Re: Just got my Looking Glass Portrait - a couple of questions


Michael Levine
 

I would like to thank Dennis for his simple explanation of quilts for the LGP. It is the first time I understood how to use SPM for that purpose. I tried my first with a problem RGBD.jpg and it is a substantial improvement.


On Mon, Sep 6, 2021 at 2:41 AM Dennis Boersma <d.a.boersma@...> wrote:

To understand how to create content for the Looking Glass Portrait (LKG) without HoloPlay Studio first some basic facts:

  • In standalone mode all the LKG does is play mp4 videos. Still images are short mp4 video’s.
  • The LKG is a normal screen with a very special lens in front of it. Production tolerances require the combination of screen and lens to be calibrated. This makes each LKG unique.
  • The calibration data is stored on the LKG in .\LKG_calibration\visual.json
  • All content stored on the LKG local storage has been created with the LKG specific calibration corrections. This makes all these files unique for your device. Copy them to another device and you won’t have the same image quality. You can download the demo files from the Looking Glass website but that is the source data that will only be converted to your LKG specific files when you install them with HoloPlay Studio.
  • You can connect the LKG to your computer USB-A port. You can use a micro-USB-to-USB-C adapter on a standard USB cable or you can use a USB-A-to-USB-C cable. This probably won’t let you power up the LKG but it will give you access to the LKG internal storage as just another file station (disk) on your computer.

On the Looking Glass User Guide pages you will find the work around for your situation. Go to https://docs.lookingglassfactory.com/3d-viewers/holoplay-studio/troubleshooting and scroll down to Syncing without HDMI connected.

Without the HDMI connection you can use HoloPlay Studio to create the mp4 files and store them on the LKG. However, you won’t have the advantage of the preview of your image while adjusting the focus, depthiness and cropping. This means that especially for the depth map based images it becomes a matter of trial and error with a lot of on-of switching and cable switching.


My experience is that in that case the best solution is to make a Quilt in StereoPhoto Maker (SPM). A quilt is a series of horizontal sequential views stored in a matrix.

If you want to start from a stereo pair, then please consult my articles on SPM Depth Map Functions in Stereoscopy 122 and 123 on how to create a depth map from a stereo pair.

Open the 2D image and depth map in SPM. Crop the image to a 3x4 aspect-ratio. Then select Edit/Looking Glass/Create LKG image from 2D+Depth map… In the window that appears you need to set the parameters for the quilt.

With LKG Parameter Setting you can load the LKG calibration data. You will need this if you select LKG Image as Output Image Type. For the Quilt Image it is not needed (HoloPlay Studio will apply the calibration data when it creates the mp4 file from the quilt). Note that to share images with other LKG owners it is best to share the quilt (or the 2D+Depth map) and not the LKG Image because the LKG image is created with the calibration data of your own LKG.

Max Deviation is the far point disparity minus the near point disparity for the left most and right most image as fraction of the image width. For a normal stereo image you would select around 30 (30 x 0.1% = 3%). On the LKG you won’t be able to see these two images at the same time with your left and right eye, but you see a pair of views inbetween. I haven’t tested yet what the ‘distance’ between these images is but a max deviation of 300 seems to work quite well. The equivalent function in HoloPlay Studio for RGBD images is the Depthiness slider.

The Number of images defines the number of views that will be put in the quilt. Looking Glass advises for optimal view a quilt of 8 columns by 6 rows, with a total of 3360 by 3360 pixels (420x560 per view). SPM current version 6.16 does not support a 48 images quilt. So best select 60 images for a 6 columns by 10 rows quilt.

F/R Position defines the grey scale value that will be placed in the zero-parallax plane. In this plane the image is the sharpest. Objects in the image closer by and further away will be less sharp. A left mouse click on the F/R Position button produces a depth map image. In this image click on the position you want to have in the zero-parallax plane. If your depth map uses white for the nearest position then also check Depth map. Further note that the F/R position affects the near point and far point disparity. With a max deviation of 300 (30%) a F/R position of 0 gives a near point disparity of 0% and a far point disparity of 30%. A F/R position of 128 gives a near point disparity of -15% and a far point disparity of 15%. This assumes that the depth map uses the full range of 0 to 255. If the range in your depth map is less you could consider a larger deviation. It may take a little trial and error to determine the best settings for the specific image. Create several quilts with different settings and afterwards delete the ones you don’t like. In HoloPlay Studio the F/R Position is set with the Focus slider.

Select Quilt Image as Output Image Type.

Single image size is the size of the individual views in the quilt. Based on the advice for optimal view select a width of 420 and a height of 560.

Now click OK to create the quilt and finally save the image.

Once you have created the quilts connect the LKG to your computer with the USB cable. The LKG should be visible as a file station (disk) as long as it is not switched on. Its name is LKG-P##### with ##### the serial number of your LKG. On your computer start HoloPlay Studio Service (runs in the background) and then HoloPlay Studio. In HoloPlay Studio click on ADD HOLOGRAM, then click on the quilt icon and IMPORT FILE. Once the file is loaded, under Properties (top right) set the correct number of columns and rows in your quilt. Repeat this for all quilts you want to add.

Now click SYNC PLAYLIST to transfer your images to the LKG.

Disconnect the LKG from the computer, connect it to power and switch it on (if your computer USB port can provide sufficient power you can leave it connected to your computer when you switch it on). The LKG will now play the images that were listed in the HoloPlay Studio playlist on your computer.

The original demo images will not be shown anymore. The reason is that these were not in the HoloPlay Studio playlist on your computer. HoloPlay Studio has added a file playlist.m3u which lists the files that are played in standalone mode. So, the demo files have not been removed, they are just not in the playlist. If you want to show all files on your LKG in standalone mode then delete the playlist.m3u file. Otherwise open the file in Notepad and add the filenames of the demo files you like (and remove the files you don’t want to show from the playlist).

Syncing the LKG with HoloPlay Studio is a one-way sync from HoloPlayStudio to the LKG. HoloPlayStudio will not check what is on your LKG playlist but maintains its own copy of the playlist on your computer. So every time you sync, it will overwrite the playlist.m3u file on your LKG. Note that when you remove an image that is already on your LKG from the HoloPlay Studio playlist, the mp4 file will not be removed from the LKG internal storage, the filename will only be removed from the playlist.m3u file. You must manually remove the mp4 files you don’t want to keep.

I have added a separate folder on the LKG internal storage with different playlists. The playlist I want to show I copy to playlist.m3u in the root folder of the LKG. This is a practical workaround until the LKG supports multiple playlists.

Having your LKG connected as an extra monitor to your computer makes importing a RGBD (2D+Depth) image more practical because you get direct feedback on the focus and depthiness. Also, you can start with a wider image which means that the software does not have to invent the missing information at the edges. With zooming and shifting you crop the image after the different views have been created. In the absence of an HDMI connection, the workflow described above provides a practical alternative.

Dennis

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