POV-Ray : Newsgroups : povray.documentation.inbuilt : Some mistake in reference 3.4.4.1.2 spotlight section Server Time: 20 Jun 2019 06:58:58 GMT
  Some mistake in reference 3.4.4.1.2 spotlight section (Message 1 to 7 of 7)  
From: And
Subject: Some mistake in reference 3.4.4.1.2 spotlight section
Date: 19 Nov 2013 09:55:00
Message: <web.528b347ce5b41d77f9d479350@news.povray.org>
I found some probable mistake in POV-Ray reference document at spotlight
section:

1. The sentence which is just two column before the light intensity multiplier
diagram states that
"The values for the radius, and tightness parameters are half the opening angles
                                ^^^^^^^^^
 of the corresponding cones, both angles have to be smaller than 90 degrees."
which tightness should be replaced by falloff. Another flaw is that it say both
angles have to be smaller than 90 degrees but I saw POV-Ray 3.7 can give an
angle more than 90 degrees in that term.

2. The description for the forth diagram in this section "To give the tightness
value full control over the spotlight's appearance use radius 0 falloff 90. As
you can see from the figure below." should be correct. ^^^^^^^^^^^^^^^^^^^
I think that is radius 90 falloff 90 for the diagram.


Post a reply to this message

From: James Holsenback
Subject: Re: Some mistake in reference 3.4.4.1.2 spotlight section
Date: 19 Nov 2013 12:52:50
Message: <528b5f22@news.povray.org>
On 11/19/2013 04:50 AM, And wrote:
> I found some probable mistake in POV-Ray reference document at spotlight
> section:
>
> 1. The sentence which is just two column before the light intensity multiplier
> diagram states that
> "The values for the radius, and tightness parameters are half the opening angles
>                                  ^^^^^^^^^
>   of the corresponding cones, both angles have to be smaller than 90 degrees."
> which tightness should be replaced by falloff.

yes I think this is just a typo ... i'll change it

> Another flaw is that it say both
> angles have to be smaller than 90 degrees but I saw POV-Ray 3.7 can give an
> angle more than 90 degrees in that term.

true enough angles greater than 90 degrees /are/ excepted ... i'm 
wondering if /have/ in the above sentence ought to be /should/

>
> 2. The description for the forth diagram in this section "To give the tightness
> value full control over the spotlight's appearance use radius 0 falloff 90. As
> you can see from the figure below." should be correct. ^^^^^^^^^^^^^^^^^^^
> I think that is radius 90 falloff 90 for the diagram.

i played around with this (quickly) and it doesn't seem to make a 
difference if it's 0 or 90

anyone else have a moment to add a bit of clarity before i decide whats 
needs to be changed?


Post a reply to this message

From: James Holsenback
Subject: Re: Some mistake in reference 3.4.4.1.2 spotlight section
Date: 19 Nov 2013 12:58:42
Message: <528b6082$1@news.povray.org>
On 11/19/2013 07:52 AM, James Holsenback wrote:
> i played around with this (quickly) and it doesn't seem to make a
> difference if it's 0 or 90

see p.b.images


Post a reply to this message

From: clipka
Subject: Re: Some mistake in reference 3.4.4.1.2 spotlight section
Date: 19 Nov 2013 14:02:22
Message: <528b6f6e@news.povray.org>
Am 19.11.2013 13:52, schrieb James Holsenback:

>> 2. The description for the forth diagram in this section "To give the
>> tightness
>> value full control over the spotlight's appearance use radius 0
>> falloff 90. As
>> you can see from the figure below." should be correct.
>> ^^^^^^^^^^^^^^^^^^^
>> I think that is radius 90 falloff 90 for the diagram.
>
> i played around with this (quickly) and it doesn't seem to make a
> difference if it's 0 or 90

It does as soon as tightness comes into play.


There /is/ something fishy about that diagram and the paragraph before 
it. The diagram says something about "negative radius", and indeed 
doesn't match a radius of 0.

I think in the long run the section should be overhauled, and give 
sample renders instead of (or at least in addition to) diagrams.


Post a reply to this message

From: James Holsenback
Subject: Re: Some mistake in reference 3.4.4.1.2 spotlight section
Date: 19 Nov 2013 14:18:47
Message: <528b7347$1@news.povray.org>
On 11/19/2013 09:02 AM, clipka wrote:
> Am 19.11.2013 13:52, schrieb James Holsenback:
>
>>> 2. The description for the forth diagram in this section "To give the
>>> tightness
>>> value full control over the spotlight's appearance use radius 0
>>> falloff 90. As
>>> you can see from the figure below." should be correct.
>>> ^^^^^^^^^^^^^^^^^^^
>>> I think that is radius 90 falloff 90 for the diagram.
>>
>> i played around with this (quickly) and it doesn't seem to make a
>> difference if it's 0 or 90
>
> It does as soon as tightness comes into play.

ah ... yes i know. i guess i should have said for a given tightness both 
radius values look practically the same

> There /is/ something fishy about that diagram and the paragraph before
> it. The diagram says something about "negative radius", and indeed
> doesn't match a radius of 0.
>
> I think in the long run the section should be overhauled, and give
> sample renders instead of (or at least in addition to) diagrams.

yeah ... there /does/ appear to be more than one rough spot, so yeah i 
agree. on my todo list (sigh)


Post a reply to this message

From: clipka
Subject: Re: Some mistake in reference 3.4.4.1.2 spotlight section
Date: 19 Nov 2013 14:45:33
Message: <528b798d@news.povray.org>
Am 19.11.2013 15:18, schrieb James Holsenback:
> On 11/19/2013 09:02 AM, clipka wrote:
>> Am 19.11.2013 13:52, schrieb James Holsenback:
>>
>>>> 2. The description for the forth diagram in this section "To give the
>>>> tightness
>>>> value full control over the spotlight's appearance use radius 0
>>>> falloff 90. As
>>>> you can see from the figure below." should be correct.
>>>> ^^^^^^^^^^^^^^^^^^^
>>>> I think that is radius 90 falloff 90 for the diagram.
>>>
>>> i played around with this (quickly) and it doesn't seem to make a
>>> difference if it's 0 or 90
>>
>> It does as soon as tightness comes into play.
>
> ah ... yes i know. i guess i should have said for a given tightness both
> radius values look practically the same

For a tightness of 0 it makes quite the difference, so there's reason to 
believe that the same goes for other small values.


Post a reply to this message

From: And
Subject: Re: Some mistake in reference 3.4.4.1.2 spotlight section
Date: 20 Nov 2013 12:10:01
Message: <web.528ca572d765f2a0f9d479350@news.povray.org>
James Holsenback <nom### [at] nonecom> wrote:
> yes I think this is just a typo ... i'll change it
Ha.

> true enough angles greater than 90 degrees /are/ excepted ... i'm
> wondering if /have/ in the above sentence ought to be /should/
Really? If this is the case, "should" is better than "have" in my opinion.


> i played around with this (quickly) and it doesn't seem to make a
> difference if it's 0 or 90
>
> anyone else have a moment to add a bit of clarity before i decide whats
> needs to be changed?
clipka <ano### [at] anonymousorg> wrote:
> For a tightness of 0 it makes quite the difference, so there's reason to
> believe that the same goes for other small values.
yes, the situation for a tightness of 0 it is not fit, so I raise this question.


Post a reply to this message

Copyright 2003-2008 Persistence of Vision Raytracer Pty. Ltd.