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Draw Polygon

Discussion in 'Scripting' started by AlexG, Jul 12, 2010.

  1. AlexG

    AlexG

    Joined:
    Jul 7, 2010
    Posts:
    45
    Hey there,

    I would like unity to draw a 3D polygon during run-time based on the location of some Vector3 vertices

    I want the entire polygon to be filled (no wireframe).

    For example, the following would draw a square:

    Code (csharp):
    1.  
    2. var theVertices = new Array();
    3.  
    4. theVertices.Push(Vector3((0,0,0));
    5. theVertices.Push(Vector3((1,0,0));
    6. theVertices.Push(Vector3((1,1,0));
    7. theVertices.Push(Vector3((0,1,0));
    8.  
    9. DrawPoly(theVertices);
    10.  
    Suggestions?
     
    folino9 likes this.
  2. laurie

    laurie

    Joined:
    Aug 31, 2009
    Posts:
    638
  3. AlexG

    AlexG

    Joined:
    Jul 7, 2010
    Posts:
    45
    Thanks for the reply.

    It looks like I have to create a new mesh. The example they provide:

    Code (csharp):
    1.  
    2. function Start  ()
    3. {
    4.      var mesh = new Mesh ();
    5.      GetComponent (MeshFilter).mesh = mesh;
    6.      mesh.vertices = newVertices;
    7.      mesh.uv = newUV;
    8.      mesh.triangles = newTriangles;
    9. }
    10.  
    I'm assuming that newVerticies, newUV, and newTriangles are all the arrays of data that I would have offhand. I'm then assigning this data to the mesh. Makes sense. Some questions:

    1) I'm looking at a function, Graphics.DrawMesh(). I can use this to draw the mesh I create without having to create a game object right?

    2A) Can I also assign this mesh to a new game object and have it draw it for me automatically? Something like this?:

    Code (csharp):
    1.  
    2. var mesh : Mesh;
    3. var gameObject : GameObject;
    4.  
    5. CreateMesh()
    6. {
    7.    var meshCreated : Mesh = new Mesh();
    8.    ///blah blah blah, create some mesh
    9.    return meshCreated
    10. }
    11.  
    12. mesh = CreateMesh();
    13.  
    14. gameObject.AddComponent("MeshFilter");
    15. gameObject.AddComponent("MeshRenderer");
    16.  
    17. gameObject.MeshFilter.mesh = mesh;
    18.  
    2B) How can I change the material for this game object? Something like this?:

    Code (csharp):
    1.  
    2. var myMaterial : Material; //Drag and drop a material onto the inspector
    3.  
    4. gameObject.MeshRenderer.Materials[0] = myMaterial;
    5.  
    Thanks,
    Alex
     
  4. AlexG

    AlexG

    Joined:
    Jul 7, 2010
    Posts:
    45
    Got it working thanks.

    If anyone is curious, here is my code

    Code (csharp):
    1.  
    2. function updatePolygon()
    3. {
    4.     for(x = 0; x < 2; x++)
    5.     {
    6.         //Destroy old game object
    7.         Destroy(myObject[x]);
    8.  
    9.         //New mesh and game object
    10.         myObject[x] = new GameObject();
    11.         myObject[x].name = "MousePolygon";
    12.         var mesh : Mesh = new Mesh();
    13.        
    14.         //Components
    15.         var MF = myObject[x].AddComponent("MeshFilter");
    16.         var MR = myObject[x].AddComponent("MeshRenderer");
    17.         //myObject[x].AddComponent();
    18.        
    19.         //Create mesh
    20.         mesh = CreateMesh(x);
    21.        
    22.         //Assign materials
    23.         MR.material = myMaterial;
    24.        
    25.         //Assign mesh to game object
    26.         MF.mesh = mesh;
    27.     }
    28. }
    29.  
    Code (csharp):
    1.  
    2. function CreateMesh(num : int)
    3. {
    4.     var x : int; //Counter
    5.  
    6.     //Create a new mesh
    7.     var mesh : Mesh = new Mesh();
    8.    
    9.     //Vertices
    10.     var vertex = new Vector3[nodePositions.length];
    11.    
    12.     for(x = 0; x < nodePositions.length; x++)
    13.     {
    14.         vertex[x] = nodePositions[x];
    15.     }
    16.    
    17.     //UVs
    18.     var uvs = new Vector2[vertex.length];
    19.    
    20.     for(x = 0; x < vertex.length; x++)
    21.     {
    22.         if((x%2) == 0)
    23.         {
    24.             uvs[x] = Vector2(0,0);
    25.         }
    26.         else
    27.         {
    28.             uvs[x] = Vector2(1,1);
    29.         }
    30.     }
    31.    
    32.     //Triangles
    33.     var tris = new int[3 * (vertex.length - 2)];    //3 verts per triangle * num triangles
    34.     var C1 : int;
    35.     var C2 : int;
    36.     var C3 : int;
    37.    
    38.     if(num == 0)
    39.     {
    40.         C1 = 0;
    41.         C2 = 1;
    42.         C3 = 2;
    43.        
    44.         for(x = 0; x < tris.length; x+=3)
    45.         {
    46.             tris[x] = C1;
    47.             tris[x+1] = C2;
    48.             tris[x+2] = C3;
    49.            
    50.             C2++;
    51.             C3++;
    52.         }
    53.     }
    54.     else
    55.     {
    56.         C1 = 0;
    57.         C2 = vertex.length - 1;
    58.         C3 = vertex.length - 2;
    59.        
    60.         for(x = 0; x < tris.length; x+=3)
    61.         {
    62.             tris[x] = C1;
    63.             tris[x+1] = C2;
    64.             tris[x+2] = C3;
    65.            
    66.             C2--;
    67.             C3--;
    68.         }  
    69.     }
    70.    
    71.     //Assign data to mesh
    72.     mesh.vertices = vertex;
    73.     mesh.uv = uvs;
    74.     mesh.triangles = tris;
    75.    
    76.     //Recalculations
    77.     mesh.RecalculateNormals();
    78.     mesh.RecalculateBounds();  
    79.     mesh.Optimize();
    80.    
    81.     //Name the mesh
    82.     mesh.name = "MyMesh";
    83.    
    84.     //Return the mesh
    85.     return mesh;
    86. }
    87.  
    This creates a mesh and attaches it to two game objects. The mesh is stitched counter-clockwise in one object, and clockwise in another game object. Then both objects are drawn on top of each other. The reason I do this is so that way the object is visible on the front and back.
     
    folino9, pachermann and knr_ like this.
  5. laurie

    laurie

    Joined:
    Aug 31, 2009
    Posts:
    638
    Glad to see you got that working :) Just out of curiosity, why do you destroy the game objects each update, rather than just using go.GetComponent("MeshFilter").mesh.Clear()?
     
    pachermann likes this.
  6. AlexG

    AlexG

    Joined:
    Jul 7, 2010
    Posts:
    45
    Cause im bad!

    Thanks for the pro tip
     
  7. rule62

    rule62

    Joined:
    Feb 14, 2011
    Posts:
    2
    Hi Alex,

    How did you actually get this to work? How to set up a scene without gameobjects to start with?

    Where does the data input into these scripts come from?

    thanks!
     
  8. HabibAli

    HabibAli

    Joined:
    Aug 19, 2013
    Posts:
    3
    Any one has a sample project for drawing polygon please?
     
  9. ciaccodavide

    ciaccodavide

    Joined:
    Jun 27, 2013
    Posts:
    1
    unity_96aman96, SerenityTn and Ryiah like this.
  10. StarManta

    StarManta

    Joined:
    Oct 23, 2006
    Posts:
    8,171
    I'm torn between complimenting what appears to be a useful and free plugin, or blasting you for necroposting just to spam your own plugin...
     
    MaxEden likes this.
  11. unity_96aman96

    unity_96aman96

    Joined:
    Nov 3, 2018
    Posts:
    2
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