http://chromatek.com/what-is-chromadepth/design-guide-2/

I've been reading their documentation, but I can't figure out if the 
progression from near to far is linear or not. I.e. is blue just as far 
from green as green is from blue? Or is it exponential? I plan on doing 
some experiments in the near future, but I can't figure out for sure 
whether this is the case.


Mike

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I took a look at that web page, and it *is* difficult to figure out how the
color blending (for depth cues) should be done.

But here's a 'thought experiment':

Let's say that on a clear day (in the real world), the distant horizon is twenty
miles away (just a guess.) Between 19 1/2 and 20 miles out, there is almost *no*
3D effect that we can discern; whereas, from your eyes to 1/2 mile out, there
is much more of a 3D effect. (In fact, the '3D appearance' of objects in a scene
becomes much more pronounced, the closer those objects are to our eyes.)

Translating that into color blending (using two random colors): If pure GREEN is
located at your eye position, and pure BLUE is 20 miles out, it would seem that
the 'middle blend' of the two colors should *not* be at the 10-mile mark, but
should be much closer to your eye position-- maybe at the 3-mile mark(?)  So, it
seems that the color blend should not be linear, but exponential in some way.

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On 1/16/2016 5:37 AM, Kenneth wrote:
> I took a look at that web page, and it *is* difficult to figure out how the
> color blending (for depth cues) should be done.
>
> But here's a 'thought experiment':
>
> Let's say that on a clear day (in the real world), the distant horizon is twenty
> miles away (just a guess.) Between 19 1/2 and 20 miles out, there is almost *no*
> 3D effect that we can discern; whereas, from your eyes to 1/2 mile out, there
> is much more of a 3D effect. (In fact, the '3D appearance' of objects in a scene
> becomes much more pronounced, the closer those objects are to our eyes.)
>
> Translating that into color blending (using two random colors): If pure GREEN is
> located at your eye position, and pure BLUE is 20 miles out, it would seem that
> the 'middle blend' of the two colors should *not* be at the 10-mile mark, but
> should be much closer to your eye position-- maybe at the 3-mile mark(?)  So, it
> seems that the color blend should not be linear, but exponential in some way.
>
>
>
>


In section 3.4.2.1.3 Angles of the docs it gives the following formula:

direction_length = 0.5 * right_length / tan(angle / 2)

Maybe distance is related to the perceived change in foreshortening in 
the same way, based on tan(angle)?

Mike

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Am 16.01.2016 um 06:53 schrieb Mike Horvath:
> http://chromatek.com/what-is-chromadepth/design-guide-2/
> 
> I've been reading their documentation, but I can't figure out if the
> progression from near to far is linear or not. I.e. is blue just as far
> from green as green is from blue? Or is it exponential? I plan on doing
> some experiments in the near future, but I can't figure out for sure
> whether this is the case.

Strictly speaking you can expect depth cues to progress in steps:
There's one fixed distance corresponding to Red, one corresponding to
Green, and one corresponding to Blue. All of which will depend on your
display's primary colours.

Any colour in between just corresponds to a superposition of two
different depths.

This is especially true if you have a wide-gamut display, i.e. each
primary covers only a narrow band of wavelengths.

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I created the following pigment to be used with ChromaDepth glasses:

	pigment
	{
		gradient vnormalize(Camera_Location - Camera_LookAt) * -1
		color_map
		{
			[0/4 srgb <1,0,0,>]
			[1/4 srgb <1,1,0,>]
			[2/4 srgb <0,1,0,>]
			[3/4 srgb <0,1,1,>]
			[4/4 srgb <0,0,1,>]
		}
		scale vlength(Camera_Location - Camera_LookAt) * 100
		translate Camera_Location
	}

However, the relationship between distance and color is linear in my 
example. How do I change this so that the hue is based on atan(distance 
from camera)? Thanks!


Mike

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On 1/17/2016 11:07 PM, Mike Horvath wrote:
> I created the following pigment to be used with ChromaDepth glasses:
>
>      pigment
>      {
>          gradient vnormalize(Camera_Location - Camera_LookAt) * -1
>          color_map
>          {
>              [0/4 srgb <1,0,0,>]
>              [1/4 srgb <1,1,0,>]
>              [2/4 srgb <0,1,0,>]
>              [3/4 srgb <0,1,1,>]
>              [4/4 srgb <0,0,1,>]
>          }
>          scale vlength(Camera_Location - Camera_LookAt) * 100
>          translate Camera_Location
>      }
>
> However, the relationship between distance and color is linear in my
> example. How do I change this so that the hue is based on atan(distance
> from camera)? Thanks!
>
>
> Mike

Or maybe it should be twice the distance from the camera location to 
look_at?


Mike

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On 1/16/2016 2:44 PM, clipka wrote:
> Am 16.01.2016 um 06:53 schrieb Mike Horvath:
>> http://chromatek.com/what-is-chromadepth/design-guide-2/
>>
>> I've been reading their documentation, but I can't figure out if the
>> progression from near to far is linear or not. I.e. is blue just as far
>> from green as green is from blue? Or is it exponential? I plan on doing
>> some experiments in the near future, but I can't figure out for sure
>> whether this is the case.
>
> Strictly speaking you can expect depth cues to progress in steps:
> There's one fixed distance corresponding to Red, one corresponding to
> Green, and one corresponding to Blue. All of which will depend on your
> display's primary colours.
>
> Any colour in between just corresponds to a superposition of two
> different depths.
>
> This is especially true if you have a wide-gamut display, i.e. each
> primary covers only a narrow band of wavelengths.
>

Are you sure? Yellow definitely looks closer than blue, and blends 
smoothly into the neighboring colors.

I *have* noticed a superposition when looking at magenta. It looks both 
closer and farther than other colors next to it. It's a hard sensation 
to describe.

Mike

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On 1/19/2016 5:37 AM, Mike Horvath wrote:
> On 1/16/2016 2:44 PM, clipka wrote:
>> Am 16.01.2016 um 06:53 schrieb Mike Horvath:
>>> http://chromatek.com/what-is-chromadepth/design-guide-2/
>>>
>>> I've been reading their documentation, but I can't figure out if the
>>> progression from near to far is linear or not. I.e. is blue just as far
>>> from green as green is from blue? Or is it exponential? I plan on doing
>>> some experiments in the near future, but I can't figure out for sure
>>> whether this is the case.
>>
>> Strictly speaking you can expect depth cues to progress in steps:
>> There's one fixed distance corresponding to Red, one corresponding to
>> Green, and one corresponding to Blue. All of which will depend on your
>> display's primary colours.
>>
>> Any colour in between just corresponds to a superposition of two
>> different depths.
>>
>> This is especially true if you have a wide-gamut display, i.e. each
>> primary covers only a narrow band of wavelengths.
>>
>
> Are you sure? Yellow definitely looks closer than blue, and blends
> smoothly into the neighboring colors.
>
> I *have* noticed a superposition when looking at magenta. It looks both
> closer and farther than other colors next to it. It's a hard sensation
> to describe.
>
> Mike

Forgot to say that this lead me to believe that spectral colors are the 
only ones that work properly. Magenta is not a spectral color.


Mike

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Le 16-01-19 05:37, Mike Horvath a écrit :
> On 1/16/2016 2:44 PM, clipka wrote:
>> Am 16.01.2016 um 06:53 schrieb Mike Horvath:
>>> http://chromatek.com/what-is-chromadepth/design-guide-2/
>>>
>>> I've been reading their documentation, but I can't figure out if the
>>> progression from near to far is linear or not. I.e. is blue just as far
>>> from green as green is from blue? Or is it exponential? I plan on doing
>>> some experiments in the near future, but I can't figure out for sure
>>> whether this is the case.
>>
>> Strictly speaking you can expect depth cues to progress in steps:
>> There's one fixed distance corresponding to Red, one corresponding to
>> Green, and one corresponding to Blue. All of which will depend on your
>> display's primary colours.
>>
>> Any colour in between just corresponds to a superposition of two
>> different depths.
>>
>> This is especially true if you have a wide-gamut display, i.e. each
>> primary covers only a narrow band of wavelengths.
>>
>
> Are you sure? Yellow definitely looks closer than blue, and blends
> smoothly into the neighboring colors.
>
> I *have* noticed a superposition when looking at magenta. It looks both
> closer and farther than other colors next to it. It's a hard sensation
> to describe.
>
> Mike

Magenta is a mix of red and blue, both ends of the spectrum.
So, the red part looks closer, and the blue part looks farther.

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Am 19.01.2016 um 11:41 schrieb Mike Horvath:

>>> Strictly speaking you can expect depth cues to progress in steps:
>>> There's one fixed distance corresponding to Red, one corresponding to
>>> Green, and one corresponding to Blue. All of which will depend on your
>>> display's primary colours.
>>>
>>> Any colour in between just corresponds to a superposition of two
>>> different depths.
>>>
>>> This is especially true if you have a wide-gamut display, i.e. each
>>> primary covers only a narrow band of wavelengths.
>>>
>>
>> Are you sure? Yellow definitely looks closer than blue, and blends
>> smoothly into the neighboring colors.
>>
>> I *have* noticed a superposition when looking at magenta. It looks both
>> closer and farther than other colors next to it. It's a hard sensation
>> to describe.
>>
>> Mike
> 
> Forgot to say that this lead me to believe that spectral colors are the
> only ones that work properly. Magenta is not a spectral color.

Which is exactly what I'm saying: In computer displays, anything except
pure Red, pure Green or pure Blue is /never/ a spectral colour -- it's
always a superposition of those three basic colours.

In classic displays, even those are not pure spectral colours -- which
"blurs" them in depth and thus makes the superposition-nature of
in-between colours less obvious.

Wide-gamut displays, on the other hand, require comparatively "pure"
primary colours to achieve their wide gamut, which "sharpens" them in
depth, and thus will easily reveal the superposition-nature of
in-between colours.

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