On 07.02.2015 20:49, IronLogic wrote:

> I expect this question has been asked before, but i'm wondering whether there is
> a specific reason why POV-Ray only supports soft shadows on Area lights,
> considering its age and all the other features it has (e.g. radiosity,
> volumetrics, photon mapping etc.).

 From the documentation:

   "Any type of light source may be an area light."

In essence, the "area_light" keyword in POV-Ray should probably be
regarded as the name of the option that enables "soft shadows" for any
given light source (although it can do more with "area_illumination").

Also, since you mention radiosity, that will also give you soft
shadows appropriate for the geometry of the objects that are emitting
or scattering light.

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Le_Forgeron <jgr### [at] freefr> wrote:

> What is GI, AO ?
>
> About soft shadow... if it's a point of light, it cannot be soft.-
>
> Or you have a definition of point that is no more a point.
>
> Area lights have many optimisation (such as adaptative) which can be
> used to have real large array without the cost of as many point lights.
>
> jitter, orient & circular are cool too.
>
> http://www.povray.org/documentation/3.7.0/r3_4.html#r3_4_4_1_5
>
> Maybe wanting something like the fading cone of spot light ?

GI = Indirect Lighting (Like Radiosity), AO is a fast method of faking shadows
in crevices, which helps enormously when faking indirect lighting to speed up
renders.

Also you can have soft shadows with point lights (or in fact any light), many
other render engines do it. You just have to trace a bunch of shadow rays up
towards the light rather than just one, and give them a semi-random offset
between the direction of the light and a user defined maximum (which defines how
soft the shadow is). The more rays you trace the cleaner it will be.

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Christian Froeschlin <chr### [at] chrfrde> wrote:

>  From the documentation:
>
>    "Any type of light source may be an area light."
>
> In essence, the "area_light" keyword in POV-Ray should probably be
> regarded as the name of the option that enables "soft shadows" for any
> given light source (although it can do more with "area_illumination").
>
> Also, since you mention radiosity, that will also give you soft
> shadows appropriate for the geometry of the objects that are emitting
> or scattering light.

Ah thanks, that worked well. I was under the impression you could either have a
point, directional, or area light, but it seems some of their features are very
much 'stackable'.

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> Also you can have soft shadows with point lights (or in fact any light), many
> other render engines do it. You just have to trace a bunch of shadow rays up
> towards the light rather than just one, and give them a semi-random offset
> between the direction of the light and a user defined maximum (which defines how
> soft the shadow is). The more rays you trace the cleaner it will be.

How is that still a point light then?
I'm not really familiar with many render engines, but as far as I 
understand, it's the same with every renderer: to get soft shadows, you 
either fake it with blurry shadow maps, or you have to use lights of a 
size>0, which means it's not a point light anymore.

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On Sun, 08 Feb 2015 18:02:26 +0200, IronLogic <nomail@nomail> wrote:

> Le_Forgeron <jgr### [at] freefr> wrote:
>
>> What is GI, AO ?
>>
>> About soft shadow... if it's a point of light, it cannot be soft.-
>>
>> Or you have a definition of point that is no more a point.
>>
>> Area lights have many optimisation (such as adaptative) which can be
>> used to have real large array without the cost of as many point lights.
>>
>> jitter, orient & circular are cool too.
>>
>> http://www.povray.org/documentation/3.7.0/r3_4.html#r3_4_4_1_5
>>
>> Maybe wanting something like the fading cone of spot light ?
>
> GI = Indirect Lighting (Like Radiosity), AO is a fast method of faking  
> shadows
> in crevices, which helps enormously when faking indirect lighting to  
> speed up
> renders.
>
> Also you can have soft shadows with point lights (or in fact any light),  
> many
> other render engines do it. You just have to trace a bunch of shadow  
> rays up
> towards the light rather than just one, and give them a semi-random  
> offset
> between the direction of the light and a user defined maximum (which  
> defines how
> soft the shadow is). The more rays you trace the cleaner it will be.
>
>

Do you mean like the shadows in Sky Captain and Toy Story 1?

Such shadows are totally unrealistic because they are blurred the same  
amount not matter how far away they are from the object. Just because  
other renderers do it, doesn't mean it is correct. These soft shadows are  
a scan-line renderer shortcut for actual area light shadows that render  
longer. Pov-Ray is not a scan-line renderer, it is a ray-tracer. I suggest  
you use an Area Light with jitter, circular and orient, and making it the  
size of the globe it represents to give you a more realistic soft shadow.

Take a look at any soft shadow in real life and you will see that where  
the shadow meats the object casting it, the shadow is sharp. The further  
away the shadow is from the object, the softer the shadow is.

-- 
-Nekar Xenos-

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On Sun, 08 Feb 2015 18:07:18 +0200, IronLogic <nomail@nomail> wrote:

> Christian Froeschlin <chr### [at] chrfrde> wrote:
>
>>  From the documentation:
>>
>>    "Any type of light source may be an area light."
>>
>> In essence, the "area_light" keyword in POV-Ray should probably be
>> regarded as the name of the option that enables "soft shadows" for any
>> given light source (although it can do more with "area_illumination").
>>
>> Also, since you mention radiosity, that will also give you soft
>> shadows appropriate for the geometry of the objects that are emitting
>> or scattering light.
>
> Ah thanks, that worked well. I was under the impression you could either  
> have a
> point, directional, or area light, but it seems some of their features  
> are very
> much 'stackable'.
>
>

In that case you can ignore my previous comment :)

-- 
-Nekar Xenos-

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Am 08.02.2015 um 17:02 schrieb IronLogic:

> Also you can have soft shadows with point lights (or in fact any light), many
> other render engines do it. You just have to trace a bunch of shadow rays up
> towards the light rather than just one, and give them a semi-random offset
> between the direction of the light and a user defined maximum (which defines how
> soft the shadow is). The more rays you trace the cleaner it will be.

Well, that's /exactly/ what POV-Ray area lights do in the "circular 
orient jitter" mode - except that POV-Ray uses stratified sampling in 
that mode rather than purely random offsets, and that it also still 
supports adaptive supersampling in that mode.

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> Le_Forgeron <jgr### [at] freefr> wrote:
>
>> What is GI, AO ?
>>
>> About soft shadow... if it's a point of light, it cannot be soft.-
>>
>> Or you have a definition of point that is no more a point.
>>
>> Area lights have many optimisation (such as adaptative) which can be
>> used to have real large array without the cost of as many point lights.
>>
>> jitter, orient & circular are cool too.
>>
>> http://www.povray.org/documentation/3.7.0/r3_4.html#r3_4_4_1_5
>>
>> Maybe wanting something like the fading cone of spot light ?
>
> GI = Indirect Lighting (Like Radiosity), AO is a fast method of faking shadows
> in crevices, which helps enormously when faking indirect lighting to speed up
> renders.
>
> Also you can have soft shadows with point lights (or in fact any light), many
> other render engines do it. You just have to trace a bunch of shadow rays up
> towards the light rather than just one, and give them a semi-random offset
> between the direction of the light and a user defined maximum (which defines how
> soft the shadow is). The more rays you trace the cleaner it will be.
>
>

Does AO mean ambient oclusion? If that's the case, it's only a tiny 
subset of radiosity. It lack the ability to take into account the colour 
and reflectivity of the ocluding object: it may be black or white and 
cause exactly the same darkening.

NO, it's absolutely impossible to have any kind of soft shadow from a 
point light. Other renderers may /fake/ soft shadows, like you can 
/fake/ focal blur, in a non-realistic way.
The mechanism that you mention is faking it. It's probably no faster, 
nor beter, than using an area_light in POV-Ray.

Just use a light source, add area_light, the dimentions of the area, and 
the number of sub-lights. Greatly improve the performances by using 
adaptive. Great controll, good performance.
The larger the number of sub-lights, the cleaner the result. Make the 
dimention larger to get broader penumbrae.


Alain

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> Christian Froeschlin <chr### [at] chrfrde> wrote:
>
>>   From the documentation:
>>
>>     "Any type of light source may be an area light."
>>
>> In essence, the "area_light" keyword in POV-Ray should probably be
>> regarded as the name of the option that enables "soft shadows" for any
>> given light source (although it can do more with "area_illumination").
>>
>> Also, since you mention radiosity, that will also give you soft
>> shadows appropriate for the geometry of the objects that are emitting
>> or scattering light.
>
> Ah thanks, that worked well. I was under the impression you could either have a
> point, directional, or area light, but it seems some of their features are very
> much 'stackable'.
>
>

area_light is an option.
spot_light, cylindrical and parallel are also options.
You can have a light with area_light, parallel AND spot_light without 
any problem.

Also, if you want to use photons, to have forward tracing, ALL light but 
shadowless emit photons by default.

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"Nekar Xenos" <nek### [at] gmailcom> wrote:

> Do you mean like the shadows in Sky Captain and Toy Story 1?
>
> Such shadows are totally unrealistic because they are blurred the same
> amount not matter how far away they are from the object. Just because
> other renderers do it, doesn't mean it is correct. These soft shadows are
> a scan-line renderer shortcut for actual area light shadows that render
> longer. Pov-Ray is not a scan-line renderer, it is a ray-tracer. I suggest
> you use an Area Light with jitter, circular and orient, and making it the
> size of the globe it represents to give you a more realistic soft shadow.
>
> Take a look at any soft shadow in real life and you will see that where
> the shadow meats the object casting it, the shadow is sharp. The further
> away the shadow is from the object, the softer the shadow is.

I think you're thinking of shadow maps. What I mean is a commonly used method of
faking 'true' soft shadows that do spread out the further away an object is from
the thing it casts its shadow onto, no matter what type of light source is used.

In this method the shadow rays would be traced from the hitpoint and spread out
more the father away the object casting the shadow is, causing a softer shadow
to form. For example, a shadow ray would hit a ground plane, then something like
16 shadow rays could then be traced from the hitpoint on the ground plane up to
a light source, each randomly offset from the path to the light source by say 10
degrees.
     That would give you a ~20 degree 'cone' of shadow rays going up from the
hitpoint to the light. Some shadow rays would hit an object, e.g. a sphere, and
some would miss, so then the average colour of all those rays would be a shade
of grey. The closer towards an object the more rays would hit the sphere,
leading to a darker colour and vice versa. And the farther away the object is
the more rays from farther hitpoints would hit it too, leading to a much more
'spread out' and softer shadow.

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