x: 0.5, y: 0.5, z: 1, w: 0.665}

Assets/Swarm/Shader/Crawler.compute

@@ -9,11 +9,12 @@
 #include "SimplexNoise3D.cginc"
 
 RWStructuredBuffer<float4> PositionBuffer;
-StructuredBuffer<float4> PositionBufferRO;
-
 RWStructuredBuffer<float4> TangentBuffer;
 RWStructuredBuffer<float4> NormalBuffer;
 
+StructuredBuffer<float4> PositionBufferRO;
+
+// Distance field volume (gradient.xyz, distance)
 Texture3D<float4> DFVolume;
 SamplerState samplerDFVolume;
 
@@ -23,55 +24,48 @@ CBUFFER_START(Params)
     uint IndexOffset0;
     uint IndexOffset1;
     uint IndexOffset2;
-    float Time;
     float Speed;
-    float Constraint;
     float NoiseFrequency;
+    float NoiseSpread;
     float NoiseOffset;
+    float Time;
 CBUFFER_END
 
-float UVRandom(float u, float v)
+float Random(float u, float v)
 {
     float f = dot(float2(12.9898, 78.233), float2(u, v));
     return frac(43758.5453 * sin(f));
 }
 
+// Nearly uniformly distributed random vector in the unit sphere.
+float3 RandomPoint(float id)
+{
+    float u = Random(id * 0.01334, 0.3728) * UNITY_PI * 2;
+    float z = Random(0.8372, id * 0.01197) * 2 - 1;
+    float l = Random(4.438, id * 0.01938 - 4.378);
+    return float3(float2(cos(u), sin(u)) * sqrt(1 - z * z), z) * sqrt(l);
+}
+
 float4 SampleVolume(float3 p)
 {
-    return DFVolume.SampleLevel(samplerDFVolume, p * 0.5 + 0.5, 0);
+    return DFVolume.SampleLevel(samplerDFVolume, p + 0.5, 0);
 }
 
 [numthreads(64, 1, 1)]
 void CrawlerInit(uint id : SV_DispatchThreadID)
 {
-    // Get a random point.
-    float x = UVRandom(id * 0.01334, 0.3728);
-    float y = UVRandom(0.8372, id * 0.01197);
-    float z = UVRandom(4.438, id * 0.01938 - 4.378);
-    float4 p = float4(x, y, z, 0) * 0.5 - 0.25;
-    float d = SampleVolume(p);
-
-    // Swizzle and compre, choose one with closer distance.
-    {
-        float4 p2 = p.yzxw;
-        float d2 = SampleVolume(p2);
-        p = d2 < d ? p2 : p;
-        d = min(d, d2);
-    }
-
-    // Swizzle again.
-    {
-        float4 p2 = p.zxyw;
-        float d2 = SampleVolume(p2);
-        p = d2 < d ? p2 : p;
-        d = min(d, d2);
-    }
+    // Pick two random points and use closer one.
+    float3 p1 = RandomPoint(id + 0.0) / 3;
+    float3 p2 = RandomPoint(id + 0.5) / 3;
+    float d1 = SampleVolume(p1).w;
+    float d2 = SampleVolume(p2).w;
+    float3 p = d1 < d2 ? p1 : p2;
 
     // Fill the position/tangent/normal buffer.
     for (uint i = 0; i < HistoryLength; i++)
     {
         uint offs = id + i * InstanceCount;
-        PositionBuffer[offs] = p;
+        PositionBuffer[offs] = float4(p, 0);
         TangentBuffer[offs] = float4(0, 0, 1, 0);
         NormalBuffer[offs] = float4(1, 0, 0, 0);
     }
@@ -83,17 +77,18 @@ void CrawlerUpdate(uint id : SV_DispatchThreadID)
     // Retrieve the previous position.
     float3 p = PositionBuffer[IndexOffset1 + id].xyz;
 
-    // Distance field (gradient.x, y, z, distance).
-    float4 df = SampleVolume(p) * Constraint;
+    // Sample the point in the distance field.
+    float4 df = SampleVolume(p);
 
-    // Two independent noise fields (not completely independent though).
-    float4 sn1 = snoise(10.33 + p.xyz * NoiseFrequency + NoiseOffset);
-    float4 sn2 = snoise(32.38 - p.yzx * NoiseFrequency + NoiseOffset);
+    // Two independent noise fields.
+    float3 offs = float3(0, NoiseOffset, id * NoiseSpread);
+    float4 sn1 = snoise(98.4898 + p * NoiseFrequency + offs);
+    float4 sn2 = snoise( 1.2278 - p * NoiseFrequency + offs);
 
-    // Apply the boundary condition to the first noise field.
+    // Apply the boundary condition (distance field) to the first noise field.
     sn1.xyz = -sn1.xyz * df.w + df.xyz * sn1.w;
 
-    // Apply the divergence free noise field to the position.
+    // Construct the divergence-free noise field and apply it to the point.
     p += cross(sn1.xyz, sn2.xyz) * Speed;
 
     // Update the buffer.