unity3d - Unity 2D: dynamically create a hole in a image -

i using unity 2d , trying achieve simple effect. making candy crush saga - game.

i have grid items. in every level grid field can have different shapes, created @ runtime (a dark grey area in middle of background). background still image (blue sky , green hills). when pieces (for example blue pentagon) fall down top must hidden until enter grid field area (dark grey); in practice background image (sky , hills) no more background, foreground hole represented grey area. grey field composed tiles sprite sheet.

i have prepared picture, cannot load here unfortunately yet.

i have no idea how achieve effect in unity. have idea?

the simple solution create static levels graphics hole, not want create them because waste of time , waste of memory, want able create effect @ runtime.

i thinking creating dynamic bitmap mask hole shape using sprite sheet. using bitmap mask material example applied image in foreground , make hole.

i hope clear enough.

thank you! camillo

click on texture in unity editor

change "texture type" "texture" "advanced"

check "read/write enabled" checkbox

change "format" form "automatic compressed" "rgba 32 bit"

i attached component raw image (you can attach else, change "rawimage image" part)

this create hole dimensions 100x100 @ position 10,10 of image, make sure texture @ least 110x110 large.

using unityengine; using unityengine.ui;  public class holeinimage : monobehaviour {    public rawimage image;     void start()    {       // change original:       texture2d texture = image.texture texture2d;        // use change copy (and not original)       //texture2d texture = instantiate(image.maintexture) texture2d;       //image.maintexture = texture;        color[] colors = new color[100*100];        for( int = 0; < 100*100; ++i )          colors[i] = color.clear;        texture.setpixels( 10, 10, 100, 100, colors );        texture.apply(false);    } } 

edit:

hole defined 1 or more sprites:

do same these sprites: (advanced, read/write enabled, rgba 32 bit)

for example: if sprite white , hole defined black:

      for( int = 0; < 100*100; ++i )          colors[i] = color.clear; 

change to:

      texture2d holetex; // set in editor, must have same dimensions (100x100 in example)       color[] hole = holetex.getpixels();       for( int = 0; < 100*100; ++i )       {          if( hole[i] == color.black ) // sprite black, there hole              colors[i] = color.clear;       }