Reference Talk:Vector Expressions - Revision history

Wfpokorny: /* Functions (max_extent 3.7.1 changes) */ new section

2016-08-25T16:14:20Z

Functions (max_extent 3.7.1 changes): new section

Le Forgeron at 17:46, 7 July 2016

2016-07-07T17:46:52Z

Le Forgeron at 14:59, 7 July 2016

2016-07-07T14:59:39Z

Le Forgeron: reporting problem of accessing the 5D vector's components

2016-07-07T14:50:27Z

reporting problem of accessing the 5D vector's components

New page

From question of Bald Eagle in povray.advanced-users, 2016-07-07, that page is missing how to access the fifth component of a 5D vector.

The answer is to see it as a colour: .red, .green, .blue, .filter, .transmit

x,u,red -> 1st
y,v,green -> 2nd
z,blue -> 3rd
t,filter -> 4th
transmit -> 5th

(as a colour, there is also .grey, but that's another story)

--[[User:Le Forgeron|Le Forgeron]] 14:50, 7 July 2016 (UTC)

← Older revision		Revision as of 16:14, 25 August 2016
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	--[[User:Le Forgeron\|Le Forgeron]] 17:46, 7 July 2016 (UTC)		--[[User:Le Forgeron\|Le Forgeron]] 17:46, 7 July 2016 (UTC)
		+
		+	== Functions (max_extent 3.7.1 changes) ==
		+
		+
		+	* Suggest replacing existing max_extent(pigment_indetifier) discussion with the following to match 3.7.1 changes.
		+
		+	<p>Version 3.7 added support for reading the x,y pixel resolution of an image via a pigment identifier. Version 3.7.1 extends this support to images and df3 files used in normal and density identifiers.</p>
		+
		+	<p>When the identifier is passed to max_extent(), the resolution is returned as a 3 value vector. In the case of images the z value of the vector is set to 0.</p>
		+
		+	<p>A background matte example:</p>
		+
		+	<pre>
		+	#declare MatteImage = pigment { image_map { "YourImage.jpg" } }
		+
		+	#declare Resolution = max_extent ( MatteImage );
		+
		+	#declare MatteNormalizationScale =
		+	<min(1,Resolution.x/Resolution.y),
		+	min(1,Resolution.y/Resolution.x),1>;
		+
		+	box { 0, <1,1,0.001>
		+	pigment { MatteImage }
		+	scale MatteNormalizationScale // Fit matte to unit square
		+	scale MatteSceneScale // Size matte for scene
		+	}
		+	</pre>
		+
		+	<p>To fit a df3 with unequal x,y,z ranges inside unit cube without distortion, the set up for the scaling variable is:</p>
		+
		+	<pre>
		+	#declare Density0 = density { density_file df3 "A20x30x40.df3" interpolate 0 }
		+	#declare Df3MapRange = max_extent(Density0);
		+	#declare Df3NormalizationScale =
		+	<min(1,Df3MapRange.x/max(Df3MapRange.y,Df3MapRange.z)),
		+	min(1,Df3MapRange.y/max(Df3MapRange.x,Df3MapRange.z)),
		+	min(1,Df3MapRange.z/max(Df3MapRange.x,Df3MapRange.y))>;
		+	</pre>

← Older revision		Revision as of 17:46, 7 July 2016
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	--[[User:Le Forgeron\|Le Forgeron]] 14:50, 7 July 2016 (UTC)		--[[User:Le Forgeron\|Le Forgeron]] 14:50, 7 July 2016 (UTC)
		+
		+	As stated in the talk page of Vector Expressions:
		+	The page Vector sends to Numeric Expression, but that one dismiss any details about DOT_ITEM by sending back to Vector / Colour Pages, none of which cover the subject.
		+
		+	In Numerics Expressions page, we have "The DOT_ITEM syntax is actually a vector or color operator but it returns a float value. See Vector Operators or Color Operators for details".
		+
		+	It reminds me of the house that get you mad, in Asterix (The twelve tasks of Asterix, 8th task): To get permit A38, you need the blue sheet... to get the blue sheet, you need to apply with the pink and green ...
		+
		+	Here the loop is smaller, but no one would give a newbie the information about getting a component from a vector (or colour).
		+
		+	I would suggest to leave "Numeric_Expressions" as it is so far, and adding, in both "Vector_Expressions" and "Colour_Expressions", a dedicated section about getting individual component out of a vector and colour.
		+
		+	In that section, the illustration of dot item with a basic example. Such as:
		+
		+	#declare Vector = < 1, 2, 3, 4, 5>;
		+	#declare First_Component_1 = Vector.red;// 1
		+	#declare First_Component_2 = Vector.u;// 1
		+	#declare First_Component_3 = Vector.x;// 1
		+	#declare Second_Component_1 = Vector.green;// 2
		+	#declare Second_Component_2 = Vector.v;// 2
		+	#declare Second_Component_3 = Vector.y;// 2
		+	#declare Third_Component_1 = Vector.blue;// 3
		+	#declare Third_Component_2 = Vector.z;// 3
		+	#declare Fourth_Component_1 = Vector.filter;// 4
		+	#declare Fourth_Component_2 = Vector.t;// 4
		+	#declare Fifth_Component = Vector.transmit;// 5
		+
		+	(and repeat with a Colour= rgbtf <...> )
		+
		+	The section need a visible title (visible in Table of content)
		+
		+	--[[User:Le Forgeron\|Le Forgeron]] 17:46, 7 July 2016 (UTC)

@@ Line 4: / Line 4: @@
 x,u,red -> 1st
 y,v,green -> 2nd
 z,blue -> 3rd
 t,filter -> 4th
 transmit -> 5th
 (as a colour, there is also .grey, but that's another story)
 --[[User:Le Forgeron|Le Forgeron]] 14:50, 7 July 2016 (UTC)