From 9504c2236c2afa63d34bfcd8fdd5382ea95bbae6 Mon Sep 17 00:00:00 2001
From: Colin McMillen <colin@semicolin.games>
Date: Mon, 9 Mar 2020 14:47:21 -0400
Subject: [PATCH] LinesOfSight: support multiple NPCs

---
 Shared/LinesOfSight.cs | 51 +++++++++++++++++++++++++++++-------------
 1 file changed, 36 insertions(+), 15 deletions(-)

diff --git a/Shared/LinesOfSight.cs b/Shared/LinesOfSight.cs
index 3227514..15a2650 100644
--- a/Shared/LinesOfSight.cs
+++ b/Shared/LinesOfSight.cs
@@ -5,18 +5,27 @@ using System;
 namespace SemiColinGames {
   public sealed class LinesOfSight : IDisposable {
 
-    const int NUM_EDGE_VERTICES = 60;
+    // Max number of NPCs whose vision cones will be shown at once.
+    const int MAX_NPCS = 4;
+
+    // Number of edge vertices per vision cone.
+    const int NUM_EDGE_VERTICES = 30;
 
     readonly VertexBuffer vertexBuffer;
     readonly IndexBuffer indexBuffer;
-    // coneVertices[0] is the eye position; the rest are the edge vertices.
-    readonly VertexPositionColor[] coneVertices = new VertexPositionColor[NUM_EDGE_VERTICES + 1];
+    readonly bool[] coneEnabled = new bool[MAX_NPCS];
+    // coneVertices[i][0] is the eye position; the rest are the edge vertices.
+    readonly VertexPositionColor[][] coneVertices = new VertexPositionColor[MAX_NPCS][];
     // The number of total triangles drawn is one less than the number of edge points.
     readonly int[] indices = new int[(NUM_EDGE_VERTICES - 1) * 3];
 
     Color color = Color.FromNonPremultiplied(new Vector4(0, 0, 1, 0.6f));
 
     public LinesOfSight(GraphicsDevice graphics) {
+      for (int i = 0; i < MAX_NPCS; i++) {
+        coneVertices[i] = new VertexPositionColor[NUM_EDGE_VERTICES + 1];
+      }
+
       vertexBuffer = new VertexBuffer(
            graphics, typeof(VertexPositionColor), NUM_EDGE_VERTICES * 3, BufferUsage.WriteOnly);
       indexBuffer = new IndexBuffer(
@@ -34,8 +43,16 @@ namespace SemiColinGames {
     }
 
     public void Update(NPC[] npcs, AABB[] collisionTargets) {
-      NPC npc = npcs[0];
+      for (int i = 0; i < MAX_NPCS; i++) {
+        coneEnabled[i] = false;
+      }
+      for (int i = 0; i < MAX_NPCS; i++) {
+        UpdateNpc(i, npcs[i], collisionTargets);
+      }
+    }
 
+    private void UpdateNpc(int index, NPC npc, AABB[] collisionTargets) {
+      coneEnabled[index] = true;
       Vector2 eyePos = npc.EyePosition;
       float visionRange = npc.VisionRange;
       Vector2 ray = npc.VisionRay;
@@ -44,7 +61,7 @@ namespace SemiColinGames {
       float visionRangeSq = visionRange * visionRange;
       float fovStep = fov / (NUM_EDGE_VERTICES - 1);
 
-      coneVertices[0] = new VertexPositionColor(new Vector3(npc.EyePosition, 0), color);
+      coneVertices[index][0] = new VertexPositionColor(new Vector3(npc.EyePosition, 0), color);
       for (int i = 0; i < NUM_EDGE_VERTICES; i++) {
         float angle = -fov / 2 + fovStep * i;
         Vector2 rotated = ray.Rotate(angle);
@@ -73,26 +90,30 @@ namespace SemiColinGames {
 
         float tint = 0.6f - hitTime / 2;
         Color tinted = Color.FromNonPremultiplied(new Vector4(0, 0, 1, tint));
-        coneVertices[i + 1] = new VertexPositionColor(new Vector3(closestHit, 0), tinted);
+        coneVertices[index][i + 1] = new VertexPositionColor(new Vector3(closestHit, 0), tinted);
       }
     }
 
     public void Draw(GraphicsDevice graphics, BasicEffect lightingEffect) {
-
       for (int i = 0; i < NUM_EDGE_VERTICES - 1; i++) {
         indices[i * 3] = 0;
         indices[i * 3 + 1] = i + 1;
         indices[i * 3 + 2] = i + 2;
       }
 
-      vertexBuffer.SetData(coneVertices);
-      indexBuffer.SetData(indices);
-      graphics.SetVertexBuffer(vertexBuffer);
-      graphics.Indices = indexBuffer;
-
-      foreach (EffectPass pass in lightingEffect.CurrentTechnique.Passes) {
-        pass.Apply();
-        graphics.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, indices.Length / 3);
+      for (int npcIndex = 0; npcIndex < MAX_NPCS; npcIndex++) {
+        if (!coneEnabled[npcIndex]) {
+          continue;
+        }
+        vertexBuffer.SetData(coneVertices[npcIndex]);
+        indexBuffer.SetData(indices);
+        graphics.SetVertexBuffer(vertexBuffer);
+        graphics.Indices = indexBuffer;
+
+        foreach (EffectPass pass in lightingEffect.CurrentTechnique.Passes) {
+          pass.Apply();
+          graphics.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, indices.Length / 3);
+        }
       }
     }
   }