Alex McGilvray

LevelViz 002 Vantage point system first version review

March 20th, 2016

I’ve just gotten the first version of LevelViz done. It consists of 2 parts. LevelViz itself and a small environment I’m doing in Unreal to help show off how it works. Here is a screenshot from yesterday showing the kitchen area of the environment I’m working on.

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It introduces the concept of vantage points which are essentially static cameras placed around the level. The author then links these vantage points together and you end up with a graph of camera connections. From this graph the UI is generated with navigation widgets.

Here is a video I put of of me authoring some vantage points, linking them together and then viewing the level and generated UI to navigate around the environment.

Here is how the overall development and process works

For example here are 3 vantage points that are linked.

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The red lines between the cameras are editor only lines I draw between camreas so you can see their relations. Any 2 cameras with a red line joining them are cameras that can be transitioned between each other. If you were on one camera with 2 red lines leading to other camera then the UI would generate 2 buttons on the screen with thumbnails that show the other cameras view. If you press them then your camera will transition to the camera at the other end of the red line.

The UI is pretty simple right now. It has a series of image custom widgets that have render target textures. There some functionality to tell the UI which image widgets are bound to which vantage points. When that binding happens the image widget’s render target is drawn to by the vantage point. Right now it’s fully rendering to the target all the time but my plan is to change that to only render once when the level loads so that I can get a performance benefit. This project is mainly for static scenes and I want it to be used on touch devices so using a lot of render targets that are actively drawing all the time is not a good idea for performance. Especially when it can be logically offloaded to the loading phase rather than the ingame phase.

Here is an ingame shot of what it would look like if you were at a vantage point with 2 links to other vantage points. Clicking either thumbnail would trigger a transition to the linked vantage point.

04

The vantage points are implemented solely in C++ and I’ve begun to do some work to make editing vantage points easier for the user. There are 2 parts to this.

The first part is relatively simple. I override PostEditChangeProperty(FPropertyChangedEvent & PropertyChangedEvent) of type AActor. This is so when I select a vantage point and link it to another vantage point the linking is bi-direction. I do this all in code. This is to reduce a significant amount of tedium for the user setting up links between vantage points on both sides.

The second part involves customizing the details panel for my vantage point actor type. What I want to to is implement a custom editor in the details panel for vantage points so things like blend time and curves could be edited rather than just the default array view that the unreal engine provides by default. I’m currently in the process of figuring this out but I have a basic custom editor setup that currently only displays a button per object. Here is an image to hopefully better explain what I’m trying to do.

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Just to get the custom details up takes a fair amount of work and understanding of some core concepts.

The first step is you need to create a new code module. By default a new code project in unreal generates a runtime module. What we need to modify the editor though is an editor module. The unreal module system takes a little while to get acquainted to but once you figure it out it’s a great pattern for making modular, composable applications and editor extensions with the unreal engine.

I’ve been quite surprised at how reasonable the build time for unreal engine c++ projects. I suspect their module system helps a lot to reduce build times by simply being able to better determine when to not build something. Anyone serious about programming in the unreal engine environment should put the following module documentation on their reading list.

https://wiki.unrealengine.com/Creating_an_Editor_Module

The second step is you need to make a class that inherits from IDetailCustomization. I should warn 4.10+ users. I found that the typenames in the 4.9 documentation no longer exist in the codebase. I had to do a fair amount of grepping through engine code to see how details customization was implmented in 4.10. It’s generally the same but a lot of the typenames have changed so keep that in mind if you are having trouble with details customization in 4.10.

Once you inherit from IDetailCustomization you can ovveride a method called CustomizeDetails(IDetailLayoutBuilder& DetailBuilder) which as you see will pass you a builder object. With this you can modify how the detail panel is built and inject your own UI code.

Finally the last step involves drawing the UI using Slate which is the Unreal engine’s GUI drawing framework. Slate is really interesting. It’s essentially a declarative UI focused DSL that is built from liberal operator overloading. This means that while it looks different, it’s actually valid C++ and as such benefits from a lot of compile time error checking. It’s quite cool but also carries a bit of a learning curve. Here’s a snippet that simply draws the 2 buttons in the screenshot above. This is run once per button (the code is inside a loop).

	
VantagePointCategory.AddCustomRow(LOCTEXT("MergeSearchText", "Merge"))
.WholeRowContent()
[
SNew(SHorizontalBox)
+ SHorizontalBox::Slot()
.AutoWidth()
.Padding(2.0f, 0.0f)
.VAlign(VAlign_Center)
.HAlign(HAlign_Left)
[
SNew(SButton)
.Text(ButtonText)
]
];

 

I wasn’t particularly happy with the first version of my UI. So while I will be working on making a much nicer UI I will also be focusing on making the UMG content asset abstract enough that if a user wanted to create their own UI they would only need to make a new UMG widget and inherit from my custom UMG class. They could then have all the data they need from the plugin to create their own UI if they choose to do so.

Essentially I provide the model, controller and an optional view and the user can choose to create a new view if they like.

That covers the broad picture of what has been done for this update but I wanted to touch on one more thing. The ocean and sky system. This is part of a large ongoing unreal engine community project which you can use in your unreal projects. The group of people involved in this have been doing amazing work. If you want to learn more about the ocean and sky system the home of the project is on this unreal forums thread :

https://forums.unrealengine.com/showthread.php?42092-Community-Project-WIP-Weather-amp-Ocean-Water-Shader

Here’s a screenshot of the systems in my scene.

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