Geometry shader used to verify normals of 3d object

tutorial19_Geometry_Normal_Shader/Readme.txt

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+The tutorial contains geometry shaders aimed to generate and verify the correct disposition of the normals of a uv wrapped texture on a 3d object.
+It contains 3 shaders 
+vertex shader
+geometry shader
+fragement shader

tutorial19_Geometry_Normal_Shader/model-geometry-fragment-normal.frag

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+
+// Fragment shader for simple coloured rendering of the normals
+
+#version 330 core
+//declaring the vec4 color variable
+
+out vec4 FragColor;
+
+
+
+void main()
+{ 
+    //assigning the fragment shader with the vec4 color.
+
+    FragColor = vec4(1.0,1.0,0.5,1.0);
+}

tutorial19_Geometry_Normal_Shader/model-geometry-shader-normal.gs

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+//geometry shader to draw the normals
+
+#version 330 core
+
+//Since the normals are to be drawn at the 3 vertices of the raster triangle,the vertices have an upper bound of 3
+//line_strip specifies the normals to be drawn adjacent to each other on each of the 3 vertices of a triangle
+
+
+layout(triangles) in;
+layout(line_strip,max_vertices=3) out;
+
+//interface block inherited from the vertex shader
+
+in VS_OUT{
+
+vec3 normal;
+
+}gs_in[];
+
+//magnitude of the length of the normals
+float magnitude=0.4;
+
+//generator function which will assign the normals based on the 3 indices (0,1,2) of each triangle
+void generateLine(int index)
+{
+//gets the position and draws the normal from the vertices 
+   gl_Position=gl_in[index].gl_Position;
+
+
+   EmitVertex();
+   gl_Position=gl_in[index].gl_Position + vec4(gs_in[index].normal,0.0)*magnitude;
+   EmitVertex();
+   EndPrimitive(); 
+
+}
+
+void main()
+{
+//line is generated from the vertices
+  generateLine(0);
+  generateLine(1);
+  generateLine(2);
+}

tutorial19_Geometry_Normal_Shader/model-geometry-vertex-normal.vs

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+//geometry shader used for debugging the general position of the normals of the texture wrapping.
+//Used to decide whether the normals have been loaded properly.
+
+#version 330 core
+
+//vertex attributes position and normals
+
+layout (location = 0) in vec3 aPos;
+layout (location = 1) in vec3 aNormal;
+
+//interface block to be passed to the geometry shader 
+//passing only the normal attribute to the geometry shader
+
+
+out VS_OUT{
+
+ vec3 normal;
+}vs_out;
+
+//MVP matrix loading
+
+
+uniform mat4 model;
+uniform mat4 view;
+uniform mat4 projection;
+
+void main()
+{
+    //generate normal matrix to convert to NDC (Normalized Device Coordinates)
+
+     mat3 normalMatrix= mat3(transpose(inverse(view*model)));
+
+//normalizing the normals of the vertices 
+
+     vs_out.normal=normalize(vec3(projection * vec4(normalMatrix * aNormal,0.0)));  
+
+    gl_Position = projection * view * model * vec4(aPos, 1.0);
+}