use DrawIndexedPrimitives; fixes #41

GitOrigin-RevId: 6cc7429d0b

Shared/LinesOfSight.cs

@@ -5,25 +5,29 @@ using System;
 namespace SemiColinGames {
   class LinesOfSight {
 
-    const int numConePoints = 60;
-    VertexPositionColor[] conePoints = new VertexPositionColor[numConePoints];
+    const int numEdgeVertices = 60;
+    // coneVertices[0] is the eye position; the rest are the edge vertices.
+    VertexPositionColor[] coneVertices = new VertexPositionColor[numEdgeVertices + 1];
     Color color = Color.FromNonPremultiplied(new Vector4(0, 0, 1, 0.6f));
-    VertexPositionColor[] vertices = new VertexPositionColor[numConePoints * 3];
+    // The number of total triangles drawn is one less than the number of edge points.
+    int[] indices = new int[(numEdgeVertices - 1) * 3];
     VertexBuffer vertexBuffer;
+    IndexBuffer indexBuffer;
 
     public LinesOfSight(GraphicsDevice graphics) {
       vertexBuffer = new VertexBuffer(
-           graphics, typeof(VertexPositionColor), numConePoints * 3, BufferUsage.WriteOnly);
+           graphics, typeof(VertexPositionColor), numEdgeVertices * 3, BufferUsage.WriteOnly);
+      indexBuffer = new IndexBuffer(
+          graphics, typeof(int), indices.Length, BufferUsage.WriteOnly);
     }
 
     public void Update(Player player, AABB[] collisionTargets) {
-      // TODO: DrawIndexedPrimitives
       Vector2 eyePos = player.EyePosition;
 
       float visionRange = 150;
       float visionRangeSq = visionRange * visionRange;
       float fov = FMath.DegToRad(120);
-      float fovStep = fov / (numConePoints - 1);
+      float fovStep = fov / (numEdgeVertices - 1);
 
       Vector2 ray = new Vector2(visionRange * player.GetFacing, 0);
       if (player.GetPose == Player.Pose.Stretching) {
@@ -33,7 +37,8 @@ namespace SemiColinGames {
         ray = ray.Rotate(player.GetFacing * FMath.DegToRad(30));
       }
 
-      for (int i = 0; i < conePoints.Length; i++) {
+      coneVertices[0] = new VertexPositionColor(new Vector3(player.EyePosition, 0), color);
+      for (int i = 0; i < numEdgeVertices; i++) {
         float angle = -fov / 2 + fovStep * i;
         Vector2 rotated = ray.Rotate(angle);
         Vector2 closestHit = Vector2.Add(eyePos, rotated);
@@ -61,28 +66,27 @@ namespace SemiColinGames {
 
         float tint = 0.6f - hitTime / 2;
         Color tinted = Color.FromNonPremultiplied(new Vector4(0, 0, 1, tint));
-        conePoints[i] = new VertexPositionColor(new Vector3(closestHit, 0), tinted);
+        coneVertices[i + 1] = new VertexPositionColor(new Vector3(closestHit, 0), tinted);
       }
     }
 
     public void Draw(Player player, AABB[] collisionTargets, GraphicsDevice graphics,
         BasicEffect lightingEffect) {
 
-      VertexPositionColor eyeVertex = new VertexPositionColor(
-          new Vector3(player.EyePosition, 0), color);
-      for (int i = 0; i < numConePoints - 1; i++) {
-        vertices[i * 3] = eyeVertex;
-        vertices[i * 3 + 1] = conePoints[i];
-        vertices[i * 3 + 2] = conePoints[i + 1];
+      for (int i = 0; i < numEdgeVertices - 1; i++) {
+        indices[i * 3] = 0;
+        indices[i * 3 + 1] = i + 1;
+        indices[i * 3 + 2] = i + 2;
       }
 
-      vertexBuffer.SetData<VertexPositionColor>(vertices);
-
+      vertexBuffer.SetData(coneVertices);
+      indexBuffer.SetData(indices);
       graphics.SetVertexBuffer(vertexBuffer);
+      graphics.Indices = indexBuffer;
 
       foreach (EffectPass pass in lightingEffect.CurrentTechnique.Passes) {
         pass.Apply();
-        graphics.DrawPrimitives(PrimitiveType.TriangleList, 0, vertices.Length / 3);
+        graphics.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, coneVertices.Length, 0, indices.Length / 3);
       }
     }
   }