100 lines
3.4 KiB
C#
100 lines
3.4 KiB
C#
using Microsoft.Xna.Framework;
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using Microsoft.Xna.Framework.Graphics;
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using System;
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namespace SemiColinGames {
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public sealed class LinesOfSight : IDisposable {
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const int NUM_EDGE_VERTICES = 60;
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readonly VertexBuffer vertexBuffer;
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readonly IndexBuffer indexBuffer;
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// coneVertices[0] is the eye position; the rest are the edge vertices.
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readonly VertexPositionColor[] coneVertices = new VertexPositionColor[NUM_EDGE_VERTICES + 1];
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// The number of total triangles drawn is one less than the number of edge points.
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readonly int[] indices = new int[(NUM_EDGE_VERTICES - 1) * 3];
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Color color = Color.FromNonPremultiplied(new Vector4(0, 0, 1, 0.6f));
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public LinesOfSight(GraphicsDevice graphics) {
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vertexBuffer = new VertexBuffer(
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graphics, typeof(VertexPositionColor), NUM_EDGE_VERTICES * 3, BufferUsage.WriteOnly);
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indexBuffer = new IndexBuffer(
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graphics, typeof(int), indices.Length, BufferUsage.WriteOnly);
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}
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~LinesOfSight() {
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Dispose();
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}
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public void Dispose() {
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vertexBuffer.Dispose();
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indexBuffer.Dispose();
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GC.SuppressFinalize(this);
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}
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public void Update(NPC[] npcs, AABB[] collisionTargets) {
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NPC npc = npcs[0];
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Vector2 eyePos = npc.EyePosition;
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float visionRange = npc.VisionRange;
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Vector2 ray = npc.VisionRay;
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float fov = npc.FieldOfView;
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float visionRangeSq = visionRange * visionRange;
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float fovStep = fov / (NUM_EDGE_VERTICES - 1);
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coneVertices[0] = new VertexPositionColor(new Vector3(npc.EyePosition, 0), color);
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for (int i = 0; i < NUM_EDGE_VERTICES; i++) {
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float angle = -fov / 2 + fovStep * i;
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Vector2 rotated = ray.Rotate(angle);
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Vector2 closestHit = Vector2.Add(eyePos, rotated);
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float hitTime = 1f;
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Vector2 halfTileSize = new Vector2(World.TileSize / 2.0f, World.TileSize / 2.0f);
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for (int j = 0; j < collisionTargets.Length; j++) {
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AABB box = collisionTargets[j];
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if (Math.Abs(box.Position.X - npc.Position.X) > visionRange + halfTileSize.X) {
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continue;
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}
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Vector2 delta = Vector2.Add(halfTileSize, Vector2.Subtract(box.Position, eyePos));
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if (delta.LengthSquared() > visionRangeSq) {
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continue;
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}
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Hit? maybeHit = box.IntersectSegment(eyePos, rotated);
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if (maybeHit != null) {
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Hit hit = maybeHit.Value;
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if (hit.Time < hitTime) {
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hitTime = hit.Time;
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closestHit = hit.Position;
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}
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}
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}
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float tint = 0.6f - hitTime / 2;
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Color tinted = Color.FromNonPremultiplied(new Vector4(0, 0, 1, tint));
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coneVertices[i + 1] = new VertexPositionColor(new Vector3(closestHit, 0), tinted);
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}
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}
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public void Draw(GraphicsDevice graphics, BasicEffect lightingEffect) {
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for (int i = 0; i < NUM_EDGE_VERTICES - 1; i++) {
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indices[i * 3] = 0;
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indices[i * 3 + 1] = i + 1;
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indices[i * 3 + 2] = i + 2;
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}
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vertexBuffer.SetData(coneVertices);
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indexBuffer.SetData(indices);
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graphics.SetVertexBuffer(vertexBuffer);
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graphics.Indices = indexBuffer;
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foreach (EffectPass pass in lightingEffect.CurrentTechnique.Passes) {
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pass.Apply();
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graphics.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, indices.Length / 3);
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}
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}
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}
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}
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