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</script></nav></div><div class="container mainContainer docsContainer"><div class="wrapper"><div class="post"><header class="postHeader"></header><article><div><span><h1><a class="anchor" aria-hidden="true" id="meshes-and-io"></a><a href="#meshes-and-io" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>Meshes and IO</h1>
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<p>The Meshes object represents a batch of triangulated meshes, and is central to
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much of the functionality of PyTorch3D. There is no insistence that each mesh in
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the batch has the same number of vertices or faces. When available, it can store
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other data which pertains to the mesh, for example face normals, face areas
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and textures.</p>
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<p>Two common file formats for storing single meshes are ".obj" and ".ply" files,
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and PyTorch3D has functions for reading these.</p>
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<h2><a class="anchor" aria-hidden="true" id="obj"></a><a href="#obj" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>OBJ</h2>
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<p>Obj files have a standard way to store extra information about a mesh. Given an
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obj file, it can be read with</p>
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<pre><code class="hljs"> verts, faces, aux = load<span class="hljs-constructor">_obj(<span class="hljs-params">filename</span>)</span>
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</code></pre>
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<p>which sets <code>verts</code> to be a (V,3)-tensor of vertices and <code>faces.verts_idx</code> to be
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an (F,3)- tensor of the vertex-indices of each of the corners of the faces.
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Faces which are not triangles will be split into triangles. <code>aux</code> is an object
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which may contain normals, uv coordinates, material colors and textures if they
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are present, and <code>faces</code> may additionally contain indices into these normals,
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textures and materials in its NamedTuple structure. A Meshes object containing a
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single mesh can be created from just the vertices and faces using</p>
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<pre><code class="hljs"> meshes = <span class="hljs-constructor">Meshes(<span class="hljs-params">verts</span>=[<span class="hljs-params">verts</span>], <span class="hljs-params">faces</span>=[<span class="hljs-params">faces</span>.<span class="hljs-params">verts_idx</span>])</span>
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</code></pre>
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<p>If there is texture information in the <code>.obj</code> it can be used to initialize a
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<code>Textures</code> class which is passed into the <code>Meshes</code> constructor. Currently we
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support loading of texture maps for meshes which have one texture map for the
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entire mesh e.g.</p>
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<pre><code class="hljs"><span class="hljs-attr">verts_uvs</span> = aux.verts_uvs[None, ...] <span class="hljs-comment"># (1, V, 2)</span>
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<span class="hljs-attr">faces_uvs</span> = faces.textures_idx[None, ...] <span class="hljs-comment"># (1, F, 3)</span>
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<span class="hljs-attr">tex_maps</span> = aux.texture_images
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<span class="hljs-comment"># tex_maps is a dictionary of {material name: texture image}.</span>
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<span class="hljs-comment"># Take the first image:</span>
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<span class="hljs-attr">texture_image</span> = list(tex_maps.values())[<span class="hljs-number">0</span>]
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<span class="hljs-attr">texture_image</span> = texture_image[None, ...] <span class="hljs-comment"># (1, H, W, 3)</span>
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<span class="hljs-comment"># Create a textures object</span>
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<span class="hljs-attr">tex</span> = Textures(verts_uvs=verts_uvs, faces_uvs=faces_uvs, maps=texture_image)
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<span class="hljs-comment"># Initialise the mesh with textures</span>
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<span class="hljs-attr">meshes</span> = Meshes(verts=[verts], faces=[faces.verts_idx], textures=tex)
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</code></pre>
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<p>The <code>load_objs_as_meshes</code> function provides this procedure.</p>
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<h2><a class="anchor" aria-hidden="true" id="ply"></a><a href="#ply" aria-hidden="true" class="hash-link"><svg class="hash-link-icon" aria-hidden="true" height="16" version="1.1" viewBox="0 0 16 16" width="16"><path fill-rule="evenodd" d="M4 9h1v1H4c-1.5 0-3-1.69-3-3.5S2.55 3 4 3h4c1.45 0 3 1.69 3 3.5 0 1.41-.91 2.72-2 3.25V8.59c.58-.45 1-1.27 1-2.09C10 5.22 8.98 4 8 4H4c-.98 0-2 1.22-2 2.5S3 9 4 9zm9-3h-1v1h1c1 0 2 1.22 2 2.5S13.98 12 13 12H9c-.98 0-2-1.22-2-2.5 0-.83.42-1.64 1-2.09V6.25c-1.09.53-2 1.84-2 3.25C6 11.31 7.55 13 9 13h4c1.45 0 3-1.69 3-3.5S14.5 6 13 6z"></path></svg></a>PLY</h2>
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<p>Ply files are flexible in the way they store additional information. PyTorch3D
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provides a function just to read the vertices and faces from a ply file.
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The call</p>
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<pre><code class="hljs"> verts, faces = load<span class="hljs-constructor">_ply(<span class="hljs-params">filename</span>)</span>
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</code></pre>
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<p>sets <code>verts</code> to be a (V,3)-tensor of vertices and <code>faces</code> to be an (F,3)-
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tensor of the vertex-indices of each of the corners of the faces. Faces which
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are not triangles will be split into triangles. A Meshes object containing a
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single mesh can be created from this data using</p>
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<pre><code class="hljs"> meshes = <span class="hljs-constructor">Meshes(<span class="hljs-params">verts</span>=[<span class="hljs-params">verts</span>], <span class="hljs-params">faces</span>=[<span class="hljs-params">faces</span>])</span>
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</code></pre>
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</span></div></article></div><div class="docs-prevnext"><a class="docs-prev button" href="/docs/io"><span class="arrow-prev">← </span><span>File IO</span></a><a class="docs-next button" href="/docs/datasets"><span>Data loaders</span><span class="arrow-next"> →</span></a></div></div></div><nav class="onPageNav"><ul class="toc-headings"><li><a href="#obj">OBJ</a></li><li><a href="#ply">PLY</a></li></ul></nav></div><footer class="nav-footer" id="footer"><section class="sitemap"><div class="footerSection"><div class="social"><a class="github-button" href="https://github.com/facebookresearch/pytorch3d" data-count-href="https://github.com/facebookresearch/pytorch3d/stargazers" data-show-count="true" data-count-aria-label="# stargazers on GitHub" aria-label="Star PyTorch3D on GitHub">pytorch3d</a></div></div></section><a href="https://opensource.facebook.com/" target="_blank" rel="noreferrer noopener" class="fbOpenSource"><img src="/img/oss_logo.png" alt="Facebook Open Source" width="170" height="45"/></a><section class="copyright">Copyright © 2024 Meta Platforms, Inc<br/>Legal:<a href="https://opensource.facebook.com/legal/privacy/" target="_blank" rel="noreferrer noopener">Privacy</a><a href="https://opensource.facebook.com/legal/terms/" target="_blank" rel="noreferrer noopener">Terms</a></section></footer></div></body></html> |