GLSL中的KD树

layout(std140) uniform node{
  ivec4 splitPoint;
  int dataPtr;
} nodes[1024];

整个阵列形成一个 Ahnentafel List .

在C++中,结构看起来像这样:

struct Node{
  glm::ivec4 splitPoint;
  GLint dataPtr;
  GLint padding[3];
};

我相信这是正确的,我上传了在缓冲区中构建的树。作为检查,我将缓冲区映射到主内存并检查值:

0x08AB6890     +0  +256    +0    +1    -1  -858993460  -858993460  -858993460
0x08AB68B0   +256    +0    +0    +0    -1  -858993460  -858993460  -858993460
0x08AB68D0   +256  +256    +0    +0    -1  -858993460  -858993460  -858993460
[...]
0x08AB7070     +0    +0    +0    +0 +2362  -858993460  -858993460  -858993460

float distanceFromSplitPlane;
while(nodes[n].dataPtr == -1){

  // get split direction
  vec3 splitDir = vec3(0,0,0);
  if(nodes[n].splitDir == 0)
    splitDir.x = 1;
  else if(nodes[n].splitDir == 1)
    splitDir.y = 1;
  else 
    splitDir.z = 1;


  // calculate distance of ray starting point to the split plane
  distanceFromSplitPlane = dot(startP.xyz-(nodes[n].splitPoint.xyz/511.0), splitDir);

  // depending on the side advance in the tree
  if(distanceFromSplitPlane >= 0)
    n = 2 * n + 1;
  else
    n = 2 * n + 2;
}

// we should new be located in a leaf node and therefor have a value in dataPtr
gl_FragColor = vec4(dataPtr/6000.0, 0,1,1);

在这一点上,屏幕上应该有一个随机的颜色模式。但在大多数情况下,什么都看不见。

我尝试直接从节点获取值并得到正确的结果。。。所以我认为统一块数据的动态索引有问题。