Tutorial: Designing a 3D world

1. Introduction

In this chapter we show how you can design 3D world using Castle Game Engine editor. We assume you have already read the overview of the viewport and scenes.

You will learn:

  • How to create a project,

  • design 3D contents in a viewport,

  • add scenes to display and animate glTF models,

  • control camera at design-time (in editor) and run-time (determines what the user sees),

  • control navigation at design-time (in editor) and run-time (determines how the user can move in your 3D world),

  • manipulate lights.

2. Complete tutorial code

The complete result of this tutorial is in the Castle Game Engine. Just open the project examples/viewport_and_scenes/viewport_3d_tutorial in the editor. If at any point you get lost, just look there.

3. Create empty project, add a viewport

  1. Run Castle Game Engine editor, create a new project using the Empty template.

    Create new project

  2. Open the data/gamestatemain.castle-user-interface design using the Files panel at the bottom of the editor. Enter data subdirectory and double-click on gamestatemain.castle-user-interface.

    Open the design

  3. Add a TCastleViewport by right-clicking on Group1 (the root component in the hierarchy) and choosing "Add User Interface → Viewport (3D)".

    Add viewport

    The new viewport includes by default:

    • a camera, that determines what is visible (initially) for the user,

    • a light source, so that things are not completely black,

    • a 3D plane,

    • a background (by default just some gradient to simulate ground and sky, and see where the horizon is).

    Delete now the 3D plane (Plane1). The rest of components will be useful for us.

    Note that viewport has by default FullSize set to true and so it fills the entire design area. If you want, you can set FullSize to false and resize the viewport however you want.

    You want to move the new viewport in the hierarchy, such that it is underneath the LabelFps component. This way you will see FPS counter over the viewport.

    Added viewport - without Plane1 and with fixed LabelFps order

4. Add a scene showing the 3D car, adjust camera, lights and navigation

  1. Add a TCastleScene to TCastleViewport.Items. It is easiest to do by right-clicking on the Items in the editor hierarchy (panel on the left side), and choosing "Add Transform → Scene (TCastleScene)" from the menu that appears.

    Add scene After adding a scene

  2. Now you need some 3D assets to actually play with.

    We advise at this point that you take the sample 3D asset of a car and road we have in our examples. Open in your file manager the examples/viewport_and_scenes/cars_demo/data subdirectory of your Castle Game Engine sources. Select there the files:

    • car.bin

    • car.gltf

    • road.bin

    • road.gltf

    • Whole textures/ subdirectory.

    • Optionally, select also car.blend and road.blend. Castle Game Engine doesn’t read .blend files, but you can modify them in Blender and export to glTF, to play with what you can do in 3D.

    Files to copy

    Copy these files into your new project, into the data subdirectory. It is easiest to open it by right-clicking on data in CGE editor, and choosing "Open In File Manager" from the context menu that appears.

    If you already have some 3D assets (see 3D assets formats we support) you can of course use at this point already.

  3. Try the preview feature of the editor at this point. Just select (click once) the car.gltf file. If you copied everything correctly (including car.bin and textures/), it will display the 3D car model in a preview window that appears in the bottom-right corner.


  4. Set your Scene1.URL property to the car.gltf model in your data. To do this, select Scene1 in the hierarchy (left panel of the editor), then look for URL in the object inspector (right panel of the editor), and click on the small button with 3 dots …​ in the edit field next to the URL. This will open a normal dialog window, where you should select the car.gltf in your project’s data.

    Once you accepted this, note that the Scene1.URL changed the castle-data:/car.gltf. In general, this is an URL of the file. It uses a special castle-data protocol to indicate that the file is in the project’s special data directory.

    Note that instead of clicking on the button with 3 dots, you could have also pasted the URL castle-data:/car.gltf in the edit field. It’s a simple text field, you can edit it like any other text field if you need to, and it will reload the loaded model. You can set the URL to empty always to unload the model.

    Added car

  5. Select the Camera1 to see a preview of what is visible from the point of view of this camera. This is what the user will see right after running the application.

    Initial camera position and direction

    You can adjust the camera in 2 ways:

    1. Fly around in the design by holding right mouse button and pressing AWSD (move forward, backward, strafe) and QE (move up, down) keys. Change the speed using mouse wheel. Once you have a view that satisfies you, use the menu item "Viewport → Align Camera To View" (key Ctrl + 0) to align camera to the view.

    2. Or use the "Move Transform", "Rotate Transform" tools to move / rotate the camera. Observe the preview (you can "pin" it using the appropriate button) to see the results.

    Better camera position

  6. Allow user to navigate during the game. For start, we recommend using the TCastleExamineNavigation. Right click on the Viewport1 and choose "Add User Interface → Navigation/Examine". This will add ExamineNavigation1 component to your hierarchy.

    Other navigation methods are available, like TCastleWalkNavigation to walk or fly. You can also just control the camera completely through your own code, not relying on any built-in TCastleNavigation descendant. For example, you can process the keyboard input in your state to move/rotate the camera.
  7. Move the light a bit higher. Switch to "Move Transform" tool, select the light, and drag it up.

    Light moved up

5. Run the game

Run the game at this point! Just press F9 in the editor.

Game running

6. Play animation

There is a simple animation called wheels_turning defined in the car.gltf model. Let’s configure the scene to automatically play it.

To do this, just edit the AutoAnimation property. You can choose one of the existing animations using the combo box there. Leave the AutoAnimationLoop property at default value of true to make the animation looping.

Playing animation

During the game, you can switch the animation to a different one. You can do this by setting the AutoAnimation and AutoAnimationLoop from code, but usually it is more comfortable to use the PlayAnimation method. Chapter Writing code to modify scenes and transformations shows how to do this.

7. Add a road and more cars

Your viewport may contain many scenes. This is how you can design 3D game levels using the Castle Game Engine editor — just add various TCastleTransform (including TCastleScene) instances to the viewport, and arrange them (move, rotate, scale) as needed.

  1. Add another scene to the viewport (right-click on the Items property of the viewport).

    Call it SceneRoad (edit the Name property in object inspector, or press F2 in the hierarchy to edit the name).

    Set its URL to point to the castle-data:/road.gltf model.

    Add another scene Edit scene name Set road URL

  2. Edit the car scene name too, to make it more obvious in the hierarchy. Right now it is called Scene1, we recommend to edit it to SceneCar now.

  3. Add more cars. While you could add new TCastleScene instances, by repeating the process above, it is easier to use "Duplicate" command (key shortcut Ctrl + D) available when you righ-click on the SceneCar.

    New car scenes, named like SceneCar1, SceneCar2…​, will appear at the same position as the original car. Use the "Move Transform" tool to show a "gizmo", to move each car to a unique position. Click and drag on one of the arrows to move the car.

    You can observe that moving the car using gizmo also updates it’s Translation property in the Layout tab. You can also move the car by just editing the numbers there, to manually input X, Y, Z movement values.

    Duplicate scenes Move scenes

8. Run the game again

Run the game again at this point, to test that you can view the road and animated cars. Just press F9 in the editor.

Game running with many cars and road

9. Walk around the level

Now that we have constructed a simple 3D world, composed of multiple scenes (cars and road), it would be nice to walk around in this world using typical FPS (first-person shooter) controls.

  1. We recommend first to duplicate the SceneRoad a few times, to have a large floor area to walk on.

    Multiple road scenes to create a large floor

  2. Switch navigation mode to walk. To do this, select ExamineNavigation1 component and delete it (just press Delete key), then add to Viewport1 new navigation by right-clicking and choosing "Add User Interface → Navigation/Walk". This will add WalkNavigation1.

  3. Change the TCastleWalkNavigation.MoveSpeed property of your WalkNavigation1 to move faster. We recommend to set it to 10 now, which means you will move with speed of 10 units (meters) per second. This is not realistic (people are not that fast), but it allows for comfortable testing. Players in games often move unrealistically fast.

    Adjust walk navigation MoveSpeed

  4. Increase the TCastleWalkNavigation.PreferredHeight of the WalkNavigation1 component. The default value is 1.6, which means that player’s height is 1.6 meters when standing — this corresponds to a normal (not very tall) human. For games, reasonable (but still somewhat realistic) values could be considered between 1.6 and 2.0 (players in games are often tall).

    For this demo, for now, we recommend you set this value to a big number: 4.0. This is not realistic at all (humans are rarely 4 meters tall :) ), but it will allow to test walking quickly, and will allow you to "walk over" cars. It also matches the unrealistic

    Adjust PreferredHeight

10. Run the game - final test!

Run the game again with F9. Walk using:

  • A W S D keys to move (forward, backward, strafe).

  • C key to crouch.

  • Space key to jump.

  • Drag with left mouse button to move and rotate.

  • Use mouse scroll wheel to raise your head / bow down.

Walk over the cars and jump over them to test collisions and gravity.

Game running with walking

11. Further things

11.1. Lighting

You can add, modify, delete lights on the level.

To add a new light in Castle Game Engine editor simply click on the Items property of the viewport and choose a new Add Transform → Light…​_. Then move/rotate the light as needed. The following light sources are available:

  • TCastlePointLight - omnidirectional light that shines with a certain Color, Intensity and Radius. The rotation of this light doesn’t matter, only the position influences the actual effect.

  • TCastleDirectionalLight - light that shines along a certain direction, with certain Color and Intensity. It approximates a light source that is very very far away, like a real-world sun. The position of this light source doesn’t matter, only the rotation influences the actual effect.

  • TCastleSpotLight - light that shines from a given position, in a given direction, within a cone. The cone angle is configurable (by CutOffAngle and BeamWidth), as well as Color, Intensity and Radius.

You can also place a light as a child of the camera. This is an easy way to make a headlight. Simply add a TCastleDirectionalLight instance as Camera child to have a headlight, i.e. light shining in the direction you are currently looking.

Watch the presentation how to use light components:

11.2. "Mouse look" navigation

The walk navigation is easiest if you use mouse look. It will allow to move the mouse to rotate around.

11.2.1. Turn on by default

You can activate this by just setting WalkNavigation1.MouseLook property to true. Setting this property doesn’t change the navigation in the editor, but once you run the game the mouse look will work. The game will grab your mouse, and you will rotate by moving the mouse.

Note that, as we grabbed the mouse but didn’t provide any way to "escape" from it, you cannot easily close the game window by clicking on the usual "close" button on the window frame. Just press Alt+F4 on most systems to close it.

11.2.2. Allow to turn on/off using code

Instead of having the mouse look just active by default, we can make it active e.g. only once you click the right mouse button. Clicking the button again could deactivate it.

Such behavior has to be implemented using the code. Chapter Writing code to modify scenes and transformations describes how to edit the game code. We don’t want to get ahead of ourselves…​ But actually it is quite easy. Just edit the code/gamestatemain.pas file, and

  1. Add CastleCameras unit to the uses clause in the interface.

  2. Declare WalkNavigation1: TCastleWalkNavigation; inside the private section of the TStateMain, under the comment { Components designed using CGE editor, loaded from gamestatemain.castle-user-interface. }.

  3. In TStateMain.Start implementation, add this code:

    WalkNavigation1 := DesignedComponent('WalkNavigation1') as TCastleWalkNavigation;
  4. In TStateMain.Press implementation, add this code:

    if Event.IsMouseButton(buttonRight) then
      WalkNavigation1.MouseLook := not WalkNavigation1.MouseLook;

11.3. More precise collisions

The collisions work correctly in this simple demo, as both the road and cars have simple shapes that can be approximated using boxes. In general, your levels will probably have more complicated shapes. To make any shape work nicely with default navigation collisions, set the Spatial property of your scenes to include the ssDynamicCollisions flag. We recommend to include also the ssRendering flag to optimize the display of scenes with multiple shapes.

Do this for all your scenes, both cars and roads. Note that you can select multiple scenes in the hierarchy with Ctrl and then edit the Spatial property of all selected scenes at one.

Edit Spatial of all scenes

11.4. Multiple instances of the same scene (using TCastleTransformReference)

It is possible to optimize the usage of resources, when you want to instantiate the same resource multiple times, and each instance has the same state (which means that it is static, or plays the same animation).

  1. Remove the car copies you made with "Duplicate" command earlier. You’ll add copies in a different way. Leave only one car, SceneCar.

  2. To make things more intuitive in the following points, remove any translation you may had on SceneCar. You can do this using "Reset Transform" in the "Layout" tab of the object inspector. You could also just type 0 0 0 into the SceneCar.Translation value.

    If you need to translate even this one car, then add an intermediate transformation like TransformCar. Add this to Viewport.Items, and drag SceneCar to be a child of TransformCar. Then you can change translation of TransformCar to move your 1st car.
    You can also just disregard this advise, and leave non-zero translation on SceneCar. It works, but it means that each reference also has a shift — you’ll see what we mean by this next. It may be non-intuitive at the beginning.
  3. Add a TCastleTransformReference to the Viewport.Items.

    1. Set it’s Reference property to point to the SceneCar.

    2. And move it wherever you like.

    3. Change it’s name to be something better than default TransformReference1. We propose to change it to SceneCarReference1.

  4. Duplicate the SceneCarReference1 as many times as you want to, and translate each instance differently.

Done. Now you can have lots of cars — yet they all share the same data, by referencing (in memory) the same SceneCar instances. This is great to conserve resources and speed when you need a lot of instances of something. E.g. this would be great for trees on a big outdoors level.

To improve this documentation just edit the source of this page in AsciiDoctor (simple wiki-like syntax) and create a pull request to Castle Game Engine WWW (cge-www) repository.