flow like the river

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

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+/**
+ * Afterimage shader
+ * I created this effect inspired by a demo on codepen:
+ * https://codepen.io/brunoimbrizi/pen/MoRJaN?page=1&
+ */
+
+const AfterimageShader = {
+
+	name: 'AfterimageShader',
+
+	uniforms: {
+
+		'damp': { value: 0.96 },
+		'tOld': { value: null },
+		'tNew': { value: null }
+
+	},
+
+	vertexShader: /* glsl */`
+
+		varying vec2 vUv;
+
+		void main() {
+
+			vUv = uv;
+			gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );
+
+		}`,
+
+	fragmentShader: /* glsl */`
+
+		uniform float damp;
+
+		uniform sampler2D tOld;
+		uniform sampler2D tNew;
+
+		varying vec2 vUv;
+
+		vec4 when_gt( vec4 x, float y ) {
+
+			return max( sign( x - y ), 0.0 );
+
+		}
+
+		void main() {
+
+			vec4 texelOld = texture2D( tOld, vUv );
+			vec4 texelNew = texture2D( tNew, vUv );
+
+			texelOld *= damp * when_gt( texelOld, 0.1 );
+
+			gl_FragColor = max(texelNew, texelOld);
+
+		}`
+
+};
+
+export { AfterimageShader };