func NewKdTreeBuilder(mesh *TriangleMesh, buildParams BuildParams) *KdTreeBuilder {
// max count is chosen such that maxTrianglesCount * 2 is still
// an int32, this simplifies implementation.
const maxTrianglesCount = 0x3fffffff // max ~ 1 billion triangles
if mesh.GetTrianglesCount() > maxTrianglesCount {
common.RuntimeError(fmt.Sprintf(
"exceeded the maximum number of mesh triangles: %d",
maxTrianglesCount))
}
if buildParams.MaxDepth <= 0 {
trianglesCountLog :=
math.Floor(math.Log2(float64(mesh.GetTrianglesCount())))
buildParams.MaxDepth =
int(math.Floor(0.5 + 8.0 + 1.3*trianglesCountLog))
}
if buildParams.MaxDepth > maxTraversalDepth {
buildParams.MaxDepth = maxTraversalDepth
}
builder := &KdTreeBuilder{
mesh: mesh,
buildParams: buildParams,
}
if buildParams.CollectStats {
builder.buildStats.enabled = true
}
return builder
}
func LoadTriangleMesh(fileName string) *TriangleMesh {
const (
headerSize = 80
facetSize = 50
maxVerticesCount = math.MaxInt32
maxTrianglesCount = math.MaxInt32
)
file, err := os.Open(fileName)
common.Check(err)
defer file.Close()
// get file size
stat, err := file.Stat()
common.Check(err)
fileSize := stat.Size()
// read file content
fileContent := make([]byte, fileSize)
bytesRead, err := file.Read(fileContent)
common.Check(err)
if int64(bytesRead) != fileSize {
common.RuntimeError(fmt.Sprintf("failed to read %d bytes from file %s",
fileSize, fileName))
}
// validate file content
asciiStlHeader := []byte{0x73, 0x6f, 0x6c, 0x69, 0x64}
if bytes.Equal(fileContent[0:5], asciiStlHeader) {
common.RuntimeError("ascii stl files are not supported: " + fileName)
}
if fileSize < headerSize+4 {
common.RuntimeError("invalid binary stl file: " + fileName)
}
buffer := bytes.NewBuffer(fileContent[headerSize:])
var trianglesCount int32
err = binary.Read(buffer, binary.LittleEndian, &trianglesCount)
common.Check(err)
if trianglesCount > maxTrianglesCount {
common.RuntimeError("triangles limit exceeded: " + fileName)
}
expectedSize := int64(headerSize + 4 + trianglesCount*facetSize)
if fileSize != expectedSize {
common.RuntimeError("invalid size of binary stl file: " + fileName)
}
// read mesh data
mesh := new(TriangleMesh)
mesh.normals = make([]Vector32, trianglesCount)
mesh.triangles = make([][3]int32, trianglesCount)
uniqueVertices := make(map[Vector32]int32)
for i := 0; i < int(trianglesCount); i++ {
binary.Read(buffer, binary.LittleEndian, &mesh.normals[i])
for k := 0; k < 3; k++ {
var v Vector32
binary.Read(buffer, binary.LittleEndian, &v)
vertexIndex, found := uniqueVertices[v]
if !found {
if len(mesh.vertices) > maxVerticesCount {
common.RuntimeError("vertices limit exceeded: " + fileName)
}
vertexIndex = int32(len(mesh.vertices))
uniqueVertices[v] = vertexIndex
mesh.vertices = append(mesh.vertices, v)
}
mesh.triangles[i][k] = vertexIndex
}
var attribsCount uint16
binary.Read(buffer, binary.LittleEndian, &attribsCount)
}
return mesh
}
func (builder *KdTreeBuilder) buildNode(nodeBounds BBox32, nodeTriangles []int32,
depth int, offset0 int, offset1 int) {
if len(builder.nodes) >= maxNodesCount {
common.RuntimeError(fmt.Sprintf(
"maximum number of KdTree nodes has been reached: %d",
maxNodesCount))
}
// check if leaf node should be created
if len(nodeTriangles) <= builder.buildParams.LeafTrianglesLimit || depth == 0 {
builder.createLeaf(nodeTriangles)
builder.buildStats.newLeaf(len(nodeTriangles),
builder.buildParams.MaxDepth-depth)
return
}
// select split position
split := builder.selectSplit(nodeBounds, nodeTriangles)
if split.edge == -1 {
builder.createLeaf(nodeTriangles)
builder.buildStats.newLeaf(len(nodeTriangles),
builder.buildParams.MaxDepth-depth)
return
}
splitPosition := builder.edgesBuffer[split.edge].positionOnAxis
// classify triangles with respect to split
n0 := 0
for i := int32(0); i < split.edge; i++ {
if builder.edgesBuffer[i].isStart() {
builder.trianglesBuffer[offset0+n0] =
builder.edgesBuffer[i].triangleIndex()
n0++
}
}
n1 := 0
for i := split.edge + 1; i < int32(2*len(nodeTriangles)); i++ {
if builder.edgesBuffer[i].isEnd() {
builder.trianglesBuffer[offset1+n1] =
builder.edgesBuffer[i].triangleIndex()
n1++
}
}
// add interior node and recursively create children nodes
thisNodeIndex := len(builder.nodes)
builder.nodes = append(builder.nodes, node{})
bounds0 := nodeBounds
bounds0.maxPoint[split.axis] = splitPosition
builder.buildNode(bounds0, builder.trianglesBuffer[0:n0], depth-1, 0,
offset1+n1)
aboveChild := int32(len(builder.nodes))
builder.nodes[thisNodeIndex].initInteriorNode(split.axis, aboveChild,
splitPosition)
bounds1 := nodeBounds
bounds1.minPoint[split.axis] = splitPosition
builder.buildNode(bounds1, builder.trianglesBuffer[offset1:offset1+n1],
depth-1, 0, offset1)
}
