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Dorchester Center, MA 02124
In this series about the Apple Vision Pro, this sub-series on Monitor Replacement and Business/Text applications started with Part 5A, which discussed scaling, text grid fitting, and binocular overlap issues. Part 5B starts by documenting some of Apple’s claims that the AVP would be good for business and text applications. It then discusses the pincushion distortion common in VR optics and likely in the AVP and the radial effect of distortion on resolution in terms of pixels per degree (ppd).
The prior parts, 5A, and 5B, provide setup and background information for what started as a simple “Shootout” between a VR virtual monitor and physical monitors. As discussed in 5A, my office setup has a 34″ 22:9 3440×1440 main monitor with a 27″ 4K (3840×2160) monitor on the right side, which is a “modern” multiple monitor setup that costs ~$1,000. I will use these two monitors plus a 15.5″ 4K OLED Laptop display to compare to the Meta Quest Pro (MQP) since I don’t have an Apple AVP and then extrapolate the results to the AVP.
I will be saving my overall assessment, comments, and conclusions about VR for Office Applications for Part 5D rather than somewhat burying them at the end of this article.
A point to be made by using spreadsheets to generate the patterns is that if you have to make text bigger to be readable, you are lowering the information density and are less productive. Lowering the information density with bigger fonts is also true when reading documents, particularly when scanning web pages or documents for information.
Improving font readability is not solely about increasing their size. VR headsets will have imperfect optics that cause distortions, focus problems, chromatic aberrations, and loss of contrast. These issues make it harder to read fonts below a certain size. In Part 5A, I discussed how scaling/resampling and the inability to grid fit when simulating virtual monitors could cause fonts to appear blurry and scintillate/wiggle when locked in 3-D space, leading to reduced readability and distraction.
As discussed in Part 5A, with Meta’s Horizon Desktop, each virtual monitor is reported to Windows as 1920 by 1200 pixels. When sitting at the nominal position of working at the desktop, the center virtual monitor fills about 880 physical pixels of the MQP’s display. So roughly 1200 virtual pixels are resampled into 880 vertical pixels in the center of view or by about 64%. As discussed in Part 5B, the scaling factor is variable due to severe pincushion distortion of the optics and the (impossible to turn off) curved screen effect in Meta Horizons.
The picture below shows the whole FOV captured by the camera before cropping shot through the left eye. The camera was aligned for the best image quality in the center of the virtual monitor.
Analogous to Nyquist sampling, when you scale pixel rendered image, you want about 2X (linearly) the number of pixels in the display of the source image to render it reasonably faithfully. Below left is a 1920 by 1200 pixel test pattern (a 1920×1080 pattern padded on the top and bottom), “native” to what the MQP reports to Windows. On the right is the picture cropped to that same center monitor.
The picture was taken at 405mp, then scaled down by 3X linearly and cropped. When taking high-resolution display pictures, some amount of moiré in color and intensity is inevitable. The moiré is also affected by scaling and JPEG compression.
Below is a center crop from the original test pattern that has been 2x pixel-replicated to show the detail in the pattern.
Below is a crop from the full-resolution image with reduced exposure to show sub-pixel (color element) detail. Notice how the 1-pixel wide lines are completely blurred, and the test is just becoming fully formed at about Arial 11 point (close to, but not the same scale as used in the MS Excel Calibri 11pt tests to follow). Click on the image to see the full resolution that the camera captured (3275 x 3971 pixels).
The scaling process might lose a little detail for things like pictures and videos of the real world (such as the picture of the elf in the test pattern), but it will be almost impossible for a human to notice most of the time. Pictures of the real world don’t have the level of pixel-to-pixel contrast and fine detail caused by small text and other computer-generated objects.
For the desktop “shootout,” I picked the 34” 22:9 and 27” 4k monitors I regularly use (side by side as shown in Part 5A), plus a Dell 15.5” 4K laptop display. An Excel spreadsheet is used with various displays to demonstrate the amount of content that can be seen at one time on a screen. The spreadsheet allows for flexible changing of how the screen is scaled for various resolutions and text sizes, and the number of cells measures the information density. For repeatability, a screen capture of each spreadsheet was taken and then played back in full-screen mode (Appendix 1 includes the source test patterns)
The pictures below show the relative FOVs of the MQP and various physical monitors taken with the same camera and lens. The camera was approximately 0.5 meters from the center of the physical monitors, and the headset was at the initial position at the MQP’s Horizon Desktop. All the pictures were cropped to the size of a single physical or virtual monitor.
The following is the basic data:
The pictures below show the MQP with MS Windows display text scaling set to 100% (below left) and 175% (below middle). The 175% scaling would result in fonts with about the same number of pixels per font as the Apple Vision Pro (but with a larger angular resolution). Also included below (right) is the 15.5″ 4K display with 250% scaling (as recommended by Windows).
The camera was aimed and focused at the center of the MQP, the best case for it, as the optical quality falls off radially (discussed in Part 5B). The text sharpness is the same for the physical monitors from center to outside, but they have some brightness variation due to their edge illumination.
Each picture above was initially taken 24,576 x 16,384 (405mp) by “pixel shifting” the 45MP R5 camera sensor to support capturing the whole FOV while capturing better than pixel-level detail from the various displays. In all the pictures above, including the composite image with multiple monitors, each image was reduced linearly by 3X.
The crops below show the full resolution (3x linearly the images above) of the center of the various monitors. As the camera, lines, and scaling are identical, the relative sizes are what you would see looking through the headset for the MQP sitting at the desktop and the physical monitors at about 0.5 meters. I have also included a 2X magnification of the MQP’s images.
With Windows 100% text scaling, the 11pt font on the MQP is about the same size as it is on the 34” 22:9 monitor at 100%, the 27” 4K monitor at 150% scaling, and the 15.5” 4K monitor at 250% scaling. But while the fonts are readable on the physical monitor, they are a blurry mess on the MQP at 100%. The MQP at 150% and 175% is “readable” but certainly does not look as sharp as the physical monitors.
Apple’s AVP has about 175% linear pixel density of the MQP. Thus the 175% case gives a reasonable idea of how text should look on the AVP. For comparison below, the MQP’s 175% case has been scaled to match the size of the 34” 22:9 and 27” 4K monitors at 100%. While the text is “readable” and about the same size, it is much softer/blurrier than the physical monitor. Some of this softness is due to optics, but a large part is due to scaling. While the AVP may have better optics and a text rendering pipeline, they still don’t have the resolution to compete on content density and readability with a relatively inexpensive physical monitor.
Thomas Kumlehn had an interesting comment on Part 5B (with my bold highlighting) that I would like to address:
After the VisionPro keynote in a Developer talk at WWDC, Apple mentioned that they rewrote the entire render stack, including the way text is rendered. Please do not extrapolate from the text rendering of the MQP, as Meta has the tech to do foveated rendering but decided to not ship it because it reduced FPS.
Based on my understanding, the AVP will “render from scratch” instead of rendering an intermediate image that is then rescaled as is done with the MQP discussed in Part 5A. While rendering from scratch has a theoretical advantage regarding text image quality, it may not make a big difference in practice. With an ~40 pixels per degree (ppd) display, the strokes and dots of what should be readable small text will be on the order of 1 pixel wide. The AVP will still have to deal with approximately pixel-width objects straddling four or more pixels, as discussed in Part 5A: Simplified Scaling Example – Rendering a Pixel Size Dot.
I wanted to evaluate the MQP pancake optics more than I did in Part 5B. Meta’s Horizon Desktop interface was very limiting. So I decided to try out immersed Virtual Desktop software. Immersed has much more flexibility in the resolution, size, placements, and the ability to select flat or curved monitors. Importantly for my testing, I could create a large, flat virtual 4K monitor that could fill the entire FOV with a single test pattern (the pattern is included in Appendix 1).
Unfortunately, while the immersed software had the basic features I wanted, I found it difficult to precisely control the size and positioning of the virtual monitor (more on this later). Due to these difficulties, I just tried to fill the display with the test pattern with only a roughly perpendicular to the headset/camera monitor. It was a painfully time-consuming process, and I never could get the monitor where it seems perfectly perpendicular.
Below is a picture of the whole (camera) FOV taken at 405mp and then scaled down to 45mp. The image is a bit underexposed to show the sub-pixel (color) detail when viewed at full resolution. In taking the picture, I determined that the MQPs pancake optics focus appears to be a “dished,” with the focus in the center slightly different than on the outsides. The picture was taken focusing between the center and outside focus and using f11 to increase the photograph’s depth of focus. For a person using the headset, this dishing of the focus is likely not a problem as their eye will refocus based on their center of vision.
As discussed in Part 5B, the MQP’s pancake optics have severe pincushion distortion, requiring significant digital pre-correction to make the net result flat/rectilinear. Most notably, the outside areas of the display have about 1/3rd the linear pixel per degree of the center.
Next are shown 9 crops from the full-resolution (click to see) picture at the center, the four corners, top, bottom, left, and right of the camera’s FOV.
The main thing I learned out of this exercised is the apparent dish in focus of the optics and the fall off in brightness. I had determine the change in resolution in the studies shown in Part 5B.
While the immersed had the features I wanted, it was difficult to control the setup of the monitors. The software feels very “beta,” and the interface I got differed from most of the help documentation and videos, suggesting it is a work in progress. In particular, I could’t figure out how to pin the screen, as the control for pinning shown in the help guides/videos didn’t seem to exist on my version. So I had to start from scratch on each session and often within a session.
Trying to orient and resize the screen with controllers or hand gestures was needlessly difficult. I would highly suggest immersed look at some of the 3-D CAD software controls of 3-D models. For example, it would be great to have a single (virtual) button that would position the center monitor directly in front and perpendicular to the user. It would also be a good idea to allow separate control for tilt, virtual distance, and zoom/resize while keeping the monitor centered.
It seemed to be “aware” of things in the room which only served to fight what I wanted to do. I was left contorting my wrist to try and get the monitor roughly perpendicular and then playing with the corners to try and both resized and center the monitor. The interface also appears to conflate “resizing” with moving the monitor closer. While moving the virtual monitor closer or resizing affect the size of everything, the effect will be different when the head moves. I would have a home (perpendicular and center) “button,” and then left-right, up-down, tilt, distance, and size controls.
To be fair, I wanted to set up the screen for a few pictures, and I may have overlooked something. Still, I found the user interface could be vastley better for the setting up the monitors, and the controller or gesture monitor size and positioning were a big fail in my use.
BTW, I don’t want to just pick on immersed for this “all-in-one” control problem. I have found it a pain on every VR and AR/MR headset I have tried that supports virtual monitors to give the user good simple intuitive controls for placing the monitors in the 3D space. Meta Horizons Desktop goes to the extreme of giving no control and overly curved screens.
This series-within-a-series on the VR and the AVP use as an “office monitor replacement” has become rather long with many pictures and examples. I plan to wrap up this series within the series on the AVP with a separate article on issues to consider and my conclusions.
Below is a gallery of PNG file test patterns used in this article. Click on each thumbnail to see the full-resolution test pattern.
As discussed in Appendix 3: Confabulating typeface “points” (pt) with With Pixels – A Brief History, at font “point” is defined as 1/72nd of an inch (some use 1/72.272 or thereabout – it is a complicated history). Microsoft throws the concept of 96 dots per inch (dpi) as 100%. But it is not that simple.
I wanted to share measurements regarding the Calibri 11pt font size. After measuring it on my monitor with a resolution of 110 pixels per inch (PPI), I found that it translates to approximately 8.44pt (8.44/72 inches). However, when factoring in the monitor PPI of 110 and Windows DPI of 96, the font size increases to ~9.67pt. Alternatively, when using a monitor PPI of 72, the font size increases to ~12.89pt. Interestingly, if printed assuming a resolution of 96ppi, the font reaches the standard 11pt size. It seems Windows apply some additional scaling on the screen. Nevertheless, I regularly use the 11pt 100% font size on my 110ppi monitor, which is the Windows default in Excel and Word, and it is also the basis for the test patterns.
As discussed in 5A’s Appendix 2: Notes on Pictures, some moiré issues will be unavoidable when taking high-resolution pictures of a display device. As noted in that Appendix, all pictures in Lens Shootout were taken with the same camera and lens, and the original images were captured at 405 megapixels (Canon R5 “IBIS sensor shift” mode) and then scaled down by 3X. All test patterns used in this article are included in the Appendix below.