【DX11地形篇】2-地形网格

参考教程

Tutorial 1: Grid and Camera Movement

学习记录

  本篇主要介绍对地形网格的绘制，代码基于上一篇内容。

  既然说是地形网格，那么自然是以网格为主。我们之前在 ModelClass 中读取模型文件来创建模型数据，在 TerrainClass 中则是使用代码生成网格。首先来看我们 TerrainClass 的声明：

////////////////////////////////////////////////////////////////////////////////
// Class name: TerrainClass
////////////////////////////////////////////////////////////////////////////////
class TerrainClass
{
private:
	struct VertexType
	{
		XMFLOAT3 position;
		XMFLOAT4 color;
	};

public:
	TerrainClass();
	TerrainClass(const TerrainClass&);
	~TerrainClass();

	bool Initialize(ID3D11Device*);
	void Shutdown();
	bool Render(ID3D11DeviceContext*);

	int GetIndexCount();

private:
	bool InitializeBuffers(ID3D11Device*);
	void ShutdownBuffers();
	void RenderBuffers(ID3D11DeviceContext*);

private:
	ID3D11Buffer *m_vertexBuffer, *m_indexBuffer;
	int m_vertexCount, m_indexCount;
};

  和 ModelClass 几乎相同。在它的 InitializeBuffers 方法中，我们使用代码生成顶点和索引数据，代码如下：

bool TerrainClass::InitializeBuffers(ID3D11Device* device)
{
	VertexType* vertices;
	unsigned long* indices;
	D3D11_BUFFER_DESC vertexBufferDesc, indexBufferDesc;
	D3D11_SUBRESOURCE_DATA vertexData, indexData;
	HRESULT result;
	int i, j, terrainWidth, terrainHeight, index;
	XMFLOAT4 color;
	float positionX, positionZ;


	// Set the height and width of the terrain grid.
	terrainHeight = 256;
	terrainWidth = 256;

	// Set the color of the terrain grid.
	color = XMFLOAT4(0.5f, 0.5f, 0.5f, 1.0f);
	
	// Calculate the number of vertices in the terrain.
	m_vertexCount = (terrainWidth - 1) * (terrainHeight - 1) * 8;

	// Set the index count to the same as the vertex count.
	m_indexCount = m_vertexCount;

	// Create the vertex array.
	vertices = new VertexType[m_vertexCount];
	if(!vertices)
	{
		return false;
	}

	// Create the index array.
	indices = new unsigned long[m_indexCount];
	if(!indices)
	{
		return false;
	}
	
	// Initialize the index into the vertex and index arrays.
	index = 0;

	// Load the vertex array and index array with data.
	for(j=0; j<(terrainHeight-1); j++)
	{
		for(i=0; i<(terrainWidth-1); i++)
		{
			// Line 1 - Upper left.
			positionX = (float)i;
			positionZ = (float)(j + 1);

			vertices[index].position = XMFLOAT3(positionX, 0.0f, positionZ);
			vertices[index].color = color;
			indices[index] = index;
			index++;

			// Line 1 - Upper right.
			positionX = (float)(i + 1);
			positionZ = (float)(j + 1);

			vertices[index].position = XMFLOAT3(positionX, 0.0f, positionZ);
			vertices[index].color = color;
			indices[index] = index;
			index++;

			// Line 2 - Upper right
			positionX = (float)(i + 1);
			positionZ = (float)(j + 1);

			vertices[index].position = XMFLOAT3(positionX, 0.0f, positionZ);
			vertices[index].color = color;
			indices[index] = index;
			index++;

			// Line 2 - Bottom right.
			positionX = (float)(i + 1);
			positionZ = (float)j;

			vertices[index].position = XMFLOAT3(positionX, 0.0f, positionZ);
			vertices[index].color = color;
			indices[index] = index;
			index++;

			// Line 3 - Bottom right.
			positionX = (float)(i + 1);
			positionZ = (float)j;

			vertices[index].position = XMFLOAT3(positionX, 0.0f, positionZ);
			vertices[index].color = color;
			indices[index] = index;
			index++;

			// Line 3 - Bottom left.
			positionX = (float)i;
			positionZ = (float)j;

			vertices[index].position = XMFLOAT3(positionX, 0.0f, positionZ);
			vertices[index].color = color;
			indices[index] = index;
			index++;

			// Line 4 - Bottom left.
			positionX = (float)i;
			positionZ = (float)j;

			vertices[index].position = XMFLOAT3(positionX, 0.0f, positionZ);
			vertices[index].color = color;
			indices[index] = index;
			index++;

			// Line 4 - Upper left.
			positionX = (float)i;
			positionZ = (float)(j + 1);

			vertices[index].position = XMFLOAT3(positionX, 0.0f, positionZ);
			vertices[index].color = color;
			indices[index] = index;
			index++;
		}
	}

	// Set up the description of the static vertex buffer.
	vertexBufferDesc.Usage = D3D11_USAGE_DEFAULT;
	vertexBufferDesc.ByteWidth = sizeof(VertexType) * m_vertexCount;
	vertexBufferDesc.BindFlags = D3D11_BIND_VERTEX_BUFFER;
	vertexBufferDesc.CPUAccessFlags = 0;
	vertexBufferDesc.MiscFlags = 0;
	vertexBufferDesc.StructureByteStride = 0;

	// Give the subresource structure a pointer to the vertex data.
	vertexData.pSysMem = vertices;
	vertexData.SysMemPitch = 0;
	vertexData.SysMemSlicePitch = 0;

	// Now create the vertex buffer.
	result = device->CreateBuffer(&vertexBufferDesc, &vertexData, &m_vertexBuffer);
	if(FAILED(result))
	{
		return false;
	}

	// Set up the description of the static index buffer.
	indexBufferDesc.Usage = D3D11_USAGE_DEFAULT;
	indexBufferDesc.ByteWidth = sizeof(unsigned long) * m_indexCount;
	indexBufferDesc.BindFlags = D3D11_BIND_INDEX_BUFFER;
	indexBufferDesc.CPUAccessFlags = 0;
	indexBufferDesc.MiscFlags = 0;
	indexBufferDesc.StructureByteStride = 0;

	// Give the subresource structure a pointer to the index data.
	indexData.pSysMem = indices;
	indexData.SysMemPitch = 0;
	indexData.SysMemSlicePitch = 0;

	// Create the index buffer.
	result = device->CreateBuffer(&indexBufferDesc, &indexData, &m_indexBuffer);
	if(FAILED(result))
	{
		return false;
	}

	// Release the arrays now that the buffers have been created and loaded.
	delete [] vertices;
	vertices = 0;

	delete [] indices;
	indices = 0;

	return true;
}

  可以看到我们是以四条线的方式来确定每一个四边形，所以在绘制图元类型的时候我们选用线绘制：

// Set the type of primitive that should be rendered from this vertex buffer, in this case lines.
deviceContext->IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY_LINELIST);

  最终效果（高处往下看）：

  源代码：DX11TerrainTutorial-GridAndCameraMovement