POV-Ray : Newsgroups : povray.advanced-users : looks_like (again) Server Time: 19 Dec 2018 07:15:00 GMT
  looks_like (again) (Message 1 to 6 of 6)  
From: Mike Horvath
Subject: looks_like (again)
Date: 10 Mar 2018 22:36:27
Message: <5aa45deb$1@news.povray.org>
I have the following settings. However, I can't get the sun_object to 
appear visible. What am I doing wrong? Thanks.

Mike



// -------------------------------------------------------------
// Universe

#declare feet_units			= 20;							// LDU per foot
#declare mile_units			= 5280 * feet_units;
#declare plate_size			=   32 * feet_units;
#declare earth_fudge		= 1/10;							// precision issues in POV-Ray 
necessitate this
#declare earth_radius		= 3959 * mile_units * earth_fudge;
#declare earth_circum		= floor(2 * pi * earth_radius / plate_size) * 
plate_size;
#declare earth_radius		= earth_circum/2/pi;
#declare longitude_div		= earth_circum/plate_size;
#declare sun_fudge			= 1/100000;
#declare sun_radius			=   432288 * mile_units * sun_fudge;
#declare sun_distance		= 92960000 * mile_units * sun_fudge;
#declare cloud_min_radius	=  1 * mile_units * earth_fudge;
#declare cloud_max_radius	=  2 * mile_units * earth_fudge;
#declare atmos_max_radius	= 10 * mile_units * earth_fudge;


// -------------------------------------------------------------
// Lights

#include "sunpos.inc"

#declare light_source_location	= <1,-1,1> * sun_distance * SunPos(2018, 
3, 6, 9, 15, -75, 43.2087409, -71.7123404);	// Year, Month, Day, Time 
(24hr), Lstm, LAT, LONG

#declare sun_object = sphere
{
	<0,0,0>, sun_radius
	pigment {color rgb 1}
	finish {emission 1}
}

light_source
{
	light_source_location
	rgb 1
	looks_like
	{
		sun_object
	}
	parallel
	point_at <0,0,0>
}


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From: omniverse
Subject: Re: looks_like (again)
Date: 11 Mar 2018 00:00:01
Message: <web.5aa4709df45d15ce9c5d6c810@news.povray.org>
Mike Horvath <mik### [at] gmailcom> wrote:
> I have the following settings. However, I can't get the sun_object to
> appear visible. What am I doing wrong? Thanks.

Well, I think it's a problem with distance.

If the location is divided by 10 billion, or multiplied by 1e-10 (one ten
billionth) it will show the sun when a camera at <0,0,0> is set to look_at the
sun location.

light_source
{
 light_source_location*1e-10
 rgb 1
 looks_like
 {
  sun_object
 }
 parallel
 point_at <0,0,0>
}

camera {
 location <0,0,0>
 look_at light_source_location
}


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From: Mike Horvath
Subject: Re: looks_like (again)
Date: 11 Mar 2018 00:29:48
Message: <5aa4787c$1@news.povray.org>
On 3/10/2018 6:56 PM, omniverse wrote:
> Mike Horvath <mik### [at] gmailcom> wrote:
>> I have the following settings. However, I can't get the sun_object to
>> appear visible. What am I doing wrong? Thanks.
> 
> Well, I think it's a problem with distance.
> 
> If the location is divided by 10 billion, or multiplied by 1e-10 (one ten
> billionth) it will show the sun when a camera at <0,0,0> is set to look_at the
> sun location.
> 
> light_source
> {
>   light_source_location*1e-10
>   rgb 1
>   looks_like
>   {
>    sun_object
>   }
>   parallel
>   point_at <0,0,0>
> }
> 
> camera {
>   location <0,0,0>
>   look_at light_source_location
> }
> 
> 
> 

I was able to work it out. Thanks for your help!


Mike


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From: Mike Horvath
Subject: Re: looks_like (again)
Date: 11 Mar 2018 00:29:58
Message: <5aa47886$1@news.povray.org>
Disregard.


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From: Alain
Subject: Re: looks_like (again)
Date: 11 Mar 2018 00:33:44
Message: <5aa47968$1@news.povray.org>
Le 18-03-10 à 18:56, omniverse a écrit :
> Mike Horvath <mik### [at] gmailcom> wrote:
>> I have the following settings. However, I can't get the sun_object to
>> appear visible. What am I doing wrong? Thanks.
> 
> Well, I think it's a problem with distance.
> 
> If the location is divided by 10 billion, or multiplied by 1e-10 (one ten
> billionth) it will show the sun when a camera at <0,0,0> is set to look_at the
> sun location.
> 
> light_source
> {
>   light_source_location*1e-10
>   rgb 1
>   looks_like
>   {
>    sun_object
>   }
>   parallel
>   point_at <0,0,0>
> }
> 
> camera {
>   location <0,0,0>
>   look_at light_source_location
> }
> 
> 
> 

This happen when the dimensions range become to large. You get hit with 
precision loss.
Try to keep your range of scales to less than 1e6 if at all possible.
If your smallest object is about 1 unit in size, the farthest object 
should be located at less than 1000000 unit away.

If dividing the Sun's location by 1e10 makes the sun_object visible, 
it's obvious that your scale range is WAY to large !
When using a parallel light, you can always safely place it much closer, 
if you also take care to scale it down proportionally.


Alain


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From: Mike Horvath
Subject: Re: looks_like (again)
Date: 13 Mar 2018 04:07:55
Message: <5aa74e9b$1@news.povray.org>
On 3/10/2018 7:29 PM, Mike Horvath wrote:
> On 3/10/2018 6:56 PM, omniverse wrote:
>> Mike Horvath <mik### [at] gmailcom> wrote:
>>> I have the following settings. However, I can't get the sun_object to
>>> appear visible. What am I doing wrong? Thanks.
>>
>> Well, I think it's a problem with distance.
>>
>> If the location is divided by 10 billion, or multiplied by 1e-10 (one ten
>> billionth) it will show the sun when a camera at <0,0,0> is set to 
>> look_at the
>> sun location.
>>
>> light_source
>> {
>>   light_source_location*1e-10
>>   rgb 1
>>   looks_like
>>   {
>>    sun_object
>>   }
>>   parallel
>>   point_at <0,0,0>
>> }
>>
>> camera {
>>   location <0,0,0>
>>   look_at light_source_location
>> }
>>
>>
>>
> 
> I was able to work it out. Thanks for your help!
> 
> 
> Mike


The problem was that "sunpos.inc" was returning values that were already 
scaled to a large degree. When I vnormalized these values things started 
working correctly.


Mike


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