109 lines
3.7 KiB
Markdown
109 lines
3.7 KiB
Markdown
---
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title: "Renderer"
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date: 2019-05-22T14:16:06-07:00
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weight: 30
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---
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A Renderer is responsible for reading the game state and telling the game engine what to draw to the screen.
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{{% notice note %}}
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Remember: Encompass isn't a game engine and it doesn't have a rendering system. So Renderers aren't actually doing the rendering, it is just a way of structuring how we tell the game engine what to render.
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{{% /notice %}}
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There are two kinds of renderers: GeneralRenderers and OrderedRenderers.
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A GeneralRenderer is a Renderer which reads the game state in order to draw elements to the screen. It also requires a layer, which represents the order in which the Draw method will execute in relation to other Renderers.
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If you were using FNA, a GeneralRenderer might look like this:
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```cs
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using System;
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using Encompass;
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using Microsoft.Xna.Framework;
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using MyGame.Components;
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using MyGame.Messages;
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namespace MyGame.Renderers
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{
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public class GridRenderer : GeneralRenderer
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{
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private int gridSize;
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private PrimitiveDrawer primitiveDrawer;
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public GridRenderer(PrimitiveDrawer primitiveDrawer)
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{
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this.primitiveDrawer = primitiveDrawer;
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this.gridSize = 16;
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}
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public override void Render()
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{
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if (SomeComponent<EditorModeComponent>() && SomeComponent<MouseComponent>())
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{
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var entity = ReadEntity<MouseComponent>();
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var transformComponent = GetComponent<TransformComponent>(entity);
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Rectangle rectangle = new Rectangle
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{
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X = (transformComponent.Position.X / gridSize) * gridSize,
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Y = (transformComponent.Position.Y / gridSize) * gridSize,
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Width = gridSize,
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Height = gridSize
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};
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primitiveDrawer.DrawBorder(rectangle, 0, new System.Numerics.Vector2(1, 1), Color.White, 1);
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}
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}
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}
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}
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```
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This GeneralRenderer will draw a rectangle at the position of the mouse on the screen if an `EditorModeComponent` exists in the world.
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GeneralRenderers are great for things like a heads-up display, where we always want a group of particular elements to be drawn at a specific layer regardless of the specifics of the game state.
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An OrderedRenderer provides a structure for the common pattern of wanting to draw an individual Component at a specific layer. OrderedRenderers must specify a component that implements IDrawableComponent.
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If you were using FNA, an OrderedRenderer might look like this:
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```cs
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using Encompass;
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using Microsoft.Xna.Framework.Graphics;
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using MyGame.Components;
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using MyGame.Extensions;
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using System;
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using System.Numerics;
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namespace MyGame.Renderers
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{
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public class Texture2DRenderer : OrderedRenderer<Texture2DComponent>
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{
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private SpriteBatch spriteBatch;
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public Texture2DRenderer(SpriteBatch spriteBatch)
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{
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this.spriteBatch = spriteBatch;
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}
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public override void Render(Entity entity, Texture2DComponent textureComponent)
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{
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var transformComponent = GetComponent<TransformComponent>(entity);
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spriteBatch.Draw(
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textureComponent.Texture,
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transformComponent.Position,
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null,
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textureComponent.Color,
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transformComponent.Rotation,
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textureComponent.Origin,
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transformComponent.Scale,
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SpriteEffects.None,
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0
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);
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}
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}
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}
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```
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For 2D games, you will need to use layers to be specific about the order in which elements are drawn to the screen. For a 3D game you will probably end up delegating most of the rendering to some kind of scene/camera system.
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