POV-Ray : Newsgroups : povray.advanced-users : map_type 1 Server Time
30 Nov 2022 12:15:28 EST (-0500)
  map_type 1 (Message 1 to 8 of 8)  
From: Mike Horvath
Subject: map_type 1
Date: 23 Jul 2018 20:51:44
Message: <5b567820$1@news.povray.org>
If I apply an image_map to an ellipsoid using map_type 1, will the 
effect be like what is pictured? (See attachment.)

Mike


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Attachments:
Download 'cone_of_latitude_mono_uvmap.png' (38 KB)

Preview of image 'cone_of_latitude_mono_uvmap.png'
cone_of_latitude_mono_uvmap.png


 

From: clipka
Subject: Re: map_type 1
Date: 24 Jul 2018 03:54:32
Message: <5b56db38$1@news.povray.org>
Am 24.07.2018 um 02:51 schrieb Mike Horvath:
> If I apply an image_map to an ellipsoid using map_type 1, will the
> effect be like what is pictured? (See attachment.)

Yes.


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From: Mike Horvath
Subject: Re: map_type 1
Date: 24 Jul 2018 04:30:16
Message: <5b56e398$1@news.povray.org>
On 7/24/2018 3:54 AM, clipka wrote:
> Am 24.07.2018 um 02:51 schrieb Mike Horvath:
>> If I apply an image_map to an ellipsoid using map_type 1, will the
>> effect be like what is pictured? (See attachment.)
> 
> Yes.
> 

Next obvious question: Is there a way to tweak the map and make it 
conform to an ellipsoid? E.g. perpendicular to the ellipsoid's tangents?


Mike


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Attachments:
Download 'cone_of_latitude_mono_uvmap_b.png' (52 KB)

Preview of image 'cone_of_latitude_mono_uvmap_b.png'
cone_of_latitude_mono_uvmap_b.png


 

From: clipka
Subject: Re: map_type 1
Date: 24 Jul 2018 04:55:35
Message: <5b56e987$1@news.povray.org>
Am 24.07.2018 um 10:30 schrieb Mike Horvath:
> On 7/24/2018 3:54 AM, clipka wrote:
>> Am 24.07.2018 um 02:51 schrieb Mike Horvath:
>>> If I apply an image_map to an ellipsoid using map_type 1, will the
>>> effect be like what is pictured? (See attachment.)
>>
>> Yes.
>>
> 
> Next obvious question: Is there a way to tweak the map and make it
> conform to an ellipsoid? E.g. perpendicular to the ellipsoid's tangents?

You can scale the pigment. If you scale it vertically by the quotient of
the ellipsoid's minor and major diameters d/D (or if you create the
object as a pigmented sphere and then turn it into an ellipsoid by
scaling), you'll get the same effect as projecting from the sphere to
the ellipsoid vertically.

If you scale it vertically by a factor somewhere between 1 and d/D,
you'll get other projections from sphere to ellipsoid, though I'm not
sure if any one of them happens to match the projection you've depicted.

If all else fails, you can roll your own projection by using the new
`user_defined` pattern, and employ functions that fetch their values
from suitable locations in the original image map (via the pattern
function mechanism).


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From: Mike Horvath
Subject: Re: map_type 1
Date: 24 Jul 2018 05:23:17
Message: <5b56f005$1@news.povray.org>
I screwed up the last drawing unfortunately. I will post another later.


On 7/24/2018 4:55 AM, clipka wrote:
> If all else fails, you can roll your own projection by using the new
> `user_defined` pattern, and employ functions that fetch their values
> from suitable locations in the original image map (via the pattern
> function mechanism).
> 

I will check the docs as that looks interesting.


Mike


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From: clipka
Subject: Re: map_type 1
Date: 24 Jul 2018 05:45:52
Message: <5b56f550$1@news.povray.org>
Am 24.07.2018 um 11:23 schrieb Mike Horvath:
> I screwed up the last drawing unfortunately. I will post another later.

A propos:

https://youtu.be/xdIjYBtnvZU

Maybe that geometric property might be of use to you.


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From: Mike Horvath
Subject: Re: map_type 1
Date: 24 Jul 2018 05:50:20
Message: <5b56f65c@news.povray.org>
Here are all three images again.


On 7/24/2018 5:45 AM, clipka wrote:
> Am 24.07.2018 um 11:23 schrieb Mike Horvath:
>> I screwed up the last drawing unfortunately. I will post another later.
> 
> A propos:
> 
> https://youtu.be/xdIjYBtnvZU
> 
> Maybe that geometric property might be of use to you.
> 

I will watch this in the morning. Thanks!


Mike


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Attachments:
Download 'cone_of_latitude_mono_uvmap_a.png' (45 KB) Download 'cone_of_latitude_mono_uvmap_b.png' (52 KB) Download 'cone_of_latitude_mono_uvmap_c.png' (40 KB)

Preview of image 'cone_of_latitude_mono_uvmap_a.png'
cone_of_latitude_mono_uvmap_a.png

Preview of image 'cone_of_latitude_mono_uvmap_b.png'
cone_of_latitude_mono_uvmap_b.png

Preview of image 'cone_of_latitude_mono_uvmap_c.png'
cone_of_latitude_mono_uvmap_c.png


 

From: Mike Horvath
Subject: Re: map_type 1
Date: 24 Jul 2018 17:49:21
Message: <5b579ee1$1@news.povray.org>
On 7/24/2018 4:55 AM, clipka wrote:
> If all else fails, you can roll your own projection by using the new
> `user_defined` pattern, and employ functions that fetch their values
> from suitable locations in the original image map (via the pattern
> function mechanism).

So, I can alter the original image map (the bitmap featuring continents, 
oceans, etc.) in this manner?


Mike


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