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<div class="textblock"><p>Section: <a class="el" href="sec_vtkcommon.html">Visualization Toolkit Common Classes</a> </p>
<h1><a class="anchor" id="Usage"></a>
Usage</h1>
<p>vtkImplicitFunction specifies an abstract interface for implicit functions. Implicit functions are real valued functions defined in 3D space, w = F(x,y,z). Two primitive operations are required: the ability to evaluate the function, and the function gradient at a given point. The implicit function divides space into three regions: on the surface (F(x,y,z)=w), outside of the surface (F(x,y,z)>c), and inside the surface (F(x,y,z)<c). (When c is zero, positive values are outside, negative values are inside, and zero is on the surface. Note also that the function gradient points from inside to outside.)</p>
<p>Implicit functions are very powerful. It is possible to represent almost any type of geometry with the level sets w = const, especially if you use boolean combinations of implicit functions (see vtkImplicitBoolean).</p>
<p>vtkImplicitFunction provides a mechanism to transform the implicit function(s) via a vtkAbstractTransform. This capability can be used to translate, orient, scale, or warp implicit functions. For example, a sphere implicit function can be transformed into an oriented ellipse.</p>
<p>To create an instance of class vtkImplicitFunction, simply invoke its constructor as follows </p>
<pre class="fragment"> obj = vtkImplicitFunction
</pre> <h1><a class="anchor" id="Methods"></a>
Methods</h1>
<p>The class vtkImplicitFunction has several methods that can be used. They are listed below. Note that the documentation is translated automatically from the VTK sources, and may not be completely intelligible. When in doubt, consult the VTK website. In the methods listed below, <code>obj</code> is an instance of the vtkImplicitFunction class. </p>
<ul>
<li>
<code>string = obj.GetClassName ()</code> </li>
<li>
<code>int = obj.IsA (string name)</code> </li>
<li>
<code>vtkImplicitFunction = obj.NewInstance ()</code> </li>
<li>
<code>vtkImplicitFunction = obj.SafeDownCast (vtkObject o)</code> </li>
<li>
<code>long = obj.GetMTime ()</code> - Overload standard modified time function. If Transform is modified, then this object is modified as well. </li>
<li>
<code>double = obj.FunctionValue (double x[3])</code> - Evaluate function at position x-y-z and return value. Point x[3] is transformed through transform (if provided). </li>
<li>
<code>double = obj.FunctionValue (double x, double y, double z)</code> - Evaluate function at position x-y-z and return value. Point x[3] is transformed through transform (if provided). </li>
<li>
<code>obj.FunctionGradient (double x[3], double g[3])</code> - Evaluate function gradient at position x-y-z and pass back vector. Point x[3] is transformed through transform (if provided). </li>
<li>
<code>double = obj.FunctionGradient (double x[3])</code> - Evaluate function gradient at position x-y-z and pass back vector. Point x[3] is transformed through transform (if provided). </li>
<li>
<code>double = obj.FunctionGradient (double x, double y, double z)</code> - Evaluate function gradient at position x-y-z and pass back vector. Point x[3] is transformed through transform (if provided). </li>
<li>
<code>obj.SetTransform (vtkAbstractTransform )</code> - Set/Get a transformation to apply to input points before executing the implicit function. </li>
<li>
<code>obj.SetTransform (double elements[16])</code> - Set/Get a transformation to apply to input points before executing the implicit function. </li>
<li>
<code>vtkAbstractTransform = obj.GetTransform ()</code> - Set/Get a transformation to apply to input points before executing the implicit function. </li>
<li>
<code>double = obj.EvaluateFunction (double x[3])</code> - Evaluate function at position x-y-z and return value. You should generally not call this method directly, you should use FunctionValue() instead. This method must be implemented by any derived class. </li>
<li>
<code>double = obj.EvaluateFunction (double x, double y, double z)</code> - Evaluate function at position x-y-z and return value. You should generally not call this method directly, you should use FunctionValue() instead. This method must be implemented by any derived class. </li>
<li>
<code>obj.EvaluateGradient (double x[3], double g[3])</code> - Evaluate function gradient at position x-y-z and pass back vector. You should generally not call this method directly, you should use FunctionGradient() instead. This method must be implemented by any derived class. </li>
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