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Am 22.07.2017 um 11:04 schrieb jr:
> On 22/07/2017 06:16, omniverse wrote:
>> And guess I should have asked why "254" instead of the usual 0 to 255.
>> Won't matter really, you only need to change the numbers to what you
>> want.
>
> simple memory fault :-( I thought I'd read 254 being the max # entries
> but, checking, the doc does say "from 2 to 256 entries".
... and, as a matter of fact, that's no longer valid for current
versions anyway ;)
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Le 22/07/2017 à 00:28, jr a écrit :
> hi,
>
> can someone please point me to a color_map example which provides a
> smooth blend/gradient from (ideally) blue at 0 to red at 1 in 254
> increments? I'd prefer a solution which does not require (an array of)
> named colours.
>
> thank you, jr.
>
You can try this :
// --- build colors map ---------------------------------
#declare colorStart = <1.00, 0.00, 0.00>; // Red
#declare colorEnd = <0.00, 0.00, 1.00>; // Blue
#declare colorDelta = colorEnd - colorStart;
#declare nStep = 64; // or others values
#declare colorStep = colorDelta/(nStep);
#declare myMap = color_map {
#declare index = 0;
#while (index <= nStep)
#declare c = colorStart + index*colorStep;
#declare s = index/nStep;
[ s rgb c]
#declare index=index+1;
#end
}
// --- use colors map --------------------------------
box {
<0, 0, 0>,< 5, 5, 100>
pigment {
gradient z
color_map { myMap }
scale <1,1,100>
}
}
--
Kurtz le pirate
Compagnie de la Banquise
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Le 22/07/2017 à 00:28, jr a écrit :
> hi,
>
> can someone please point me to a color_map example which provides a
> smooth blend/gradient from (ideally) blue at 0 to red at 1 in 254
> increments? I'd prefer a solution which does not require (an array of)
> named colours.
From Blue to Red... in which colorspace would the transition be ?
The naive might expects a change in Hue, in HSV or HSL colorspace, with
a vibrant magenta at 0.5 (or going the other way on the circle, blue,
cyan, green, yellow, red ?)
You might want to have a look at the CHSL2RGB macro from colors.inc and
use it in the code provided in the other posts of this thread.
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clipka <ano### [at] anonymous org> wrote:
> Am 22.07.2017 um 06:26 schrieb omniverse:
So to clarify the next thing said:
[0, 1 color <0,0,1> color <1,0,0>]
> That syntax is obsolete, and should be avoided. Instead, use the
> following for exactly the same effect:
And again, clarify this to be written as:
[0 color <0,0,1>]
[1 color <1,0,0>]
I am so far behind the times! Old habits and haphazard methods.
And in case anyone else is wondering, documentation for color_map AND blend_mode
is at:
http://wiki.povray.org/content/Reference:Color_Map
FYI, note to clipka... your example using blend_mode lacks either keywords color
or rgb, POV-Ray wants at least one of those in there. Obvious or not, my chance
to nitpick. ;)
And something curious going on, I'm not sure about, when I add blend_mode to my
example; I can't get the same appearance as yours, which seems to remove the
purple color between blue and red.
Mine just looks the same no matter what blend_mode is set to. Don't know if it's
the incremental steps thing, but I also took out the 2nd color and let a single
color statement do the for loop. No change.
So a heads up goes to OP jr about it anyway.
Bob
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hi,
On 22/07/2017 19:21, omniverse wrote:
> And in case anyone else is wondering, documentation for color_map AND
blend_mode
> is at:
>
> http://wiki.povray.org/content/Reference:Color_Map
>
thanks, just found that the online documentation is out of date.
> And something curious going on, I'm not sure about, when I add
blend_mode ...
> So a heads up goes to OP jr about it anyway.
ouch. ;-)
On 22/07/2017 11:06, clipka wrote:
>> but, checking, the doc does say "from 2 to 256 entries".
>
> ... and, as a matter of fact, that's no longer valid for current
> versions anyway ;)
so, what /is/ the legal range now?
On 22/07/2017 11:55, kurtz le pirate wrote:
> You can try this :
thank you, very clear example. the multiplication by the colour is
neat, it would never have occurred to me.
On 22/07/2017 19:11, Le_Forgeron wrote:
> From Blue to Red... in which colorspace would the transition be ?
already way over my head, I'm afraid to say.
the purpose of the map is to best present the range of values present in
a DF3 file, ie good contrast even when the difference in values is small.
> You might want to have a look at the CHSL2RGB macro from colors.inc and
> use it in the code provided in the other posts of this thread.
thanks, I'll look into this.
regards, jr.
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jr <cre### [at] gmailcom> wrote:
> hi,
>
> On 22/07/2017 19:21, omniverse wrote:
> > And in case anyone else is wondering, documentation for color_map AND
> blend_mode
> > is at:
> >
> > http://wiki.povray.org/content/Reference:Color_Map
> >
>
> thanks, just found that the online documentation is out of date.
>
>
> > And something curious going on, I'm not sure about, when I add
> blend_mode ...
> > So a heads up goes to OP jr about it anyway.
>
> ouch. ;-)
>
>
>
>
> On 22/07/2017 11:06, clipka wrote:
> >> but, checking, the doc does say "from 2 to 256 entries".
> >
> > ... and, as a matter of fact, that's no longer valid for current
> > versions anyway ;)
>
> so, what /is/ the legal range now?
Don't know that myself but I tried up to the hundred millions and ran out of
patience waiting for the parse while memory went up to 1 gig.
I think DF3 is 8, 16 and 32 bit. Which I believe translates to 256, 2048 and
16384.
Bob
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Le 17-07-21 à 18:28, jr a écrit :
> hi,
>
> can someone please point me to a color_map example which provides a
> smooth blend/gradient from (ideally) blue at 0 to red at 1 in 254
> increments? I'd prefer a solution which does not require (an array of)
> named colours.
>
> thank you, jr.
>
You don't need to chop your gradient into many pieces:
//The nice and simple way
pigment{gradient x colour_map{[0 rgb<0,0,1>][1 rgb<1,0,0>]}}}
If you want the long and painfull way...:
//The long and ugly way
#declare Steps=1024;
pigment{gradient x colour_map{
#for(I, 0,1,1/Steps)
[I rgb<I,0,1-I>]
//As of version 3.7, maps are no longer limited to 256 entries
#end
}}}
Both should give exactly the same result when using assumed_gamma 1.
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Le 17-07-22 à 20:35, omniverse a écrit :
> jr <cre### [at] gmailcom> wrote:
>> hi,
>>
>> On 22/07/2017 19:21, omniverse wrote:
>>> And in case anyone else is wondering, documentation for color_map AND
>> blend_mode
>>> is at:
>>>
>>> http://wiki.povray.org/content/Reference:Color_Map
>>>
>>
>> thanks, just found that the online documentation is out of date.
>>
>>
>>> And something curious going on, I'm not sure about, when I add
>> blend_mode ...
>>> So a heads up goes to OP jr about it anyway.
>>
>> ouch. ;-)
>>
>>
>>
>>
>> On 22/07/2017 11:06, clipka wrote:
>>>> but, checking, the doc does say "from 2 to 256 entries".
>>>
>>> ... and, as a matter of fact, that's no longer valid for current
>>> versions anyway ;)
>>
>> so, what /is/ the legal range now?
>
> Don't know that myself but I tried up to the hundred millions and ran out of
> patience waiting for the parse while memory went up to 1 gig.
>
> I think DF3 is 8, 16 and 32 bit. Which I believe translates to 256, 2048 and
> 16384.
>
> Bob
>
>
>
8 bits is 256 values
16 bits is 65365 values
and 32 bits is a little over 4 billions values.
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Am 22.07.2017 um 20:21 schrieb omniverse:
> FYI, note to clipka... your example using blend_mode lacks either keywords color
> or rgb, POV-Ray wants at least one of those in there. Obvious or not, my chance
> to nitpick. ;)
I stand nitpicked indeed ;)
> And something curious going on, I'm not sure about, when I add blend_mode to my
> example; I can't get the same appearance as yours, which seems to remove the
> purple color between blue and red.
> Mine just looks the same no matter what blend_mode is set to. Don't know if it's
> the incremental steps thing, but I also took out the 2nd color and let a single
> color statement do the for loop. No change.
That's because `blend_mode` only controls how POV-Ray interpolates
/between/ individual colour map entries; the entries themselves are
always taken as specified.
Since you're pre-computing some ~250 entries between blue and red,
render-time interpolation is only performed on colours that are very
close anyway, so that `blend_mode` has virtually no effect: Your colour
map is dominated by whatever interpolation formula you have implemented
in SDL, which in this particular case happens to match `blend_mode 0`
(the default).
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Am 22.07.2017 um 21:54 schrieb jr:
> On 22/07/2017 11:06, clipka wrote:
>>> but, checking, the doc does say "from 2 to 256 entries".
>>
>> ... and, as a matter of fact, that's no longer valid for current
>> versions anyway ;)
>
> so, what /is/ the legal range now?
From 2 to whatever your computer's main memory can handle ;)
(Technically that's including virtual memory, but exceeding physical RAM
during render can lead to serious performance degradation.)
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