why cesium can not display the terrain? about cesium-terrain-builder HOT 5 OPEN

if (terrainFile == NULL) {
    throw CTBException("Failed to open file");
}

// Write the height data,float应该是4 * TILE_CELL_SIZE
//if (gzwrite(terrainFile, mHeights.data(), TILE_CELL_SIZE * 2) == 0)
if (fwrite( mHeights.data(),  sizeof(i_terrain_height),TILE_CELL_SIZE, terrainFile) == 0)
{
    fclose(terrainFile);
    throw CTBException("Failed to write height data");
}

// Write the child flags
if (fputc(mChildren,terrainFile ) == -1) {
    fclose(terrainFile);
    throw CTBException("Failed to write child flags");
}

// Write the water mask
if (fwrite(mMask,sizeof(char), mMaskLength,terrainFile ) == 0) {
    fclose(terrainFile);
    throw CTBException("Failed to write water mask");
}

fclose(terrainFile);

if (terrainFile == NULL) {
    throw CTBException("Failed to open file");
}

// Write the height data,float应该是4 * TILE_CELL_SIZE
//if (gzwrite(terrainFile, mHeights.data(), TILE_CELL_SIZE * 2) == 0)
if (gzwrite(terrainFile, mHeights.data(), TILE_CELL_SIZE * sizeof(i_terrain_height)) == 0)
{
    gzclose(terrainFile);
    throw CTBException("Failed to write height data");
}

// Write the child flags
if (gzputc(terrainFile, mChildren) == -1) {
    gzclose(terrainFile);
    throw CTBException("Failed to write child flags");
}

// Write the water mask
if (gzwrite(terrainFile, mMask, mMaskLength) == 0) {
    gzclose(terrainFile);
    throw CTBException("Failed to write water mask");
}

// Try and close the file
switch (gzclose(terrainFile)) {
case Z_OK:
    break;
case Z_STREAM_ERROR:
case Z_ERRNO:
case Z_MEM_ERROR:
case Z_BUF_ERROR:
default:
    throw CTBException("Failed to close file");
}