Introduction

The IPositionedSizedObject is the base interface for all visual objects in the RenderingLibrary (the core game engine used by Gum), and it is also implemented by the GraphicalUiElement. It provides properties for position, size, rotation, and parent/child relationships.

Members

• RenderingLibrary.IPositionedSizedObject.GetAbsoluteX

• RenderingLibrary.IPositionedSizedObject.GetAbsoluteY

Introduction

The RenderingLibrary.Camera object provides control over the viewable area when rendering Gum objects (and any other non-Gum object added directly to the rendering library). In many cases FlatRedBall games do not interact with this object. If the RenderingLibrary.Camera is not modified, then the top-left corner is (0,0) and all objects render at 1:1 scale. Strictly speaking, the Camera object belongs to the RenderingLibrary, which is a basic rendering engine used by Gum. However, most FlatRedBall games use the RenderingLibrary to render Gum, so in many cases it can be thought of as the "Gum camera". The RenderingLibrary.Camera enables simple modifications to how Gum objects are rendered, such as adjusting zoom and offset values.

Accessing the Camera

By default, games that use Gum rely on the Default set of RenderingLibrary objects. Therefore, the following code can be used to access the camera:

var gumCamera = RenderingLibrary.SystemManagers.Default.Renderer.Camera;

Moving the Camera

The Camera can be moved by changing its X and Y values. Moving the Camera will adjust the position of all on-screen Gum objects. The following code can be used to move the Camera up and down with up and down arrow keys:

void CustomActivity(bool firstTimeCalled)
{
    var keyboard = InputManager.Keyboard;

    var gumCamera = RenderingLibrary.SystemManagers.Default.Renderer.Camera;

    if(keyboard.KeyPushed(Keys.Up))
    {
        gumCamera.Y-=5;
    }
    if (keyboard.KeyPushed(Keys.Down))
    {
        gumCamera.Y+=5;
    }
}

Introduction

The TextRenderingMode property controls the approach that the RenderingLibrary uses to render Text objects internally. The following two approaches are supported:

• TextRenderingMode.RenderTarget

• TextRenderingMode.CharacterByCharacter

By default the RenderingLibrary sets the TextRenderingMode to CharacterByCharacter.

CharacterByCharacter

TextRenderingMode.CharacterByCharacter renders each character separately, similar to a situation where each character in a Text object is a separate Sprite object. This approach has a number of benefits:

• There is no practical limit to the number of characters in a single Text object, nor is there a practical limit to the maximum dimensions of the Text character.

• If the Font uses the same texture as other Gum graphics, the RenderingLibrary will not introduce new state changes (RenderBreaks) when rendering text and non-text objects.

CharacterByCharacter offers the most flexibility to rendering, and can greatly improve performance when a game includes a large number of Text objects, such as list boxes or a large number of buttons.

RenderTarget

TextRenderingMode.RenderTarget renders each character separately to an intermediary RenderTarget, and then renders that render target directly to the screen. This approach has the following benefit:

• Very large Text objects which do not change often will render more quickly, as the engine only has to process one large sprite rather than hundreds or even thousands of individual sprites (letters) each frame.

While this approach can be useful for large text blocks (such as multiple paragraphs of text or scrolling credits), it will reduce performance in many situations because it requires switching render states for each text object.

Setting TextRenderingMode

TextRenderingMode is a static property which applies to all Text objects. It can be set and changed at any time, as shown in the following code:

When to Change TextRenderingMode

No set guidelines exist for when to use one rendering mode vs. another; however, in general if you have a large number of individual text objects, it is likely you will want to place the font in the same texture as the rest of your UI and use the TextRenderingMode.CharacterByCharacter. This is especially important on mobile apps. If you suspect that your game is suffering from performance due to rendering each character individually, you can swap the TextRenderingMode and compare your game's frame rate - the most important thing is to set your game up early to use the same texture for fonts and the rest of the UI.

Layers are containers which can be used to control the draw order of objects. Layers provide an alternative to setting the Z value of graphical objects for rendering. Typically layers are created for categories of objects such as:

• Game HUD

• Pause Menu

• Popups

• Command UI (UI which may be used in an RTS to give commands to units)