Reference:Crackle Pattern - Revision history

Jholsenback: version changes

2017-06-26T10:14:57Z

version changes

Jholsenback: tag changed

2016-07-17T13:41:38Z

tag changed

Clipka: added repeat

2016-05-04T21:27:11Z

added repeat

Le Forgeron at 08:41, 1 March 2014

2014-03-01T08:41:01Z

Jholsenback: 1 revision: Reference Migration Initial Load

2012-03-15T19:05:19Z

1 revision: Reference Migration Initial Load

Jholsenback: 1 revision: Initial Load (TF)

2012-03-11T22:27:58Z

1 revision: Initial Load (TF)

New page

[[Category:Patterns]]
{{#indexentry:crackle, keyword}}
{{#indexentry:crackle, pattern}}
{{#indexentry:keyword, crackle}}
{{#indexentry:pattern, crackle}}
{{#indexentry:form, crackle}}
{{#indexentry:keyword, form}}
{{#indexentry:metric, crackle}}
{{#indexentry:keyword, metric}}
{{#indexentry:offset, crackle}}
{{#indexentry:keyword, offset}}
{{#indexentry:solid, crackle}}
{{#indexentry:keyword, solid}}
{{#indexentry:form}}
{{#indexentry:metric}}
{{#indexentry:solid}}
The <code>crackle</code> pattern is a set of random tiled multifaceted cells. The crackle pattern is only semi-procedural, requiring random values to be computed and cached for subsequent queries, with a fixed amount of data per unit-cube in crackle pattern coordinate space. Scaled smaller than the density of actual ray-object-intersections computed, it will eventually lead to a separate crackle cache entry being created for each and every intersection. After the cache reaches a certain size (currently 30mb per thread), new entries for that particular block will be discarded after they are calculated. Starting a new block will allow the caching to resume working again. While discarding the data is of course inefficient, it's still preferable to chewing up 100% of the available physical RAM and then hitting the swap-file.

There is a choice between different types:

Standard Crackle
Mathematically, the set crackle(p)=0 is a 3D Voronoi diagram of a field of semi random points and crackle(p) < 0 is the distance from the set along the shortest path (a Voronoi diagram is the locus of points equidistant from their two nearest neighbors from a set of disjoint points, like the membranes in suds are to the centers of the bubbles).
<ul>
<li>With a large scale and no turbulence it makes a pretty good stone wall or floor.</li>
<li>With a small scale and no turbulence it makes a pretty good crackle ceramic glaze.</li>
<li>Using high turbulence it makes a good marble that avoids the problem of apparent
parallel layers in traditional marble.</li>
</ul>

Form
<pre>
pigment {
crackle form <FORM_VECTOR>
[PIGMENT_ITEMS ...]
}

normal {
crackle [Bump_Size]
form <FORM_VECTOR>
[NORMAL_ITEMS ...]
}
</pre>
Form determines the linear combination of distances used to create the pattern. Form is a vector.
<ul>
<li>The first component determines the multiple of the distance to the closest point to be used in determining the value of the pattern at a particular point.</li>
<li>The second component determines the coefficient applied to the second-closest distance.</li>
<li>The third component corresponds to the third-closest distance.</li>
</ul>
The standard form is <-1,1,0> (also the default), corresponding to the difference in the distances to the closest and second-closest points in the cell array. Another commonly-used form is <1,0,0>, corresponding to the distance to the closest point, which produces a pattern that looks roughly like a random collection of intersecting spheres or cells.
<ul>
<li>Other forms can create very interesting effects, but it is best to keep the sum of the coefficients low.</li>
<li>If the final computed value is too low or too high, the resultant pigment will be saturated with the color at the low or high end of the <code>color_map</code>. In this case, try multiplying the form vector by a constant.</li>
</ul>

Metric
<pre>
pigment {
crackle metric METRIC_VALUE
[PIGMENT_ITEMS ...]
}

normal {
crackle [Bump_Size]
metric METRIC_VALUE
[NORMAL_ITEMS ...]
}
</pre>
Changing the metric changes the function used to determine which cell center is closer, for purposes of determining which cell a particular point falls in. The standard Euclidean distance function has a metric of 2. Changing the metric value changes the boundaries of the cells. A metric value of 3, for example, causes the boundaries to curve, while a very large metric constrains the boundaries to a very small set of possible orientations.
<ul>
<li>The default for metric is 2, as used by the standard crackle texture.</li>
<li>Metrics other than 1 or 2 can lead to substantially longer render times, as the method used to calculate such metrics is not as efficient.</li>
</ul>

Offset
<pre>
pigment {
crackle offset OFFSET_VALUE
[PIGMENT_ITEMS ...]
}

normal {
crackle [Bump_Size]
offset OFFSET_VALUE
[NORMAL_ITEMS ...]
}
</pre>
The offset is used to displace the pattern from the standard xyz space along a fourth dimension.
<ul>
<li>It can be used to round off the pointy parts of a cellular normal texture or procedural heightfield by keeping the distances from becoming zero.</li>
<li>It can also be used to move the calculated values into a specific range if the result is saturated at one end of the color_map.</li>
<li>The default offset is zero.</li>
</ul>

Solid
<pre>
pigment {
crackle solid
[PIGMENT_ITEMS ...]
}

normal {
crackle [Bump_Size]
solid
[NORMAL_ITEMS ...]
}
</pre>
Causes the same value to be generated for every point within a specific cell. This has practical applications in making easy stained-glass windows or flagstones. There is no provision for mortar, but mortar may be created by layering or texture-mapping a
standard crackle texture with a solid one. The default for this parameter is off.

@@ Line 107: / Line 107: @@
+   }
 </pre>
-<p>{{New}} to version 3.7.1 <code>repeat</code> causes the pattern to repeat seamlessly at regular intervals along the X, Y and/or Z axis, as specified by the corresponding components of the specified vector. Values of 0 indicate no repetition along the corresponding axis. For technical reasons, only integer intervals are supported. The default for this parameter is <code><0,0,0></code>, i.e. no repetition.</p>
+<p>{{New}} to version 3.8 <code>repeat</code> causes the pattern to repeat seamlessly at regular intervals along the X, Y and/or Z axis, as specified by the corresponding components of the specified vector. Values of 0 indicate no repetition along the corresponding axis. For technical reasons, only integer intervals are supported. The default for this parameter is <code><0,0,0></code>, i.e. no repetition.</p>
 <p><strong>Solid</strong></p>

@@ Line 107: / Line 107: @@
+   }
 </pre>
-<p>{{New.3.7.1}} Causes the pattern to repeat seamlessly at regular intervals along the X, Y and/or Z axis, as specified by the corresponding components of the specified vector. Values of 0 indicate no repetition along the corresponding axis. For technical reasons, only integer intervals are supported. The default for this parameter is <code><0,0,0></code>, i.e. no repetition.</p>
+<p>{{New}} to version 3.7.1 <code>repeat</code> causes the pattern to repeat seamlessly at regular intervals along the X, Y and/or Z axis, as specified by the corresponding components of the specified vector. Values of 0 indicate no repetition along the corresponding axis. For technical reasons, only integer intervals are supported. The default for this parameter is <code><0,0,0></code>, i.e. no repetition.</p>
 <p><strong>Solid</strong></p>

@@ Line 15: / Line 15: @@
 {{#indexentry:metric}}
 {{#indexentry:solid}}
 <p>The <code>crackle</code> pattern is a set of random tiled multifaceted cells. The crackle pattern is only semi-procedural, requiring random values to be computed and cached for subsequent queries, with a fixed amount of data per unit-cube in crackle pattern coordinate space. Scaled smaller than the density of actual ray-object-intersections computed, it will eventually lead to a separate crackle cache entry being created for each and every intersection. After the cache reaches a certain size (currently 30mb per thread), new entries for that particular block will be discarded after they are calculated. Starting a new block will allow the caching to resume working again. While discarding the data is of course inefficient, it's still preferable to chewing up 100% of the available physical RAM and then hitting the swap-file.</p>
@@ Line 91: / Line 93: @@
 <li>The default offset is zero.</li>
 </ul>
 <p><strong>Solid</strong></p>

← Older revision		Revision as of 08:41, 1 March 2014
Line 107:		Line 107:
	<p>Causes the same value to be generated for every point within a specific cell. This has practical applications in making easy stained-glass windows or flagstones. There is no provision for mortar, but mortar may be created by layering or texture-mapping a		<p>Causes the same value to be generated for every point within a specific cell. This has practical applications in making easy stained-glass windows or flagstones. There is no provision for mortar, but mortar may be created by layering or texture-mapping a
	standard crackle texture with a solid one. The default for this parameter is off.</p>		standard crackle texture with a solid one. The default for this parameter is off.</p>
		+
		+	<table class="centered" width="420px" cellpadding="0" cellspacing="10">
		+	<tr>
		+	<td>[[Image:RefImgCracklePigment.png\|center\|200px<!--centered--->]]</td>
		+	<td>[[Image:RefImgCrackleNormal.png\|center\|200px<!--centered--->]]</td>
		+	</tr>
		+	<tr>
		+	<td colspan="2"><p class="caption">crackle pattern used as pigment and normal respectively</p></td>
		+	</tr>
		+	</table>

← Older revision	Revision as of 19:05, 15 March 2012
(No difference)