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copied!<p><a href="http://www.opengl.org/wiki/Vertex_Shader#Multiple_attributes" rel="noreferrer">Arrays of vertex attributes</a> are legal in OpenGL. However, each member of the array takes up a <em>separate</em> attribute index. They are allocated contiguously, starting from whatever attribute index you give <code>patch_data</code>. Since you're using GLSL 4.00, you should also be specifying attribute locations explicitly with <code>layout(location = #)</code>.</p> <p>So if you do this:</p> <pre><code>layout(location = 1) in vec3 patch_data[1 + 2 * max_valence]; </code></pre> <p>Then <code>patch_data</code> will cover all attribute indices on the half-open range from 1 to <code>1 + (1 + 2 * max_valence)</code>.</p> <p>Each array entry is, from the OpenGL side, a <em>separate attribute</em>. Therefore, you need a separate <a href="http://www.opengl.org/wiki/GLAPI/glVertexAttribPointer" rel="noreferrer"><code>glVertexAttribPointer</code></a> call for each separate array index.</p> <p>So if your array data in memory looks like an array of 13 vec3's, tightly packed, then you need to do this:</p> <pre><code>for(int attrib = 0; attrib < 1 + (2 * max_valence); ++attrib) { glVertexAttribPointer(attrib + 1, //Attribute index starts at 1. 3, //Each attribute is a vec3. GL_FLOAT, //Change as appropriate to the data you're passing. GL_FALSE, //Change as appropriate to the data you're passing. sizeof(float) * 3 * (1 + (2 * max_valence)), //Assuming that these array attributes aren't interleaved with anything else. reinterpret_cast<void*>(baseOffset + (attrib * 3 * sizeof(float))) //Where baseOffset is the start of the array data in the buffer object. ); } </code></pre>

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