HSV color for opc.js

examples/node/opc.js

@@ -8,6 +8,11 @@
 var net = require('net');
 var fs = require('fs');
 
+
+/********************************************************************************
+ * Core OPC Client
+ */
+
 var OPC = function(host, port)
 {
     this.host = host;
@@ -15,12 +20,6 @@ var OPC = function(host, port)
     this.pixelBuffer = null;
 };
 
-OPC.loadModel = function(filename)
-{
-    // Synchronously load a JSON model from a file on disk
-    return JSON.parse(fs.readFileSync(filename))
-}
-
 OPC.prototype._reconnect = function()
 {
     var _this = this;
@@ -105,6 +104,11 @@ OPC.prototype.mapPixels = function(fn, model)
     this.writePixels();
 }
 
+
+/********************************************************************************
+ * Client convenience methods
+ */
+
 OPC.prototype.mapParticles = function(particles, model)
 {
     // Set all pixels, by mapping a particle system to each element of "model".
@@ -140,4 +144,44 @@ OPC.prototype.mapParticles = function(particles, model)
     this.mapPixels(shader, model);
 }
 
+
+/********************************************************************************
+ * Global convenience methods
+ */
+
+OPC.loadModel = function(filename)
+{
+    // Synchronously load a JSON model from a file on disk
+    return JSON.parse(fs.readFileSync(filename))
+}
+
+OPC.hsv = function(h, s, v)
+{
+    /*
+     * Converts an HSV color value to RGB.
+     *
+     * Normal hsv range is in [0, 1], RGB range is [0, 255].
+     * Colors may extend outside these bounds. Hue values will wrap.
+     *
+     * Based on tinycolor:
+     * https://github.com/bgrins/TinyColor/blob/master/tinycolor.js
+     * 2013-08-10, Brian Grinstead, MIT License
+     */
+
+    h *= 6;
+
+    var i = h | 0,
+        f = h - i,
+        p = v * (1 - s),
+        q = v * (1 - f * s),
+        t = v * (1 - (1 - f) * s),
+        mod = i % 6,
+        r = [v, q, p, p, t, v][mod],
+        g = [t, v, v, q, p, p][mod],
+        b = [p, p, t, v, v, q][mod];
+
+    return [ r * 255, g * 255, b * 255 ];
+}
+
+
 module.exports = OPC;

examples/node/particle_trail.js

@@ -9,23 +9,25 @@ var client = new OPC('localhost', 7890);
 
 function draw() {
 
-    var t = 0.009 * new Date().getTime();
+    var time = 0.009 * new Date().getTime();
     var numParticles = 200;
     var particles = [];
 
     for (var i = 0; i < numParticles; i++) {
+        var s = i / numParticles;
 
-        var r = 0.2 + 1.5 * i / numParticles;
-        var x = r * Math.cos(t);
-        var y = r * Math.sin(t + 10.0 * Math.sin(t * 0.15));
+        var radius = 0.2 + 1.5 * s;
+        var theta = time + 0.04 * i;
+        var x = radius * Math.cos(theta);
+        var y = radius * Math.sin(theta + 10.0 * Math.sin(theta * 0.15));
+        var hue = time * 0.01 + s * 0.2;
 
         particles[i] = {
             point: [0, x, y],
-            intensity: 40 * i / numParticles,
+            intensity: 0.2 * s,
             falloff: 60,
-            color: [0.9, 0.2, i * 0.01]
+            color: OPC.hsv(hue, 0.5, 0.8)
         };
-        t += 0.04;
     }
 
     client.mapParticles(particles, model);