Set v_texCoord in mystery mode

src/RenderWebGL.js

@@ -139,6 +139,13 @@ class RenderWebGL extends EventEmitter {
             throw new Error('Could not get WebGL context: this browser or environment may not support WebGL.');
         }
 
+        this._mystery = {
+            modeActive: false,
+            mouseMoveListener: null,
+            bufferInfo: null,
+            mouseCoords: [0, 0]
+        };
+
         /** @type {RenderWebGL.UseGpuModes} */
         this._useGpuMode = RenderWebGL.UseGpuModes.Automatic;
 
@@ -242,6 +249,7 @@ class RenderWebGL extends EventEmitter {
     resize (pixelsWide, pixelsTall) {
         const {canvas} = this._gl;
         const pixelRatio = window.devicePixelRatio || 1;
+
         const newWidth = pixelsWide * pixelRatio;
         const newHeight = pixelsTall * pixelRatio;
 
@@ -250,10 +258,16 @@ class RenderWebGL extends EventEmitter {
         if (canvas.width !== newWidth || canvas.height !== newHeight) {
             canvas.width = newWidth;
             canvas.height = newHeight;
+            
+            if (this._mystery.modeActive && this._mystery.bufferInfo) {
+                twgl.resizeFramebufferInfo(this._gl, this._mystery.bufferInfo, [
+                    {format: this._gl.RGBA}
+                ], pixelsWide * pixelRatio, pixelsTall * pixelRatio);
+            }
+
             // Resizing the canvas causes it to be cleared, so redraw it.
             this.draw();
         }
-
     }
 
     /**
@@ -653,7 +667,43 @@ class RenderWebGL extends EventEmitter {
         gl.clearColor(...this._backgroundColor4f);
         gl.clear(gl.COLOR_BUFFER_BIT);
 
-        this._drawThese(this._drawList, ShaderManager.DRAW_MODE.default, this._projection);
+        let drawList = this._drawList;
+        if (this._mystery.modeActive) {
+            drawList = drawList.slice(1);
+            twgl.bindFramebufferInfo(gl, this._mystery.bufferInfo);
+            gl.clearColor(0, 0, 0, 0);
+            gl.clear(gl.COLOR_BUFFER_BIT);
+        }
+        this._drawThese(drawList, ShaderManager.DRAW_MODE.default, this._projection);
+
+        if (this._mystery.modeActive) {
+            // draw all layers except for the bottom layer onto the mystery buffer
+            twgl.bindFramebufferInfo(gl, null);
+            gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
+            this._drawThese([this._drawList[0]], ShaderManager.DRAW_MODE.default, this._projection);
+
+            this._doExitDrawRegion();
+            const newShader = this._shaderManager.getShader(ShaderManager.DRAW_MODE.mystery, 0);
+            this._regionId = newShader;
+
+            // draw mystery buffer to main buffer
+            gl.useProgram(newShader.program);
+            twgl.setBuffersAndAttributes(gl, newShader, this._bufferInfo);
+            const uniforms = {
+                u_projectionMatrix: this._projection,
+                u_modelMatrix: twgl.m4.identity(),
+                u_skin: this._mystery.bufferInfo.attachments[0],
+                u_mousePosition: this._mystery.mouseCoords
+            };
+
+            twgl.setTextureParameters(
+                gl, uniforms.u_skin, {minMag: gl.LINEAR}
+            );
+
+            twgl.setUniforms(newShader, uniforms);
+            twgl.drawBufferInfo(gl, this._bufferInfo, gl.TRIANGLES);
+        }
+
         if (this._snapshotCallbacks.length > 0) {
             const snapshot = gl.canvas.toDataURL();
             this._snapshotCallbacks.forEach(cb => cb(snapshot));
@@ -2083,6 +2133,32 @@ class RenderWebGL extends EventEmitter {
         return dst;
     }
 
+    setMysteryMode (enableMysteryMode) {
+        this._mystery.modeActive = enableMysteryMode;
+
+        if (enableMysteryMode) {
+            this._mystery.bufferInfo = twgl.createFramebufferInfo(
+                this._gl,
+                [{format: this._gl.RGBA}],
+                this._gl.drawingBufferWidth,
+                this._gl.drawingBufferHeight
+            );
+
+            this._mystery.mouseMoveListener = event => {
+                const rect = this.canvas.getBoundingClientRect();
+                this._mystery.mouseCoords[0] = (event.clientX - rect.left) / rect.width;
+                this._mystery.mouseCoords[1] = (event.clientY - rect.top) / rect.height;
+            };
+
+            document.addEventListener('mousemove', this._mystery.mouseMoveListener);
+        } else {
+            if (this._mystery.bufferInfo) {
+                this._gl.deleteFramebuffer(this._mystery.bufferInfo.framebuffer);
+            }
+            document.removeEventListener('mousemove', this._mystery.mouseMoveListener);
+        }
+    }
+
     /**
      * @callback RenderWebGL#snapshotCallback
      * @param {string} dataURI Data URI of the snapshot of the renderer

src/ShaderManager.js

@@ -181,7 +181,9 @@ ShaderManager.DRAW_MODE = {
     /**
      * Draw the background in a certain color. Must sometimes be used instead of gl.clear.
      */
-    background: 'background'
+    background: 'background',
+
+    mystery: 'mystery'
 };
 
 module.exports = ShaderManager;

src/shaders/sprite.frag

@@ -43,6 +43,10 @@ uniform float u_lineLength;
 uniform vec4 u_backgroundColor;
 #endif // DRAW_MODE_background
 
+#ifdef DRAW_MODE_mystery
+uniform vec2 u_mousePosition;
+#endif
+
 uniform sampler2D u_skin;
 
 #ifndef DRAW_MODE_background
@@ -118,6 +122,15 @@ void main()
 	#if !(defined(DRAW_MODE_line) || defined(DRAW_MODE_background))
 	vec2 texcoord0 = v_texCoord;
 
+	#ifdef DRAW_MODE_mystery
+	vec2 mysteryCoord = texcoord0;
+	vec2 offset = vec2(u_mousePosition.x, 1.0 - u_mousePosition.y);
+	mysteryCoord -= offset;
+	const float SCALE_FACTOR = 0.85;
+	mysteryCoord *= vec2(SCALE_FACTOR, SCALE_FACTOR);
+	mysteryCoord += offset;
+	#endif
+
 	#ifdef ENABLE_mosaic
 	texcoord0 = fract(u_mosaic * texcoord0);
 	#endif // ENABLE_mosaic
@@ -161,6 +174,21 @@ void main()
 
 	gl_FragColor = texture2D(u_skin, texcoord0);
 
+	#ifdef DRAW_MODE_mystery
+	const vec4 SHADOW_COLOR = vec4(0.0, 0.0, 0.0, 0.5);
+	const float SHADOW_BLUR = 0.0025;
+
+	float shadowSample1 = texture2D(u_skin, mysteryCoord + vec2(SHADOW_BLUR, SHADOW_BLUR)).a;
+	float shadowSample2 = texture2D(u_skin, mysteryCoord + vec2(-SHADOW_BLUR, SHADOW_BLUR)).a;
+	float shadowSample3 = texture2D(u_skin, mysteryCoord + vec2(SHADOW_BLUR, -SHADOW_BLUR)).a;
+	float shadowSample4 = texture2D(u_skin, mysteryCoord + vec2(-SHADOW_BLUR, -SHADOW_BLUR)).a;
+
+	float shadowAlpha = (shadowSample1 + shadowSample2 + shadowSample3 + shadowSample4) * 0.25;
+
+	vec4 shadow = SHADOW_COLOR * shadowAlpha;
+	gl_FragColor = gl_FragColor + (shadow * (1.0 - gl_FragColor.a));
+	#endif
+
 	#if defined(ENABLE_color) || defined(ENABLE_brightness)
 	// Divide premultiplied alpha values for proper color processing
 	// Add epsilon to avoid dividing by 0 for fully transparent pixels

src/shaders/sprite.vert

@@ -68,6 +68,9 @@ void main() {
 	gl_Position = vec4(position, 0, 1);
 	#elif defined(DRAW_MODE_background)
 	gl_Position = vec4(a_position * 2.0, 0, 1);
+	#elif defined(DRAW_MODE_mystery)
+	gl_Position = vec4(a_position * vec2(-2.0, 2.0), 0.0, 1.0);
+	v_texCoord = a_texCoord;
 	#else
 	gl_Position = u_projectionMatrix * u_modelMatrix * vec4(a_position, 0, 1);
 	v_texCoord = a_texCoord;