Volume data can come from various 3D scanning, scientific simulations, or distance transformation from 3D meshes; You may need to preprocess your volume data for this version. We used .iso as an extension for the input volume data which has scalar values (floating-point type) on a regular 3D grid, ranging from -1 to 1. The isovalue is defined as being 0. If the given volume is not defined on a regular grid with power-of-two size (2^n + 1), virtual padding (i.e., fill up -1 for empty space) should be applied.

Preprocess raw volume data or sets of 2D image files to a binary output file with an extension .iso in the following order:

for (i = 0; i < resolution; i++)

for (j = 0; j < resolution; j++)

for (k = 0; k < resolution; k++)

fwrite(&scalar, sizeof(float), 1, output);

• Drag & drop one .iso file, e.g. eight257.iso;
• Specify unit sizes for the grid;
  The default unit size is 1 for x,y, and z (1*1*1);
  For Headscan, try 0.8 for x,y and 1.5 for z (0.8*0.8*1.5);
  For Bonsai, 0.59 for x,y and 1 for z (0.59*0.59*1);
  For mrihead, 0.02 for x,y and 0.015 for z (0.02*0.02*0.015).
  
  And check the box if you like to save binary octree with geometry for faster reading later.
  




• Drag & drop one bbm file for reading a previously extracted isosurface, e.g. eight257.bbm, then eight257.con and eight257.geo will automatically be read;
• Choose a viewpoint (use the mouse):
•     left button: x/y translation;
•     right button: z translation;
•     both: rotation (press 'ctrl+s' to switch the rotation axis).

The isosurface Eight from a volume in a 257*257*257 grid.
 

Progressive Encoding

Press Ctrl+D, then the following dialog pops up:

• File name: Give an output file name (i.e., e8) then 4 output files (i.e., e8_header.txt, e8.sign, e8.leaf, e8.geo) will be generated;The output files are separated to show the size of compressed sign bitstream, leaf bitstream and geometry bitstream. Those files can be intertwined into a single file, obviously.
• Geometry encoding option:The default encodes geometry. Click the box "No Geometry" if no geometry encoding is wanted;
• Geo. Quantization Enter number of bins for quantizing localized coordinates. Usually 8~10 for x,y and 18~20 for z. For Temple model, try 30~40 for x,y and 60~80 for z;

In the above example of result for Eight, bitrates as bit per vertex(b/v), compressed file sizes for sign bitstream, leaf bitstream, geometry bitstream and the total as byte are shown. To show bytes transferred progressively, connectivity bits (sign + leaf) upto octree level 8 (i.e., 257*257*257 grid) are listed.

Progressive Decoding

• Press Ctrl-Shift-D with a window open to decode progressively;
• Open or drag & drop a *_header.txt" in the background without a window to just decode in full. *.sign, *.leaf, and *.geo will read in automatically.;





• Give the same name you specified during encoding. e.g. e8 in the current example. Then e8_header.txt, e8.sign, e8.leaf, and e8.geo will be read in.;
• Press "OK" to decode.;

Decoding options:

• Visual debugging: displays intermediate levels of details at each level and/or at the rate of given number of polygons generated;
• Delay: in ms, between each update. May be useful to simulate the delay in transmission.

Here is examples of decoding Buddha and Bonsai in 257*257*257 grids.