center line

content/pong/scoring/center_line.md

@@ -8,52 +8,84 @@ Now we need to draw the center line.
 
 This will be a fairly basic GeneralRenderer - it doesn't need to react to anything.
 
-```ts
-import { GeneralRenderer } from "encompass-ecs";
+In **PongFE/Renderers/CenterLineRenderer.cs**:
 
-export class CenterLineRenderer extends GeneralRenderer {
-    public layer = 0;
+```cs
+using System;
+using Encompass;
+using Microsoft.Xna.Framework;
+using Microsoft.Xna.Framework.Graphics;
+using PongFE.Components;
 
-    private middle: number;
-    private height: number;
+namespace PongFE.Renderers
+{
+    public class CenterLineRenderer : GeneralRenderer
+    {
+        public SpriteBatch SpriteBatch { get; }
+        public Texture2D WhitePixel { get; }
 
-    public initialize(middle: number, height: number) {
-        this.middle = middle;
-        this.height = height;
-    }
-
-    public render() {
-        love.graphics.setLineWidth(2);
-        this.dotted_line(this.middle, 0, this.middle, this.height, 10, 10);
-    }
-
-    private dotted_line(x1: number, y1: number, x2: number, y2: number, dash: number, gap: number) {
-        const dx = x2 - x1;
-        const dy = y2 - y1;
-        const angle = math.atan2(dy, dx);
-        const st = dash + gap;
-        const len = math.sqrt(dx * dx + dy * dy);
-        const nm = (len - dash) / st;
-
-        love.graphics.push();
-
-        love.graphics.translate(x1, y1);
-        love.graphics.rotate(angle);
-        for (let i = 0; i < nm; i++) {
-            love.graphics.line(i * st + gap * 0.5, 0, i * st + dash + gap * 0.5, 0);
+        public CenterLineRenderer(SpriteBatch spriteBatch, Texture2D whitePixel)
+        {
+            SpriteBatch = spriteBatch;
+            WhitePixel = whitePixel;
         }
 
-        love.graphics.pop();
+        public override void Render()
+        {
+            ref readonly var playAreaComponent = ref ReadComponent<PlayAreaComponent>();
+
+            DrawDottedLine(playAreaComponent.Width / 2, 0, playAreaComponent.Width / 2, playAreaComponent.Height, 20, 20);
+        }
+
+        private void DrawDottedLine(float x1, float y1, float x2, float y2, int dash, int gap)
+        {
+            var dx = x2 - x1;
+            var dy = y2 - y1;
+            var angle = Math.Atan2(dy, dx);
+            var st = dash + gap;
+            var len = Math.Sqrt(dx * dx + dy * dy);
+            var nm = (len - dash) / st;
+
+            SpriteBatch.End();
+            SpriteBatch.Begin(
+                SpriteSortMode.Deferred,
+                null,
+                null,
+                null,
+                null,
+                null,
+                Matrix.CreateRotationZ((float)angle) * Matrix.CreateTranslation(x1, y1, 0)
+            );
+
+            for (var i = 0; i < nm; i++)
+            {
+                SpriteBatch.Draw(
+                    WhitePixel,
+                    new Rectangle(
+                        (int)(i * st + gap * 0.5),
+                        0,
+                        dash,
+                        1
+                    ),
+                    Color.White
+                );
+            }
+
+            SpriteBatch.End();
+            SpriteBatch.Begin(SpriteSortMode.Deferred, BlendState.NonPremultiplied);
+        }
     }
 }
 ```
 
-I took the dotted line draw procedure from [this helpful forum post](https://love2d.org/forums/viewtopic.php?t=83295) and modified it slightly. Thanks Ref!
+I figured out the math for the dotted line procedure so you don't have to. You're welcome.
 
-Add it to the WorldBuilder...
+The main magic to understand here is the matrix transformation - the gist of it is that a matrix transformation lets us apply a translation, rotation, and scaling operation all at once and very efficiently. Here we compose a rotation and a translation matrix together so that we can just draw simple rectangles to create the dashed line. Then every SpriteBatch draw rectangle has this transformation applied to it.
+
+Add our CenterLineRenderer to the WorldBuilder...
 
 ```ts
-world_builder.add_renderer(CenterLineRenderer).initialize(play_area_width * 0.5, play_area_height);
+WorldBuilder.AddRenderer(new CenterLineRendereR());
 ```
 
-![center line](/images/center_line.png)
+![center dashed line](/images/center_line.png)

content/pong/scoring/display_scaling.md

@@ -125,6 +125,9 @@ Let's revise our **ScoreRenderer** too.
         }
     }
 ```
+
+We have introduced a new method above, **ReadComponent**. ReadComponent allows us to read a single arbitrary component of a given type. It is useful when we have a single component of a certain type in the world and we want to just grab data from it.
+
 Now, in our draw method, we will have the Encompass World draw to our GameRenderTarget, and then we will draw that render target using the transform matrix we get from ResolutionScaler.
 
 ```cs