make checkerboard a background with transparency. close #2

shader-test/source/PlayState.kiss

@@ -1,6 +1,7 @@
 (import flixel.FlxState)
 (import flixel.FlxG)
 (import flixel.FlxSprite)
+(import flixel.util.FlxColor)
 (import openfl.filters.BitmapFilter)
 (import openfl.filters.ShaderFilter)
 
@@ -10,9 +11,11 @@
 
 (method &override :Void create []
     (super.create)
+    (set FlxG.camera.bgColor FlxColor.TRANSPARENT)
     (let [bg (new FlxSprite 0 0 "assets/images/apTestRoomEdited.jpg")]
-        (bg.setGraphicSize FlxG.width FlxG.height)
+        (bg.setGraphicSize (iHalf FlxG.width) (iHalf FlxG.height))
         (bg.screenCenter)
+        (set bg.alpha 0.5)
         (add bg))
     (set shader (new kiss_flixel.shaders.CheckerBoard))
     // (set shader.data.invert.value [true])

src/kiss_flixel/shaders/CheckerBoard.frag

@@ -6,6 +6,10 @@ uniform float checkSize = 64;
 
 void main()
 {
+    vec4 color = flixel_texture2D(bitmap, openfl_TextureCoordv);
+
+    float transparency = 1.0 - color.a;
+
     vec2 position = openfl_TextureCoordv * iResolution + cameraPos;
     float row = floor(position.y / checkSize);
     float col = floor(position.x / checkSize);
@@ -16,5 +20,6 @@ void main()
     vec4 oddColor = oddRow ? color1 : color2;
     vec4 evenColor = oddRow ? color2 : color1;
 
-    gl_FragColor = oddCol ? oddColor: evenColor;
+    vec4 bgColor = oddCol ? oddColor: evenColor;
+    gl_FragColor = color + bgColor * transparency;
 }