flow like the river

VISUALIZACION/node_modules/three/examples/jsm/shaders/MirrorShader.js

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+/**
+ * Mirror Shader
+ * Copies half the input to the other half
+ *
+ * side: side of input to mirror (0 = left, 1 = right, 2 = top, 3 = bottom)
+ */
+
+const MirrorShader = {
+
+	name: 'MirrorShader',
+
+	uniforms: {
+
+		'tDiffuse': { value: null },
+		'side': { value: 1 }
+
+	},
+
+	vertexShader: /* glsl */`
+
+		varying vec2 vUv;
+
+		void main() {
+
+			vUv = uv;
+			gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );
+
+		}`,
+
+	fragmentShader: /* glsl */`
+
+		uniform sampler2D tDiffuse;
+		uniform int side;
+
+		varying vec2 vUv;
+
+		void main() {
+
+			vec2 p = vUv;
+			if (side == 0){
+				if (p.x > 0.5) p.x = 1.0 - p.x;
+			}else if (side == 1){
+				if (p.x < 0.5) p.x = 1.0 - p.x;
+			}else if (side == 2){
+				if (p.y < 0.5) p.y = 1.0 - p.y;
+			}else if (side == 3){
+				if (p.y > 0.5) p.y = 1.0 - p.y;
+			}
+			vec4 color = texture2D(tDiffuse, p);
+			gl_FragColor = color;
+
+		}`
+
+};
+
+export { MirrorShader };