Reference:Background - Revision history

Clipka: canonicalize a version number

2021-06-09T14:59:30Z

canonicalize a version number

Jholsenback: 1 revision: Reference Migration Initial Load

2012-03-15T19:05:05Z

1 revision: Reference Migration Initial Load

Jholsenback: 1 revision: Initial Load (TF)

2012-03-11T22:25:10Z

1 revision: Initial Load (TF)

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[[Category:Atmospheric Effects]]
{{#indexentry:background, keyword}}
A background color can be specified if desired. Any ray that does not hit an object will be colored with this color. The default background is black. The syntax for <code>background</code> is:
<pre>
BACKGROUND:
background {COLOR}
</pre>
Note: As of version 3.7 some changes have been made to the way alpha is handled when <code>+ua</code> is activated. 
<ul>
<li> In previous versions, specifying a background with the <code>background</code> keyword would by default supply a background with transmit set to 1.0 (i.e. fully transparent provided that <code>+ua</code> is being used). This is no longer the case. While the default background is transparent, any background specified in a scene file (unless 3.6 or earlier compatibility is being used) will now be opaque unless transmit is explicitly given. In other words, use <code>rgbft<></code> rather than <code>rgb<></code> in the background statement if you want the old behavior.</li>
<li> The way that objects are blended with the background has changed. Previously the color of the background was not taken into account when calculating effects of transmission through translucent objects when <code>+ua</code> is in effect (i.e. where the background could otherwise have been seen through the object). Now, however, the background color is taken into account, even if it is not otherwise visible. Blending is performed in the same way regardless of the presence of background transparency.</li>
</ul>
Note: When using <code>Output_Alpha=on</code> or <code>+ua</code> with legacy scenes (the <code>#version</code> directive set to less than 3.7) the <code>background</code> will be suppressed, except in reflections.

@@ Line 8: / Line 8: @@
 <p class ="Note"><strong>Note:</strong> As of version 3.7 some changes have been made to the way alpha is handled when <code>+ua</code> is activated. </p>
 <ul>
-<li> In previous versions, specifying a background with the <code>background</code> keyword would by default supply a background with transmit set to 1.0 (i.e. fully transparent provided that <code>+ua</code> is being used). This is no longer the case. While the default background is transparent, any background specified in a scene file (unless 3.6 or earlier compatibility is being used) will now be opaque unless transmit is explicitly given. In other words, use <code>rgbft&lt;&gt;</code> rather than <code>rgb&lt;&gt;</code> in the background statement if you want the old behavior.</li>
+<li> In previous versions, specifying a background with the <code>background</code> keyword would by default supply a background with transmit set to 1.0 (i.e. fully transparent provided that <code>+ua</code> is being used). This is no longer the case. While the default background is transparent, any background specified in a scene file (unless v3.6 or earlier compatibility is being used) will now be opaque unless transmit is explicitly given. In other words, use <code>rgbft&lt;&gt;</code> rather than <code>rgb&lt;&gt;</code> in the background statement if you want the old behavior.</li>
 <li> The way that objects are blended with the background has changed. Previously the color of the background was not taken into account when calculating effects of transmission through translucent objects when <code>+ua</code> is in effect (i.e. where the background could otherwise have been seen through the object). Now, however, the background color is taken into account, even if it is not otherwise visible. Blending is performed in the same way regardless of the presence of background transparency.</li>
 </ul>
 <p class="Note"><strong>Note:</strong> When using <code>Output_Alpha=on</code> or <code>+ua</code> with legacy scenes (the <code>#version</code> directive set to less than 3.7) the <code>background</code> will be suppressed, except in reflections.</p>

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