ios - 在结构中传递法线
<p><p>我正在尝试在 OpenGL ES 2.0 iOS 中绘制一个 3D 立方体。我创建了一个结构，通过它我试图容纳与立方体相关的各种信息(位置坐标、纹理映射、法线)。现在我需要告诉 OpenGL 在哪里可以找到这个结构中的法线。一切都正确编译和渲染，但我在下面显示的最后一行给了我这个警告:</p>
<p><code>不兼容的整数到指针转换将“unsigned long”传递给“const GLvoid *”类型的参数(又名“const void *”)</code></p>
<p>为什么我的代码返回一个无符号长整数？我不知道如何修改它以获取该行所要求的指针。谁能看到我做错了什么？谢谢。</p>
<p>这是结构:</p>
<pre><code>typedef struct {
GLKVector3 positionCoordinates;
GLKVector2 textureCoordinates;
GLKVector3 normalCoordinates;
} VertexData;
</code></pre>
<p>坐标数据:</p>
<pre><code>VertexData cameraVertices[] = {
//{ position x, position y, position z}, {texture}, {normalX, normalY, normalZ}
{ { 0.5f, -0.5f, -0.5f}, {0.0f, 0.0f}, { 1.0f,0.0f,0.0f} }, // rightward facing (+X)
{ { 0.5f,0.5f, -0.5f}, {1.0f, 0.0f}, { 1.0f,0.0f,0.0f} },
{ { 0.5f, -0.5f,0.5f}, {0.0f, 1.0f}, { 1.0f,0.0f,0.0f} },
{ { 0.5f, -0.5f,0.5f}, {0.0f, 1.0f}, { 1.0f,0.0f,0.0f} },
{ { 0.5f,0.5f, -0.5f}, {1.0f, 0.0f}, { 1.0f,0.0f,0.0f} },
{ { 0.5f,0.5f,0.5f}, {1.0f, 1.0f}, { 1.0f,0.0f,0.0f} },
{ { 0.5f,0.5f, -0.5f}, {0.0f, 0.0f}, { 0.0f,1.0f,0.0f} }, // upward facing (+Y)
{ {-0.5f,0.5f, -0.5f}, {1.0f, 0.0f}, { 0.0f,1.0f,0.0f} },
{ { 0.5f,0.5f,0.5f}, {0.0f, 1.0f}, { 0.0f,1.0f,0.0f} },
{ { 0.5f,0.5f,0.5f}, {0.0f, 1.0f}, { 0.0f,1.0f,0.0f} },
{ {-0.5f,0.5f, -0.5f}, {1.0f, 0.0f}, { 0.0f,1.0f,0.0f} },
{ {-0.5f,0.5f,0.5f}, {1.0f, 1.0f}, { 0.0f,1.0f,0.0f} },
{ {-0.5f,0.5f, -0.5f}, {0.0f, 0.0f}, {-1.0f,0.0f,0.0f} }, // leftward facing (-X)
{ {-0.5f, -0.5f, -0.5f}, {1.0f, 0.0f}, {-1.0f,0.0f,0.0f} },
{ {-0.5f,0.5f,0.5f}, {0.0f, 1.0f}, {-1.0f,0.0f,0.0f} },
{ {-0.5f,0.5f,0.5f}, {0.0f, 1.0f}, {-1.0f,0.0f,0.0f} },
{ {-0.5f, -0.5f, -0.5f}, {1.0f, 0.0f}, {-1.0f,0.0f,0.0f} },
{ {-0.5f, -0.5f,0.5f}, {1.0f, 1.0f}, {-1.0f,0.0f,0.0f} },
{ {-0.5f, -0.5f, -0.5f}, {0.0f, 0.0f}, { 0.0f, -1.0f,0.0f} }, // downward facing (-Y)
{ { 0.5f, -0.5f, -0.5f}, {1.0f, 0.0f}, { 0.0f, -1.0f,0.0f} },
{ {-0.5f, -0.5f,0.5f}, {0.0f, 1.0f}, { 0.0f, -1.0f,0.0f} },
{ {-0.5f, -0.5f,0.5f}, {0.0f, 1.0f}, { 0.0f, -1.0f,0.0f} },
{ { 0.5f, -0.5f, -0.5f}, {1.0f, 0.0f}, { 0.0f, -1.0f,0.0f} },
{ { 0.5f, -0.5f,0.5f}, {1.0f, 1.0f}, { 0.0f, -1.0f,0.0f} },
{ { 0.5f,0.5f,0.5f}, {0.0f, 0.0f}, { 0.0f,0.0f,1.0f} }, // forward facing (+Z)
{ {-0.5f,0.5f,0.5f}, {1.0f, 0.0f}, { 0.0f,0.0f,1.0f} },
{ { 0.5f, -0.5f,0.5f}, {0.0f, 1.0f}, { 0.0f,0.0f,1.0f} },
{ { 0.5f, -0.5f,0.5f}, {0.0f, 1.0f}, { 0.0f,0.0f,1.0f} },
{ {-0.5f,0.5f,0.5f}, {1.0f, 0.0f}, { 0.0f,0.0f,1.0f} },
{ {-0.5f, -0.5f,0.5f}, {1.0f, 1.0f}, { 0.0f,0.0f,1.0f} },
{ { 0.5f, -0.5f, -0.5f}, {0.0f, 0.0f}, { 0.0f,0.0f, -1.0f} }, // rear facing (-Z)
{ {-0.5f, -0.5f, -0.5f}, {1.0f, 0.0f}, { 0.0f,0.0f, -1.0f} },
{ { 0.5f,0.5f, -0.5f}, {0.0f, 1.0f}, { 0.0f,0.0f, -1.0f} },
{ { 0.5f,0.5f, -0.5f}, {0.0f, 1.0f}, { 0.0f,0.0f, -1.0f} },
{ {-0.5f, -0.5f, -0.5f}, {1.0f, 0.0f}, { 0.0f,0.0f, -1.0f} },
{ {-0.5f,0.5f, -0.5f}, {1.0f, 1.0f}, { 0.0f,0.0f, -1.0f} },
};
</code></pre>
<p>以及相关的代码行(基本上在viewDidLoad中):</p>
<pre><code>glEnableVertexAttribArray(GLKVertexAttribPosition);
glVertexAttribPointer(GLKVertexAttribPosition, 3, GL_FLOAT, GL_FALSE, sizeof(VertexData), offsetof(VertexData, positionCoordinates));
glEnableVertexAttribArray(GLKVertexAttribNormal);
glVertexAttribPointer(GLKVertexAttribNormal, 3, GL_FLOAT, GL_FALSE, sizeof(VertexData), offsetof(VertexData, normalCoordinates));
</code></pre></p>
<br><hr><h1><strong>Best Answer-推荐答案</ strong></h1><br>
<p><p>嗯，这里的根本问题是 <code>offsetof</code> 宏不返回指针!它以 <code>size_t</code> 形式返回偏移量。由于 <code>size_t</code> 的大小和 <code>GLvoid *</code> 的大小可能不同，所以不要这样使用 <code>offsetof (...)</code> 的结果。 </p>
<p>你应该做的是:<code>(GLubyte *)0 + offsetof (...)</code>.</p></p>
<p style="font-size: 20px;">关于ios - 在结构中传递法线，我们在Stack Overflow上找到一个类似的问题：
<a href="https://stackoverflow.com/questions/19692233/" rel="noreferrer noopener nofollow" style="color: red;">
https://stackoverflow.com/questions/19692233/
</a>
</p>
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