Don't render the reflection on the far side of the floor

data/shaders/offscreen/mirror.frag

@@ -8,6 +8,7 @@ layout (binding = 2) uniform sampler2D samplerColorMap;
 
 layout (location = 0) in vec2 inUV;
 layout (location = 1) in vec4 inPos;
+layout (location = 2) in vec3 inNormal;
 
 layout (location = 0) out vec4 outFragColor;
 
@@ -15,6 +16,7 @@ void main()
 {
 	vec4 tmp = vec4(1.0 / inPos.w);
     vec4 projCoord = inPos * tmp;
+
 	// Scale and bias
     projCoord += vec4(1.0);
     projCoord *= vec4(0.5);
@@ -22,18 +24,19 @@ void main()
 	// Slow single pass blur
 	// For demonstration purposes only
 	const float blurSize = 1.0 / 512.0;	
-    vec4 reflection = vec4(0.0);
-    for (int x = -3; x <= 3; x++)
-	{
-        for (int y = -3; y <= 3; y++)
-		{
-            reflection += texture(samplerColor, vec2(projCoord.s + x * blurSize, projCoord.t + y * blurSize)) / 49.0;
-		}
-	}
-	
+
 	vec4 color = texture(samplerColorMap, inUV);
-	
 	outFragColor = color * 0.25;
-	outFragColor += reflection * 1.5 * (color.r);
-	
+
+	if (inNormal.z > 0) {
+		vec4 reflection = vec4(0.0);
+		for (int x = -3; x <= 3; x++)
+		{
+			for (int y = -3; y <= 3; y++)
+			{
+				reflection += texture(samplerColor, vec2(projCoord.s + x * blurSize, projCoord.t + y * blurSize)) / 49.0;
+			}
+		}
+		outFragColor += reflection * 1.5 * (color.r);
+	} 
 }

data/shaders/offscreen/mirror.vert

@@ -15,14 +15,19 @@ layout (binding = 0) uniform UBO
 
 layout (location = 0) out vec2 outUV;
 layout (location = 1) out vec4 outPos;
+layout (location = 2) out vec3 outNormal;
 
-out gl_PerVertex
-{
-	vec4 gl_Position;
-};
+mat3 mat3_emu(mat4 m4) {
+  return mat3(
+      m4[0][0], m4[0][1], m4[0][2],
+      m4[1][0], m4[1][1], m4[1][2],
+      m4[2][0], m4[2][1], m4[2][2]);
+}
 
 void main() 
 {
+    mat3 rotation = mat3_emu(ubo.model);
+	outNormal = rotation * inNormal;
 	outUV = inUV;
 	outPos = ubo.projection * ubo.model * vec4(inPos.xyz, 1.0);
 	gl_Position = outPos;