Reference Talk:Light Source - Revision history

Jholsenback: /* Parallel Lights */

2021-01-31T18:50:25Z

Parallel Lights

Maurice: /* Parallel Lights */

2021-01-25T17:18:32Z

Parallel Lights

Maurice: /* Suggested addition to Parallel Lights section */ new section

2021-01-25T17:17:29Z

Suggested addition to Parallel Lights section: new section

SharkD: +reply

2016-09-12T17:19:09Z

+reply

SharkD: eedit

2016-09-12T17:00:53Z

eedit

SharkD: tweak

2016-09-12T17:00:30Z

tweak

SharkD: tweak

2016-09-12T17:00:00Z

tweak

SharkD: +reply

2016-09-12T16:59:37Z

+reply

SharkD: copy-edit

2016-09-08T22:50:33Z

copy-edit

SharkD: copy-edit

2016-09-08T22:49:59Z

copy-edit

← Older revision		Revision as of 18:50, 31 January 2021
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	scene.</p>		scene.</p>
	--[[User:Maurice\|Maurice]] 17:18, 25 January 2021 (UTC)		--[[User:Maurice\|Maurice]] 17:18, 25 January 2021 (UTC)
		+	<p>Done... i also did some needed grammar cleanup</p>
		+	--[[User:Jholsenback\|jholsenback]] 18:50, 31 January 2021 (UTC)

← Older revision		Revision as of 17:18, 25 January 2021
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	distant enough from the center that it is farther than the farthest other object in your		distant enough from the center that it is farther than the farthest other object in your
	scene.</p>		scene.</p>
		+	--[[User:Maurice\|Maurice]] 17:18, 25 January 2021 (UTC)

← Older revision		Revision as of 17:17, 25 January 2021
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	:I.e. translating a light source translates the location of the source of the light and the location the light is pointing at, which could produce unwanted effects. [[User:SharkD\|SharkD]] 16:59, 12 September 2016 (UTC)		:I.e. translating a light source translates the location of the source of the light and the location the light is pointing at, which could produce unwanted effects. [[User:SharkD\|SharkD]] 16:59, 12 September 2016 (UTC)
	:You might want to update this page as well: [[Knowledgebase:Language_Questions_and_Tips#Topic_1]]. [[User:SharkD\|SharkD]] 17:19, 12 September 2016 (UTC)		:You might want to update this page as well: [[Knowledgebase:Language_Questions_and_Tips#Topic_1]]. [[User:SharkD\|SharkD]] 17:19, 12 September 2016 (UTC)
		+
		+	== Suggested addition to Parallel Lights section ==
		+
		+	From pov newsgroup wip disussion [http://news.povray.org/povray.binaries.images/thread/%3C5ffd0bab%40news.povray.org%3E/?mtop=432577&moff=10\|here] Alain Martel gave following tip":
		+	" You only need to make it just
		+	distant enough that it is farther than the farthest other object in your
		+	scene." Which I believe would make sense as a Nice tip / note right after the mention of non shadowed areas thus something alng the lines of :
		+	==Parallel Lights==
		+	{{#indexentry:parallel, light_source}}
		+	{{#indexentry:point_at, parallel}}
		+	{{#indexentry:light_source, parallel}}
		+	{{#indexentry:parallel}}
		+	{{#indexentry:point_at, light_source}}
		+	{{#indexentry:keyword, point_at}}
		+	<pre>
		+	syntax:
		+
		+	light_source {
		+	LOCATION_VECTOR, COLOR
		+	[LIGHT_SOURCE_ITEMS...]
		+	parallel
		+	point_at VECTOR
		+	}
		+	</pre>
		+
		+	<p>The <code>parallel</code> keyword can be used with any type of light source.</p>
		+	<p class="Note"><strong>Note:</strong> For normal point lights, <code>point_at</code> must come after
		+	<code>parallel</code>.</p>
		+
		+	<p>Parallel lights are useful for simulating very distant light sources, such as
		+	sunlight. As the name suggests, it makes the light rays parallel.</p>
		+	<p>Technically this is done by shooting rays from the closest point on a plane to the
		+	object intersection point. The plane is determined by a perpendicular defined by the
		+	light <code>location</code> and the <code>point_at</code> vector.</p>
		+
		+	<p>Two things must be considered when choosing the light location
		+	(specifically, its distance):</p><ol>
		+	<li>Any parts of an object <em>above</em> the light plane still get illuminated according to
		+	the light direction, but they will not cast or receive shadows.</li>
		+	<li><code>fade_distance</code> and <code>fade_power</code> use the light
		+	<code>location</code> to determine distance for light attenuation, so the attenuation
		+	still looks like that of a point source.
		+	<br>Area light also uses the light location in its calculations.</li></ol>
		+	<p class="Note"><strong>Tip:</strong> For non faded lights, you only need to make <code>location</code> just
		+	distant enough from the center that it is farther than the farthest other object in your
		+	scene.</p>

← Older revision		Revision as of 17:19, 12 September 2016
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	thus the light direction remains unimpressed.</blockquote>		thus the light direction remains unimpressed.</blockquote>
	:I.e. translating a light source translates the location of the source of the light and the location the light is pointing at, which could produce unwanted effects. [[User:SharkD\|SharkD]] 16:59, 12 September 2016 (UTC)		:I.e. translating a light source translates the location of the source of the light and the location the light is pointing at, which could produce unwanted effects. [[User:SharkD\|SharkD]] 16:59, 12 September 2016 (UTC)
		+	:You might want to update this page as well: [[Knowledgebase:Language_Questions_and_Tips#Topic_1]]. [[User:SharkD\|SharkD]] 17:19, 12 September 2016 (UTC)

@@ Line 73: / Line 73: @@
 :Oops, I was wrong. But translation is *dangerous*. As per clipka's response to my post:
-<blockquote>And that direction is unchanged: With a parallel light source, the
+<blockquote>With a parallel light source, the
 direction of all light rays depends only on the /relative/ location of
 two points: The light source's nominal center and the point_at

@@ Line 73: / Line 73: @@
 :Oops, I was wrong. But translation is *dangerous*. As per clipka's response to my post:
+:<blockquote>And that direction is unchanged: With a parallel light source, the
 direction of all light rays depends only on the /relative/ location of
 two points: The light source's nominal center and the point_at
@@ Line 81: / Line 80: @@
 location of the points, not their relative location to one another. And
 thus the light direction remains unimpressed.</blockquote>
+:I.e. translating a light source translates the location of the source of the light *and* the location the light is pointing at, which could produce unwanted effects. [[User:SharkD|SharkD]] 16:59, 12 September 2016 (UTC)

← Older revision		Revision as of 16:59, 12 September 2016
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	[[User:SharkD\|SharkD]] 22:48, 8 September 2016 (UTC)		[[User:SharkD\|SharkD]] 22:48, 8 September 2016 (UTC)
		+
		+	:Oops, I was wrong. But translation is dangerous. As per clipka's response to my post:
		+
		+	<blockquote>And that direction is unchanged: With a parallel light source, the
		+	direction of all light rays depends only on the /relative/ location of
		+	two points: The light source's nominal center and the point_at
		+	parameter. But transformations act on both these points (I've just
		+	checked the code), so a translation operation changes only the absolute
		+	location of the points, not their relative location to one another. And
		+	thus the light direction remains unimpressed.</blockquote>
		+
		+	I.e. translating a light source translates the location of the source of the light and the location the light is pointing at, which could produce unwanted effects. [[User:SharkD\|SharkD]] 16:59, 12 September 2016 (UTC)

@@ Line 56: / Line 56: @@
 </pre>
-<p>For point lights and spotlights you could also place the light source and the <code>looks_like</code> object at the origin and translate them later. But for <code>parallel</code> lights this will not work.</p>
+<p>For point lights and spotlights you could also place the light source and the <code>looks_like</code> object at the origin and translate them together later. But for <code>parallel</code> lights this will not work.</p>
 <p>If you instead want the attached object to block light then you should attach it

@@ Line 45: / Line 45: @@
 </pre>
-<p>Alternately, you could declare the object beforehand and then reference the object from within the light source, like this:</p>
+<p>Alternately, you could declare the object beforehand and reference the object from within the light source, like this:</p>
 <pre>