从加载的高度图中索引三角形的方法？

Question

我目前正在制作一种方法来加载嘈杂的高度图，但缺少三角形来这样做。我想制作一个算法来获取图像，它的宽度和高度并从中构建一个地形节点。

这是我到目前为止所拥有的，有点伪

Vertex* vertices = new Vertices[image.width * image.height];
Index* indices; // How do I judge how many indices I will have?
float scaleX = 1 / image.width;
float scaleY = 1 / image.height;
float currentYScale = 0;

for(int y = 0; y < image.height; ++y) {
    float currentXScale = 0;
    for (int x = 0; x < image.width; ++x) {
       Vertex* v = vertices[x * y];
       v.x = currentXScale;
       v.y = currentYScale;
       v.z = image[x,y]; 
       currentXScale += scaleX;
    }
    currentYScale += scaleY;
}

这足以满足我的需要，我唯一的问题是：如何计算索引的数量及其绘制三角形的位置？我对索引有些熟悉，但不知道如何以编程方式计算它们，我只能静态地这样做。

Answer 1

就你上面的代码而言，使用vertices[x * y]是不对的 - 如果你使用它，那么例如vert(2,3) == vert(3,2). 你想要的是类似的东西vertices[y * image.width + x]，但你可以通过增加一个计数器来更有效地做到这一点（见下文）。

这是我使用的等效代码。不幸的是它在 C# 中，但希望它应该说明这一点：

/// <summary>
/// Constructs the vertex and index buffers for the terrain (for use when rendering the terrain).
/// </summary>
private void ConstructBuffers()
{
    int heightmapHeight = Heightmap.GetLength(0);
    int heightmapWidth = Heightmap.GetLength(1);
    int gridHeight = heightmapHeight - 1;
    int gridWidth = heightmapWidth - 1;

    // Construct the individual vertices for the terrain.
    var vertices = new VertexPositionTexture[heightmapHeight * heightmapWidth];

    int vertIndex = 0;
    for(int y = 0; y < heightmapHeight; ++y)
    {
        for(int x = 0; x < heightmapWidth; ++x)
        {
            var position = new Vector3(x, y, Heightmap[y,x]);
            var texCoords = new Vector2(x * 2f / heightmapWidth, y * 2f / heightmapHeight);
            vertices[vertIndex++] = new VertexPositionTexture(position, texCoords);
        }
    }

    // Create the vertex buffer and fill it with the constructed vertices.
    this.VertexBuffer = new VertexBuffer(Renderer.GraphicsDevice, typeof(VertexPositionTexture), vertices.Length, BufferUsage.WriteOnly);
    this.VertexBuffer.SetData(vertices);

    // Construct the index array.
    var indices = new short[gridHeight * gridWidth * 6];    // 2 triangles per grid square x 3 vertices per triangle

    int indicesIndex = 0;
    for(int y = 0; y < gridHeight; ++y)
    {
        for(int x = 0; x < gridWidth; ++x)
        {
            int start = y * heightmapWidth + x;
            indices[indicesIndex++] = (short)start;
            indices[indicesIndex++] = (short)(start + 1);
            indices[indicesIndex++] = (short)(start + heightmapWidth);
            indices[indicesIndex++] = (short)(start + 1);
            indices[indicesIndex++] = (short)(start + 1 + heightmapWidth);
            indices[indicesIndex++] = (short)(start + heightmapWidth);
        }
    }

    // Create the index buffer.
    this.IndexBuffer = new IndexBuffer(Renderer.GraphicsDevice, typeof(short), indices.Length, BufferUsage.WriteOnly);
    this.IndexBuffer.SetData(indices);
}

我想关键是，给定一个 size 的高度图heightmapHeight * heightmapWidth，您需要(heightmapHeight - 1) * (heightmapWidth - 1) * 6索引，因为您正在绘制：

• 2 每个网格正方形的三角形
• 3 每个三角形的顶点
• (heightmapHeight - 1) * (heightmapWidth - 1) 地形中的网格方块。