I decided to take it easy this weekend and do an entry for the first phase of the Mapcore Unreal Tournament level design competition. I haven’t played with Unreal’s brush editing tools that much so I thought this would be a good excuse to get up to speed with them. The brush tools are better than I expected but I’ve already discovered about 5 or 6 things I would change already. Working on improved brush tools for the unreal engine would definitely be an interesting and fun project to do.
Here’s an image showing a days progress from the initial sketch to a playable greyblock. Took about 5-6 hours.
Tags: mapcore_ut_competition_2016 unreal4
LevelViz 003 : Adding a plan view and a custom editor
2016-04-26 5:36 PM
For the next major feature of LevelViz I wanted to add the ability to seamless transition into a plan view so people could see a topdown view of the scene (as well as possibly side and front views). This is very similar tohow you see a orthographic projection of the top, front and side views of a scene in most 3d authoring packages. The idea is to essentially be able to generate nice drawings of the scene with little to nowork required from the scene author.
Here is a preview of what the functionality looks like right now :
To accomplish this I had to do a few things. First I needed to get a decent looking outline effect. Second I needed to create a small editor for selecting the geometry that will contribute to the plan view. Finally I needed a way to figure out how to manipulate the camera so that it can seamless transition into a nice framing of the plan view. I’ll cover each of these 3 major steps over the course of this development log post.
Essentially what I want is clean lines around the bounds of a static mesh for each mesh we choose to be part of the plan view.
I considered a few options on how to get the look for the plan view. At first I considered rendering as a wireframe but the issue with the default method of rendering as a wireframe is that by the point the mesh is processed on the GPU it has become triangulated which is not something desirable for this type of drawing. Here’s what it looks like :
One way I could have possibly fixed this is by not rendering an edge who’s two attached faces are co-planar. It’s possible this could have worked but I was worried about issues with non-desirable edges who adjacent faces were slightly non-co-planar rendering by accident. I could somewhat reduce this issue by introducing a co-planarity thresholdbut I started to worry about other edge cases I haven’t anticipated plus while considering this method I came upon another method that accomplishes the same effect but with less room for edge case errors.
What I did was render all the objects of interest to a depth buffer then used edge detection to give them a render outline. I used a well known edge detection technique which luckily has ample documentation on how to implement using the unreal engine and their material system. Here’s what it looks like :
Next I wanted to be able to select various static meshes to be flagged as meshes which contribute to the drawing of the plan view.
The core of this plugin relies on placing a “ViewManager” actor into a scene. The view manager does a lot of management of various objects relevant to the plugin such as tracking vantage points as well as storing the array of meshes which will contribute to the plan view. Now I could have just exposed the plan view mesh array so I can add them one by one with the eye dropper but that is tedious. I wanted a way to select a group of meshes and add them to the plan view. The problem here is that if I select a bunch of meshes then I’m no longer selecting the view manager and as such I can’t add them to the view manager array.
To solve this what I decided I needed to do was make a small floating window which persists even when the view manager is not selected. This was a good opportunity for me to start digging deep into what it takes to augment the editor further than simple details customization. I studied up on Michael Noland’s essential “Extending the Editor” youtube video which is by far my favorite training video Epic has produced because rather than going every detail to the point of being tedious he shows the major ways you can extend the editor then points the audience to various types and keywords we can look up in the engine source code to see how stuff is done. One of the great things about a video like this is it’s very resistant to obsolescence when new versions of the Unreal engine are released. Implementation details change frequently but the overall concepts are the same.
After studying how an editor is implemented and doing some small experiments adding my own commands I concluded that my use case doesn’t justify a new full blown editor but rather just a new window. You launch the window from the view managers details panel and it persists until you close it. Here’s how you would launch it (the view manager is selected in this image).
Setting this up is fairly easy. First I have to setup a new button for launching the editor. This is fairly straightforward, I do a details customization on the view manager where I add the button.
From here when the button is clicked in the callback I request a reference to my editor module which has a data member that is the type of my editor and from there I launch the editor. This is how I launch the editor.
This is weird for a number of reasons. First it doesn’t implement IModuleInterface which I had suspected was required. Second it somehow creates an instance of FViewManagerEditor which I would have thought might have involved calling the default constructor. As a test I made the default ctor private and made a specialized ctor and it STILL managed to create a valid instance of this class. I did some light digging through the source code for the module manager singleton and couldn’t find any template magic that was somehow able to create a valid instance of my editor without a default ctor.
There is one issue however. The editor will crash on exit trying to find a module. I suspect that while this works, it’s a side effect and is not intended to be used that way and is probably dying on module de-initialization. Requesting my actual module with the editor as a data member avoids the crash.
Anyways from here I simply add 4 buttons for all the actions I wish to perform. When a button performs an action that requires a reference to the view manager I do a heavy query of all the objects in the editors world for the view manager then cache that reference. With my view manager reference available to my editor, adding and removing objects from the plan view is easy. It’s merely a matter of getting an array of all selected static mesh objects and adding them to the view managers array of plan meshes.
Setting up the transitionNext I wanted to be able to do a nice transition to plan view from any arbitrary vantage point. There’s a few challenges to this.
First is the camera projection. The camera is using a perspective projection matrix which is not ideal for a top-down plan view. This would cause the plans to look like they are jumping out at you rather than look like a top down drawing. This requires switching the camera to use an orthographic projection matrix. This is very easy to do in Unreal, in fact it’s a matter of setting a single boolean as well as setting up the typical values that go into setting up an orthographic projection matrix such as defining the width and height of the projection volume. What Unreal doesn’t provide is a way to smoothly lerp from perspective to orthographic projection matrices. This will be something I’ll be tackling in the near future.
Next is generating a transform for the camera position to look down on the scene. To do this I added a post-process component to the view manager which the user can setup to define the region for the plan view. I need the post-process component for the outline rendering so this essentially kills two birds with one stone.This way I make the transform conform to the rotation of the post-process volume as well as use it to derive the parameters for setting up the orthographic projection matrix.
One thing I still need to do is add an editor-only arrow component so people can know which direction is up on the plan when it’s generated.
Here’s what the volume looks like in the editor.
And here is the topdown plan view generated from this volume when viewing ingame (sorry about the little test icon in there, that’s something I’m currently working on that’s unfinished).
If the view is a little confusing here is a roughly aligned view in the editor of what the plan view is displaying.
If this blog post was a little much to take in I apologize. These development blogs I treat like a stream of consciousness and make a point to try to keep the time to write them under an hour so I can actually focus on development
Tags: levelviz unreal4
LevelViz 002 Vantage point system first version review
2016-03-20 12:58 PM
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.
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.
The red lines between the cameras areeditor 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.
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 overridePostEditChangeProperty(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.
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.
The second step is you need to make a class that inherits fromIDetailCustomization. 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 calledCustomizeDetails(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).
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 :