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From: [GDS|Entropy]
Subject: strange behavior, lightsource + lookslike + media
Date: 28 Oct 2011 07:50:01
Message: <web.4eaa95c011cbbbbd77e50e540@news.povray.org>
I do not understand why the position of this object controls its appearance.
Any clues?

I seem to have covered all position based params with the macro variable...

Source below:

// ----------------------------------------

camera
{
    right x*image_width/image_height
    location  <0, 0, -5>
    look_at   <0, 0, 0>
}

// ----------------------------------------

#macro BlackHoleWarp(Iterations, Falloff, Strength, Position, Radius)
    #local counter = 0; // set counter to 0
    #while (counter < Iterations)

        warp
        {
            black_hole Position, Radius
            falloff Falloff
            strength Strength
            turbulence 0.4
        }

        #local counter = counter + 1;
    #end
#end

#macro Glow(glowPosition, glowRadius, glowColor)
light_source
{
    glowPosition
    color rgb glowColor
    looks_like
    {
        sphere
        {
            glowPosition, glowRadius
            hollow
            pigment
            {
                rgbt <0, 0, 0, 1>
            }
            interior
            {
                media
                {
                    intervals 1 //  scale this in relation to distance from
camera
                    samples 1, 1
                    emission glowColor
                    density
                    {
                        spherical
                        scale 3
                        density_map
                        {
                            [0.0 rgb glowColor * 0.000]
                            [0.8 rgb glowColor * 0.250]
                            [0.9 rgb glowColor * 0.750]
                            [1.0 rgb glowColor * 1.000]
                        }
                    }
                    density
                    {
                        spherical
                        density_map
                        {
                            [0.00 color rgb glowColor * 0.000]
                            [ 0.90
                                granite
                                color_map
                                {
                                    [0 color rgb glowColor * 0.750]
                                    [1 color rgb glowColor * 0.250]
                                }
                                //BlackHoleWarp(4, 1, 1, glowPosition, 1)
                            ]
                            [1.00 color rgb glowColor * 1.500]
                        }
                    }
                }
            }
            finish
            {
                reflection 0
                diffuse 0
                ambient 0
                phong 0
                specular 0
                brilliance 0
            }
        }
    }
}
#end

Glow(<2, 0, 0>, 2, <1, 1, 1>)
Glow(<0, 0, 0>, 2, <0.5, 0.5, 0.55> * 1.5)
Glow(<-2, 0, 0>, 2, <0, 0.5, 0.5> * 1.5)

plane
{
    <0, 1, 0>, 0
    hollow
    texture
    {
        pigment
        {
            color rgb <0.5, 0.5, 0.55>
        }
    }
    scale <1, 1, 1>
    translate <0, -1, 0>
}


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Attachments:
Download 'mediaglow2011_0.png' (55 KB)

Preview of image 'mediaglow2011_0.png'
mediaglow2011_0.png


 

From: clipka
Subject: Re: strange behavior, lightsource + lookslike + media
Date: 28 Oct 2011 08:43:31
Message: <4eaaa373@news.povray.org>
Am 28.10.2011 13:45, schrieb [GDS|Entropy]:
> I do not understand why the position of this object controls its appearance.
> Any clues?

Yes: You failed to translate the sperical pattern to the desired position.

I suggest to compose the Glow thing at <0,0,0>, and finally translate it 
to where you want it:

> #macro Glow(glowPosition, glowRadius, glowColor)
> light_source
> {
>      glowPosition
replace this line with:
        <0,0,0>

>      color rgb glowColor
>      looks_like
>      {
>          sphere
>          {
>              glowPosition, glowRadius
replace this line with:
                <0,0,0>, glowRadius

>              hollow
>              pigment
>              {
>                  rgbt<0, 0, 0, 1>
>              }
>              interior
>              {
>                  media
>                  {
>                      intervals 1 //  scale this ...
>                      samples 1, 1
>                      emission glowColor
>                      density
>                      {
>                          spherical
>                          scale 3
>                          density_map
>                          {
>                              [0.0 rgb glowColor * 0.000]
>                              [0.8 rgb glowColor * 0.250]
>                              [0.9 rgb glowColor * 0.750]
>                              [1.0 rgb glowColor * 1.000]
>                          }
>                      }
>                      density
>                      {
>                          spherical
>                          density_map
>                          {
>                              [0.00 color rgb glowColor * 0.000]
>                              [ 0.90
>                                  granite
>                                  color_map
>                                  {
>                                      [0 color rgb glowColor * 0.750]
>                                      [1 color rgb glowColor * 0.250]
>                                  }
>                                  //BlackHoleWarp(4, 1, 1, glowPosition, 1)
remove this line (or keep it commented out)

>                              ]
>                              [1.00 color rgb glowColor * 1.500]
>                          }
>                      }
>                  }
>              }
>              finish
>              {
>                  reflection 0
>                  diffuse 0
>                  ambient 0
>                  phong 0
>                  specular 0
>                  brilliance 0
>              }
>          }
>      }

insert here:
        translate glowPosition

> }
> #end


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From: [GDS|Entropy]
Subject: Re: strange behavior, lightsource + lookslike + media
Date: 28 Oct 2011 09:40:00
Message: <web.4eaaafc3693b004877e50e540@news.povray.org>
clipka <ano### [at] anonymousorg> wrote:
>snip

Good catch!

However, instead of two hemispheres 1 unit away from the central glow sphere,
they are now inside it. The issue of appearance altering with translation
persists.

I can see that the light source has translated, but it almost looks like the
media didn't.

Weird...

Ian


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Attachments:
Download 'mediaglow2011_0.png' (46 KB)

Preview of image 'mediaglow2011_0.png'
mediaglow2011_0.png


 

From: clipka
Subject: Re: strange behavior, lightsource + lookslike + media
Date: 29 Oct 2011 08:48:42
Message: <4eabf62a@news.povray.org>
Am 28.10.2011 15:36, schrieb [GDS|Entropy]:
> However, instead of two hemispheres 1 unit away from the central glow sphere,
> they are now inside it. The issue of appearance altering with translation
> persists.
>
> I can see that the light source has translated, but it almost looks like the
> media didn't.
>
> Weird...

To be honest, you just discovered a bug in 3.7.RC3 there. Apparently, 
when a light source is translated, the looks_like object is translated 
as well, but not its members (such as media).

3.6.2 does it right. Gotta fix this.


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From: clipka
Subject: Re: strange behavior, lightsource + lookslike + media
Date: 29 Oct 2011 08:57:44
Message: <4eabf848$1@news.povray.org>
Am 29.10.2011 14:48, schrieb clipka:
> To be honest, you just discovered a bug in 3.7.RC3 there. Apparently,
> when a light source is translated, the looks_like object is translated
> as well, but not its members (such as media).

The issue can be worked around by creating the light source at the 
target location - as you originally did; but note that a looks_like 
object always needs to be specified as if the light source was at <0,0,0>.

Thus the following code should work with both 3.6.2 and 3.7.0.RC3:


 > #macro Glow(glowPosition, glowRadius, glowColor)
 > light_source
 > {
 >      glowPosition
Leave this line as is.

 >      color rgb glowColor
 >      looks_like
 >      {
 >          sphere
 >          {
 >              glowPosition, glowRadius
Replace this line with:
                <0,0,0>, glowRadius

 >              hollow
 >              pigment
 >              {
 >                  rgbt<0, 0, 0, 1>
 >              }
 >              interior
 >              {
 >                  media
 >                  {
 >                      intervals 1 //  scale this ...
 >                      samples 1, 1
 >                      emission glowColor
 >                      density
 >                      {
 >                          spherical
 >                          scale 3
 >                          density_map
 >                          {
 >                              [0.0 rgb glowColor * 0.000]
 >                              [0.8 rgb glowColor * 0.250]
 >                              [0.9 rgb glowColor * 0.750]
 >                              [1.0 rgb glowColor * 1.000]
 >                          }
 >                      }
 >                      density
 >                      {
 >                          spherical
 >                          density_map
 >                          {
 >                              [0.00 color rgb glowColor * 0.000]
 >                              [ 0.90
 >                                  granite
 >                                  color_map
 >                                  {
 >                                      [0 color rgb glowColor * 0.750]
 >                                      [1 color rgb glowColor * 0.250]
 >                                  }
 >                      //BlackHoleWarp(4, 1, 1, glowPosition, 1)
You'll probably need to replace this line with the following (in case 
you ultimately decide to re-activate it):
                        //BlackHoleWarp(4, 1, 1, <0,0,0>, 1)

 >                              ]
 >                              [1.00 color rgb glowColor * 1.500]
 >                          }
 >                      }
 >                  }
 >              }
 >              finish
 >              {
 >                  reflection 0
 >                  diffuse 0
 >                  ambient 0
 >                  phong 0
 >                  specular 0
 >                  brilliance 0
 >              }
 >          }
 >      }

Do NOT insert a translate here.

 > }
 > #end


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From: Alain
Subject: Re: strange behavior, lightsource + lookslike + media
Date: 29 Oct 2011 14:20:54
Message: <4eac4406@news.povray.org>

> I do not understand why the position of this object controls its appearance.
> Any clues?
>
> I seem to have covered all position based params with the macro variable...
>
> Source below:
>
> // ----------------------------------------
>
> camera
> {
>      right x*image_width/image_height
>      location<0, 0, -5>
>      look_at<0, 0, 0>
> }
>
> // ----------------------------------------
>
> #macro BlackHoleWarp(Iterations, Falloff, Strength, Position, Radius)
>      #local counter = 0; // set counter to 0
>      #while (counter<  Iterations)
>
>          warp
>          {
>              black_hole Position, Radius
>              falloff Falloff
>              strength Strength
>              turbulence 0.4
>          }
>
>          #local counter = counter + 1;
>      #end
> #end
>
> #macro Glow(glowPosition, glowRadius, glowColor)
> light_source
> {
>      glowPosition
>      color rgb glowColor
>      looks_like
>      {
>          sphere
>          {
>              glowPosition, glowRadius

A looks_like object location is relative to it's associated light_source.

This light_source have it's looks like correctly placed:
(texture intentionaly omited)
light_source{<100,0,0> rgb 1 looks_like{sphere{0, 1}}}

In your case, using <0,0,0> as the looks_like object location ALSO 
translate the media to the correct location.

This one don't, it's located at <200,0,0>:
light_source{<100,0,0> rgb 1 looks_like{sphere{<100,0,0>, 1}}}

Any contained media will be located relative to the light_source, but no 
longer with the container.


Some media hints:
intervals MUST remains at 1
samples NEVER use the second parameter when using the default smpling 
method: method 3.

As it is, you take only one sample at the mid point of the container and 
assume that it don't change.

Also, your containers overlap each other. As the spherical pattern have 
an effective radius of 1, reducing your containers radius to that value 
suppress the overlap, and some changes related to the location.


Alain


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From: Alain
Subject: Re: strange behavior, lightsource + lookslike + media
Date: 29 Oct 2011 14:29:59
Message: <4eac4627@news.povray.org>

> Am 28.10.2011 15:36, schrieb [GDS|Entropy]:
>> However, instead of two hemispheres 1 unit away from the central glow
>> sphere,
>> they are now inside it. The issue of appearance altering with translation
>> persists.
>>
>> I can see that the light source has translated, but it almost looks
>> like the
>> media didn't.
>>
>> Weird...
>
> To be honest, you just discovered a bug in 3.7.RC3 there. Apparently,
> when a light source is translated, the looks_like object is translated
> as well, but not its members (such as media).
>
> 3.6.2 does it right. Gotta fix this.

I don't know if it's realy a bug, I like to call it an improvement.
Anyway, as it is now, it makes it reasier to correctly place the 
looks_like at the same place as the light_source.

You can have something like:
#macro My_light(Location, Colour) = light_source{Location, Colour 
looks_like{Some_Object}}}

As long as the object is defined at the origin, then, for any value of 
Location, the looks_like object will be at the correct location.

That behaviour did NOT change since the early betas of version 3.7.


Alain


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From: clipka
Subject: Re: strange behavior, lightsource + lookslike + media
Date: 29 Oct 2011 15:09:34
Message: <4eac4f6e$1@news.povray.org>
Am 29.10.2011 20:29, schrieb Alain:

>> To be honest, you just discovered a bug in 3.7.RC3 there. Apparently,
>> when a light source is translated, the looks_like object is translated
>> as well, but not its members (such as media).
>>
>> 3.6.2 does it right. Gotta fix this.
>
> I don't know if it's realy a bug, I like to call it an improvement.
> Anyway, as it is now, it makes it reasier to correctly place the
> looks_like at the same place as the light_source.

No, it's definitely a bug: If you create the light source at <0,0,0>, 
add a looks_like object, then finally translate the whole thing, then 
the looks_like object moves (same as per 3.6) - but its texture and 
media fails to move with it. That definitely does /not/ make things simpler.


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From: D103
Subject: Re: strange behavior, lightsource + lookslike + media
Date: 30 Oct 2011 01:50:01
Message: <web.4eace579693b00485ae2687f0@news.povray.org>
clipka <ano### [at] anonymousorg> wrote:
> Am 29.10.2011 20:29, schrieb Alain:

> >> To be honest, you just discovered a bug in 3.7.RC3 there. Apparently,
> >> when a light source is translated, the looks_like object is translated
> >> as well, but not its members (such as media).
> >>
> >> 3.6.2 does it right. Gotta fix this.
> >
> > I don't know if it's realy a bug, I like to call it an improvement.
> > Anyway, as it is now, it makes it reasier to correctly place the
> > looks_like at the same place as the light_source.
>
> No, it's definitely a bug: If you create the light source at <0,0,0>,
> add a looks_like object, then finally translate the whole thing, then
> the looks_like object moves (same as per 3.6) - but its texture and
> media fails to move with it. That definitely does /not/ make things simpler.

If this is the case, then it explains a similar problem I came across while
making a star in 3.7.0 RC3. I worked around it using a union of a light_source
and a sphere with media and translating that instead.

Regards,
D103


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From: Alain
Subject: Re: strange behavior, lightsource + lookslike + media
Date: 30 Oct 2011 17:04:02
Message: <4eadbbc2@news.povray.org>

> Am 29.10.2011 20:29, schrieb Alain:

>>> To be honest, you just discovered a bug in 3.7.RC3 there. Apparently,
>>> when a light source is translated, the looks_like object is translated
>>> as well, but not its members (such as media).
>>>
>>> 3.6.2 does it right. Gotta fix this.
>>
>> I don't know if it's realy a bug, I like to call it an improvement.
>> Anyway, as it is now, it makes it reasier to correctly place the
>> looks_like at the same place as the light_source.
>
> No, it's definitely a bug: If you create the light source at <0,0,0>,
> add a looks_like object, then finally translate the whole thing, then
> the looks_like object moves (same as per 3.6) - but its texture and
> media fails to move with it. That definitely does /not/ make things
> simpler.

THAT part is definitively a bug. The transform must affect everything, 
especialy any texture and media.

The part I do like is that the looks_like object is centered on the 
light_source whatever it's effective INITIAL location.


Alain


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