【发布时间】：2021-08-30 08:08:41
【问题描述】：
我正在尝试将八叉树展平为一个数组，以便将其传递给 GPU。我想从我的八叉树中获取数据，将其加载到 Voxel 结构的向量中，然后将其发送到 GPU。我在开始时将 2 个体素插入八叉树。这些是我的插入函数：
template<typename T>
Octree<T>::Octree(glm::vec3 position, float octreeSize, int depth) : root(position, 1.0f), depth(depth), octreeSize(octreeSize), transform(1.0f)
{
insert(glm::vec3(0.5, 0.1, 0.7f), true);
insert(glm::vec3(-0.5, -0.1, -0.7f), true);
transform = glm::translate(transform, glm::vec3(0, 0, 5));
}
template<typename T>
void Octree<T>::insert(glm::vec3 pos, T data)
{
root.subdivide(pos, data, depth, 1.0f);
}
template<typename T>
int Octree<T>::Node::getIndexOfPosition(glm::vec3 lookupPosition, glm::vec3 nodePosition) const
{
int index = 0;
index |= lookupPosition.y > nodePosition.y ? 4 : 0;
index |= lookupPosition.x > nodePosition.x ? 2 : 0;
index |= lookupPosition.z > nodePosition.z ? 1 : 0;
return index;
}
template<typename T>
void Octree<T>::Node:: subdivide(glm::vec3 targetPos, T value, int divDepth, float parentSize)
{
int subdivIndex = getIndexOfPosition(targetPos, position);
if(children.empty())
{
for(int i = 0; i < 8; i++)
{
glm::vec3 newPos = position;
float sizeModifier = parentSize * 0.5f;
if ((i & 4) == 4)
newPos.y += sizeModifier;
else
newPos.y -= sizeModifier;
if ((i & 2) == 2)
newPos.x += sizeModifier;
else
newPos.x -= sizeModifier;
if ((i & 1) == 1)
newPos.z += sizeModifier;
else
newPos.z -= sizeModifier;
Node newNode(newPos, sizeModifier);
children.push_back(newNode);
}
}
if (divDepth > 0)
{
//std::cout << "Subdividing" << std::endl;
children[subdivIndex].subdivide(targetPos, value, divDepth - 1, parentSize*0.5f);
}
else
{
children[subdivIndex].data = value;
}
}
我的体素结构：
struct Voxel
{
Voxel(): pIndex(-1), index(-1), pos(90000.f), col(0.f) { for (int & i : cIdx) i = -1; }
int cIdx[8]; // The indexes of the child nodes in the vector
int index; // The current index of this voxel within the vector
int pIndex;
glm::vec4 pos;
glm::vec4 col;
};
目前我正在预先遍历我的八叉树，我递归地遍历每个节点子节点（如果有的话），将当前体素子索引设置为当前索引，然后对其所有子节点执行相同操作。最后，一旦我们位于树的底部或没有子节点，将该节点推送到 GPU 上并将子节点的父索引设置为当前索引。这是我的功能：
template<typename T>
int
Octree<T>::Node::fillShaderVector(std::vector<Voxel> &voxelData, glm::mat4 octTransform, float octSize, int index) const
{
Voxel voxel;
if (isInternal())
{
int i = 0;
for (auto child: children)
{
// I think this is where we have issues
voxel.cIdx[i] = index;
index = child.fillShaderVector(voxelData, octTransform, octSize, index);
i++;
}
}
voxel.pos = glm::vec4(position, 1.0);
// Store size as the 4th element in the vector
voxel.pos.w = voxelSize;
voxel.col = glm::vec4(1.0);
voxel.index = index;
voxelData.push_back(voxel);
index++;
if (isInternal())
{
for(int i : voxel.cIdx)
voxelData[i].pIndex = voxel.index;
}
return index;
}
template<typename T>
bool Octree<T>::Node::isInternal() const
{
return !children.empty();
}
这会正确地遍历节点，并且我能够为每个体素获取正确的索引，但是我似乎无法正确设置父索引。
示例输出（为简洁起见，我删掉了很多，它从 0..56 Parent: -1 表示没有父节点，即应该只是根节点，而 child: -1，表示它是一个叶节点）：
Index: 0
Parent: 56
Children: -1 -1 -1 -1 -1 -1 -1 -1
Index: 1
Parent: 24
Children: -1 -1 -1 -1 -1 -1 -1 -1
Index: 2
Parent: 24
Children: -1 -1 -1 -1 -1 -1 -1 -1
Index: 3
Parent: 24
Children: -1 -1 -1 -1 -1 -1 -1 -1
Index: 4
Parent: 24
Children: -1 -1 -1 -1 -1 -1 -1 -1
Index: 5
Parent: 20
Children: -1 -1 -1 -1 -1 -1 -1 -1
Index: 6
Parent: 20
Children: -1 -1 -1 -1 -1 -1 -1 -1
Index: 7
Parent: 20
Children: -1 -1 -1 -1 -1 -1 -1 -1
Index: 8
Parent: 20
Children: -1 -1 -1 -1 -1 -1 -1 -1
...
Index: 16
Parent: 19
Children: -1 -1 -1 -1 -1 -1 -1 -1
Index: 17
Parent: 19
Children: -1 -1 -1 -1 -1 -1 -1 -1
Index: 18
Parent: 19
Children: -1 -1 -1 -1 -1 -1 -1 -1
Index: 19
Parent: -1
Children: 11 12 13 14 15 16 17 18
Index: 20
Parent: -1
Children: 4 5 6 7 8 9 10 11
...
Index: 47
Parent: 48
Children: -1 -1 -1 -1 -1 -1 -1 -1
Index: 48
Parent: -1
Children: 32 33 34 43 44 45 46 47
Index: 49
Parent: 55
Children: -1 -1 -1 -1 -1 -1 -1 -1
Index: 50
Parent: 55
Children: -1 -1 -1 -1 -1 -1 -1 -1
Index: 51
Parent: 55
Children: -1 -1 -1 -1 -1 -1 -1 -1
Index: 52
Parent: 55
Children: -1 -1 -1 -1 -1 -1 -1 -1
Index: 53
Parent: 55
Children: -1 -1 -1 -1 -1 -1 -1 -1
Index: 54
Parent: 55
Children: -1 -1 -1 -1 -1 -1 -1 -1
Index: 55
Parent: -1
Children: 31 32 49 50 51 52 53 54
Index: 56
Parent: -1
Children: 0 25 26 27 28 29 30 31
我在 fillShaderVector 函数中做错了什么，导致我无法准确填写父索引？
【问题讨论】：
-
您是否尝试调试过代码？
-
是的。经过数小时的失败后，我求助于堆栈溢出。
标签： c++ arrays tree tree-traversal octree