[Unity] I tried to draw to Texture. Part2

Last time, I tried to directly draw to a texture attached game object.

[ Previous: I tried to draw to Texture. Part1 ]

In the blog log, looks like many people are reading the source, so this time I’m explaining more about the logic for beginners.

Following is the C# source for drawing a texture, I added many comments so that you can understand easily this source.
This ‘Paint_Line’ method in this source attached on field’s game object is called from moving game object with position information (as UV coordinate).

[Drawing source with explanations]

public class Test_Draw : MonoBehaviour {

  // Premise: Texture is square, Moving object is cube.
  private const int C_TEXTURE_SIZE = 500;// Size of one side of the Texture
  private const int C_OBJECT_SIZE = 25; // Size of one side of the Cube
  private Color[] buffer; // Array to temporarily update color information
  private Color OBJECT_COLOR = Color.yellow; // Set a color to draw
  // Calculate the half of one size beforehand because texture will be drawn at the center of the game object
  private int object_Halfsize = (int)( C_OBJECT_SIZE / 2);
  //Detail 1:
  public void Paint_Line (Vector2 point) {
    // Convert from UV coordinate to the coordinate of the Texture
    // To use this variable for a variable of loop, convert the type to ‘int’
    int point_X = (int) (point.x * C_TEXTURE_SIZE);
    int point_Y = (int) (point.y * C_TEXTURE_SIZE);

    // Copy current color information of the Texture to ‘buffer’ array
    Texture2D mainTexture 
       = (Texture2D) GetComponent<Renderer> ().material.mainTexture;
    Color[] pixels = mainTexture.GetPixels(); // Detail 2:
    buffer = new Color[pixels.Length];
    pixels.CopyTo (buffer, 0); // Detail 3:

    // Loop the position of the Texture using X, Y coordinate around where the Cube object is located at. 
    for(int x = point_X - object_Halfsize; 
              x < point_X + object_Halfsize; x++){
        for(int y = point_Y - object_Halfsize; 
                 y < point_Y + object_Halfsize; y++){
           // Change the color at the position of the Texture on ‘buffer’
           buffer.SetValue (OBJECT_COLOR, x + C_TEXTURE_SIZE * y);

    // Reflect updated color information of ‘buffer’ to the Texture itself
    Texture2D drawTexture = new Texture2D (mainTexture.width, 
               mainTexture.height, TextureFormat.RGBA32, false);
    drawTexture.filterMode = FilterMode.Point;
    drawTexture.SetPixels (buffer); // Detail 4:
    drawTexture.Apply(); // Detail 5:
    GetComponent<Renderer> ().material.mainTexture = drawTexture;


Detail 1:
Need to use UV coordinate of the Texture as the parameter ‘Vector2 point’ of the method ‘Paint Line’.
(UV Coordinate: Origin (0,0) is the bottom left corner of a texture, and the upper right corner of a texture is (1,1). Therefore, it’s between 0 and 1.)

Detail 2:
Color[] Texture2D.GetPixels: Get the color information from a texture.

Detail 3:
CopyTo:Copying of array. If you use ‘=’ to copy array, it means just passing Reference type.
( Ref: Copy of Array in C# )

Detail 4:
Texture2D.SetPixels(Color[] colors): Apply the color information to a texture. Apply each pixel’s color array ‘colors’ (in above program, it’s ‘buffer’) to a texture.

Detail 5:
Texture2D.Apply: Actually here Applying.


[Original Japanese Site: http://blog.lab7.biz/archives/3513054.html]


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