POV-Ray : Newsgroups : povray.binaries.images : Area lights and looks_like Server Time
28 Apr 2024 23:24:16 EDT (-0400)
  Area lights and looks_like (Message 1 to 5 of 5)  
From: Mike Horvath
Subject: Area lights and looks_like
Date: 30 Jan 2016 12:26:58
Message: <56acf262@news.povray.org>
I am having a problem with an area light. Here is the code:

light_source
{
	0, lamp_color
	area_light
	+z * lamp_length, +y, lamp_number, 1
	area_illumination	on
	looks_like {lamp_bulb}
}

The lamp in this case is the spiral wrapped tube in the attached images. 
The problem is that the tube itself is not being properly lit. It should 
be lit fairly evenly along its whole length. Instead, in both the area 
light and point light examples, it is being lit heavily from the center 
and not at all from the ends. Hence, parts of the tube in both images 
are unlit from the direction of the camera.

How do I fix this?


Mike


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Attachments:
Download 'gh_scene_spinner_cutaway_e - copy_area_light.png' (443 KB) Download 'gh_scene_spinner_cutaway_e - copy_point_light.png' (118 KB)

Preview of image 'gh_scene_spinner_cutaway_e - copy_area_light.png'
gh_scene_spinner_cutaway_e - copy_area_light.png

Preview of image 'gh_scene_spinner_cutaway_e - copy_point_light.png'
gh_scene_spinner_cutaway_e - copy_point_light.png


 

From: Mike Horvath
Subject: Re: Area lights and looks_like
Date: 30 Jan 2016 14:28:19
Message: <56ad0ed3$1@news.povray.org>
On 1/30/2016 12:27 PM, Mike Horvath wrote:
> I am having a problem with an area light. Here is the code:
>
> light_source
> {
>      0, lamp_color
>      area_light
>      +z * lamp_length, +y, lamp_number, 1
>      area_illumination    on
>      looks_like {lamp_bulb}
> }
>
> The lamp in this case is the spiral wrapped tube in the attached images.
> The problem is that the tube itself is not being properly lit. It should
> be lit fairly evenly along its whole length. Instead, in both the area
> light and point light examples, it is being lit heavily from the center
> and not at all from the ends. Hence, parts of the tube in both images
> are unlit from the direction of the camera.
>
> How do I fix this?
>
>
> Mike

Oops! I added area_illumination on to the code, but didn't check to see 
if it worked. That seems to have solved the issue.

But I decided to also add emission, which was even better.


Mike


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From: clipka
Subject: Re: Area lights and looks_like
Date: 30 Jan 2016 16:39:25
Message: <56ad2d8d$1@news.povray.org>
Am 30.01.2016 um 20:28 schrieb Mike Horvath:

> Oops! I added area_illumination on to the code, but didn't check to see
> if it worked. That seems to have solved the issue.

I was just about to ask what version of POV-Ray you are using, and to
state that "area_illumination" _should_ take care this in current
versions ;)

> But I decided to also add emission, which was even better.

Yes, I guess in your case a purely emissive surface (no diffuse, no
highlights) should be the ideal solution.

Make sure to specify "no_radiosity" though.


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From: Mike Horvath
Subject: Re: Area lights and looks_like
Date: 30 Jan 2016 20:56:23
Message: <56ad69c7$1@news.povray.org>
On 1/30/2016 4:39 PM, clipka wrote:
> Make sure to specify "no_radiosity" though.
>

Could you explain what that does? The docs are very brief on the subject.


Mike


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From: clipka
Subject: Re: Area lights and looks_like
Date: 30 Jan 2016 21:24:51
Message: <56ad7073$1@news.povray.org>
Am 31.01.2016 um 02:56 schrieb Mike Horvath:
> On 1/30/2016 4:39 PM, clipka wrote:
>> Make sure to specify "no_radiosity" though.
> 
> Could you explain what that does? The docs are very brief on the subject.

It makes the radiosity code act as if the object wasn't there.

It solves the problem that a light source with a looks_like source would
illuminate the world twice if radiosity is enabled: Once via the classic
raytracing code computing the illumination from light sources, and once
via the radiosity code computing the illumination from objects (which by
default includes looks_like objects).


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