How to draw circle around an object in unity3d?

Question

I want to draw a cube on scene. I create a project on unity3d. It has main camera and directional light. I add an empty gameobject using unity gui. I create a .cs file and attached to gameobject. Content of C# file is :

using UnityEngine; 
using System.Collections;
using System.Collections.Generic;

/**
 * Simple example of creating a procedural 6 sided cube
 */
[RequireComponent (typeof (MeshFilter))] 
[RequireComponent (typeof (MeshRenderer))]
public class test : MonoBehaviour {

void Start () {
    MeshFilter meshFilter = gameObject.GetComponent<MeshFilter>();
    Mesh mesh = new Mesh ();
    meshFilter.mesh = mesh;

    mesh.vertices = new Vector3[]{
        // face 1 (xy plane, z=0)
        new Vector3(0,0,0), 
        new Vector3(1,0,0), 
        new Vector3(1,1,0), 
        new Vector3(0,1,0), 
        // face 2 (zy plane, x=1)
        new Vector3(1,0,0), 
        new Vector3(1,0,1), 
        new Vector3(1,1,1), 
        new Vector3(1,1,0), 
        // face 3 (xy plane, z=1)
        new Vector3(1,0,1), 
        new Vector3(0,0,1), 
        new Vector3(0,1,1), 
        new Vector3(1,1,1), 
        // face 4 (zy plane, x=0)
        new Vector3(0,0,1), 
        new Vector3(0,0,0), 
        new Vector3(0,1,0), 
        new Vector3(0,1,1), 
        // face 5  (zx plane, y=1)
        new Vector3(0,1,0), 
        new Vector3(1,1,0), 
        new Vector3(1,1,1), 
        new Vector3(0,1,1), 
        // face 6 (zx plane, y=0)
        new Vector3(0,0,0), 
        new Vector3(0,0,1), 
        new Vector3(1,0,1), 
        new Vector3(1,0,0), 
    };

    int faces = 6; // here a face = 2 triangles

    List<int> triangles = new List<int>();
    List<Vector2> uvs = new List<Vector2>();

    for (int i = 0; i < faces; i++) {
        int triangleOffset = i*4;
        triangles.Add(0+triangleOffset);
        triangles.Add(2+triangleOffset);
        triangles.Add(1+triangleOffset);

        triangles.Add(0+triangleOffset);
        triangles.Add(3+triangleOffset);
        triangles.Add(2+triangleOffset);

        // same uvs for all faces
        uvs.Add(new Vector2(0,0));
        uvs.Add(new Vector2(1,0));
        uvs.Add(new Vector2(1,1));
        uvs.Add(new Vector2(0,1));
    }

    mesh.triangles = triangles.ToArray();

    mesh.uv = uvs.ToArray();

    GetComponent<Renderer>().material = new Material(Shader.Find("Diffuse"));

    mesh.RecalculateNormals(); 
    mesh.RecalculateBounds (); 
    mesh.Optimize();
} 
}

This code works. Now, I want to draw circle that has perspective effects around this cube using SetPixel function. How can I do this work? I want to create a view as below

Answer 1

1 - Instead of creating a hand maded cube, why don't you user a primitive box and just set the size?

2 - One of the problems is that your "D" can be different depends on the box rotation.

For example, if your box is 0º, the D in 0º direction will be 0.5 (from center to boundary of a 1 unit cube). The sabe box, if you calculate the D in 45º direction will be 0.7 (hipotenuse).

Even if you trie to calculate the boundaries first, this boundaries will be different depens on rotation. 0º = 0.5, 45º = 0.7 and so on (the same problem)

The simple way to aprouch (that I can think now) is:

Create a primitive cube and set the desired scale. Create a plane that will represent the circle and add a transparent texture of a circle. Add the plane (circle) as a child of the box, while you resize the box, the circle will resize together.

Sorry for the grammar, english is not my native language.