Shell TomoVision

 

In this mode, you create 3D polygonal surfaces from the TAG images you created with the TAG Module.

 

In TomoVision’s algorithm, the center of each voxel is considered as a potential node for the reconstructed surface. If this node lies on the border between 2 tag values, it will be used to anchor the surface’s polygons. It is also possible to use a sub-sampling of the voxels to limit the number of polygons. When using a sub-sampling, even though the creation of the geometry uses one in N voxels, a subsequent optimization phase replaces the polygons nodes close to the tag borders using all the voxels values.

 

 

The following images show the reconstruction of a 8 nodes cube using

a)  the TomoVision algorithm.

b)  the Lorensen algorithm

 

 

Using sub-sampling for the x, y or z directions will decrease the number of polygons created. One point in N will be considered. Once the polygons are created, the geometry will be expanded using all the image’s voxels. The polygons’ nodes will be moved on the actual border between the tags, regardless of the sub-sampling value. So even though sub-sampling reduces the polygon count, it does not affect too much the surface's contour.

 

This example shows 2 Meshes created with the TomoVision algorithm: Using sub-sampling = 1 (in blue, 14524 polygons) and sub-sampling = 8 (in yellow, 444 polygons)

 

Note:

 

The shell computation is only available for 3D and sorted parallel groups.

 

From the Graphic Interface

 

 

 

TAG Value

Select the current Tag value

 

Conditions

These buttons control the surface creation conditions. For each selected Tag value, a surface will be created on the border of a Tag pixel  if:

The Tag value is greater than the Tag value of its neighbour

The Tag value is smaller than the Tag value of its neighbour

The Tag value is on the border of the volume

   

 

Voxel Sub-sampling

The number of polygons created is controlled by the sub-sampling, but the polygons’ contour will use ALL the voxels

 

Create Geometry

Clicking this button will cause sliceOmatic to compute the 3D shell around all the selected Tags

 

 

Example of reconstructions with different conditions.

 

 

 

The original TAG image:

Outside = TAG 1,

circle = TAG 2,

cross = TAG 3

 

Shell of TAG 2 with the condition

Greater

Shell of TAG 2 with the condition

Smaller

 

 

Shell of TAG 2 with the condition

Border

Shell of TAG 2 with the condition

Greater & Smaller

Shell of TAG 2 with the condition

Greater & Smaller & Border

 

 

From the Display Area

 

There is no Display Area interaction specific to this mode.

 

 

From the Keyboard

 

There is no keyboard interface specific to this mode.

 

 

From the Command Line

 

System Variables defined in this library:

 

 

$SHELL_LORENSEN_MODDE

(U8)

Shell reconstruction mode. This is a bit field with the values:

x01 = Mode Outside

x02 = Mode Inside

x04 = Mode Border

 

$SHELL_TOMO_MODDE

(U8)

 

$SHELL_TOMO_SUBSAMPLING

(A,U16)

Array of 3 sub-sampling values (x,y and z).  Sub-sampling values goes from 0 (no sub-sampling) to 10 (1 pixel every 10).

 

 

Commands recognized in this library:

 

Shell: Mode (inside|outside|border) (on|off)

Change the value of the specified bit in both $SHELL_LORENSEN_MODE and $SHELL_TOMO_MODE.

 

Shell: Sampling (x|y|z) value

Assign values to the x,y and z components of the $SHELL_TOMO_SUBSAMPLING array.

 

Shell: Compute (TomoVision|Lorensen)

Compute the polygon shell according to the select model.