68 |
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Note that this is strictly for ease of identification, and has no |
69 |
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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 |
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|
74 |
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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 |