Help! Canvas keeps telling me that I'm running out of memory.
The Short Answer
While there is no "official" amount of space you can capture in one scan, most iPads should have no problem scanning a typical residential room in full. If you are trying to scan more than a residential-sized room in one scan and running out of memory, then running out of memory is not atypical on older devices. If you are consistently running out of memory prior to finishing a room.
This FAQ chiefly concerns scanning with Canvas using a Structure Sensor.
The Long Answer
Fear not! This is a bit of a nuanced topic, but this FAQ should guide you through:
- Memory vs. storage
- What this message means
- When you should expect to see it vs. when it might be a sign that something is wrong
- How to fix it or get help
Memory vs. Storage
Before diving in, it's important to understand the difference between "memory" and "storage." It's not uncommon for customers to see this warning and wonder, "But my iPad has 256GB available! How is that possible???"
Memory refers to "RAM," which stands for random-access memory. It means, more or less, "how much can your iPad do at once?" 3D scanning is a very memory-intensive process, and most iPads have 2GB or 4GB.
Storage refers to the amount of data your iPad can hold at one time, and the options typically range from 16GB to 256GB. When using Canvas, it affects the number of scans or homes you can hold on the device at one time. Available storage has nothing to do with how much you can capture in one scan, unless you are extremely close to your iPad's storage limit (but you should see a message before you start the scan if you have less than 500MB available).
When you see a message a "low memory warning," it is referring to RAM (the 2GB or 4GB number),
not storage (the 16GB - 256GB number). The bar in the top-right corner that fills up your scan is also referring to memory, indicating how much memory is available for you to continue scanning.
What affects memory usage, and how much you can capture in one scan
iPad memory is most strongly correlated with the amount of
detail being captured in a space. It doesn't really have anything to do with the total size of the space, or what you're capturing, except for the literal amount of geometry that is getting recreated during the scan. For example, a complicated kitchen with lots of cabinets, counters, etc. will eat up memory faster than an empty room of the same size.
Generally speaking, as long as your iPad has 2GB of RAM or higher, you should be able to scan most residential-sized rooms with ease. That does
not mean that there is no residential room ever that will require more than 1 scan — large, open, and complicated living rooms might require 2 (and don't worry, you can absolutely merge multiple scans together). At the same time, you can often combine a small bathroom with the hallway or closets. These are not hard and fast rules, and every home is different, except that it's typically best to scan on a room by room basis.
For more information on how much you can capture in one scan, how you can optimize memory, and how to merge your scans into a global CAD model of a property, please read:
How big of a space can I scan?
While the amount of detail being captured in the space is the largest driver of memory usage, it's not the only thing. If your iPad has a lot of other apps open, or those apps have a lot of background activity (like background uploads, or streaming music, or the app is simply written poorly), that can also utilize more RAM, leaving less available for scanning.
Why you see this warning, and what happens if you keep scanning
As you scan a space, Canvas is reconstructing the scene in real-time. This means that geometry is being observed and recreated as you move, and that geometry is stored in your iPad's memory (the 2GB or 4GB "short-term" memory). The "memory indicator" bar in the top-right corner shows you how much memory has been used up in the scan, relative to how much you have remaining.
We have had some customers ask if this is a "timer." It is not. It is simply showing how much
detail you can still capture before Canvas will auto-save your scan to prevent data loss. Once you get about 80% full, we'll display a warning, which turns from yellow to red, like this:
You'll also notice that the bar in the top-right has turned from blue to red. This warning doesn't mean that you're going to lose any data or in any danger, it just means that if you don't finish your scan soon it will auto-save. You may also notice that if you keep scanning scanning can get a little slower and chunkier — this is because your iPad is really starting to get pushed to its limits. This won't affect the quality of your scan, it just is a little less smooth of a scanning experience.
If you do exceed the memory limits your scan will be auto-saved and you will receiving this message:
What to do if memory is running out before you can scan a full room
First, make sure you've read this article: How big of a space can I scan? Not only does this explain how much we expect you to be able to capture in a single scan, but it talks about different strategies for minimizing memory consumption during the scan.
Occasionally, your iPad operating system doesn't release memory 100% consistently. After many scans in a row you might notice that the low memory warning is happening earlier and earlier (look out for the usage bar jumping to 25%+ full as soon as you start scanning), and then eventually you can't scan a full room. You can kind of think of this like a car overheating, but luckily you don't need to stop and wait for it to cool down. Simply kill and restart the Canvas app, try to scan again, and it should start at close to zero again, allowing you to scan rooms in full. In some cases, you may need to turn your iPad fully off and back on again, and the problem should clear up.
This should only happen after many (10+) scans in a row, so if you're noticing this happen earlier, after only a few (or on your first) scans, or isn't going away after power cycling the iPad, please email firstname.lastname@example.org with the following information:
- iPad Model
- iOS Version
- If this is the first time you've used your sensor or it started happening out of the blue
We'll take it from there!