https://wiki.povray.org/content?title=Reference:Sphere_Sweep&feed=atom&action=historyReference:Sphere Sweep - Revision history2024-03-29T12:22:53ZRevision history for this page on the wikiMediaWiki 1.35.1https://wiki.povray.org/content?title=Reference:Sphere_Sweep&diff=7040&oldid=prevJholsenback: 1 revision: Reference Migration Initial Load2012-03-15T19:08:50Z<p>1 revision: Reference Migration Initial Load</p>
<table class="diff diff-contentalign-left diff-editfont-monospace" data-mw="interface">
<tr class="diff-title" lang="en">
<td colspan="1" style="background-color: #fff; color: #202122; text-align: center;">← Older revision</td>
<td colspan="1" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 19:08, 15 March 2012</td>
</tr><tr><td colspan="2" class="diff-notice" lang="en"><div class="mw-diff-empty">(No difference)</div>
</td></tr></table>Jholsenbackhttps://wiki.povray.org/content?title=Reference:Sphere_Sweep&diff=7039&oldid=prevJholsenback: 1 revision: Initial Load (TF)2012-03-11T22:27:01Z<p>1 revision: Initial Load (TF)</p>
<p><b>New page</b></p><div>[[Category:Objects]]<br />
[[Category:Finite Solid Primitives]]<br />
{{#indexentry:b_spline}} <br />
{{#indexentry:tolerance}} <br />
{{#indexentry:sphere_sweep, keyword}}<br />
{{#indexentry:keyword, sphere_sweep}} <br />
{{#indexentry:linear_spline, sphere_sweep}}<br />
{{#indexentry:keyword, linear_spline}} <br />
{{#indexentry:b_spline, sphere_sweep}}<br />
{{#indexentry:keyword, b_spline}} <br />
{{#indexentry:cubic_spline, sphere_sweep}}<br />
{{#indexentry:keyword, cubic_spline}} <br />
{{#indexentry:tolerance, sphere_sweep}}<br />
{{#indexentry:keyword, tolerance}}<br />
<p>The syntax of the <code>sphere_sweep</code> object is:</p><br />
<pre><br />
SPHERE_SWEEP:<br />
sphere_sweep {<br />
linear_spline | b_spline | cubic_spline<br />
NUM_OF_SPHERES,<br />
<br />
CENTER, RADIUS,<br />
CENTER, RADIUS,<br />
...<br />
CENTER, RADIUS<br />
[tolerance DEPTH_TOLERANCE]<br />
[OBJECT_MODIFIERS]<br />
}<br />
</pre><br />
<br />
{{#indexentry:default values, sphere_sweep}}<br />
<p>Sphere_sweep default values:</p><br />
<pre><br />
tolerance : 1.0e-6 (0.000001) <br />
</pre><br />
<br />
<p>A Sphere Sweep is the envelope of a moving sphere with varying radius, or, in other words, the<br />
space a sphere occupies during its movement along a spline.<br />
<br>Sphere Sweeps are modeled by specifying a list of single spheres which are then interpolated.<br />
<br>Three kinds of interpolation are supported:</p><ul><br />
<li><code>linear_spline</code> : Interpolating the input data with a linear function, which means<br />
that the single spheres are connected by straight tubes.</li><br />
<li><code>b_spline</code> : Approximating the input data using a cubic b-spline function, which<br />
results in a curved object.</li><br />
<li><code>cubic_spline</code> : Approximating the input data using a cubic spline,<br />
which results in a curved object.</li></ul><br />
<p>The sphere list (center and radius of each sphere) can take as many spheres as you like to describe<br />
the object, but you will need at least two spheres for a <code>linear_spline</code>, and four spheres<br />
for <code>b_spline</code> or <code>cubic_spline</code>.</p><br />
<br />
<p>Optional: The depth tolerance that should be used for the intersection calculations. This is done by<br />
adding the <code>tolerance</code> keyword and the desired value: the default distance is<br />
1.0e-6 (0.000001) and should do for most sphere sweep objects.<br />
<br>You should change this when you see dark spots on the surface of the object. These are probably<br />
caused by an effect called <em>self-shading</em>. This means that the object casts shadows onto itself at some<br />
points because of calculation errors. A ray tracing program usually defines the minimal distance a ray<br />
must travel before it actually hits another (or the same) object to avoid this effect. If this distance is<br />
chosen too small, self-shading may occur.<br />
<br>If so, specify <code>tolerance 1.0e-4</code> or higher.</p><br />
<br />
<p class="Note"><strong>Note:</strong> If these dark spots remain after raising the tolerance, you might get rid of these spots by<br />
using adaptive super-sampling (method 2) for anti-aliasing. Images look better with anti-aliasing anyway.</p><br />
<p class="Note"><strong>Note:</strong> The merge CSG operation is not recommended with Sphere Sweeps: there could be a small gap<br />
between the merged objects!</p></div>Jholsenback