Render voxels with an approximately-correct z-offset.

OpenRA.Game/Graphics/VoxelRenderer.cs

@@ -22,9 +22,9 @@ namespace OpenRA.Graphics
 		public readonly Sprite Sprite;
 		public readonly Sprite ShadowSprite;
 		public readonly float ShadowDirection;
-		public readonly float2[] ProjectedShadowBounds;
+		public readonly float3[] ProjectedShadowBounds;
 
-		public VoxelRenderProxy(Sprite sprite, Sprite shadowSprite, float2[] projectedShadowBounds, float shadowDirection)
+		public VoxelRenderProxy(Sprite sprite, Sprite shadowSprite, float3[] projectedShadowBounds, float shadowDirection)
 		{
 			Sprite = sprite;
 			ShadowSprite = shadowSprite;
@@ -145,7 +145,7 @@ namespace OpenRA.Graphics
 
 			var shadowScreenTransform = Util.MatrixMultiply(cameraTransform, invShadowTransform);
 			var shadowGroundNormal = Util.MatrixVectorMultiply(shadowTransform, groundNormal);
-			var screenCorners = new float2[4];
+			var screenCorners = new float3[4];
 			for (var j = 0; j < 4; j++)
 			{
 				// Project to ground plane
@@ -154,7 +154,7 @@ namespace OpenRA.Graphics
 
 				// Rotate to camera-space
 				corners[j] = Util.MatrixVectorMultiply(shadowScreenTransform, corners[j]);
-				screenCorners[j] = new float2(corners[j][0], corners[j][1]);
+				screenCorners[j] = new float3(corners[j][0], corners[j][1], 0);
 			}
 
 			// Shadows are rendered at twice the resolution to reduce artifacts

OpenRA.Game/Graphics/WorldRenderer.cs

@@ -126,7 +126,10 @@ namespace OpenRA.Graphics
 				return;
 
 			if (devTrait.Value != null)
+			{
 				Game.Renderer.WorldSpriteRenderer.SetDepthPreviewEnabled(devTrait.Value.ShowDepthPreview);
+				Game.Renderer.WorldRgbaSpriteRenderer.SetDepthPreviewEnabled(devTrait.Value.ShowDepthPreview);
+			}
 
 			RefreshPalette();
 

OpenRA.Mods.Common/Graphics/VoxelRenderable.cs

@@ -14,6 +14,7 @@ using System.Collections.Generic;
 using System.Drawing;
 using System.Linq;
 using OpenRA.Graphics;
+using OpenRA.Primitives;
 
 namespace OpenRA.Mods.Common.Graphics
 {
@@ -107,7 +108,12 @@ namespace OpenRA.Mods.Common.Graphics
 			{
 				var groundPos = voxel.pos - new WVec(0, 0, wr.World.Map.DistanceAboveTerrain(voxel.pos).Length);
 				var groundZ = wr.World.Map.Grid.TileSize.Height * (groundPos.Z - voxel.pos.Z) / 1024f;
-				var pxOrigin = wr.ScreenPosition(voxel.pos);
+				var pxOrigin = wr.Screen3DPosition(voxel.pos);
+
+				// HACK: We don't have enough texture channels to pass the depth data to the shader
+				// so for now just offset everything forward so that the back corner is rendered at pos.
+				pxOrigin -= new float3(0, 0, Screen3DBounds(wr).Second.X);
+
 				var shadowOrigin = pxOrigin - groundZ * (new float2(renderProxy.ShadowDirection, 1));
 
 				var psb = renderProxy.ProjectedShadowBounds;
@@ -135,12 +141,13 @@ namespace OpenRA.Mods.Common.Graphics
 				var c = Color.Purple;
 				var psb = renderProxy.ProjectedShadowBounds;
 
+				// TODO: add float3 support to WorldRgbaColorRenderer
 				Game.Renderer.WorldRgbaColorRenderer.DrawPolygon(new[]
 				{
-					shadowOrigin + psb[1],
+					shadowOrigin + psb[1].XY,
-					shadowOrigin + psb[3],
+					shadowOrigin + psb[3].XY,
-					shadowOrigin + psb[0],
+					shadowOrigin + psb[0].XY,
-					shadowOrigin + psb[2]
+					shadowOrigin + psb[2].XY
 				}, iz, c);
 
 				// Draw voxel bounding box
@@ -190,6 +197,11 @@ namespace OpenRA.Mods.Common.Graphics
 			}
 
 			public Rectangle ScreenBounds(WorldRenderer wr)
+			{
+				return Screen3DBounds(wr).First;
+			}
+
+			Pair<Rectangle, float2> Screen3DBounds(WorldRenderer wr)
 			{
 				var pxOrigin = wr.ScreenPosition(voxel.pos);
 				var draw = voxel.voxels.Where(v => v.DisableFunc == null || !v.DisableFunc());
@@ -198,8 +210,11 @@ namespace OpenRA.Mods.Common.Graphics
 
 				var minX = float.MaxValue;
 				var minY = float.MaxValue;
+				var minZ = float.MaxValue;
 				var maxX = float.MinValue;
 				var maxY = float.MinValue;
+				var maxZ = float.MinValue;
+
 				foreach (var v in draw)
 				{
 					var bounds = v.Voxel.Bounds(v.FrameFunc());
@@ -208,7 +223,7 @@ namespace OpenRA.Mods.Common.Graphics
 
 					float sx, sy, sz;
 					wr.ScreenVectorComponents(v.OffsetFunc(), out sx, out sy, out sz);
-					var pxPos = pxOrigin + new float2(sx, sy);
+					var pxPos = pxOrigin + new float3(sx, sy, sz);
 					var screenTransform = OpenRA.Graphics.Util.MatrixMultiply(cameraTransform, worldTransform);
 
 					for (var i = 0; i < 8; i++)
@@ -217,12 +232,14 @@ namespace OpenRA.Mods.Common.Graphics
 						var screen = OpenRA.Graphics.Util.MatrixVectorMultiply(screenTransform, vec);
 						minX = Math.Min(minX, pxPos.X + screen[0]);
 						minY = Math.Min(minY, pxPos.Y + screen[1]);
+						minZ = Math.Min(minZ, pxPos.Z + screen[2]);
 						maxX = Math.Max(maxX, pxPos.X + screen[0]);
 						maxY = Math.Max(maxY, pxPos.Y + screen[1]);
+						maxZ = Math.Max(minZ, pxPos.Z + screen[2]);
 					}
 				}
 
-				return Rectangle.FromLTRB((int)minX, (int)minY, (int)maxX, (int)maxY);
+				return Pair.New(Rectangle.FromLTRB((int)minX, (int)minY, (int)maxX, (int)maxY), new float2(minZ, maxZ));
 			}
 		}
 	}

glsl/rgba.frag

@@ -1,7 +1,25 @@
 uniform sampler2D DiffuseTexture;
+uniform bool EnableDepthPreview;
+
 varying vec4 vTexCoord;
 
 void main()
 {
-	gl_FragColor = texture2D(DiffuseTexture, vTexCoord.st);
+	vec4 c = texture2D(DiffuseTexture, vTexCoord.st);
+	// Discard any transparent fragments (both color and depth)
+	if (c.a == 0.0)
+		discard;
+
+	float depth = gl_FragCoord.z;
+
+	// Convert to window coords
+	gl_FragDepth = 0.5 * depth + 0.5;
+
+	if (EnableDepthPreview)
+	{
+		// Front of the depth buffer is at 0, but we want to render it as bright
+		gl_FragColor = vec4(vec3(1.0 - gl_FragDepth), 1.0);
+	}
+	else
+		gl_FragColor = c;
 }