Adapted Escape the Dawn engine.

src/Shaders/Normals.geo.glsl

@@ -0,0 +1,34 @@
+#version 430
+
+uniform mat4 MVP;
+
+layout(triangles) in;
+layout(line_strip, max_vertices = 6) out;
+
+in VertexData {
+	vec3 Position;
+	vec3 Normal;
+	vec2 TextureCoord;
+} Input[3];
+
+out VertexData {
+	vec3 Position;
+	vec3 Normal;
+	vec2 TextureCoord;
+} Output;
+
+void main()
+{
+	for (int i = 0; i < gl_in.length(); i++)
+	{
+		gl_Position = MVP * vec4(Input[i].Position, 1.0);
+		EmitVertex();
+		gl_Position = MVP * vec4(Input[i].Position + Input[i].Normal, 1.0);
+		EmitVertex();
+		EndPrimitive();
+
+		Output.Position = Input[i].Position;
+		Output.Normal = Input[i].Normal;
+		Output.TextureCoord = Input[i].TextureCoord;
+	}
+}