Viewport with scenes, camera, navigation

Viewport with 3D design

1. Viewport and scenes

1.1. Overview

The most important Castle Game Engine class to display 3D and 2D models is TCastleScene. You simply set the TCastleScene.URL property to load a model, like gltf or sprite sheet file.

You have to insert instances of scenes into a viewport (more precisely, TCastleViewport.Items tree) to make them actually visible. TCastleViewport represents a 2D viewport on a screen, within this viewport your world (3D or 2D) is displayed. Viewport is a user interface control, which means that it descends from TCastleUserInterface and it shares the same feature we’ve seen in the previous chapter about states and UI.

The scenes can be transformed (moved, rotated, scaled) within the viewport. You can arrange them in transformation groups using TCastleTransform. TCastleTransform is an ancestor of TCastleScene that doesn’t display anything by itself, but it transforms all the children.

1.2. Video

If you like to learn by watching, this is good introduction to viewport capabilities in 3D and 2D:

1.3. TCastleTransform descendants

TCastleViewport has a property TCastleViewport.Items that holds everything that the viewport displays.

You can add there any classes descending from TCastleTransform. We list the most important classes and their properties below.

1.3.1. Transform (TCastleTransform)

Use the base TCastleTransform class to transform and group the children.

The most important properties are Translation, Rotation, Scale. Operate on children using methods like Add, Remove.

1.3.2. Scene (TCastleScene)

TCastleScene is the most important class to display 3D and 2D models.

It can render, animate, perform collisions etc. Set URL to load the model. Run animation using PlayAnimation. TCastleScene descends from TCastleTransform. So you can also use Translation, Rotation, Scale to transform it. Scene can even have children. Use ExposeTransforms to attach children to animated bones in glTF skeleton.

TCastleScene allows to place and animate 3D objects in the viewport

1.3.3. Text (TCastleText)

TCastleText allows to display a text, possibly transformed in 3D.

Its most important property is TCastleText.Caption (or, if you want access the multi-line string list, TCastleText.Text). The font is configurable using TCastleText.CustomFont.

Text in 3D using TCastleText


Use TCastleText when the text is part of the game world (it moves when the camera moves) and when the text may be in 3D.

For user interface text, outside of viewport, use TCastleLabel instead. TCastleLabel and TCastleText are similar in many ways, they share some properties like Caption and CustomFont.

1.3.4. Primitives (TCastlePlane, TCastleBox, TCastleSphere, TCastleCylinder, TCastleCone)

TCastlePlane, TCastleBox, TCastleSphere, TCastleCylinder, TCastleCone are easy 3D primitives that you can use to design your world.

All of them have a configurable size, Material (set to pmPhong or pmUnlit to easily make it brighter), Color, Texture and other basics. While you could create such simple objects in any 3D authoring software (and use them through TCastleScene as well), our primitives are often very useful for quickly prototyping your game world.

Primitives in 3D

1.3.5. Image (TCastleImageTransform)

TCastleImageTransform allows to display an image inside a viewport. This is great for simple static 2D game backgrounds, that should move along with player or camera. The image has a configurable pivot, it can be repeated and resized in an easy way.

Set Url to load the image. Optionally adjust RepeatImage, Size, Pivot as you see fit.

Image in a viewport

1.3.6. Reference (TCastleTransformReference)

TCastleTransformReference makes a reference to another TCastleTransform (e.g. a single scene, or a group of scenes) to instantiate it again within the same viewport. This is an efficient way to create a lot of instances of the same object. At the end of Tutorial: Designing a 3D world we have a quick section describing how to use it.

Set TCastleTransformReference.Reference to indicate which transformation is referenced by this instance.

Many car instances

2. Camera

Camera determines what part of the world (3D or 2D) is visible in the viewport. Ready camera instance is available as TCastleViewport.Camera property. You can configure camera easily by changing its properties e.g. MyViewport.Camera.Translation := Vector3(1, 2, 3).

3. Navigation

Navigation is our term to describe a class handling user input to move the camera. Our engine provides some ready navigation classes, for example TCastleWalkNavigation implementing a typical navigation in FPS games. But you don’t have to use our ready navigation classes, you can easily just move the camera with your own code.

4. Next: Using the viewport in Castle Game Engine editor

Now that you know the basic terminology and classes, let’s see how to actually use them.

Next chapters will start by describing how to use them in our visual editor, and later we’ll show examples how to use them from Pascal. Remember that everything you do inside the editor can be done by Pascal code too. In particular, all the classes and their properties that you use within the editor are really the same classes you use from Pascal code. So whatever you can change from editor — you can also later change during the game, from code. And all the class instances that you create within the editor (like TCastleScene) — can also be created (or destroyed) in any order during the game execution.

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