Initial commit: OpenRA game engine

Fork from OpenRA/OpenRA with one-click launch script (start-ra.cmd)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

OpenRA.Mods.Common/Graphics/ContrailRenderable.cs

@@ -0,0 +1,165 @@
+#region Copyright & License Information
+/*
+ * Copyright (c) The OpenRA Developers and Contributors
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System.Linq;
+using OpenRA.Graphics;
+using OpenRA.Primitives;
+
+namespace OpenRA.Mods.Common.Graphics
+{
+	public class ContrailRenderable : IRenderable, IFinalizedRenderable
+	{
+		const int MaxSmoothLength = 4;
+
+		public int Length => trail.Length;
+
+		readonly Actor owner;
+		readonly World world;
+		readonly Color startColor;
+		readonly bool usePlayerStartColor;
+		readonly Color endColor;
+		readonly bool usePlayerEndColor;
+
+		// Store trail positions in a circular buffer
+		readonly WPos[] trail;
+		readonly WDist startWidth;
+		readonly WDist endWidth;
+		int next;
+		int length;
+		readonly int skip;
+
+		public ContrailRenderable(
+			World world, Actor owner, Color startcolor, bool usePlayerStartColor, Color endcolor, bool usePlayerEndColor,
+			WDist startWidth, WDist endWidth, int length, int skip, int zOffset)
+			: this(world, owner, new WPos[length], startWidth, endWidth, 0, 0, skip,
+				  startcolor, usePlayerStartColor, endcolor, usePlayerEndColor, zOffset)
+		{ }
+
+		ContrailRenderable(World world, Actor owner, WPos[] trail, WDist startWidth, WDist endWidth,
+			int next, int length, int skip, Color startColor, bool usePlayerStartColor, Color endColor, bool usePlayerEndColor, int zOffset)
+		{
+			this.world = world;
+			this.owner = owner;
+			this.trail = trail;
+			this.startWidth = startWidth;
+			this.endWidth = endWidth;
+			this.next = next;
+			this.length = length;
+			this.skip = skip;
+			this.startColor = startColor;
+			this.usePlayerStartColor = usePlayerStartColor;
+			this.usePlayerEndColor = usePlayerEndColor;
+			this.endColor = endColor;
+			ZOffset = zOffset;
+		}
+
+		public WPos Pos => trail[Index(next - 1)];
+		public int ZOffset { get; }
+		public bool IsDecoration => true;
+
+		public IRenderable WithZOffset(int newOffset) =>
+			new ContrailRenderable(
+				world, owner, (WPos[])trail.Clone(), startWidth, endWidth, next,
+				length, skip, startColor, usePlayerStartColor, endColor, usePlayerEndColor, newOffset);
+		public IRenderable OffsetBy(in WVec vec)
+		{
+			// Lambdas can't use 'in' variables, so capture a copy for later
+			var offset = vec;
+			return new ContrailRenderable(
+				world, owner, trail.Select(pos => pos + offset).ToArray(), startWidth, endWidth, next,
+				length, skip, startColor, usePlayerStartColor, endColor, usePlayerEndColor, ZOffset);
+		}
+
+		public IRenderable AsDecoration() { return this; }
+
+		public IFinalizedRenderable PrepareRender(WorldRenderer wr) { return this; }
+		public void Render(WorldRenderer wr)
+		{
+			// Note: The length of contrail is now actually the number of the points to draw the contrail
+			// and we require at least two points to draw a tail.
+			var renderLength = length - skip;
+			if (renderLength <= 1)
+				return;
+
+			var screenWidth = wr.ScreenVector(new WVec(1, 0, 0))[0];
+			var wcr = Game.Renderer.WorldRgbaColorRenderer;
+
+			var startColor = this.startColor;
+			if (usePlayerStartColor)
+				startColor = Color.FromArgb(this.startColor.A, owner.OwnerColor());
+
+			var endColor = this.endColor;
+			if (usePlayerEndColor)
+				endColor = Color.FromArgb(this.endColor.A, owner.OwnerColor());
+
+			// Start of the first line segment is the tail of the list - don't smooth it.
+			var curPos = trail[Index(next - skip - 1)];
+			var curColor = startColor;
+
+			for (var i = 1; i < renderLength; i++)
+			{
+				var j = next - skip - 1 - i;
+				var nextColor = Exts.ColorLerp(i / (renderLength - 1f), startColor, endColor);
+
+				var nextX = 0L;
+				var nextY = 0L;
+				var nextZ = 0L;
+				var k = 0;
+				for (; k < renderLength - i && k < MaxSmoothLength; k++)
+				{
+					var prepos = trail[Index(j - k)];
+					nextX += prepos.X;
+					nextY += prepos.Y;
+					nextZ += prepos.Z;
+				}
+
+				var nextPos = new WPos((int)(nextX / k), (int)(nextY / k), (int)(nextZ / k));
+
+				// When renderLength = 2 we are rendering only one segment, so it needs to be handled differently to avoid
+				// division by 0. For width we choose startWidth instead of the average as this makes the transition between
+				// rendering 1 and multiple segments smoother. Above checks make sure that renderLength can never be lower than 2.
+				float width;
+				if (renderLength == 2)
+					width = startWidth.Length;
+				else
+				{
+					var lerp = (i - 1f) / (renderLength - 2);
+					width = startWidth.Length * (1 - lerp) + endWidth.Length * lerp;
+				}
+
+				if (width > 0 && !world.FogObscures(curPos) && !world.FogObscures(nextPos))
+					wcr.DrawLine(wr.Screen3DPosition(curPos), wr.Screen3DPosition(nextPos), screenWidth * width, curColor, nextColor);
+
+				curPos = nextPos;
+				curColor = nextColor;
+			}
+		}
+
+		public void RenderDebugGeometry(WorldRenderer wr) { }
+		public Rectangle ScreenBounds(WorldRenderer wr) { return Rectangle.Empty; }
+
+		// Array index modulo length
+		int Index(int i)
+		{
+			var j = i % trail.Length;
+			return j < 0 ? j + trail.Length : j;
+		}
+
+		public void Update(WPos pos)
+		{
+			trail[next] = pos;
+			next = Index(next + 1);
+
+			if (length < trail.Length)
+				length++;
+		}
+	}
+}