Why is it that when I increase the radius and falloff of a spotlight at
a certain point well before 90 degrees the light appears the same;
version is 3.1g.watcom.win32.  It was my understanding that both radius
and falloff could range up to 90 degrees.


#version 3.1;

global_settings { assumed_gamma 2.2 }

camera {
  location <0, 1, -3>
  look_at  <0, 1, 0>
}

light_source {
  <-2, 1, 0>
  rgb 1
  spotlight
  point_at <-2, 1, 6>
  radius 60
  tightness 50
  falloff 65
}
light_source {
  <2, 1, 0>
  rgb 1
  spotlight
  point_at <2, 1, 6>
  radius 30
  tightness 50
  falloff 35
}

plane {
  z, 6
  hollow on
  pigment { rgb 1 }
}

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Attachments:
Download 'spot.jpg' (2 KB)

Preview of image 'spot.jpg'

I don't see the same thing. Perhaps if you rendered larger you would see a
difference.

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TonyB wrote:
> 
> I don't see the same thing. Perhaps if you rendered larger you would see a
> difference.

I bumped it up to:

light_source {
  <-2, 1, 0>
  rgb 1
  spotlight
  point_at <-2, 1, 6>
  radius 80
  tightness 50
  falloff 85
}
light_source {
  <2, 1, 0>
  rgb 1
  spotlight
  point_at <2, 1, 6>
  radius 20
  tightness 50
  falloff 25
}

A angle difference of 60 degrees!! I rendered it at 640x480 and the
spots on the wall look the same size to me.  What do you see??  I mean
you can simply sketch it out on graph paper and see that a line at 80-85
degrees should hit a lot farther out than a line 20-25 degrees.

As a matter of fact, if I'm not mistaken the radius of a spot at a
distance of 6 units and angle of 20 degrees should be 13.422... units in
radius.  A spot from an angle of 80 degrees at the same distance should
be 54.021... units in radius.

- Jerome

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Attachments:
Download 'spot2.jpg' (2 KB)

Preview of image 'spot2.jpg'

Could be the texture on the plane you're using to shine them on and only
getting a diffuse or specular appearance, not actual illumination.
I know the angle does change the size.  You might want to use 'tightness 0'
to use full broadness of them for this test too.

Bob

"Jerome Waters" <hjw### [at] mscsoftwarecom> wrote in message
news:38745493.F7260118@mscsoftware.com...
>
>
> TonyB wrote:
> >
> > I don't see the same thing. Perhaps if you rendered larger you would see
a
> > difference.
>
> I bumped it up to:
>
> light_source {
>   <-2, 1, 0>
>   rgb 1
>   spotlight
>   point_at <-2, 1, 6>
>   radius 80
>   tightness 50
>   falloff 85
> }
> light_source {
>   <2, 1, 0>
>   rgb 1
>   spotlight
>   point_at <2, 1, 6>
>   radius 20
>   tightness 50
>   falloff 25
> }
>
> A angle difference of 60 degrees!! I rendered it at 640x480 and the
> spots on the wall look the same size to me.  What do you see??  I mean
> you can simply sketch it out on graph paper and see that a line at 80-85
> degrees should hit a lot farther out than a line 20-25 degrees.
>
> As a matter of fact, if I'm not mistaken the radius of a spot at a
> distance of 6 units and angle of 20 degrees should be 13.422... units in
> radius.  A spot from an angle of 80 degrees at the same distance should
> be 54.021... units in radius.
>
> - Jerome


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Thanks Bob.

- Jerome

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