Create a mesh and color cubes


i try to make a chunksystem for my game, to place, remove and color cubes.

But my problem is that i can't color each side from a normal cube. I tried to make a mesh but i don't find out how to color spezefic areas.

Sorry for my bad english, i'm german^^

So i try that the player can place a cube on a 16*16 chunk. When the cube is placed the player should be able to color each side. like the front red, the back green etc.

I tried to make a cube out of planes, but that a way to much objects and couses into lags.

Maybe u have an idea? Please i try it now for over 3 days^^

My code for now: (I Already have a cube place system etc. This is a new try)

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 public class World_Chunks : MonoBehaviour 
     public List<MP_Chunk> thisChunk = new List<MP_Chunk>();
     void Start()
     IEnumerator FloorkRender()
         Mesh          mesh      = GetComponent<MeshFilter>().mesh;
         List<Vector3> vertices  = new List<Vector3>();
         List<Vector2> uvs       = new List<Vector2>();
         List<int>     triangles = new List<int>();
         List<Color>   colors   = new List<Color>();
         int           vertexIndex;
         vertexIndex = 0;
         for (int x = 0; x < World_ChunkLoader.instance.chunk_X_Width; x++)
             for (int z = 0; z < World_ChunkLoader.instance.chunk_Z_Width; z++)
                 MP_Chunk tempchunk = new MP_Chunk();
                 tempchunk.x        = x;
                 tempchunk.y        = 0;
                 tempchunk.z        = z;
                 tempchunk.isLoaded = false;
                 tempchunk.Render_Top    = true;
                 tempchunk.Render_Bottom = false;
                 tempchunk.Render_Left   = false;
                 tempchunk.Render_Right  = false;
                 tempchunk.Render_Back   = false;
                 tempchunk.Render_Front  = false;
                 thisChunk.Add (tempchunk);
                 vertices.Add(new Vector3(x, 0 + 1, z));
                 vertices.Add(new Vector3(x, 0 + 1, z+1));
                 vertices.Add(new Vector3(x+1, 0 + 1, z+1));
                 vertices.Add(new Vector3(x+1, 0 + 1, z));
                 colors.Add (new Color(Random.Range (1,254), Random.Range (1,254), Random.Range (1,254)));
                 colors.Add (new Color(Random.Range (1,254), Random.Range (1,254), Random.Range (1,254)));
                 colors.Add (new Color(Random.Range (1,254), Random.Range (1,254), Random.Range (1,254)));
                 colors.Add (new Color(Random.Range (1,254), Random.Range (1,254), Random.Range (1,254)));
                 // first triangle for the block top
                 // second triangle for the block top
                 // add UV
                 uvs.Add(new Vector2(0, 0));
                 uvs.Add(new Vector2(0, 1));
                 uvs.Add(new Vector2(1, 1));
                 uvs.Add(new Vector2(1, 0));
                 vertexIndex += 4;
         // Build the Mesh:
         mesh.vertices = vertices.ToArray();
         mesh.triangles = triangles.ToArray();
         mesh.colors = colors.ToArray ();
         mesh.uv = uvs.ToArray();
         // update mesh collider
         GetComponent<MeshCollider>().sharedMesh = null;
         GetComponent<MeshCollider>().sharedMesh = mesh;
         yield return null;
     void Update()
         if(Input.GetMouseButtonDown (0))
 public class MP_Chunk
     public int       x;
     public int       y;
     public int       z;
     public bool      isLoaded;
     public Transform ChunkObj;
     public bool      Render_Top;
     public bool      Render_Bottom;
     public bool      Render_Left;
     public bool      Render_Right;
     public bool      Render_Front;
     public bool      Render_Back;
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asked Feb 01, 2013 at 02:18 AM

Nelia Xurina gravatar image

Nelia Xurina
3 9 8 9

You should build the cube in an external editor and assign an independent material per face. Then, when you import it into unity, you can index the material slots and change the color at will. Good luck :)

Feb 01, 2013 at 02:31 AM youngapprentice

It would be better to use Color32 instead of Color; then you can use 0 to 255, and it's 4X less expensive for RAM usage and is faster. Naturally you'd use Mesh.colors32.

Feb 01, 2013 at 02:56 AM Eric5h5

A couple more ideas. If you build each face with its own vertices, the you can change the uv coordinates for each face depending on what color you want it to be. I've not played with vertex color, but I believe you could reset the vertex colors for a face as well. RaycastHit gives back a triangle index, so you can build a map between each triangle and its vertices so when you get a click on a triangle you know which uv coordinates to change or which vertices to assign new colors to.

Feb 01, 2013 at 07:36 AM robertbu

I don't understand ur ideas... A new cube...Then i have the Problem that i have 16*16 cubes in 256 Chunks...that are 16*16*256 cubes. That give a huge lag is think. Colors32 doesnt work too. And how can i build each face with own vertices? And how to detect it

Feb 01, 2013 at 02:31 PM Nelia Xurina
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1 answer: sort voted first

The basic idea is to build each face with its own vertices. This increases the vertex count, but not the triangle count. Each face has it own set of vertices, then you can color the face by either by using a Vertex Colored shader and changing the vertex colors, or by using a texture atlas and changing the UV coordinates to a different point in the atlas.

There are three scripts below. The first is a very simple vertex shader, the second creates a cube mesh and processes the hit on a triangle in that mesh. The third processes the mouse click and passed the triangle index. If you setup all three correctly, you will be able to click on a cube face to change it to random color.

This is the simplest vertex color shader I know. If you Google "Unity3d Vertex Colored Shader" you will find others with more features.

 Shader "Custom/Vertex Colored" {
 Properties {
     SubShader {
             Pass {
                     ColorMaterial AmbientAndDiffuse

The following code builds a cube. The mesh does not have to be a cube to work. The more important ingredient is that each face you want to color has its own set of vertices. Attach the script to an empty game object that has these three components: a) MeshCollider b) Renderer, c) MeshFilter.

 public class VertixColorPlay : MonoBehaviour {
     private Mesh mesh;
     void Start () {
         MeshFilter mf = GetComponent<MeshFilter>();
         if (mf == null) return;
         mesh = MakeCube(2.0f);
         mf.mesh = mesh;
         MeshCollider mc = GetComponent<MeshCollider>();
         if (mc != null)
             mc.sharedMesh = mesh;
     public void ChangeColor(int iTriangle)
         Color colorT = new Color(Random.Range (0.0f, 1.0f), Random.Range (0.0f, 1.0f), Random.Range (0.0f, 1.0f), 1.0f);
         Color[] colors = mesh.colors;
         int iStart = mesh.triangles[iTriangle*3];
         for (int i = iStart; i < iStart+4; i++)
             colors[i] = colorT;
         mesh.colors = colors;
     Mesh MakeCube(float fSize)
         float fHS = fSize / 2.0f;
         Mesh mesh = new Mesh();    
         mesh.vertices = new Vector3[] {
             new Vector3(-fHS,  fHS, -fHS), new Vector3( fHS,  fHS, -fHS), new Vector3( fHS, -fHS, -fHS), new Vector3(-fHS, -fHS, -fHS),  // Front
             new Vector3(-fHS,  fHS,  fHS), new Vector3( fHS,  fHS,  fHS), new Vector3( fHS,  fHS, -fHS), new Vector3(-fHS,  fHS, -fHS),  // Top
             new Vector3(-fHS, -fHS,  fHS), new Vector3( fHS, -fHS,  fHS), new Vector3( fHS,  fHS,  fHS), new Vector3(-fHS,  fHS,  fHS),  // Back
             new Vector3(-fHS, -fHS, -fHS), new Vector3( fHS, -fHS, -fHS), new Vector3( fHS, -fHS,  fHS), new Vector3(-fHS, -fHS,  fHS),  // Bottom
             new Vector3(-fHS,  fHS,  fHS), new Vector3(-fHS,  fHS, -fHS), new Vector3(-fHS, -fHS, -fHS), new Vector3(-fHS, -fHS,  fHS),  // Left
             new Vector3( fHS,  fHS, -fHS), new Vector3( fHS,  fHS,  fHS), new Vector3( fHS, -fHS,  fHS), new Vector3( fHS, -fHS, -fHS)}; // right
         int[] triangles = new int[mesh.vertices.Length / 4 * 2 * 3];
         int iPos = 0;
         for (int i = 0; i < mesh.vertices.Length; i = i + 4) {
             triangles[iPos++] = i;
             triangles[iPos++] = i+1;
             triangles[iPos++] = i+2;
             triangles[iPos++] = i;
             triangles[iPos++] = i+2;
             triangles[iPos++] = i+3;
         mesh.triangles = triangles;
         Color colorT = Color.red;
         Color[] colors = new Color[mesh.vertices.Length];
         for (int i = 0; i < colors.Length; i++) {
             if ((i % 4) == 0)
                 colorT = new Color(Random.Range (0.0f, 1.0f), Random.Range (0.0f, 1.0f), Random.Range (0.0f, 1.0f), 1.0f);
             colors[i] = colorT;
         mesh.colors = colors;
         return mesh;

Note the statement "int iStart = mesh.triangles[iTriangle*3];" works to find the beginning index of the four vertices (or four colors matched to the indices) because the two trangles both use the first of the four points as the start of each rectangle.

And here is a script that does the Raycasting and triggers the change in color. Attach it to an empty game object.

 public class RaycastToColorTriangle : MonoBehaviour {
     void Update () {
         if (Input.GetMouseButtonDown (0)) {
             Ray ray = Camera.main.ScreenPointToRay (Input.mousePosition);
             RaycastHit hit;
             if (Physics.Raycast(ray, out hit))
                 VertixColorPlay vcp = hit.collider.gameObject.GetComponent<VertixColorPlay>();
                 if (vcp != null)
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answered Feb 02, 2013 at 05:43 AM

robertbu gravatar image

110k 21 39 185

This is beautiful! But it doesn't work 100%. But i can Fix that. Thank u

Feb 02, 2013 at 03:45 PM Nelia Xurina

What problem did you find that it doesn't work 100%?

Feb 02, 2013 at 04:07 PM robertbu

Okay, i can't fix it. I try to save the color of each side...But i don't get it. I want that the player can spawn and delete new Cubes. But how to save the color?

And how can i delete a Cube? It's so difficult...

My code: http://pastebin.com/0KaPTq36

Feb 02, 2013 at 05:06 PM Nelia Xurina

Uhm...it's not 256 Cubes. It is 1 of 256 Chunks where each is 16*128*16 so...more than 256...i think...so 100.000? :D

I had already the easy way...but it's to much lag on a PC (It's not a mobile game). The code for now works very well. Only the saving color and Deleting a Cube is not perfekt.

Maybe u can help? When yes...do u have skype? I wan't to learn

Feb 02, 2013 at 06:17 PM Nelia Xurina

If you really have 100,000 cubes, then you have another problem to deal with. Unity has a maximum of 60,000 vertices on imported objects which I assume is also a limit for runtime created meshes. Which means you will likely have to deal with multiple meshes. Putting that issue aside, I can suggest an approach for solving your current issues.

You will need to create a couple of additional data structures. For each side, you will have an entry with two pieces of information: a) the first triangle in the triangle array and b) a use count (the number of blocks that share that face). Since your mesh seems to be regular, your use count could be a boolean that indicates if a side is shared.

The second data structure represents a block. It is an array of block info structures. Each structure has a link to all six faces info entries for each face in the first data structure.

To delete a cube, you find the cube in your cube info array. For each side, if the use count is 1 (i.e. not shared), you remove the face. To get the color of a face, simply use the index of the first point in the triangle to get the color from the colors array in the mesh.

If you really delete the triangles and vertices for a side, you will need to update your Face Info and Block Info arrays. As an alternative consider setting all the vertices to the same position and/or setting the coordinates of the vertices beyond the camera. You could then keep a list of unused faces that just need to have their vertices reset when a new face is created (and you avoid the need for updating your parallel data structures).

This is just one approach based on my limited understanding of your project.

Feb 03, 2013 at 05:43 PM robertbu
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asked: Feb 01, 2013 at 02:18 AM

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Last Updated: Feb 12 at 10:19 AM