diff --git a/OpenRA.Game/Graphics/Util.cs b/OpenRA.Game/Graphics/Util.cs
index cb99bd0039..95c3b6242f 100644
--- a/OpenRA.Game/Graphics/Util.cs
+++ b/OpenRA.Game/Graphics/Util.cs
@@ -19,7 +19,6 @@ namespace OpenRA.Graphics
 	{
 		// yes, our channel order is nuts.
 		static readonly int[] ChannelMasks = { 2, 1, 0, 3 };
-		static readonly float[] ChannelSelect = { 0.2f, 0.4f, 0.6f, 0.8f };
 
 		public static void FastCreateQuad(Vertex[] vertices, float3 o, Sprite r, float paletteTextureIndex, int nv, float3 size)
 		{
@@ -35,7 +34,9 @@ namespace OpenRA.Graphics
 			float st = 0;
 			float sr = 0;
 			float sb = 0;
-			var attribC = ChannelSelect[(int)r.Channel];
+
+			// See shp.vert for documentation on the channel attribute format
+			var attribC = ((byte)r.Channel) << 1 | 0x01;
 
 			var ss = r as SpriteWithSecondaryData;
 			if (ss != null)
@@ -43,16 +44,18 @@ namespace OpenRA.Graphics
 				sl = ss.SecondaryLeft;
 				st = ss.SecondaryTop;
 				sr = ss.SecondaryRight;
-				sb = ss.SecondaryBottom;
-				attribC = -(attribC + ChannelSelect[(int)ss.SecondaryChannel] / 10);
+				sb = ss.SecondaryBottom;
+
+				attribC |= ((byte)ss.SecondaryChannel) << 4 | 0x08;
 			}
 
-			vertices[nv] = new Vertex(a, r.Left, r.Top, sl, st, paletteTextureIndex, attribC);
-			vertices[nv + 1] = new Vertex(b, r.Right, r.Top, sr, st, paletteTextureIndex, attribC);
-			vertices[nv + 2] = new Vertex(c, r.Right, r.Bottom, sr, sb, paletteTextureIndex, attribC);
-			vertices[nv + 3] = new Vertex(c, r.Right, r.Bottom, sr, sb, paletteTextureIndex, attribC);
-			vertices[nv + 4] = new Vertex(d, r.Left, r.Bottom, sl, sb, paletteTextureIndex, attribC);
-			vertices[nv + 5] = new Vertex(a, r.Left, r.Top, sl, st, paletteTextureIndex, attribC);
+			var fAttribC = (float)attribC;
+			vertices[nv] = new Vertex(a, r.Left, r.Top, sl, st, paletteTextureIndex, fAttribC);
+			vertices[nv + 1] = new Vertex(b, r.Right, r.Top, sr, st, paletteTextureIndex, fAttribC);
+			vertices[nv + 2] = new Vertex(c, r.Right, r.Bottom, sr, sb, paletteTextureIndex, fAttribC);
+			vertices[nv + 3] = new Vertex(c, r.Right, r.Bottom, sr, sb, paletteTextureIndex, fAttribC);
+			vertices[nv + 4] = new Vertex(d, r.Left, r.Bottom, sl, sb, paletteTextureIndex, fAttribC);
+			vertices[nv + 5] = new Vertex(a, r.Left, r.Top, sl, st, paletteTextureIndex, fAttribC);
 		}
 
 		public static void FastCopyIntoChannel(Sprite dest, byte[] src)
diff --git a/glsl/shp.vert b/glsl/shp.vert
index b245dbbdb9..6186401131 100644
--- a/glsl/shp.vert
+++ b/glsl/shp.vert
@@ -10,21 +10,45 @@ varying vec4 vChannelMask;
 varying vec4 vDepthMask;
 varying vec4 vColorFraction;
 
-vec4 DecodeChannelMask(float x)
+vec2 UnpackChannelAttributes(float x)
 {
-	if (x > 0.7)
+	// The channel attributes float encodes a set of attributes
+	// stored as flags in the mantissa of the unnormalized float value.
+	// Bits 3-5 define the behaviour of the secondary texture channel:
+	//    000: Channel is not used
+	//    001, 011, 101, 111: Sample depth sprite from channel R,G,B,A
+	// Bits 0-2 define the behaviour of the primary texture channel:
+	//    000: Channel is not used (aVertexTexCoord instead defines a color value)
+	//    001, 011, 101, 111: Sample paletted sprite from channel R,G,B,A
+
+	float secondaryChannel = 0.0;
+	if (x >= 32.0) { x -= 32.0;  secondaryChannel += 4.0; }
+	if (x >= 16.0) { x -= 16.0;  secondaryChannel += 2.0; }
+	if (x >= 8.0) { x -= 8.0;  secondaryChannel += 1.0; }
+	
+	float primaryChannel = 0.0;
+	if (x >= 4.0) { x -= 4.0;  primaryChannel += 4.0; }
+	if (x >= 2.0) { x -= 2.0;  primaryChannel += 2.0; }
+	if (x >= 1.0) { x -= 1.0;  primaryChannel += 1.0; }
+
+	return vec2(primaryChannel, secondaryChannel);
+}
+
+vec4 SelectChannelMask(float x)
+{
+	if (x >= 7.0)
 		return vec4(0,0,0,1);
-	if (x > 0.5)
+	if (x >= 5.0)
 		return vec4(0,0,1,0);
-	if (x > 0.3)
+	if (x >= 3.0)
 		return vec4(0,1,0,0);
-	if (x > 0.0)
+	if (x >= 1.0)
 		return vec4(1,0,0,0);
 
 	return vec4(0, 0, 0, 0);
 }
 
-vec4 DecodeColorFraction(float x)
+vec4 SelectColorFraction(float x)
 {
 	if (x > 0.0)
 		return vec4(0, 0, 0, 0);
@@ -37,13 +61,9 @@ void main()
 	gl_Position = vec4((aVertexPosition.xyz - Scroll.xyz) * r1 + r2, 1);
 	vTexCoord = aVertexTexCoord;
 	vTexMetadata = aVertexTexMetadata;
-	vChannelMask = DecodeChannelMask(abs(aVertexTexMetadata.t));
-	vColorFraction = DecodeColorFraction(abs(aVertexTexMetadata.t));
-	if (aVertexTexMetadata.t < 0.0)
-	{
-		float x = -aVertexTexMetadata.t * 10.0;
-		vDepthMask = DecodeChannelMask(x - floor(x));
-	}
-	else
-		vDepthMask = vec4(0,0,0,0);
+	
+	vec2 attrib = UnpackChannelAttributes(aVertexTexMetadata.t);
+	vChannelMask = SelectChannelMask(attrib.s);
+	vColorFraction = SelectColorFraction(attrib.s);
+	vDepthMask = SelectChannelMask(attrib.t);
 }