Fog of War

This is an old post migrated from my previous blog (10/01/2012). I apologize if any info seems outdated.

Many RTS games have a fog of war system. I want to share a portion of code that I used to accomplish this in Unity for the MOBA Project. I used a fairly basic approach and there are certainly more elegant ways to accomplish this. I will be showing how to calculated the pixel of intersection of a plane that is the fog of war.

First, I created the fog by placing a plane over the entire level. The plane has a dark translucent material in order to look something like fog. Then the idea is that; when a player or unit is between the fog and the camera, an area in the texture would be alphaed    out exposing that portion of the map.

To figure out the point in the texture between the unit/player and the camera I used a raytrace. Be sure to set up a mask, that way you only are casting against the plane that is the fog of war.

LayerMask mask = LayerMask.NameToLayer("FogOfWar");
RaycastHit hit;
mask=~mask;
if(Physics.Raycast(ray, out hit, dist, mask.value))
{//calc intersect pixel here}

Pixel data is stored as a 1D array. Only the texture coordinate information from the Raycast is available. What is important to is the actual pixel where the ray intersects with the fog of war plane. The code below is how to calculate that pixel from texture coordinate information.

if(hit.collider == null)
return;
Texture2D tex = hit.collider.renderer.material.mainTexture as Texture2D;
if(tex == null)
return;
int row = (int)(tex.width * hit.textureCoord.x); //row
int column = (int)(tex.height * hit.textureCoord.y);//col
 
//calc pixel in via text coords
int pixIn = (column * tex.width) - (tex.width - row);
//now alpha this pixel and an area around it
}

In the code above, pixIn and an area around it will be alphaed exposing the map below the fog.

From there it us up to you how to alpha the texture. I’m currently doing this procedurally with a buffer. I hope this helps someone getting started on a system like this. I’ll post some pics below of my first iteration. Please post any questions in the comments.

C to Unity Callback

This is an old post migrated from my previous blog (09/01/2012). I apologize if any info seems outdated.

This post will be sort of specific to those of you who may be writing/integrating an unmanaged API into Unity.

You might find yourself in a situation where some event or request may take place in your API and you need to notify Unity of this. One option is polling and that might be fine…but sometimes that can be sloppy, somewhat inefficient, or maybe just a poor way of solving your problem. Another option using callback.

In my simple example, the API is going to receive a network message then via function pointers we will call a function in Unity passing in the message . I’m actually going to be yanking some of this code directly out of my GummyNet API.

The first thing you want to do is define the type of function used for the callback. Notice that I’m passing the info, a string, as a parameter.

typedef void (__stdcall *OnGummyMessage_Callback)(char*);

You then need to set up a handler. We will be assigning our Unity function to this.

static OnGummyMessage_Callback OnGummyMessage;

You will also need a C function that Unity calls to assign the function pointer. It might look something like this:

EXPORT_API void SetCallback_OnGummyMessage(OnGummyMessage_Callback funcPtr)
{
 OnGummyMessage = funcPtr;
}

Now the Unity Side. Our objective here is to write the import for our set function. Declare delegate object (basically a  function pointer) that defines our method type instantiate it, and pass it to via our set function.

//Declaring the delegate
public delegate void OnGummyMessage_Callback(string msg);
 
//Instantiate the delegate and pass it
void RegisterCallbacks()
{
 OnGummyMessage_Callback onMsgCB = new OnGummyMessage_Callback(this.OnGummyMessage);
 SetCallback_OnGummyMessage(onMsgCB);
}
 
public void OnGummyMessage(string msg)
{
 print("receveied msg: " +msg);
}
 
//Importing the set function
[DllImport ("gummy_server")]
private static extern void SetCallback_OnGummyMessage(OnGummyMessage_Callback funcPtr);

Now when we Invoke our handler (shown below) in the API the C# OnGummyMessage should get called 

...
//pass the message
OnGummyMessage((char*)data );
...

Procedural Skinned Mesh In Unity

This is an old post migrated from my previous blog (08/31/2012). I apologize if any info seems outdated.

In a current project I am faced with the challenge of needing to make tons of characters available to players. All the characters are of the same rig but are very complex with several systems such as: leg animator, gestures, animation groups, different sensory systems, ‘anchor transforms’ for weapons/etc…tons of stuff. So making a change to the smallest thing can be a real pain in the pipeline if there is a prefab for each character model variation.

So the ideal solution is have one character prefab and load in different models…easy right? Well it’s not so straight forward with systems that have to be baked on the fbx object and sometimes abstracting those systems to a higher level game object can be nearly impossible.

There are a couple ways to tackle this one. But I’m going to post some code particular to a procedural method of creating a character. It could use some optimization but it gets the point across 

When you import an fbx with bones it should have a SkinnedMeshRenderer component on it. As far as coding goes there is a “sharedmesh” member — typeof(Mesh). This is the mesh with all the info that constructs it. The members of mesh we are concerned about are: vertices, uv, triangles, boneWeights, and bindposes. Unity actually has an example constructing an object from scratch that will help shed some light on what these are – EXAMPLE.

Here is my version of this process with a character. Please be aware at the end I use the bones from the source SkinnedMeshRenderer. You’ll want to copy and instantiate new bones and bind to those for a completely separate character…I just skipped that for my demo purposes because drawing the mesh on those bones was okay for me 

Here is the code:

using System.Collections;

using System.Collections.Generic;

using System.Linq;

//add this script to a gameobject...then be sure to set the source in inspector

public class Test : MonoBehaviour {

    //source models skinnedMeshRenderer

    public SkinnedMeshRenderer s;

    void Start()

        {

        //gameObject.AddComponent<animation>(); //using sources animation to test.

             gameObject.AddComponent<skinnedmeshrenderer>();

        SkinnedMeshRenderer renderer = GetComponent<skinnedmeshrenderer>();

              Mesh mesh = new Mesh();

        ////////////VERTS

        List<vector3> verts = new List<vector3>();

        for(int i = 0; i &lt; s.sharedMesh.vertices.Length; i++)

        {

            Vector3 v = s.sharedMesh.vertices[i];

            verts.Add(new Vector3(v.x, v.y, v.z));

        }

             mesh.vertices = verts.ToArray();

        ////////////UVS

        List<vector2> uvs = new List<vector2>();

        for(int i = 0; i &lt; s.sharedMesh.uv.Length; i++)

        {

            Vector2 uv = s.sharedMesh.uv[i];

            uvs.Add(new Vector2(uv.x, uv.y));

        }

         mesh.uv = uvs.ToArray();

        ////////////TRIS

        List<int> tris = new List<int>();

        for(int i = 0; i &lt; s.sharedMesh.triangles.Length; i++)

        {

            int t = s.sharedMesh.triangles[i];

            tris.Add(t);

        }

        mesh.triangles = tris.ToArray();

        mesh.RecalculateNormals();

         renderer.material = new Material(Shader.Find(" Diffuse"));

        //BONE WEIGHTS

        List<boneweight> weights = new List<boneweight>();

        for(int i = 0; i &lt; s.sharedMesh.boneWeights.Length; i++)

        {

            BoneWeight b = new BoneWeight();

            b.boneIndex0 = s.sharedMesh.boneWeights[i].boneIndex0;

            b.weight0 = s.sharedMesh.boneWeights[i].weight0;

            b.boneIndex1 = s.sharedMesh.boneWeights[i].boneIndex1;

            b.weight1 = s.sharedMesh.boneWeights[i].weight1;

            b.boneIndex2 = s.sharedMesh.boneWeights[i].boneIndex2;

            b.weight2 = s.sharedMesh.boneWeights[i].weight2;

            b.boneIndex3 = s.sharedMesh.boneWeights[i].boneIndex3;

            b.weight3 = s.sharedMesh.boneWeights[i].weight3;

            weights.Add(b);

        }

        mesh.boneWeights = weights.ToArray();

             //BINDPOSES

        List<matrix4x4> bindPoses = new List<matrix4x4>();

        for(int i = 0; i &lt; s.sharedMesh.bindposes.Length; i++)

        {

            Matrix4x4 m = new Matrix4x4();

            Matrix4x4 mm = s.sharedMesh.bindposes[i];

            m.m00 = mm.m00;     m.m01 = mm.m01;     m.m02 = mm.m02;     m.m03 = mm.m03;

            m.m10 = mm.m10;     m.m11 = mm.m11;     m.m12 = mm.m12;     m.m13 = mm.m13; 

            m.m20 = mm.m20;     m.m21 = mm.m21;     m.m22 = mm.m22;     m.m23 = mm.m23;     

            m.m30 = mm.m30;     m.m31 = mm.m31;     m.m32 = mm.m32;     m.m33 = mm.m33; 

            bindPoses.Add(m);

        }

        mesh.bindposes = bindPoses.ToArray();

              //using sources bones...could make a copy here instead.

             renderer.bones = s.bones;

             renderer.sharedMesh = mesh;

        //play an animation here to test

        transform.parent.animation.Play("Walk");

    }

}