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I'm trying to use a spotlight, and getting some results that aren't what
I expected. Please forgive me for dropping a code fragment in here...
light_source {
<0, -3.4515, -1.701>
color White
spotlight
radius 40
falloff 60
tightness 0
point_at <0, -3.1989, -60>
}
I expected to see a cone of illumination along the surface of my
model... and I did, sort of... but the intensity of the light was much
lower than I expected, and instead of reaching all the way to the
point_at location, it faded within ten units of the source.
Can someone suggest how to turn up the intensity?
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In article <3D5### [at] mac com>, Dawn McKnight <blu### [at] mac com>
wrote:
> I expected to see a cone of illumination along the surface of my
> model... and I did, sort of... but the intensity of the light was much
> lower than I expected, and instead of reaching all the way to the
> point_at location, it faded within ten units of the source.
Probably due to the angle of the surface to the light direction. You
could lower the brilliance value of the surface finish, but that will
affect all shading of that surface.
> Can someone suggest how to turn up the intensity?
Specify a brighter color for the light source. Values > 1 are perfectly
acceptable, they will just wash things out in some cases. You can even
specify negative values, though that isn't realistic.
--
Christopher James Huff <cja### [at] earthlink net>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tag povray org
http://tag.povray.org/
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> Probably due to the angle of the surface to the light direction. You
> could lower the brilliance value of the surface finish, but that will
> affect all shading of that surface.
You're saying that the angle is too acute? At what zenith range do
spotlights work best?
Thanks for the information about values greater than one... I'll try it.
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In article <3D5### [at] mac com>,
Dawn McKnight <blu### [at] mac com> wrote:
> > Probably due to the angle of the surface to the light direction. You
> > could lower the brilliance value of the surface finish, but that will
> > affect all shading of that surface.
>
> You're saying that the angle is too acute? At what zenith range do
> spotlights work best?
Wrong question. Any light will light a surface most brightly when its
direction is perpendicular to the surface, parallel to the surface
normal. Your description makes it sound like the light is very nearly
parallel to the surface, so shading will make it dimmer. It isn't that
the spotlight isn't working right, it is doing exactly what it should.
Another possibility is that the point_at location is inside the shape,
or otherwise positioned to make the light get blocked by the shape. You
only gave an example of the spotlight, so I can't really say. Try a
point light and see how the surface gets illuminated. If that fixes the
problem, there is something wrong with the point_at, radius, or falloff.
--
Christopher James Huff <cja### [at] earthlink net>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tag povray org
http://tag.povray.org/
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Christopher James Huff <chr### [at] mac com> wrote:
> Any light will light a surface most brightly when its
> direction is perpendicular to the surface, parallel to the surface
> normal.
Only with diffuse lighting. Specular lighting (controlled with the
phong or specular keywords in finish) is another story. :)
--
#macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb M()}}
N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}// - Warp -
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> Any light will light a surface most brightly when its
> direction is perpendicular to the surface, parallel to the surface
> normal. Your description makes it sound like the light is very nearly
> parallel to the surface, so shading will make it dimmer.
Okay; thanks. I played around with it, and found a way to get the
effect I wanted, by faking it... putting an aparent light source (a
sphere with a high ambient, low diffuse finish), and then putting the
actual spotlight further out from wht I'm trying to illuminate.
It looks about right, and I feel less 'wrong' about doing it that way,
because I know that all of the spotlights on the Movie Enterprises were
faked with off-model pin sources.
So, yeah... thanks again, Christopher.
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