treehouse/content/programming/unreal-engine.tree

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- this is that really cool game engine I work with on a daily basis

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    + so I have a lot of stuff to say about living with it

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        - both the fun and the good, and that which ruins my mood

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+ ### Blueprint

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    + NOTE TO SELF: this section could really use some screenshots

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        - I don't have UE installed on my home computer yet, so you'll have to take my word for a lot of these things

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        - anyways back to your regularly scheduled bullet points, *\*ahem\**

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    + Blueprint, _my arch nemesis!_

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        - _WHAT! you don't remember me? how rude!_

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    - actually I really like Blueprint

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        + lots of visual languages generally feel really unpleasant to write (looking at you Scratch), but somehow Blueprint feels like exactly the opposite

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            - (it's possible Scratch got better since I last used it like 5 years ago but I remember it being pretty cumbersome to use.
              I had no reason to revisit it since so I simply don't know if it's any better now, but if it is, [let's chat][branch:hello]!)

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    + writing Blueprints is actually pretty darn nice and there's a lot to learn from the editor UX and basic refactoring tools

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        + when you drag your mouse out of a pin, and a window will pop up giving you suggestions on what could be connected there

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            + then you select from the list and it creates the node, autoconnecting stuff as necessary

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                - one of the nicer autoconnections it can do is when you want to call a function on an actor component

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                    - instance functions require you to pass in a `self` to call the function on

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                    - so what it does is it suggests functions to call on all the _concrete components
                    you already have in your actor_, and when you select something like `Destroy Component (DefaultSceneRoot)`,
                    it'll not only create a function call node, but also hook up `DefaultSceneRoot` as its `self` parameter

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        + when you try to connect two pins of incompatible types, it'll automatically insert a conversion node for you

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            - Blueprint is strongly typed so you can't just pass in a `Float` where a `String` is expected, but luckily this makes the system way less painful

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            - I do have a gripe with this though and it's where it places the node. it tries very hard to center it but unfortunately never succeeds.

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                + perhaps a bug I could fix one day?

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        - from [Oskar Kogut](https://github.com/kretoskar): if you change a `BlueprintCallable` function to `const` (or otherwise make it pure,) the editor will automatically correct the `Exec` pin flow for you

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    + the design of Blueprint the Language is pretty dated - it is still an imperative language and has a concept similar to statements (`Exec` pins), which breaks the entire idea of pure data
    flow and introduces control flow into the mix

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        - this split is called _pure_ and _impure_ nodes, where impure nodes are those that perform control flow (ie. those with `Exec` pins)

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        + this results in weird edge cases like needing two separate node types to handle branching (one that can have side effects - `Branch`, and another that can't - `Select`)

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            - `Branch` is used to shuttle control flow between two `Exec` lines, based on a `Bool`. you get a `True` branch and a `False` branch

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            + and `Select` is used to choose a value based on another value, kind of like a ternary in C++

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                - however it is quite annoying because you can only switch on enums (and other stuff that has a finite set of values,) whereas with `Branch` you can use any `Bool` condition you want

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                + this would be fine if not for the existence of Gameplay Tags, which precisely _do not_ have a finite set of values

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                    - there is a `Switch on Gameplay Tag` node, but that is for control flow and not data flow!

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                    - this isn't an unsolvable problem but it illustrates the pure vs impure issue pretty well - you'd have to duplicate the implementation of `Switch on Gameplay Tag` to have
                        a version without an `Exec` pin

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        + I'm seeing a bit of a semblance to the classic [function coloring problem][def:article/function_coloring]

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            + except where it usually applies to the `async` concept found in most modern programming languages, here it applies to the concept of control flow vs data flow

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                - and speaking of `async`, [Blueprint handles the classic `async` problem very gracefully][branch:01H8Y0CKD106HXQAJK87XV0H93]!

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        + despite its flaws, one of Blueprint's strengths is asynchronous and latent tasks

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            - since control flow is based on those `Exec` pins, you can easily map your classic concept of callbacks to simply firing off the appropriate `Exec` pin

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            - for example the node for playing animations (`Play AnimMontage`) has a few pins coming out of it that signal playback events like `On Ended`, `On Blend Out`, `On Interrupted`

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                - and you wouldn't even know these are implemented as delegates in C++landia. it just feels like a first-class feature

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            - the only gripe I have is that you can only have latent nodes in the main event graph (you cannot have them within functions)

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                - which is annoying but not terrible, since most of that latent, high level gameplay logic happens inside the main event graph anyways

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    + the editor UI, despite [being helpful as it is][branch:01H8Y0CKD1G06CG62XWZ02JREC], is far from perfect

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        - it's actually quite janky and there tend to be brief flashes of content falling into place

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            - this is true of other parts of the Unreal editor UI but I'll focus on Blueprint here

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        + node UIs are laid out lazily, by default using an algorithm that does not produce precise results for pin locations

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            - which means that when you first load a Blueprint, some of the wires will be bent in weird ways, and will fall into place as you zoom out and explore the graph more

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                - the effect looks quite janky and really upsets my inner perfectionist

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        + as you zoom out, the nodes start looking just a little bit different due to font sizes being snapped to integers

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            - at very low zoom levels, nodes stop rendering their text altogether, which makes their layout shift even more.

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                - the effect of this is that nodes themselves take up less space, and it appears as though there is more space between them than there actually is

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                    - which can make it frustrating to lay nodes out on a large scale, because you'll only find out your nodes are overlapping when you zoom in real close

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            - there's a `Straighten Connection` feature, which you can use to make your graphs look more aesthetically pleasing, but it only straightens the nodes such that they look good on the current zoom level

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                - so what'll happen with it sometimes is you'll straighten a connection, then zoom in, and the connection won't be quite straight because of the aforementioned layout shift

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    + maintaining Blueprints in a large project could be a lot better

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        + with regards to your graphs becoming really large

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            - everybody kinda sorta just formats nodes however they see fit, and there is no unified autoformatter

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                - there's a reason people say Go's tooling is frickin' amazing, you know. it keeps codebases consistent!

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                + this results in what we Hat in Time modders used to call _Kismetti_ in the Unreal Engine 3 days but nowadays we'd call _Blueprintti_

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                    + which is a portmanteau of Blueprint and spaghetti.

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                        - I can't believe I remembered the spelling of that word. *portmanteau*.

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                - there are plugins on the marketplace that solve this, but I refuse to believe Epic Games doesn't have this problem themselves

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                    - I'd guess it's just not very high up their priorities

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            - refactoring your nodes is a hell of a pain. Blueprint is kind of write-only

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                - say you're calling `ApplyGameplayEffectToTarget` a bunch of times and you want to replace those occurrences with a custom function that wraps `ApplyGameplayEffectToTarget`
                with some extra semantic information, to make it more discoverable, searchable, and easy to use

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                    - well then good luck :hueh:

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                    - in a text-based language you could use a dumb search and replace to accomplish this task, but there is no such thing in Blueprint. :cry:

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        + with regards to assets (how long this darn stuff takes to load)

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            - the biggest offender here being that hard references are the default

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                - thus you can add a Mesh Component to your Blueprint and it'll load *the entire mesh with all the textures and skeleton and everything* when you wanna tweak a variable or some logic in the event graph

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                    - and not asynchronously in the background, you will have to _wait_ for it to finish loading. which is pretty annoying

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    + the runtime performance isn't the best for a few reasons

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        - the VM isn't implemented in the most optimal way

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            - I've analyzed this in my [`dispatchers` repository][def:dispatchers/repo] if you wanna have a read

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        - and that hard reference thing can make gameplay stutter when you're loading in new assets, but that's a more widespread issue than just with Blueprints

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        - but in reality most of the logic you're implementing in Blueprints (high-level gameplay stuff) shouldn't be that performance sensitive

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            - and it's not hard to extract the performance sensitive parts to C++ because Blueprint offers tools for refactoring your code

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    - but all that doesn't prevent me from liking it!

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        - since it's way more pleasant to write game logic in than C++, given that you don't need to wait a minute for your code to recompile.