Using Layer Parameters to Create Sprite Context

summary

Use the layer's depth value to specify the context of the sprite.

Operating environment

Prerequisites

Operating environment

substance

Normally, when you draw a sprite, it is drawn so that what you draw later is in front of you, but by sorting by depth value, you can make the context clear regardless of the order in which the SpriteBatch.Draw method is called.

To sort by sprite depth value, specify "SpriteSortMode.BackToFront" as the first argument to the "SpriteBatch.Begin" method. It is a processing method that draws from the sprite in the back and overwrites the sprite in the foreground.

// 一つでも半透明、透明要素があるスプライトの場合はこちらの引数を使用
this.spriteBatch.Begin(SpriteSortMode.BackToFront, null);

However, if you want to draw only a sprite that is semi-transparent or has no transparent elements at all, you can draw it faster by specifying the following.

// 深度バッファを使用して前後関係を有効にし描画するように指定
// 完全な不透明スプライトのみ描画する場合はこちらが高速
this.spriteBatch.Begin(SpriteSortMode.FrontToBack,
                       BlendState.Opaque,
                       null,
                       DepthStencilState.Default,
                       null);

The fourth argument is "DepthStencilState.Default", which also writes "depth" information to each pixel when the sprite is drawn. When the depth information is written, it is possible to determine that the object to be drawn (in pixels) after that position does not need to be written, so the drawing cost is greatly reduced.

For the above reasons, if you draw the sprite in the foreground first, the drawing cost of the sprite that overlaps behind it will decrease, so it is sorted so that it is drawn from the front by specifying "SpriteSortMode.FrontToBack" as the first argument to draw from the foreground.

However, this is only useful when drawing an opaque sprite with a completely negligible color element behind it. In the case of semi-transparent or opaque sprites, the depth value is written to each pixel even if it is a semi-transparent or transparent pixel, so if you draw from the front, the sprite behind you will not be displayed. This is why "SpriteSortMode.BackToFront" is specified in the character drawing. (Because pixels other than the shape of the text are transparent)

By the way, as a result of a test of drawing 30,000 sprites in my environment, it was about 3 times faster to draw from the front using the depth value than from the back. Of course, it depends on the number of sheets to be drawn, the degree of overlap, the size, etc., as well as the execution environment, so please try it yourself.

SpriteBatch.Begin method

Call it before drawing the sprite. Internally, we are making the necessary settings for drawing sprites.

To draw a sprite, specify a depth value as the ninth argument to the SpriteBatch.Draw method. The values that can be set here are in the range of 0.0~1.0, with 0.0 being the foremost and 1.0 being the backmost.

// 最背面に描画(赤)
this.spriteBatch.Draw(this.texture, new Vector2(150.0f, 50.0f), null,
    Color.Red, 0.0f, Vector2.Zero, 1.0f, SpriteEffects.None, 1.0f);

// 最前面に描画(緑)
this.spriteBatch.Draw(this.texture, new Vector2(110.0f, 90.0f), null,
    Color.Green, 0.0f, Vector2.Zero, 1.0f, SpriteEffects.None, 0.0f);

// ２つのスプライトの間に描画(青)
this.spriteBatch.Draw(this.texture, new Vector2(190.0f, 130.0f), null,
    Color.Blue, 0.0f, Vector2.Zero, 1.0f, SpriteEffects.None, 0.5f);

SpriteBatch.Draw method

Adds a sprite to the sprite drawing batch list.

In the above program, the SpriteBatch.Draw method is called in the order of "red", "green", and "blue", but each depth value is set to "red (1.0)", "green (0.0)", and "blue (0.5)", so you can see that red is drawn at the back and green is drawn in the foreground.

All Codes

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Media;
#if WINDOWS_PHONE
using Microsoft.Xna.Framework.Input.Touch;
#endif

namespace LayerDepthSprite
{
    /// <summary>
    /// ゲームメインクラス
    /// </summary>
    public class GameMain : Microsoft.Xna.Framework.Game
    {
        /// <summary>
        /// グラフィックデバイス管理クラス
        /// </summary>
        private GraphicsDeviceManager graphics = null;

        /// <summary>
        /// スプライトのバッチ化クラス
        /// </summary>
        private SpriteBatch spriteBatch = null;

        /// <summary>
        /// テクスチャー
        /// </summary>
        private Texture2D texture = null;


        /// <summary>
        /// GameMain コンストラクタ
        /// </summary>
        public GameMain()
        {
            // グラフィックデバイス管理クラスの作成
            this.graphics = new GraphicsDeviceManager(this);

            // ゲームコンテンツのルートディレクトリを設定
            this.Content.RootDirectory = "Content";

#if WINDOWS_PHONE
            // Windows Phone のデフォルトのフレームレートは 30 FPS
            this.TargetElapsedTime = TimeSpan.FromTicks(333333);

            // バックバッファサイズの設定
            this.graphics.PreferredBackBufferWidth = 480;
            this.graphics.PreferredBackBufferHeight = 800;

            // フルスクリーン表示
            this.graphics.IsFullScreen = true;
#endif
        }

        /// <summary>
        /// ゲームが始まる前の初期化処理を行うメソッド
        /// グラフィック以外のデータの読み込み、コンポーネントの初期化を行う
        /// </summary>
        protected override void Initialize()
        {
            // TODO: ここに初期化ロジックを書いてください

            // コンポーネントの初期化などを行います
            base.Initialize();
        }

        /// <summary>
        /// ゲームが始まるときに一回だけ呼ばれ
        /// すべてのゲームコンテンツを読み込みます
        /// </summary>
        protected override void LoadContent()
        {
            // テクスチャーを描画するためのスプライトバッチクラスを作成します
            this.spriteBatch = new SpriteBatch(this.GraphicsDevice);

            // テクスチャーをコンテンツパイプラインから読み込む
            this.texture = this.Content.Load<Texture2D>("Texture");
        }

        /// <summary>
        /// ゲームが終了するときに一回だけ呼ばれ
        /// すべてのゲームコンテンツをアンロードします
        /// </summary>
        protected override void UnloadContent()
        {
            // TODO: ContentManager で管理されていないコンテンツを
            //       ここでアンロードしてください
        }

        /// <summary>
        /// 描画以外のデータ更新等の処理を行うメソッド
        /// 主に入力処理、衝突判定などの物理計算、オーディオの再生など
        /// </summary>
        /// <param name="gameTime">このメソッドが呼ばれたときのゲーム時間</param>
        protected override void Update(GameTime gameTime)
        {
            // Xbox 360 コントローラ、Windows Phone の BACK ボタンを押したときに
            // ゲームを終了させます
            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
            {
                this.Exit();
            }

            // TODO: ここに更新処理を記述してください

            // 登録された GameComponent を更新する
            base.Update(gameTime);
        }

        /// <summary>
        /// 描画処理を行うメソッド
        /// </summary>
        /// <param name="gameTime">このメソッドが呼ばれたときのゲーム時間</param>
        protected override void Draw(GameTime gameTime)
        {
            // 画面を指定した色でクリアします
            this.GraphicsDevice.Clear(Color.CornflowerBlue);

            // 深度バッファを使用して前後関係を有効にし描画するように指定
            // 完全な不透明スプライトのみ描画する場合はこちらが高速
            this.spriteBatch.Begin(SpriteSortMode.FrontToBack,
                                   BlendState.Opaque,
                                   null,
                                   DepthStencilState.Default,
                                   null);

            // 一つでも半透明、透明要素があるスプライトの場合はこちらの引数を使用
            //this.spriteBatch.Begin(SpriteSortMode.BackToFront, null);

            // 最背面に描画(赤)
            this.spriteBatch.Draw(this.texture, new Vector2(150.0f, 50.0f), null,
                Color.Red, 0.0f, Vector2.Zero, 1.0f, SpriteEffects.None, 1.0f);

            // 最前面に描画(緑)
            this.spriteBatch.Draw(this.texture, new Vector2(110.0f, 90.0f), null,
                Color.Green, 0.0f, Vector2.Zero, 1.0f, SpriteEffects.None, 0.0f);

            // ２つのスプライトの間に描画(青)
            this.spriteBatch.Draw(this.texture, new Vector2(190.0f, 130.0f), null,
                Color.Blue, 0.0f, Vector2.Zero, 1.0f, SpriteEffects.None, 0.5f);

            // スプライトの一括描画
            this.spriteBatch.End();

            // 登録された DrawableGameComponent を描画する
            base.Draw(gameTime);
        }
    }
}