int QuadTree::CountTriangles(float positionX, float positionZ, float width)
{
int count, i;
bool result;
// Initialize the count to zero.
count = 0;
// Go through all the triangles in the entire mesh and check which ones should be inside this node.
for(i=0; i<m_triangleCount; i++)
{
// If the triangle is inside the node then increment the count by one.
result = IsTriangleContained(i, positionX, positionZ, width);
if(result == true)
{
count++;
}
}
return count;
}
void QuadTreeClass::CreateTreeNode(NodeType* node, float positionX, float positionZ, float width, ID3D10Device* device)
{
int numTriangles, i, count, vertexCount, index, vertexIndex;
float offsetX, offsetZ;
VertexType* vertices;
unsigned long* indices;
bool result;
D3D10_BUFFER_DESC vertexBufferDesc, indexBufferDesc;
D3D10_SUBRESOURCE_DATA vertexData, indexData;
// Store the node position and size.
node->positionX = positionX;
node->positionZ = positionZ;
node->width = width;
// Initialize the triangle count to zero for the node.
node->triangleCount = 0;
// Initialize the vertex and index buffer to null.
node->vertexBuffer = 0;
node->indexBuffer = 0;
// Initialize the vertex array to null.
node->vertexArray = 0;
// Initialize the children nodes of this node to null.
node->nodes[0] = 0;
node->nodes[1] = 0;
node->nodes[2] = 0;
node->nodes[3] = 0;
// Count the number of triangles that are inside this node.
numTriangles = CountTriangles(positionX, positionZ, width);
// Case 1: If there are no triangles in this node then return as it is empty and requires no processing.
if (numTriangles == 0)
{
return;
}
// Case 2: If there are too many triangles in this node then split it into four equal sized smaller tree nodes.
if (numTriangles > MAX_TRIANGLES)
{
for (i = 0; i<4; i++)
{
// Calculate the position offsets for the new child node.
offsetX = (((i % 2) < 1) ? -1.0f : 1.0f) * (width / 4.0f);
offsetZ = (((i % 4) < 2) ? -1.0f : 1.0f) * (width / 4.0f);
// See if there are any triangles in the new node.
count = CountTriangles((positionX + offsetX), (positionZ + offsetZ), (width / 2.0f));
if (count > 0)
{
// If there are triangles inside where this new node would be then create the child node.
node->nodes[i] = new NodeType;
// Extend the tree starting from this new child node now.
CreateTreeNode(node->nodes[i], (positionX + offsetX), (positionZ + offsetZ), (width / 2.0f), device);
}
}
return;
}
// Case 3: If this node is not empty and the triangle count for it is less than the max then
// this node is at the bottom of the tree so create the list of triangles to store in it.
node->triangleCount = numTriangles;
// Calculate the number of vertices.
vertexCount = numTriangles * 3;
// Create the vertex array.
vertices = new VertexType[vertexCount];
// Create the index array.
indices = new unsigned long[vertexCount];
// Create the vertex array.
node->vertexArray = new VectorType[vertexCount];
// Initialize the index for this new vertex and index array.
index = 0;
// Go through all the triangles in the vertex list.
for (i = 0; i<m_triangleCount; i++)
{
// If the triangle is inside this node then add it to the vertex array.
result = IsTriangleContained(i, positionX, positionZ, width);
if (result == true)
{
// Calculate the index into the terrain vertex list.
vertexIndex = i * 3;
// Get the three vertices of this triangle from the vertex list.
vertices[index].position = m_vertexList[vertexIndex].position;
vertices[index].texture = m_vertexList[vertexIndex].texture;
vertices[index].normal = m_vertexList[vertexIndex].normal;
indices[index] = index;
// Also store the vertex position information in the node vertex array.
node->vertexArray[index].x = m_vertexList[vertexIndex].position.x;
node->vertexArray[index].y = m_vertexList[vertexIndex].position.y;
node->vertexArray[index].z = m_vertexList[vertexIndex].position.z;
// Increment the indexes.
index++;
vertexIndex++;
// Do the same for the next point.
vertices[index].position = m_vertexList[vertexIndex].position;
vertices[index].texture = m_vertexList[vertexIndex].texture;
vertices[index].normal = m_vertexList[vertexIndex].normal;
indices[index] = index;
node->vertexArray[index].x = m_vertexList[vertexIndex].position.x;
node->vertexArray[index].y = m_vertexList[vertexIndex].position.y;
node->vertexArray[index].z = m_vertexList[vertexIndex].position.z;
index++;
vertexIndex++;
// Do the same for the next point also.
vertices[index].position = m_vertexList[vertexIndex].position;
vertices[index].texture = m_vertexList[vertexIndex].texture;
vertices[index].normal = m_vertexList[vertexIndex].normal;
indices[index] = index;
node->vertexArray[index].x = m_vertexList[vertexIndex].position.x;
node->vertexArray[index].y = m_vertexList[vertexIndex].position.y;
node->vertexArray[index].z = m_vertexList[vertexIndex].position.z;
index++;
}
}
// Set up the description of the vertex buffer.
vertexBufferDesc.Usage = D3D10_USAGE_DEFAULT;
vertexBufferDesc.ByteWidth = sizeof(VertexType) * vertexCount;
vertexBufferDesc.BindFlags = D3D10_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 finally create the vertex buffer.
device->CreateBuffer(&vertexBufferDesc, &vertexData, &node->vertexBuffer);
// Set up the description of the index buffer.
indexBufferDesc.Usage = D3D10_USAGE_DEFAULT;
indexBufferDesc.ByteWidth = sizeof(unsigned long) * vertexCount;
indexBufferDesc.BindFlags = D3D10_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.
device->CreateBuffer(&indexBufferDesc, &indexData, &node->indexBuffer);
// Release the vertex and index arrays now that the data is stored in the buffers in the node.
delete[] vertices;
vertices = 0;
delete[] indices;
indices = 0;
return;
}
