Solar Panels (#936)

Content.Server/GameObjects/EntitySystems/PowerSolarSystem.cs

@@ -0,0 +1,65 @@
+using Content.Server.GameObjects.Components.Power;
+using JetBrains.Annotations;
+using Robust.Shared.GameObjects;
+using Robust.Shared.GameObjects.Systems;
+using Robust.Shared.Maths;
+using System;
+
+namespace Content.Server.GameObjects.EntitySystems
+{
+    /// <summary>
+    ///     Responsible for maintaining the solar-panel sun angle and updating <see cref='SolarPanelComponent'/> coverage.
+    /// </summary>
+    [UsedImplicitly]
+    public class PowerSolarSystem: EntitySystem
+    {
+        /// <summary>
+        /// The current sun angle.
+        /// </summary>
+        public Angle TowardsSun = Angle.South;
+
+        public override void Initialize()
+        {
+            EntityQuery = new TypeEntityQuery(typeof(SolarPanelComponent));
+        }
+
+        public override void Update(float frameTime)
+        {
+            TowardsSun += Angle.FromDegrees(frameTime / 10);
+            TowardsSun = TowardsSun.Reduced();
+            foreach (var entity in RelevantEntities)
+            {
+                // In the 'sunRelative' coordinate system:
+                // the sun is considered to be an infinite distance directly up.
+                // this is the rotation of the panel relative to that.
+                // directly upwards (theta = 0) = coverage 1
+                // left/right 90 degrees (abs(theta) = (pi / 2)) = coverage 0
+                // directly downwards (abs(theta) = pi) = coverage -1
+                // as TowardsSun + = CCW,
+                // panelRelativeToSun should - = CW
+                var panelRelativeToSun = entity.Transform.WorldRotation - TowardsSun;
+                // essentially, given cos = X & sin = Y & Y is 'downwards',
+                // then for the first 90 degrees of rotation in either direction,
+                // this plots the lower-right quadrant of a circle.
+                // now basically assume a line going from the negated X/Y to there,
+                // and that's the hypothetical solar panel.
+                //
+                // since, again, the sun is considered to be an infinite distance upwards,
+                // this essentially means Cos(panelRelativeToSun) is half of the cross-section,
+                // and since the full cross-section has a max of 2, effectively-halving it is fine.
+                //
+                // as for when it goes negative, it only does that when (abs(theta) > pi)
+                // and that's expected behavior.
+                float coverage = (float) Math.Max(0, Math.Cos(panelRelativeToSun));
+
+                // Would determine occlusion, but that requires raytraces.
+                // And I'm not sure where those are in the codebase.
+                // Luckily, auto-rotation isn't in yet, so it won't matter anyway.
+
+                // Total coverage calculated; apply it to the panel.
+                var panel = entity.GetComponent<SolarPanelComponent>();
+                panel.Coverage = coverage;
+            }
+        }
+    }
+}