Fixing Google VR View

May 12, 2019

Google VR View provides a way to deliver 360 images and videos to your viewers based on their device. If the person is browsing on a desktop, then he’ll get an experience which some other libraries could provide as well (like Panellum). However when the visitor is using a smartphone, then it surpasses other libraries: if the phone is not in a VR headset then the viewer can explore the scene using the phone’s orientation, and if the phone is inside a VR headset then the library provides an appropriate stereoscopic projection for a true 360 experience.

Google has a nice Code Lab which walks you through serving both 360 images and videos: Code Lab. Here is the developer page for the technology (see the VR View for Web section): 360° Media. I embraced the VR View for Web and created a concept page: website, source.

Based on that I created several websites commemorating some events, like:

As you can see these websites use the same concept: they are based on a material styled Jekyll theme, they use Bootstrap and hosted on GitHub. Each scene has a 360 image and 360 video snippet. The video is provided by YouTube but the image is served by the Google VR View for Web. For the latter I went for self hosting, so each site has a copy of the necessary files. Just as listed in the README of Google’s repository: VR View files. As you see the whole repository is now in an archived state.

Since I created the first of these 360 websites it occured to me several times that I wanted to brag about and demo them on my phone. However my phone showed clearly some bug regarding the accelerometer reading because the view didn’t smoothly follow the orientation of the phone but it was swirling around violently.

The first two occasions I updated the files from the Google V1R View for Web repository, and that seemed to make the bug go away. However the last time I encountered that bug the repository was already archived so I needed to roll up my sleeves and debug. First, I examined the symptoms more closely. I noticed that although the view was swirling around violently when I was moving the phone, when I tried to hold it steady the view was just shaking pretty bad but not swirling as much. It was almost clear that there must have been some translation factor mismatch while calculating the rotation from the accelerator readings. Maybe even along with some axis swaps? I jumped into the source code with that in mind.

I yanked out the Utils.isR7()source line and all related lines, since that is clearly some leftover of a hack from the past. Then the meat is here:

// With iOS and Firefox Android, rotationRate is reported in degrees,
// so we first convert to radians.
if (this.isIOS || this.isFirefoxAndroid) {
  this.gyroscope.multiplyScalar(Math.PI / 180);

Well, guess what: looks like mobile Chrome also needs this deg -> rad conversion. With that division by 180 the violent swirling went away and everything is back smooth at it was originally. Now I just have to test if it’s also functioning as intended when the phone is in a VR headset.

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