5.1.11 Blob

The mathematical objects discussed so far are not well suited for modeling natural forms like a human hand for example. Although the digits are roughly speaking cylinder connecting the joints which are approximately spheres, the transition between the spheres and the cylinders should be smooth. This can be modeled by the blob object. The syntax of a blob object is:

BLOB:
  blob { [threshold FLOAT] BLOB_ITEM ... BLOB_ITEM 
    [BLOB_MODIFIERS] }

BLOB_ITEM:
  sphere { CENTER, RADIUS, [strength] STRENGTH 
    [COMPONENT_MODIFIERS] } |
  cylinder { BASE_CENTER, CAP_CENTER, RADIUS, 
    STRENGTH [COMPONENT_MODIFIERS] }

COMPONENT_MODIFIERS:
  [TEXTURE] & [PIGMENT] & [NORMAL] & [FINISH] & [TRANSFORMATION...]

BLOB_MODIFIERS:
  [hierarchy [BOOL]] & [sturm [BOOL]] & [OBJECT_MODIFIERS]

See also:

• [pov:6.5.1.1]Blob
• [pov:3.6.1]Blob Object
• Rune Johansen: runevision :: rune's blob tutorialrune|vision :: rune's blob tutorial
  blobs.asp.html
• Jeff Lee: Understanding Blobs in POV-Ray
  blobs.html

A point in space belongs to this object if the sum of its densities

$$\operatorname{density} = \operatorname{strength}*\left(1-\left(\frac{\operatorname{distance}}{\operatorname{radius}}\right)^2\right)^2$$

with respect to all the BLOB_ITEM's is at least the thresh hold THRESH_HOLD.

Figure: Blobs