| 68 |
|
Note that this is strictly for ease of identification, and has no |
| 69 |
|
real meaning as far as the geometric description goes. In contrast, |
| 70 |
|
the transform entity is very significant as it determines how enclosing |
| 71 |
< |
objects are to be scaled and placed in the final description. |
| 71 |
> |
objects are to be scaled and placed in the final description. Hierarchical |
| 72 |
> |
contexts may be nested in any way, but should not overlap. |
| 73 |
|
|
| 74 |
|
Without further ado, here are the proposed entities and their interpretations: |
| 75 |
|
|
| 97 |
|
sph vc radius sphere |
| 98 |
|
cyl v1 radius v2 truncated right cylinder (open-ended) |
| 99 |
|
cone v1 rad1 v2 rad2 truncated right cone (open-ended) |
| 100 |
< |
prism v1 v2 v3 .. length right prism (closed solid) |
| 100 |
> |
prism v1 v2 v3 .. length truncated right prism (closed solid) |
| 101 |
|
ring vc rmin rmax circular ring with inner and outer radii |
| 102 |
|
torus vc rmin rmax circular torus with inner and outer radii |
| 103 |
|
xf [xform] begin/end transformation context |
| 210 |
|
included in the other material parameters. All colors are absolute, |
| 211 |
|
e.g. spectral reflectance or transmittance under uniform white light. |
| 212 |
|
|
| 213 |
< |
A CIE xy chromaticity pair is the most basic color specification. |
| 214 |
< |
A full spectrum is the most general specification, and the starting |
| 215 |
< |
(i.e. minimum) and ending (i.e. maximum) wavelengths are given along |
| 216 |
< |
with a set of evenly spaced values. Wavelengths are given in nanometers, |
| 217 |
< |
and must be within the range of 380-780. The spectral values themselves |
| 218 |
< |
are located starting at the first wavelength and proceeding at even |
| 219 |
< |
increments to the ending wavelength. The values in between will be |
| 220 |
< |
interpolated as necessary, so there must be at least two specified points. |
| 221 |
< |
The color mixing entity is intended not only for the mixing of named |
| 222 |
< |
colors, but also for color specifications using an arbitrary set |
| 223 |
< |
of basis functions. The actual totals for spectral and mixing |
| 224 |
< |
coefficients is irrelevant, since the results will be normalized. |
| 213 |
> |
A CIE xy chromaticity pair is the most basic color specification. A |
| 214 |
> |
full spectrum is the most general specification, and the starting (i.e. |
| 215 |
> |
minimum) and ending (i.e. maximum) wavelengths are given along with a |
| 216 |
> |
set of evenly spaced values. Wavelengths are given in nanometers, and |
| 217 |
> |
must be within the range of 380-780. The spectral values themselves, |
| 218 |
> |
which can be thought of as relative power density per nanometer, start |
| 219 |
> |
at the first wavelength and proceed at even increments to the last |
| 220 |
> |
wavelength. The values in between will be interpolated as necessary, |
| 221 |
> |
so there must be at least two specified points. The color mixing |
| 222 |
> |
entity is intended not only for the mixing of named colors, but also |
| 223 |
> |
for color specifications using an arbitrary set of basis functions. |
| 224 |
> |
The mixing coefficients are in effect relative luminances for each |
| 225 |
> |
color "primary." The actual total of the mixing coefficients or |
| 226 |
> |
spectral values is irrelevant, since the results will always be |
| 227 |
> |
normalized. |
| 228 |
|
|
| 229 |
|
Diffuse emittance is always given in SI units of lumens/meter^2. Note that |
| 230 |
|
this is emittance, not exitance, and does not include light reflected or |
| 266 |
|
and a length value. The prism will be extruded so that the end-face |
| 267 |
|
points outward, unless the length value is negative, in which case the |
| 268 |
|
object is extruded in the opposite direction, resulting in inward- |
| 269 |
< |
directed surface normals. |
| 269 |
> |
directed surface normals. If surface normals are specified for the |
| 270 |
> |
vertices, they will be applied to the side faces but not the end |
| 271 |
> |
faces, and they must generally point in the appropriate direction |
| 272 |
> |
(i.e. in or out depending on whether extrusion is negative or positive). |
| 273 |
|
|
| 274 |
|
A sphere, cylinder or cone with negative radii is interpreted as having |
| 275 |
|
an inward facing surface normal. Otherwise, the normal is assumed |
