Related topics include:
For an overview and a list of lookup tables, see
Lookup Tables.
Each entry of a texture mapping table binds a set of
attributes to a referenced texture map resource.
The same texture map resource may be referenced by multiple
texture mapping table entries.
---------------------------------------------------------------------------------------------------------------------
Table Value Description Fallback PEX
Mask
---------------------------------------------------------------------------------------------------------------------
PEXLUTVTMIDs 5.2
number of resources (n) 0
unused
list of texture map resources
PEXLUTVTMRenderingControl 5.2
rendering control PEXTMRCPostLight
PEXLUTVTMParameterizationMethod 5.2
parameterization method PEXTMPMReflectionSphereVRC
PEXLUTVTMFPDataIndex(a) 5.2
floating-point data index 0
PEXLUTVTMReflectionMatrix(b) 5.2
reflection matrix Identity
reflection matrix hints Identity
PEXLUTVTMOrientationMatrix 5.2
orientation matrix Identity
orientation matrix hints Identity
PEXLUTVTMCompositionMethod 5.2
composition method PEXTMCMReplace
PEXLUTVTMChannelSelector(c) 5.2
channel selector PEXTMChannelRed
PEXLUTVTMEnvironmentColor(d) 5.2
environment color {PEXColorTypeRGB, (0.0, 0.0, 0.0)}
PEXLUTVTMBackgroundColor(e) 5.2
background color {PEXColorTypeRGB, (0.0, 0.0, 0.0)}
PEXLUTVTMSampleMethod 5.2
minification sample method PEXTMSMSingleBase
magnification sample method PEXTMSMSingleBase
PEXLUTVTMBoundaryConditions 5.2
t0 boundary condition PEXTMBCWrap
t1 boundary condition PEXTMBCWrap
t2 boundary condition PEXTMBCWrap
unused
PEXLUTVTMClampMethod(f) 5.2
boundary clamp method PEXTMBCMDiscontinue
PEXLUTVTMClampColor(g) 5.2
boundary clamp color {PEXColorTypeRGB, (0.0, 0.0, 0.0)}
PEXLUTVTMSamplingHints 5.2
depth sampling bias hint 0.0
t0 frequency hint 1.0
t1 frequency hint 1.0
t2 frequency hint 1.0
PEXLUTVTMAll5_2 (selects entire table entry) 5.2
---------------------------------------------------------------------------------------------------------------------
- (a)
- Value fp data index is ignored unless value parameterization method selects method FloatData.
- (b)
- Value reflection matrix is ignored unless value parameterization method selects method ReflectionSphereVRC or ReflectionSphereWC.
- (c)
- Value channel number is ignored unless value composition method selects method BlendEnvColor.
- (d)
- Value environment color is ignored unless value composition method selects method BlendEnvColor.
- (e)
- Value background color is ignored unless value composition method selects method DecalBackground.
- (f)
- Value clamping method is ignored unless value boundary conditions selects condition ClampExplicitMethod.
- (g)
- Value clamp color is ignored unless value boundary conditions selects condition ClampExplicitMethod and value clamping method selects method Color.
Related topics include:
The texture mapping table is accessed when rendering
surface primitives if the pipeline state's
interior style
is PEXInteriorStyleTexture and the
pipeline state's
active textures
field is non-empty.
If the pipeline state's
facet distinguish flag
is True, then the implementation accesses the texture
mapping table when rendering back-facing facets if the
pipeline state's
bf interior style
is
PEXInteriorStyleTexture and the pipeline state's
bf active textures
field is non-empty.
The active textures lists select entries of the texture
mapping table which each represent a texture map and an
associated set of attributes.
If the number of entries in the active textures list exceeds
the maximum number of texture maps which can be applied to a
single facet, then the implementation ignores the texture
maps beyond the first MaxTextureMaps indices.
Invoke request
PEXGetImpDepConstants
to inquire
MaxTextureMaps.
If the active textures list is empty, then the default
table values are used to apply the single default texture
map.
Not every texture map applies all of the texture mapping
table fields.
The descriptions of the values below indicate if, and how,
the values are applied to the texture map.
Texture mapping table value texture map ids
is used to reference the texture map resources which
define the texture map.
Texture map resources are discussed in
Texture Mapping.
The number of texture map resources needed to define a
single texture map is determined by the texture mapping
table's
parameterization method field.
All currently defined parameterization methods use a single
texture map resource to define a texture map.
If the texture map ids
fallback (an empty list) is
used, then the implementation uses the default texture map;
a black and white checkerboard of 8x8 squares.
The checkerboard is defined by a 2D array of 16x16 texels,
with each square defined by 2x2 texels.
The square at t0=t1=0.0 is white.
- rendering control:
- The texture mapping table's rendering control value
controls where in the rendering pipeline the texture map is
applied.
The currently defined values, shown below, interact heavily
with the composition method,
surface interpolation method
and
texture mapping sample frequency.
This controls whether the texture colors change the effect
of lighting on a surface primitive, or if the lighting is
performed on the textured surface.
When a texture is applied post-light, it can reduce or
obliterate any specular highlight; but if texture is applied
pre-light, then the specular highlight is retained.
- PEXTMRenderingControlPreLight -
- applies the texture map to the primitive before the
reflectance calculations.
- PEXTMRenderingControlPostLight -
- applies the texture map to the primitive after the
reflectance calculations.
See Composition Controls.
Related topics include:
The parameterization attributes control how the texture map
coordinates are derived.
There are texture map coordinates associated with each point
on the surface for which a texture map value is sampled.
They are used to select the point within the texture map
which is sampled.
There is one texture map coordinate for each dimension of
the texture map.
For example, three texture map coordinates, represented as
(t0, t1, t2), are used to sample a 3D
texture map.
The texture coordinates are normalized, that is, they range
from 0.0 to 1.0 across the texture map.
- parameterization method:
- The parameterization method field of the
texture mapping table
defines how texture map coordinates
are derived:
whether explicitly defined by the primitive's data,
calculated through a projection mapping, or determined
through some other means.
PEXlib defines the following parameterization
methods:
- PEXTMParamReflectionSphereVRC and
PEXTMParamReflectionSphereWC
- are projection mapping parameterization methods which
project a reflection vector (the 3D source texture map
coordinates) onto a sphere (the projection object) to
determine the 3D texture map coordinates
(t0, t1, t2=0.0).
The spheres have fixed orientations. The position of the
reflection vectors relative to these orientations may be
modified through the multiplication of the reflection
vectors by the reflection matrix from the
texture mapping lookup table.
The reflection vectors are always multiplied by the
reflection matrix before the reflection is performed.
For best results, the reflection transformation should
utilize only rotations.
The reflection matrix hints provide an opportunity
for optimizing this transformation.
See PEXOCCSetGlobalTransform
for an explanation of matrix hints.
- PEXTMParamVertexMCCoord
(3) -
- Sets the texture map coordinate values equal to the MC
space values of the vertex coordinates:
t0 = x; t1 = y; t2 =
z.
- PEXTMParamVertexWCCoord(3)-
- Sets the texture map coordinate values equal to the WC
space values of the vertex coordinates: t0 =
x'; t1 = y'; t2 = z'.
- PEXTMParamVertexMCNormal(3) -
- Sets the texture map coordinates equal to the MC space
value of the vertex normal.
If a normal is not explicitly supplied with the vertex, then
the calculated geometric normal is used instead.
t0 = nx; t1 = ny;
t2 = nz.
- PEXTMParamVertexWCNormal(3) -
- Sets the texture map coordinates equal to the WC space
value of the vertex normal.
If a normal is not explicitly supplied with the vertex, then
the calculated geometric normal is used instead.
t0 = nx'; t1 = ny';
t2 = nz'.
- PEXTMParamNURBUV -
- Sets the texture map coordinates equal to the u and
v parameters of the non-uniform b-spline surface:
t0 = u; t1 = v; t2 = 0.0.
If the primitive is not a non-uniform b-spline surface,
then the texture map coordinates are set to:
t0 = t1 = t2 = 0.0.
- PEXTMParamFloatData -
- The texture map coordinates are members of the vertex's
floating-point data list.
The fp data index value of the texture mapping table
is the index into the floating-point data list of the value
which is assigned to t0.
The subsequent values in the floating-point data list are
assigned to t1 and t2:
t0 = vertex_fp_data[fp data index]
t1 = vertex_fp_data[fp data index + 1] (if 2D map)
t2 = vertex_fp_data[fp data index + 2] (if 3D map)
If the primitive is a non-uniform b-spline surface, then
the values are obtained from the spline's data splines:
t0 = first value of the data spline selected by the
fp data index
t1 = first value of the data spline selected by
fp data index + 1
t2 = first value of the data spline selected by
fp data index + 2
If the number of floating-point data values is insufficient
for the dimension of the texture map, then the texture
coordinate values used are implementation-dependent.
- PEXTMParamReflectionSphereVRC -
- The infinite sphere has (0,0,0) as its origin and the
+y axis as its axis of revolution.
The texture seams lie on the positive and negative x
axes.
The source texture map coordinates are a reflection vector
(s0, s1, s2), computed to determine a
point on the interior of the sphere.
The reflection vector is calculated as follows:
where s is the reflection vector,
n is the vertex normal (explicit or calculated),
and i is the unit vector from the eyepoint
(computed as described in
View Table)
to the vertex.
This calculation is performed in VRC space, after the vertex
and its normal have been transformed to VRC space.
After this, the texture coordinates are derived as follows:
where:
- PEXTMParamReflectionSphereWC -
- The source texture map coordinates, a reflection vector
(s0,s1,s2), are normalized and
conceptually projected onto the infinite sphere (with
(0,0,0) as its origin) projection object.
The axis of revolution of the sphere is the +y axis
(in WC space).
The texture seam sweeps from the +x axis (in WC
space) in a counterclockwise direction:
[0..2PI].
The reflection vector is calculated as follows:
where s is the reflection vector,
n is the vertex normal (explicit or calculated),
and i is the unit vector from the eyepoint
(computed as described in
View Table
to the vertex.
This calculation is performed in WC space, after the vertex
and its normal have been transformed to WC space.
This parameterization method is primarily intended for use
with a perspective, as opposed to orthogonal, view
projection.
After the reflection vector is calculated, the texture
coordinates are derived as follows.
Related topics include:
Once the texture map coordinates are determined,
independent of which parameterization method was used, they
are transformed by the orientation matrix field of
the texture mapping table.
The orientation matrix hints provide an opportunity to
optimize the transformation.
See PEXOCCSetGlobalTransform
for an explanation of matrix hints.
The orientation transformation occurs before any
interpolation of the texture map coordinates across the
facet that may be required before the coordinates are used
to sample the texture map.
If the projection is perspective, then the interpolated
texture map coordinates are also adjusted according to the
pipeline state's
tm perspective correction
before the
sampling is done.
The following
provides a graphical
description of parameterization.
Texture Parameterization
Related topics include:
The currently defined composition attributes control how
the texture map color interacts with the primitive's color
to determine the primitive's color after the texture map is
applied.
The texture mapping table composition
method value specifies how the texture map is blended
with the primitive's existing data.
The currently defined composition methods assume:
- The texture is a color domain texture, i.e. it modifies
intrinsic color (including alpha) of rendered
primitives.
- The rendering color model is RGB.
The current methods have undefined behavior for rendering
color models other than RGB.
For each composition method, equations are given.
The equations given are for the input into each texture map
i and show the Cout and Aout for each
texture map i.
The output of each texture map i becomes the input of
the next texture map i+1.
The final output of the texture mapping stage is the output
of texture map n, where there are n texture
maps active for the stage.
In some PreLight rendering control cases there are
additional values used as input into each texture map i
(e.g., CW) and used as output
from the texture mapping stage (e.g., CS).
The following table defines the symbols used to define the
composition methods.
Symbols Used in Defining the Composition Methods
--------------------------------------------------------------------------------------------------------------
Symbol Description
--------------------------------------------------------------------------------------------------------------
in Primitive color components input into texture i of a texture mapping stage.
out Primitive color components output from texture i of a texture mapping stage.
R The red component.
B The blue component.
G The green component.
C R, G, and B considered together.
A The alpha component.
L The luminance component.
CW A portion of primitive color input into the PreLight texture mapping stage. CW is derived in the pre
ceding lighting stage by applying ambient and diffuse terms of the reflectance equation assuming
the primitive's color is white.
The same value of CW is input into each texture i of the texture mapping stage; it is not modified by
texture mapping.
CD Another portion of primitive color input into the PreLight texture mapping stage. CD is the ambient
and diffuse components of color derived in the preceding lighting stage by applying the reflectance
equation using the primitive's color (as opposed to assuming the primitive is white).
CS A third portion of primitive color input into the PreLight texture mapping stage. CS is the specular
component of color derived in the preceding lighting stage by applying the ambient and diffuse terms
of the reflectance equation using the primitive's color (as opposed to assuming the primitive is
white).
CS is not affected by the texture mapping stage. It is combined with the CD output from the texture
mapping stage to form the RGB components of the primitive color output from the texture mapping
stage.
CT R, G, and B of the texture map color considered together. If the texels have a luminance component
instead of RGB components, (fig)l
AT The alpha component of the texture map color.
CE When the composition method is BlendEnvColor, CE is taken from the environment color field of the
texture mapping lookup table.
CB When the composition method is DecalBackground, CB is taken from the background color field of
the texture mapping lookup table.
Γ When the composition method is Decal, Γ is taken from the texture map color. For texels defined
with RGB or RGBA components:
if the texture mapping lookup table's channel number is TMChannelRed, (fig);
if channel number is TMChannelGreen, (fig);
if channel number is TMChannelBlue, (fig), and
if there is an alpha component and channel number is TMChannelAlpha, (fig).
For texels defined with a luminance component: (fig)
The channel number constants are defined in Channel Selection Constant Values
--------------------------------------------------------------------------------------------------------------
PEXlib defines the following composition methods:
- PEXTMCompReplace -
- The texture map replaces the primitive's existing data.
The texture map data unconditionally replaces the
primitive's color.
See Composition Method
BlendEnvColor.
for more details.
Composition Method Replace
-----------------------------------------------------------------------------
Texel Rendering Control Interpolation Sample Cout Aout
Components Method Frequency
-----------------------------------------------------------------------------
RGB, L PreLight None, Color pixel (fig) and Cs (fig)
None, Color InterpDep (fig) (fig)
DotProduct, (any)
Normal
PostLight (any) (any)
RGBA, LA PreLight None, Color pixel (fig) and Cs (fig)
None, Color InterpDep (fig) (fig)
DotProduct, (any)
Normal
PostLight (any) (any)
-----------------------------------------------------------------------------
- PEXTMCompModulate -
- The texture map color and primitive color are blended.
See Composition Method
BlendEnvColor.
for more details.
Composition Method Modulate
-----------------------------------------------------------------------------
Texel Rendering Control Interpolation Sample Cout Aout
Components Method Frequency
-----------------------------------------------------------------------------
RGB, L PreLight None, Color pixel (fig) and Cs (fig)
None, Color InterpDep (fig) (fig)
DotProduct, (any)
Normal
PostLight (any) (any)
RGBA, LA PreLight None, Color pixel (fig) and Cs (fig)
None, Color InterpDep (fig) (fig)
DotProduct, (any)
Normal
PostLight (any) (any)
-----------------------------------------------------------------------------
- PEXTMCompBlendEnvColor -
- The texture map blends with the primitive's existing
environment color.
The primitive color and a constant environment color are
blended by the texture map color.
The primitive alpha is blended with the texture map alpha,
if the texture map has alpha.
See Composition Method
BlendEnvColor.
for more details.
Composition Method BlendEnvColor
---------------------------------------------------------------------------
Texel Rendering Control Interpolation Sample Cout Aout
Components Method Frequency
---------------------------------------------------------------------------
RGB, L PreLight None, Color pixel (fig) and (fig)
Cs
None, Color InterpDep (fig) (fig)
DotProduct, (any)
Normal
PostLight (any) (any)
RGBA, LA PreLight None, Color pixel (fig) and (fig)
Cs
None, Color InterpDep (fig) (fig)
DotProduct, (any)
Normal
PostLight (any) (any)
---------------------------------------------------------------------------
- PEXTMCompDecal -
- The texture map color and primitive color are blended by
the texture map alpha.
If the texture map doesn't contain alpha, then the texture
map color replaces the primitive color.
In either case, the primitive's alpha is unchanged.
See Composition Method
BlendEnvColor.
for more details.
Composition Method Decal
-----------------------------------------------------------------------------
Texel Rendering Control Interpolation Sample Cout Aout
Components Method Frequency
-----------------------------------------------------------------------------
RGB, L PreLight None, Color pixel (fig) and Cs (fig)
None, Color InterpDep (fig) (fig)
DotProduct, (any)
Normal
PostLight (any) (any)
RGBA, LA PreLight None, Color pixel (fig) (fig)
and Cs
None, Color InterpDep (fig) (fig)
DotProduct, (any)
Normal
PostLight (any) (any)
-----------------------------------------------------------------------------
- PEXTMCompDecalBackground -
- The texture map color and background color are blended
according to the texture map alpha, and this blend replaces
the primitive color.
If the texture map doesn't contain alpha,
then the texture map color replaces the primitive color.
In either case, the primitive's alpha is unchanged.
See Composition Method BlendEnvColor
for more details.
Composition Method DecalBackground
-----------------------------------------------------------------------------
Texel Rendering Control Interpolation Sample Cout Aout
Components Method Frequency
-----------------------------------------------------------------------------
RGB, L PreLight None, Color pixel (fig) and Cs (fig)
None, Color InterpDep (fig) (fig)
DotProduct, (any)
Normal
PostLight (any) (any)
RGBA, LA PreLight None, Color pixel (fig) (fig)
and Cs
None, Color InterpDep (fig) (fig)
DotProduct, (any)
Normal
PostLight (any) (any)
-----------------------------------------------------------------------------
Related topics include:
PEXlib defines the following channel selectors:
- PEXTMChannelRed -
- selects the red channel, channel 0.
- PEXTMChannelGreen -
- selects the green channel, channel 1.
- PEXTMChannelBlue -
- selects the blue channel, channel 2.
- PEXTMChannelAlpha -
- selects the alpha channel, channel 3.
Related topics include:
The sampling attributes are used to determine how a texture
map color is derived when the texture map is
sampled.
Related topics include:
The sample min and mag field of the
texture mapping table
defines the minification and magnification sample
methods.
These methods specify how texels are sampled from the
texture map and mapped to primitive pixels when the area
covered by a texel and pixel differ.
In the case of a pixel overlapping more than one texture
map texel, the texture minification method indicates how the
sample value is derived for that pixel.
In the case of a
pixel overlapping less than one texture map texel, the
texture magnification method indicates how the sample value
is derived for that pixel.
PEXlib defines the following sample methods:
- PEXTMSampleSingleBase -
- The closest single texel selected by the texture
coordinate(s) is sampled from the base texture map level.
- PEXTMSampleWeightedBase -
- The 2n (where n is the dimension
of the texture map) closest texels selected by the texture
coordinate(s) are sampled from the base texture map level.
Their weighted average is used.
- PEXTMSampleSingleInMipmap -
- The closest single texel selected by the texture
coordinate(s) is sampled from the closest texture map level
to the sample depth.
- PEXTMSampleWeightedInMipmap -
- The 2n (where n is the dimension
of the texture map) closest texels selected by the texture
coordinate(s) are sampled from the closest texture map level
to the sample depth.
Their weighted average is used.
- PEXTMSampleSingleBetweenMipmaps -
- The closest texel selected by the texture coordinate(s) is
sampled from the two closest texture map levels to the
sample depth.
The texel found at the exact sample depth by interpolation
between these two sampled texels is used.
If the sample depth is beyond the base or pinnacle texture
map levels, that level is used and this method behaves the
same as PEXTMSampleSingleInMipmap.
- PEXTMSampleWeightedBetweenMipmaps -
- The 2n (where n is the
dimension of the texture map) closest texels selected by the
texture coordinate(s) are sampled from the two closest
texture map levels to the sample depth.
A weighted average is taken of these 2n
texels on each of the texture map levels.
The texel found at the exact sample depth by interpolation
between these two calculated texels is used.
If the sample depth is beyond the base or pinnacle texture
map levels, that level is used and this method behaves the
same as PEXTMSampleWeightedInMipmap.
Related topics include:
The boundary conditions field of the
texture mapping table
specifies the texturing to be applied to the
primitive when the texture coordinates (t0,
t1, t2) select a point beyond a boundary of
the texture map.
That is, the calculated texture coordinates are outside the
range [0.0,1.0].
The boundary condition in each direction is independently
controlled.
PEXlib defines the following boundary conditions:
- PEXTMBoundaryClampExplicit -
- applies the method specified by the clamping method
field of the texture mapping table.
- PEXTMBoundaryClampBorder -
- applies the closest boundary texel.
- PEXTMBoundaryWrap -
- texel sampling wraps back to the opposite texture map
border, creating a "tiling" or
"repeating" effect of the texture map across the
primitive.
- PEXTMBoundaryMirror -
- texel sampling is reversed across the texture map, creating
a "mirrored alternating" pattern of the texture
map across the primitive.
Related topics include:
The clamping method field of the
texture mapping table
specifies whether to discontinue texturing or to use
an explicit color when boundary condition
ClampExplicitMethod is selected.
Although these are seemingly really additional boundary
conditions, they are controlled through a separate field of
the texture mapping table by design.
With this level of direction, it is always clear what the
behavior should be when a location is beyond the texture map
in more than one direction, even if the boundary conditions
for those directions differ.
PEXlib defines the following boundary clamp methods:
- PEXTMBoundaryClampExplicitDiscontinue -
- discontinues texturing.
That is, it maintains the primitive's appearance before
applying the current texture map.
- PEXTMBoundaryClampExplicitColor -
- applies the color specified by the clamp color field
of the texture mapping table.
Related topics include:
Use the
texture mapping table
sampling hints value
to adjust the selected sampling location.
The depth bias hint is used to adjust
the sampling depth.
A bias of -1.0 moves the sampling depth one level toward the
texture map's base level, effectively making the texturing
more detailed, or jaggy, than it would otherwise have been.
A bias of 2.0, for example, moves the sampling depth away
from the texture map's base level by two levels, effectively
blurring the texturing.
The following are the suggested formulae for
implementations;
PEX implementations may use other formulae
which produce a similar effect.
The extension of the suggested formulae to three-dimensional
texture maps is left unspecified.
The suggested depth bias formulae utilize the
frequency hints.
There is a frequency hint corresponding to each direction of
the texture map.
A frequency hint is set to something less than 1.0, but
greater than 0.0, if blurring in that direction would be
unacceptably high due to low spatial frequency.
A value of 1.0 for the corresponding texture map
coordinate's frequency hint indicates the spatial frequency
isn't high.
If the spatial frequency of the texture map data is unknown,
then it is best to set the values to 1.0.
Inquire TMSamplingHintsUsed with request
PEXGetImpDepConstants
to determine if the sampling hints are used.
For general information about texture mapping lookup
tables, see Texture Mapping Table.
The superseded requests
PEXSetTableEntries,
PEXGetTableEntries,
PEXGetTableEntry, and
PEXGetPredefinedEntries
do not operate on
texture mapping tables.
Valid texture mapping table indices are
in the range [1, 65535].
The fallback entry is entry 1.