func newOctree(file string) (uint32, []uint32, error) {
var (
header pack.OctreeHeader
texture uint32
data []uint32
)
fp, err := os.Open(file)
if err != nil {
return 0, nil, err
}
defer fp.Close()
if err := pack.DecodeHeader(fp, &header); err != nil {
return 0, nil, err
}
if header.Format != pack.MipR8G8B8A8UnpackUI32 {
return 0, nil, errors.New("invalid octree format")
}
nodeSize := uint64(1 + 8)
var maxSize int32
gl.GetIntegerv(gl.MAX_TEXTURE_SIZE, &maxSize)
numInts := header.NumNodes * nodeSize
if maxSize*maxSize < int32(numInts) {
panic("octree does not fit on GPU")
}
var (
height int32
width = maxSize
)
for height < width {
maxSize = width
height = int32(numInts/uint64(width)) + 1
width /= 2
}
fmt.Printf("Octree is loaded in an %vx%v, R32UI, 2D texture.\n", maxSize, height)
textureSize := maxSize * height
data = make([]uint32, textureSize)
for i := uint64(0); i < header.NumNodes; i++ {
start := i * nodeSize
if err := binary.Read(fp, binary.BigEndian, data[start:start+nodeSize]); err != nil {
return 0, nil, err
}
// Recalculate alpha value.
data[start] &= 0xffffff00
for j := uint64(1); j < 9; j++ {
if data[start+j] > 0 {
data[start] |= uint32(0x100) >> j
}
}
}
gl.GenTextures(1, &texture)
gl.ActiveTexture(gl.TEXTURE0)
gl.BindTexture(gl.TEXTURE_2D, texture)
gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST)
gl.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST)
gl.TexImage2D(
gl.TEXTURE_2D,
0,
gl.R32UI,
maxSize,
height,
0,
gl.RED_INTEGER,
gl.UNSIGNED_INT,
gl.Ptr(data))
if glErr := gl.GetError(); glErr != gl.NO_ERROR {
err = fmt.Errorf("GL error, loading octree: %x", glErr)
}
return texture, data, err
}
// ActiveTexture implements the opengl.OpenGl interface.
func (native *OpenGl) ActiveTexture(texture uint32) {
gl.ActiveTexture(texture)
}