diff --git a/src/simulator/js/FloatColorRenderer.js b/src/simulator/js/FloatColorRenderer.js
index 2cb723e3..f56aec9d 100644
--- a/src/simulator/js/FloatColorRenderer.js
+++ b/src/simulator/js/FloatColorRenderer.js
@@ -1,16 +1,6 @@
 class FloatColorRenderer {
-  constructor(ctx, origin, scale, lengthScale) {
-    const contextAttributes = {
-      alpha: true,
-      depth: false,
-      stencil: false,
-      antialias: false,
-      preserveDrawingBuffer: true,
-      premultipliedAlpha: false,
-      failIfMajorPerformanceCaveat: false
-    };
-    this.gl = ctx.canvas.getContext('webgl', contextAttributes) || 
-              ctx.canvas.getContext('experimental-webgl', contextAttributes);
+  constructor(gl, origin, scale, lengthScale) {
+    this.gl = gl;
     if (!this.gl) {
       throw new Error('Unable to initialize WebGL. Your browser may not support it.');
     }
@@ -21,7 +11,7 @@ class FloatColorRenderer {
       throw new Error('OES_texture_float not supported');
     }
 
-    this.canvas = ctx.canvas;
+    this.canvas = gl.canvas;
     this.origin = origin;
     this.scale = scale;
     this.lengthScale = lengthScale;
diff --git a/src/simulator/js/app.js b/src/simulator/js/app.js
index 3407662d..0788280f 100644
--- a/src/simulator/js/app.js
+++ b/src/simulator/js/app.js
@@ -127,7 +127,12 @@ async function startApp() {
 
   if (useFloatColorRenderer) {
     try {
-      var gl = canvasLight.getContext('webgl') || canvasLight.getContext('experimental-webgl');
+      const contextAttributes = {
+        alpha: true,
+        premultipliedAlpha: true,
+        antialias: false,
+      };
+      var gl = canvasLight.getContext('webgl', contextAttributes) || canvasLight.getContext('experimental-webgl', contextAttributes);
       var ext = gl.getSupportedExtensions('OES_texture_float');
       if (!ext) {
         throw new Error('OES_texture_float not supported');