Thanks jonc, for a patch that adds rendering of classic clouds.

First part of Mantis #964, the necessary clouds image will follow separately.

OpenSim/Client/MXP/ClientStack/MXPClientView.cs

@@ -909,6 +909,11 @@ namespace OpenSim.Client.MXP.ClientStack
             // Need to translate to MXP somehow
         }
 
+        public void SendCloudData(float[] cloudCover)
+        {
+            // Need to translate to MXP somehow
+        }
+
         public void MoveAgentIntoRegion(RegionInfo regInfo, Vector3 pos, Vector3 look)
         {
             //throw new System.NotImplementedException();

OpenSim/Framework/IClientAPI.cs

@@ -827,6 +827,7 @@ namespace OpenSim.Framework
         void SendLayerData(int px, int py, float[] map);
 
         void SendWindData(Vector2[] windSpeeds);
+        void SendCloudData(float[] cloudCover);
 
         void MoveAgentIntoRegion(RegionInfo regInfo, Vector3 pos, Vector3 look);
         void InformClientOfNeighbour(ulong neighbourHandle, IPEndPoint neighbourExternalEndPoint);

OpenSim/Region/ClientStack/LindenUDP/LLClientView.cs

@@ -1360,7 +1360,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
         }
 
         /// <summary>
-        ///  Send the region heightmap to the client
+        ///  Send the wind matrix to the client
         /// </summary>
         /// <param name="windSpeeds">16x16 array of wind speeds</param>
         public virtual void SendWindData(Vector2[] windSpeeds)
@@ -1369,13 +1369,21 @@ namespace OpenSim.Region.ClientStack.LindenUDP
         }
 
         /// <summary>
-        /// Send terrain layer information to the client.
+        ///  Send the cloud matrix to the client
+        /// </summary>
+        /// <param name="windSpeeds">16x16 array of cloud densities</param>
+        public virtual void SendCloudData(float[] cloudDensity)
+        {
+            ThreadPool.QueueUserWorkItem(new WaitCallback(DoSendCloudData), (object)cloudDensity);
+        }
+
+        /// <summary>
+        /// Send wind layer information to the client.
         /// </summary>
         /// <param name="o"></param>
         private void DoSendWindData(object o)
         {
             Vector2[] windSpeeds = (Vector2[])o;
-
             TerrainPatch[] patches = new TerrainPatch[2];
             patches[0] = new TerrainPatch();
             patches[0].Data = new float[16 * 16];
@@ -1393,10 +1401,33 @@ namespace OpenSim.Region.ClientStack.LindenUDP
 
             LayerDataPacket layerpack = TerrainCompressor.CreateLayerDataPacket(patches, TerrainPatch.LayerType.Wind);
             layerpack.Header.Zerocoded = true;
-
             OutPacket(layerpack, ThrottleOutPacketType.Wind);
         }
 
+        /// <summary>
+        /// Send cloud layer information to the client.
+        /// </summary>
+        /// <param name="o"></param>
+        private void DoSendCloudData(object o)
+        {
+            float[] cloudCover = (float[])o;
+            TerrainPatch[] patches = new TerrainPatch[1];
+            patches[0] = new TerrainPatch();
+            patches[0].Data = new float[16 * 16];
+
+            for (int y = 0; y < 16; y++)
+            {
+                for (int x = 0; x < 16; x++)
+                {
+                    patches[0].Data[y * 16 + x] = cloudCover[y * 16 + x];
+                }
+            }
+
+            LayerDataPacket layerpack = TerrainCompressor.CreateLayerDataPacket(patches, TerrainPatch.LayerType.Cloud);
+            layerpack.Header.Zerocoded = true;
+            OutPacket(layerpack, ThrottleOutPacketType.Cloud);
+        }
+
         /// <summary>
         /// Tell the client that the given neighbour region is ready to receive a child agent.
         /// </summary>

OpenSim/Region/CoreModules/World/Cloud/CloudModule.cs

@@ -0,0 +1,190 @@
+/*
+ * Copyright (c) Contributors, http://opensimulator.org/
+ * See CONTRIBUTORS.TXT for a full list of copyright holders.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of the OpenSim Project nor the
+ *       names of its contributors may be used to endorse or promote products
+ *       derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+using System;
+using System.Collections.Generic;
+using Nini.Config;
+using OpenMetaverse;
+using OpenSim.Framework;
+using OpenSim.Region.Framework.Interfaces;
+using OpenSim.Region.Framework.Scenes;
+
+namespace OpenSim.Region.CoreModules
+{
+    public class CloudModule : ICloudModule
+    {
+        private static readonly log4net.ILog m_log 
+            = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);
+
+        private Random m_rndnums = new Random(Environment.TickCount);
+        private Scene m_scene = null;
+        private bool m_ready = false;
+        private bool m_enabled = false;
+        private float m_cloudDensity = 1.0F;
+        private float[] cloudCover = new float[16 * 16];
+
+        private Dictionary<UUID, ulong> m_rootAgents = new Dictionary<UUID, ulong>();
+     
+        public void Initialise(Scene scene, IConfigSource config)
+        {
+            IConfig cloudConfig = config.Configs["Cloud"];
+
+            if (cloudConfig != null)
+            {
+                m_enabled = cloudConfig.GetBoolean("enabled", false);
+                m_cloudDensity = cloudConfig.GetFloat("density", 0.5F);
+            }
+
+            if (m_enabled)
+            {
+
+                m_scene = scene;
+
+                scene.EventManager.OnMakeChildAgent += MakeChildAgent;
+                scene.EventManager.OnAvatarEnteringNewParcel += AvatarEnteringParcel;
+                scene.EventManager.OnClientClosed += ClientLoggedOut;
+                scene.RegisterModuleInterface<ICloudModule>(this);
+
+                GenerateCloudCover();
+
+                m_ready = true;
+
+            }
+
+        }
+
+        public void PostInitialise()
+        {
+        }
+
+        public void Close()
+        {
+            if (m_enabled)
+            {
+                m_ready = false;
+                //  Remove our hooks
+                m_scene.EventManager.OnMakeChildAgent -= MakeChildAgent;
+                m_scene.EventManager.OnAvatarEnteringNewParcel -= AvatarEnteringParcel;
+                m_scene.EventManager.OnClientClosed -= ClientLoggedOut;
+            }
+        }
+
+        public string Name
+        {
+            get { return "CloudModule"; }
+        }
+
+        public bool IsSharedModule
+        {
+            get { return false; }
+        }
+
+
+        public float CloudCover(int x, int y, int z)
+        {
+            float cover = 0f;
+            x /= 16;
+            y /= 16;
+            if (x < 0) x = 0;
+            if (x > 15) x = 15;
+            if (y < 0) y = 0;
+            if (y > 15) y = 15;
+
+            if (cloudCover != null)
+            {
+                cover = cloudCover[y * 16 + x];
+            }
+
+            return cover;
+        }
+
+        public void CloudsToClient(IClientAPI client)
+        {
+            if (m_ready)
+            {
+                client.SendCloudData(cloudCover);
+            }
+        }
+
+       
+        /// <summary>
+        /// Calculate the cloud cover over the region.
+        /// </summary>
+        private void GenerateCloudCover()
+        {
+            for (int y = 0; y < 16; y++)
+            {
+                for (int x = 0; x < 16; x++)
+                {
+                    cloudCover[y * 16 + x] = (float)(m_rndnums.NextDouble()); // 0 to 1
+                    cloudCover[y * 16 + x] *= m_cloudDensity;
+                }
+            }
+        }
+
+        private void ClientLoggedOut(UUID AgentId)
+        {
+            lock (m_rootAgents)
+            {
+                if (m_rootAgents.ContainsKey(AgentId))
+                {
+                    m_rootAgents.Remove(AgentId);
+                }
+            }
+        }
+
+        private void AvatarEnteringParcel(ScenePresence avatar, int localLandID, UUID regionID)
+        {
+            lock (m_rootAgents)
+            {
+                if (m_rootAgents.ContainsKey(avatar.UUID))
+                {
+                    m_rootAgents[avatar.UUID] = avatar.RegionHandle;
+                }
+                else
+                {
+                    m_rootAgents.Add(avatar.UUID, avatar.RegionHandle);
+                    CloudsToClient(avatar.ControllingClient);
+                }
+            }
+        }
+
+        private void MakeChildAgent(ScenePresence avatar)
+        {
+            lock (m_rootAgents)
+            {
+                if (m_rootAgents.ContainsKey(avatar.UUID))
+                {
+                    if (m_rootAgents[avatar.UUID] == avatar.RegionHandle)
+                    {
+                        m_rootAgents.Remove(avatar.UUID);
+                    }
+                }
+            }
+        }
+    }
+}

OpenSim/Region/Examples/SimpleModule/MyNpcCharacter.cs

@@ -439,6 +439,8 @@ namespace OpenSim.Region.Examples.SimpleModule
 
         public virtual void SendWindData(Vector2[] windSpeeds) { }
 
+        public virtual void SendCloudData(float[] cloudCover) { }
+
         public virtual void MoveAgentIntoRegion(RegionInfo regInfo, Vector3 pos, Vector3 look)
         {
         }

OpenSim/Region/Framework/Interfaces/ICloudModule.cs

@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) Contributors, http://opensimulator.org/
+ * See CONTRIBUTORS.TXT for a full list of copyright holders.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of the OpenSim Project nor the
+ *       names of its contributors may be used to endorse or promote products
+ *       derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+
+namespace OpenSim.Region.Framework.Interfaces
+{
+    public interface ICloudModule : IRegionModule
+    {
+        /// <summary>
+        /// Retrieves the cloud density at the given region coordinates
+        /// </summary>
+        float CloudCover(int x, int y, int z);
+    }
+}

OpenSim/Region/OptionalModules/World/NPC/NPCAvatar.cs

@@ -528,6 +528,8 @@ namespace OpenSim.Region.OptionalModules.World.NPC
 
         public virtual void SendWindData(Vector2[] windSpeeds) { }
 
+        public virtual void SendCloudData(float[] cloudCover) { }
+
         public virtual void MoveAgentIntoRegion(RegionInfo regInfo, Vector3 pos, Vector3 look)
         {
         }

OpenSim/Region/ScriptEngine/Shared/Api/Implementation/LSL_Api.cs

@@ -1027,7 +1027,18 @@ namespace OpenSim.Region.ScriptEngine.Shared.Api
         public LSL_Float llCloud(LSL_Vector offset)
         {
             m_host.AddScriptLPS(1);
-            return 0;
+            float cloudCover = 0f;
+            ICloudModule module = World.RequestModuleInterface<ICloudModule>();
+            if (module != null)
+            {
+                Vector3 pos = m_host.GetWorldPosition();
+                int x = (int)(pos.X + offset.x);
+                int y = (int)(pos.Y + offset.y);
+
+                cloudCover = module.CloudCover(x, y, 0);
+
+            }
+            return cloudCover;
         }
 
         public LSL_Vector llWind(LSL_Vector offset)

OpenSim/Tests/Common/Mock/TestClient.cs

@@ -491,6 +491,8 @@ namespace OpenSim.Tests.Common.Mock
 
         public virtual void SendWindData(Vector2[] windSpeeds) { }
 
+        public virtual void SendCloudData(float[] cloudCover) { }
+
         public virtual void MoveAgentIntoRegion(RegionInfo regInfo, Vector3 pos, Vector3 look)
         {
         }

bin/OpenSim.ini.example

@@ -702,6 +702,14 @@
     ; Adjusts wind strength. 0.0 = no wind, 1.0 = normal wind.  Default is 1.0
     strength = 1.0
 	
+[Cloud]
+    ; Enable this to generate classic particle clouds above the sim.
+    ; default is disabled - turn it on here
+    enabled = true
+
+    ; Density of cloud cover 0.0 to 1.0
+    density = 0.5
+
 
 [Trees]
     ; Enable this to allow the tree module to manage your sim trees, including growing, reproducing and dying