I have been reading a bit about widget optimization and best practices on some of the official unreal guides but am not positive I understand.
From what I have read, when an element of a widget is updated (for example health bar changes), the entire widget needs to be repainted. I am not sure what repainting exactly means, but reqardless, this would suggest to me that something like player HUD which has several elements that are both always on screen (health bar, map, resource, etc) and frequently being changed (health updates, etc) would be best divided into several individual widgets. Doing so, however, would mean that I would need to use a lot more horizontal/vertical boxes + spacers and that I need to keep track of more individual widgets. The solution (I think) is to wrap each element (health bar, ammo bar, map, etc) with an invalidation box, which essentally lets me keep lots of features within the same widget, but minimizes cost since changes to one element (updating health) would not require repainting of all other elements (ammo, map, etc) since they have the invalidation wrap. Is this correct?
Repainting means rendering the UI to textures and applying those textures on screen-space quads.
Dividing the HUD in multiple widgets is usually more due to responsibility separation and ease of design / modification than technical optimization. Separated widgets should not lead to the use of more spacers, horizontal or vertical boxes but the user widgets themselves have some overhead. I believe the overhead is minuscule especially weighted against the benefits.
Yes, your solution is valid. In fact, the invalidation box approach will work regardless if the widgets are separate or are in one large widget.
That being said I never found too much performance benefit from caching the UI on PC. Most things worth showing are changing frequently and I mostly use invalidation boxes on backgrounds, which are fast to draw anyway.
Great, thank you so much! The only reason I was thinking it would require more spacers/boxes is because I was thinking I would need to orient each HUD component in order to not require a canvas panel for each, however, since the point is to put them all together anyway, I now realize that it makes much more sense to not do that and just position them with the canas panel anchors.
Edit: actually now that I think about it, wouldn’t combining these into one widget as user widgets kind of defeat the purpose since I won’t be able to call interfaces to the individual widgets, just the parent canvas panel?
Yes, your understanding is mostly correct and shows you’re thinking about this the right way.How Repainting Works in UMGWhen a widget (or part of it) changes in a way that affects layout or paint (e.g. health value updates, text changes, visibility toggles, etc.), Slate (the underlying UI system) normally has to re-evaluate and repaint affected parts of the widget tree. In older UMG workflows or without optimization, a change in one child could cause the entire parent widget to be reprocessed. This is what the documentation refers to when talking about repainting costs.Invalidation Box – Exactly What You DescribedYes — wrapping logical groups (health bar, ammo counter, minimap, etc.) in their own Invalidation Box is one of the standard and recommended ways to optimize a complex HUD while keeping everything in a single main widget.
An Invalidation Box caches the layout, geometry, and paint of its children.
When nothing inside changes, those children are basically “free” (no tick, no prepass, no paint every frame).
When something inside does change, only that box (ideally) gets invalidated and repainted.
This is much better than having one giant un-optimized widget where every small change can ripple through everything.Best Practices for a Player HUDHere’s the modern recommended approach:
Use Invalidation Boxes per group
Health + Armor group → one Invalidation Box
Ammo + Weapon info → another
Minimap / Compass → its own
Reticle / interaction prompt → usually left Volatile (see below)
Mark frequently changing elements as Volatile
In the Details panel of a widget (e.g. Progress Bar for health, Text Block for ammo count) → Advanced → Is Volatile = True.
Volatile widgets skip caching and update every frame without invalidating the parent Invalidation Box.
Manual Invalidation when needed
When you update a value (e.g. Set Percent on health bar), you can call Invalidate Layout and Volatility on the specific Invalidation Box if it doesn’t auto-update.
Event-driven updates > Bindings
Avoid heavy property bindings that run every frame. Prefer events/dispatchers that only update when values actually change.
Multiple Widgets vs One Big Widget + Invalidation Boxes
Approach
Pros
Cons
Best For
One main HUD + Invalidation Boxes
Easier management, fewer references
Slightly heavier single widget
Most games (recommended)
Separate widgets per element
Maximum isolation
More overhead managing many widgets
Very complex / modular UIs
For a standard player HUD, one main widget + targeted Invalidation Boxes + Volatile flags is the sweet spot most developers use.Quick TipEnable Slate.EnableGlobalInvalidation in your project (Project Settings or console) — UE5 has much better default invalidation behavior than older versions.Your instinct is spot on. Using Invalidation Boxes around logical groups while keeping frequently updating elements Volatile is exactly the pattern used in many optimized projects.