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POLoading an OBJ file, how to use normals (#vertices < #normals)
 

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  1. POLoading an OBJ file, how to use normals (#vertices < #normals)
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    <p>I have an obj file and have succesfully loaded the object to opengl without using the normals given.<br> This is how it looks:<br> <img src="https://i.stack.imgur.com/Z08uO.png" alt="tree without normals"><br> The format of the file is:</p> <pre><code>v x y z vn x y z f x//x' y//y' z//z' </code></pre> <p>The displaying function of the mesh is like that:</p> <pre><code>glBegin(GL_TRIANGLES); for all faces { glVertex3f(.., .., ..); glVertex3f(.., .., ..); glVertex3f(.., .., ..); } glEnd(); </code></pre> <p>And the result is this:<br> <img src="https://i.stack.imgur.com/iMFCk.png" alt="enter image description here"></p> <p>I've read that the object might look flat due to the default normal vector that OpenGL uses for lighting equations.<br> This could be solved with normals. The normals given are 780 and the vertices 155. </p> <p>I've tried using glNorm before each glVertex3f call but the obj looks completely weird (lines, etc).</p> <p>What should I do?</p> <p><strong>EDIT #1:</strong> This is how I read the file: </p> <pre><code>void loader(class mesh &amp;tree) { int vx1, vx2, vx3, vn1, vn2, vn3; ifstream file; string line; point vec, norm; face tempface; file.open("tree.obj"); if (file.is_open() == true) { while(getline(file, line) ) { if (line.substr(0,2) == "") continue; else if (line.substr(0, 2) == "v ") { istringstream numbers(line.substr(2)); numbers &gt;&gt; vec.x &gt;&gt; vec.y &gt;&gt; vec.z; tree.vectors.push_back(vec); } else if (line.substr(0,2) == "vn") { istringstream numbers(line.substr(2)); numbers &gt;&gt; norm.x &gt;&gt; norm.y &gt;&gt; norm.z; tree.normals.push_back(norm); } else if (line.substr(0,2) == "f ") { face f; line = line.substr(2,line.length()); for (string::iterator it = line.begin(); it != line.end(); ++it) { if (*it == '/') { //erase both of the "//" line.erase(it); line.erase(it); //add a space between the numbers line.insert(it, ' '); } } istringstream inp(line); inp &gt;&gt; f.vert_indices[0] &gt;&gt; f.norm_indices[0] &gt;&gt; f.vert_indices[1] &gt;&gt; f.norm_indices[1] &gt;&gt; f.vert_indices[2] &gt;&gt; f.norm_indices[2]; tree.faces.push_back(f); } else continue; } file.close(); } } </code></pre> <p>And this is how I am displaying it:</p> <pre><code> void mesh::displayMesh() { glPushMatrix(); glBegin(GL_TRIANGLES); for(vector&lt;face&gt;::const_iterator it = faces.begin(); it != faces.end(); ++it) { //glVertex3f(normals[it-&gt;norm_indices[0] -1 ].x, normals[it-&gt;norm_indices[0] -1 ].y, normals[it-&gt;norm_indices[0] -1 ].z); glVertex3f(vectors[it-&gt;vert_indices[0] -1 ].x, vectors[it-&gt;vert_indices[0] -1 ].y, vectors[it-&gt;vert_indices[0] -1 ].z); //glVertex3f(normals[it-&gt;norm_indices[1] -1 ].x, normals[it-&gt;norm_indices[1] -1 ].y, normals[it-&gt;norm_indices[1] -1 ].z); glVertex3f(vectors[it-&gt;vert_indices[1] -1 ].x, vectors[it-&gt;vert_indices[1] -1 ].y, vectors[it-&gt;vert_indices[1] -1 ].z); //glVertex3f(normals[it-&gt;norm_indices[2] -1 ].x, normals[it-&gt;norm_indices[2] -1 ].y, normals[it-&gt;norm_indices[2] -1 ].z); glVertex3f(vectors[it-&gt;vert_indices[2] -1 ].x, vectors[it-&gt;vert_indices[2] -1 ].y, vectors[it-&gt;vert_indices[2] -1 ].z); } glEnd(); glPopMatrix(); } </code></pre> <p>The function displayMesh is called within Render function of openGL and the loader function is called into Setup OpenGL function and the mesh tree object is a global variable.</p> <p><strong>EDIT #2:</strong> This how the tree looks with the normals:<br> <img src="https://i.stack.imgur.com/sOXRv.png" alt="tree with normals"> Also <a href="http://pastebin.com/zp7gGc7h" rel="nofollow noreferrer">this is the code</a> of the setup function of OpenGL.</p>
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      1. POLoading an OBJ file, how to use normals (#vertices < #normals)
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    1. COIf you open your OBJ with Blender (or other 3D editor/viewer) it is displayed correctly?
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      1. POLoading an OBJ file, how to use normals (#vertices < #normals)
      1. USVinícius Gobbo A. de Oliveira
    2. COAdding only `glNormal3f` calls before your `glVertex3f` functions won't have an effect unless you enable both OpenGL lighting `glEnable(GL_LIGHTING)` and at least one light, e.g., `glEnable(GL_LIGHT0)`. Lighting will be computed with all of the default lighting settings for materials, light colors, etc.
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      1. POLoading an OBJ file, how to use normals (#vertices < #normals)
      1. USradical7
    3. CO@ViníciusGobboA.deOliveira: Yes, I opened it in Blender and it appears much better that when I loaded it with opengl.
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      1. POLoading an OBJ file, how to use normals (#vertices < #normals)
      1. USChris
 

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