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Create a mesh and color cubes

Hi,

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()
    {
        GameObject.DestroyImmediate(GetComponent<MeshCollider>());
        GameObject.DestroyImmediate(GetComponent<MeshFilter>());

        gameObject.AddComponent<MeshCollider>();
        gameObject.AddComponent<MeshFilter>();

        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;
        mesh.Clear();

        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
                triangles.Add(vertexIndex);
                triangles.Add(vertexIndex+1);
                triangles.Add(vertexIndex+2);

                // second triangle for the block top
                triangles.Add(vertexIndex+2);
                triangles.Add(vertexIndex+3);
                triangles.Add(vertexIndex);

                // 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();
        mesh.Optimize();
        mesh.RecalculateNormals();

        // update mesh collider
        GetComponent<MeshCollider>().sharedMesh = null;
        GetComponent<MeshCollider>().sharedMesh = mesh;
        yield return null;
    }

    void Update()
    {
        if(Input.GetMouseButtonDown (0))
            StartCoroutine(FloorkRender());
    }
}

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 6 8

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 1616 cubes in 256 Chunks...that are 1616*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;
        mesh.RecalculateNormals();
        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)
                    vcp.ChangeColor(hit.triangleIndex);
            }
        }
    }
}
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answered Feb 02, 2013 at 05:43 AM

robertbu gravatar image

robertbu
100k 18 32 94

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

You are trying to be super efficient by only generating the sides you need. And this is going to cause you a bunch of programming pain to make it work. It can be done, but you will need to track sides and have use counts for sides, and a bunch of other stuff. Before you go to all that work, I'd make sure it is necessary.

Take the code that makes a cube that I posted above and make it into a prefab. Spawn 256 of them in some pattern representative of your game. Put it on the target device and see how it performs. All of the cubes should be batched, so there will only be one draw call. Plus given what you are building, a high percentage of the faces will be culled. I suspect that having 256 game object will work just fine on most mobile platforms.

If you have a single game object per cube, then processes like deleting and saving colors becomes easy to program.

Feb 02, 2013 at 05:48 PM robertbu

Uhm...it's not 256 Cubes. It is 1 of 256 Chunks where each is 1612816 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
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asked: Feb 01, 2013 at 02:18 AM

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Last Updated: Feb 12 at 10:19 AM