1

我试图绕开我的头：

http://msdn.microsoft.com/en-us/library/bb196409.aspx

参考资料不多。它很短，很模糊，没有什么可以学习的。

我想创建一个采用 Triangle = (A class of 3 Vectors) 列表的方法，然后渲染它，然后能够用颜色或纹理填充它。

有人可以解释上述方法吗？因为我正在尝试的根本不起作用。我试过添加一个三角形。以下是我的理解，有错误的地方请指正。

创建“一个三角形”时的方法：

GraphicsDevice.DrawUserIndexedPrimitives<VertexPositionColor>
(
    PrimitiveType.TriangleStrip,
    "array of 3 VertexPositionColor?",
    0,
    (3? 9?),
    "I have no clue what to put here and why I should put it here?",
    "What do I put here?",
    "If 1 triangle, value should be = 1? 1 Triangle = 1 Primitive"
);

我需要什么才能完成这项工作？根据我传递给我的方法的三角形的数量，我是否渲染以及哪些值会根据有多少三角形而改变？

...如果成功（希望有时）我该如何填写？

请不要有模糊的简短答案，因为参考资料做得非常好。

4

1 回答 1

6

在我们开始之前，先澄清一下您的思维方式。在 XNA 中 - 您绘制线框（轮廓）三角形、填充三角形或带纹理的三角形。没有任何“现在绘制”和“稍后填充”的内容。您只能在帧缓冲区中已有的内容之上绘制其他内容。

这里还有一些关于什么是索引网格的背景。这是馈入 DrawUserIndexedPrimitives 的数据（由顶点集的索引组成的顶点和三角形）。

鉴于此，以下是绘图调用的工作方式

    _effect.Texture = texture; // This sets the texture up so the 
    // shaders associated with this effect can access it

    // The color in each vertex is modulated with the texture color 
    // and linearly interpolated across vertices
    _effect.VertexColorEnabled = true;

    foreach (var pass in _effect.CurrentTechnique.Passes)
    {
        pass.Apply(); // This sets up the shaders and their state

        // TriangleList means that the indices are understood to be 
        // multiples of 3, where the 3 vertices pointed to are comprise
        // one triangle
        _device.DrawUserIndexedPrimitives(PrimitiveType.TriangleList,

        // The vertices. Note that there can be any number of vertices in here.
        // What's important is the indices array (and the vertexOffset, primitivecount, vertexCount) that determine
        // how many of the provided vertices will actually matter for this draw call
                                                      _vertices, 
        // The offset to the first vertex that the index 0 in the index array will refer to
        // This is used to render a "part" of a bigger set of vertices, perhaps shared across
        // different objects
                                                      0,
        // The number of vertices to pick starting from vertexOffset. If the index array 
        // tried to index a vertex out of this range then the draw call will fail.
                                                      _vertices.Count,
        // The indices (count = multiple of 3) that comprise separate triangle (because we said TriangleList - 
        // the rules are different depending on the primitive type)
                                                      _indices, 
        // Again, an offset inside the indices array so a part of a larger index array can be used
                                                      0,
        // Number of indices. This HAS to be a multiple of 3 because we said we're rendering
        // a list of triangles (TrangleList).
                                                      kvp.Value.Indices.Count / 3);
    }

我希望这很清楚。如果您对每个参数和/或概念有任何具体问题，请告诉我，我可以编辑这篇文章以澄清这些观点。

希望这可以帮助！

于 2012-06-21T14:46:44.973 回答