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Use of Subcolour for Layered Textures

IP.com Disclosure Number: IPCOM000100774D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 4 page(s) / 152K

Publishing Venue

IBM

Related People

Todd, SJ: AUTHOR

Abstract

A method is disclosed that uses subcolour for layered textures in graphic products. Three dimensional textured surfaces are simulated such as upper layer of cloud cover with lower layers of land and sea texture. Attributes from multiple surface layers are combined into a single set of attributes. Coded examples are from the IBM UK Winchester Solid Modeller system but are applicable in principle to other systems.

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Use of Subcolour for Layered Textures

       A method is disclosed that uses subcolour for layered
textures in graphic products.  Three dimensional textured surfaces
are simulated such as upper layer of cloud cover with lower layers of
land and sea texture.  Attributes from multiple surface layers are
combined into a single set of attributes.  Coded examples are from
the IBM UK Winchester Solid Modeller system but are applicable in
principle to other systems.

      Texturing is a process which associates with each position in
space a set of surface attributes.  These attributes include basic
colour, gloss, colour of hilight, and the amount and colour of light
transmitted through the surface.  Where transmission through a
surface occurs, objects behind the surface can be seen. It is often
convenient to consider a single object with multiple surface layers.
If the upper layer permits transmission, the lower layer is seen.

      The article comprises two parts:
1.   A multilayer surface described by including a sublayer
identifier as one of the surface attributes.  The outermost surface
layer is associated with the object.  The next layer is associated as
the sublayer of this outer layer, and so on to any required number of
layers.
2.   The effect of a multilayer surface is closely approximated by an
appropriate combination of the surface attributes for each layer into
a single set of surface attributes.   This permits multilayer
surfaces to be handled within the surface attribute code without
impact on higher level code that performs operations such as
lightning and ray-tracing.

      Multilayer Texture Definition
The figure on the next page shows an example of a multilayer texture
in which the two important texture definition lines are:
      band(1)   colour(white ref_prop 1) subcolour(2)
      band(1)   colour(white ref_prop 0.7) subcolour(2)

      The first of these bands has an upper surface layer that is
completely see-through (ref_prop 1).  Thus we can see the fractal
subsurface (subcolour 2) clearly through the upper surface.

      The upper layer for the second band only transmits 70 percent
of light (ref_prop 1).  Thus we can see the fractal subsurface
(subcolour 2) clearly through the upper surface.

      The upper layer for the second band only transmits 70 percent
of light (ref_prop 0.7), and the other 30 percent is diffusely
radiated.  This band uses the same fractal subsurface, but it is only
seen somewhat clouded; notice the impurity of the black bands.

      Rules for Combining Surface Layers
 The rules permit the attributes for multilayer surfaces to be
combined into a single set of attributes that gives almost the same
effect.  A surface is described at the lowest level by the following
attributes:
dif_rgb   the proportion of incoming light dispersed by diffuse
radiation.
spe_rgb   the proportion of incoming light dispersed by specular
reflection.
re...