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<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>2.4. Objects</title><link rel="stylesheet" href="megapov.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.65.1"><link rel="home" href="index.html" title="MegaPOV Documentation"><link rel="up" href="references.html" title="Chapter 2. MegaPOV References"><link rel="previous" href="camera.html" title="2.3. Camera"><link rel="next" href="effects.html" title="2.5. Effects"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">2.4. Objects</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="camera.html">Prev</a> </td><th width="60%" align="center">Chapter 2. MegaPOV References</th><td width="20%" align="right"> <a accesskey="n" href="effects.html">Next</a></td></tr></table><hr></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="objects"></a>2.4. Objects</h2></div></div><div></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="common_features"></a>2.4.1. Common features</h3></div></div><div></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="inside_bounding"></a>2.4.1.1. Bounding used in inside tests</h4></div><div><div class="author"><h3 class="author"><span class="firstname">Micha</span> <span class="surname">Riser</span></h3></div></div></div><div></div></div><a class="indexterm" name="id2525183"></a><p>
    With MegaPOV, in every test using <tt class="function">Inside</tt> of objects
    the bounding object has now priority. It first tests if the point is inside the bounding.
    If it is not then it knows that it can already decide that the point is
    outside (if the object is not inversed) or that the point is inside (if the
    object is inversed).
  </p><p>
    This should increase rendering speed of complicated CSG objects, since it could eliminate
    a lot of computing steps. The inside test is firstly done for the bounding object. Only when
    this test is inside the bounding, the tests against each of the objects composing the CSG object
    will be done.
  </p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="text"></a>2.4.2. Text</h3></div></div><div></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="text_align"></a>2.4.2.1. Text enhancements</h4></div><div><div class="author"><h3 class="author"><span class="firstname">Yvo &amp; René</span> <span class="surname">Smellenbergh</span></h3></div></div></div><div></div></div><p>
	Based on the text enhancement idea of Jamis Buck and Noel Bundy, but modified and extended.
  </p><p>
	Syntax is:
	</p><pre class="synopsis"><tt class="function">text</tt> {
  <i class="parameter"><tt>the usual text stuff</tt></i>
  <i class="parameter"><tt>...</tt></i>
  [ <tt class="function">h_align_left</tt> | <tt class="function">h_align_center</tt> | <tt class="function">h_align_right</tt> ]
  [ <tt class="function">v_align_top</tt> | <tt class="function">v_align_center</tt> | <tt class="function">v_align_bottom</tt> ]
}</pre><p>
  </p><p>
	<tt class="function">h_align_left</tt><a class="indexterm" name="id2525128"></a>
	By adding this keyword to the text block, the text string (including horizontal offset) is aligned horizontally so that its most
	left point touches the y-axis. This is identical to the default alignment.
  </p><p>
	<tt class="function">h_align_center</tt><a class="indexterm" name="id2526627"></a>
	By adding this keyword to the text block, the text string (including horizontal offset) is aligned horizontally so that it extends
	equally on both sides of the y-axis.
  </p><p>
	<tt class="function">h_align_right</tt><a class="indexterm" name="id2526650"></a>
	By adding this keyword to the text block, the text string (including horizontal offset) is aligned horizontally so that its most
	right point touches the y-axis.
  </p><p>
	<tt class="function">v_align_top</tt><a class="indexterm" name="id2526673"></a>
	By adding this keyword to the text block, the  text string (including vertical offset) is aligned vertically so that its highest
	point touches the x-axis.
  </p><p>
	<tt class="function">v_align_center</tt><a class="indexterm" name="id2526696"></a>
	By adding this keyword to the text block, the text string (including vertical offset) is aligned vertically so that its middle
	height sits on the x-axis.
  </p><p>
	<tt class="function">v_align_bottom</tt><a class="indexterm" name="id2526719"></a>
	By adding this keyword to the text block, the text string (including vertical offset) is aligned vertically so that its lowest point
	sits on the x-axis.
  </p><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Note"><tr><td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="icons/note.gif"></td><th align="left">Note</th></tr><tr><td colspan="2" align="left" valign="top"><p>
    When no alignment is specified, the <span class="trademark">POV-Ray</span>&#8482; defaults are used. Horizontally to the left and vertically on the base line.
   </p><p>
	The old keyword "position" of previous MegaPOV versions is no longer supported.
  </p></td></tr></table></div></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="cloth"></a>2.4.3. Cloth simulation</h3></div><div><div class="author"><h3 class="author"><span class="firstname">Christophe</span> <span class="surname">Bouffartigue</span></h3></div></div></div><div></div></div><p>
    <tt class="function">simcloth</tt> allows to simulate cloth in MegaPOV. The cloth patch is rectangular, and interacts with its
    environment (gravity, some obstructing objects, wind, ...).
  </p><p>Syntax is:
    </p><pre class="synopsis">  <tt class="function">simcloth</tt> {
    [ <tt class="function">environment</tt> <i class="parameter"><tt>OBJECT-IDENTIFIER</tt></i> ]
    [ <tt class="function">friction</tt> <i class="parameter"><tt>FLOAT</tt></i> ]
    [ <tt class="function">gravity</tt> <i class="parameter"><tt>VECTOR</tt></i> ]
    [ <tt class="function">wind</tt> { <i class="parameter"><tt>PIGMENT</tt></i> } ]
    [ <tt class="function">viscosity</tt> <i class="parameter"><tt>FLOAT</tt></i> ]
    [ <tt class="function">neighbors</tt> <i class="parameter"><tt>0</tt></i> | <i class="parameter"><tt>1</tt></i> ]
    [ <tt class="function">internal_collision</tt> <tt class="function">on</tt> | <tt class="function">off</tt> ]
    [ <tt class="function">damping</tt> <i class="parameter"><tt>FLOAT</tt></i> ]
    [ <tt class="function">intervals</tt> <i class="parameter"><tt>FLOAT</tt></i> ]
    [ <tt class="function">iterations</tt> <i class="parameter"><tt>INTEGER</tt></i> ]
    <tt class="function">input</tt> <i class="parameter"><tt>STRING</tt></i>
    [ <tt class="function">output</tt> <i class="parameter"><tt>STRING</tt></i> ]
    [ <tt class="function">mesh_output</tt> <i class="parameter"><tt>STRING</tt></i> ]
    [ <tt class="function">smooth_mesh</tt> <tt class="function">on</tt> | <tt class="function">off</tt> ]
    [ <tt class="function">uv_mesh</tt> <tt class="function">on</tt> | <tt class="function">off</tt> ]
  }</pre><p>
  </p><p>
    <tt class="function">environment</tt>   is followed by an object identifier. The object should be declared before <tt class="function">simcloth</tt> {}.
    This object defines the environment that will interact with the cloth. Although any object can be used, it is recommended
    to use objects which have well-defined interiors.
  </p><p>
    <tt class="function">friction</tt>  is a coefficient specifying energy loss when the cloth touches the environment.
    A low value (&lt;= 0) means a lot of friction and strongly slows the movement of the cloth.
    A high value (&gt;= 1) will allow the cloth to slide over the objects (but not to bounce off ...).
    Default value is 1.0
   </p><p>
     <tt class="function">gravity</tt>  Specifies the direction and the strength of gravity. The default value is &lt;0, 0, 0&gt;.
   </p><p>
     <tt class="function">wind</tt>  A pigment is used to define the direction and strength of the wind in every space location.
     At a given point, the wind is defined by the red, green and blue components of the pigment at this point.
     You can explicitly declare the pigment, or use an already declared identifier. Don't forget that the color
     components can take any value you want (negative ones, greater than one, ...)
   </p><p>
     <tt class="function">viscosity</tt>  Specifies the influence of the wind and air friction on the cloth. The default value
     is 0 (no influence).
   </p><p>
     <tt class="function">neighbors</tt>  Specifies the number of neighbors that are joined by springs at each point. <tt class="function">neighbors</tt> 0
     is for 8 neighbors (faster but rougher calculation), and <tt class="function">neighbors</tt> 1 (default value) is for 24 neighbors
     (slower calculation, but better results).
   </p><p>
     <tt class="function">internal_collision</tt>  Activates or deactivates internal collision management (cloth against itself). This
     problem is handled by added springs between points that are too close together. System instability probability
     is increased, and you must, most often, decrease the intervals parameter (see below). Deactivated by default
     (warning: much longer parsing when activated).
   </p><p>
     <tt class="function">damping</tt>  General energy loss parameter, it limits the accumulation of the model approximations and
     errors. A value lower than 0.95 (default value) is strongly recommended.
   </p><p>
     <tt class="function">intervals</tt>  specifies the time interval between each iteration. Keep it low. Default value is 0.05.
   </p><p>
     <tt class="function">iterations</tt>  It's the number of iterations to calculate.
   </p><p>
     <tt class="function">input</tt> Filename of the starting *.cth file. The only required parameter, since you need a cloth to start with.
     For a complete description of the *.cth file format, see below.
   </p><p>
     <tt class="function">output</tt>  Filename of the ending *.cth file. If this parameter is specified, the result of the simulation
     is saved. Useful for animations, or for a multi-stage calculation.
   </p><p>
     <tt class="function">mesh_output</tt>  Allow the program to output a file (with specified name), containing tons of triangles,
     corresponding to the cloth points after the simulation. It allows you to save the result of a simulation, in
     a format usable by other <span class="trademark">POV-Ray</span>&#8482; versions (official or unofficial).
   </p><p>
     <tt class="function">smooth_mesh</tt> Activate or deactivate the creation of smooth_triangle's if the mesh_output option is activated.
     Deactivated by default.
   </p><p>
     <tt class="function">uv_mesh</tt>  Activates or deactivates uv coordinates within the triangle (or smooth_triangle) if the mesh_output
     option is activated. UV coordinates go from  &lt;0, 0&gt; to &lt;1, 1&gt;. Deactivated by default.
   </p><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="id2527541"></a>2.4.3.1. Description of the .cth file format:</h4></div></div><div></div></div><p>
       The file format is simple: the first line describes the cloth dimensions (number of points <i class="parameter"><tt>n1</tt></i> and
       <i class="parameter"><tt>n2</tt></i>, normalized length between 2 neighbors <i class="parameter"><tt>nlng</tt></i>), and the springs strength
       <i class="parameter"><tt>ks</tt></i>. The other lines describe the location in space and velocity of each point. All values (3 for
       location, 3 for speed) are separated by commas, and each line is terminated by a comma as well.
     </p><p>
       Then, there are the constraints definitions. Constraints are 3 coefficients (1 for each axis) that will control
       the velocity vector of a given point of the cloth. It will be possible, for instance, to slow down a corner of the
       cloth along one axis, to completely stop it along another axis, and let it free along the last one. A constraint is
       defined by an integer (index), and 3 floating point coefficients, representing the constraint
       (respectively on x, y, z axis), all this on the same line and separated by commas. The index is the rank of the
       point (beginning at 0) in order of declaration of the cloth points. Constraints can be declared in any order.
     </p><p>
       You could see the cloth as 2 arrays of vectors Points[n1][n2], and Velocity[n1][n2], and its constraints
       <tt class="function">Index</tt><i class="parameter"><tt>n</tt></i>, <tt class="function">coef</tt><i class="parameter"><tt>n</tt></i>.
       The <tt class="filename">*.cth</tt> file will look like this:
     </p><pre class="programlisting">n1, n2, nlng, ks,
Points[0][0], Velocity[0][0],
Points[0][1], Velocity[0][1],
...
Points[0][n2-1], Velocity[0][n2-1],
Points[1][0], Velocity[1][0],
Points[1][1], Velocity[1][1],
...
Points[1][n2-1], Velocity[1][n2-1],
Points[2][0], Velocity[2][0],
...
...
Points[n1-1][n2-1], Velocity[n1-1][n2-1],
Index1, coef1[x], coef1[y], coef1[z],
Index2, coef2[x], coef2[y], coef2[z],
Index3, coef3[x], coef3[y], coef3[z],</pre><p>
      For an example of a macro writing such a file (see <a href="tutorials.html#writecloth" title="4.1.1.1.1. Writing a *.cth file">Section 4.1.1.1.1, &#8220;Writing a *.cth file&#8221;</a>).
    </p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="isosurface"></a>2.4.4. Isosurface</h3></div></div><div></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="iso_message"></a>2.4.4.1. Control of max gradient message</h4></div><div><div class="author"><h3 class="author"><span class="firstname">Yvo &amp; René</span> <span class="surname">Smellenbergh</span></h3></div></div></div><div></div></div><p>
	In <span class="trademark">POV-Ray</span>&#8482; 3.5 the messages concerning the <tt class="function">max_gradient</tt> follow a heuristic method to be displayed.
	This means that the message only appears when the difference with the set <tt class="function">max_gradient</tt> is more
	than a certain percentage. Also when using a loop with hundreds of isosurfaces which have different
	<tt class="function">max_gradient</tt>'s, you need to wait after the render for all those messages to be displayed: this can
	take several minutes. Basically, you cannot control these messages.
  </p><p>
	In MegaPOV 1.0 you can use the keyword <tt class="function">message</tt><a class="indexterm" name="id2524518"></a> to control the message flow:
	</p><div class="itemizedlist"><ul type="disc" compact><li><tt class="function">message</tt> <tt class="function">on</tt>  will always show all max_gradient messages</li><li><tt class="function">message</tt> <tt class="function">off</tt>  will never show a max_gradient message</li><li>without a <tt class="function">message</tt> keyword the default heuristic method will be used</li></ul></div><p>
	This keyword is used in the <tt class="function">isosurface</tt>{} block and should be used after the <tt class="function">function</tt>{} block and before any material.
  </p><p>
  By using conditional expressions, you can now control messages in a loop.
  </p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="light"></a>2.4.5. Light Sources</h3></div></div><div></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="area_light_mtl"></a>2.4.5.1. Area Light <tt class="function">max_trace_level</tt></h4></div><div><div class="author"><h3 class="author"><span class="firstname">Christoph</span> <span class="surname">Hormann</span></h3></div></div></div><div></div></div><p>
	Normally area lights are handled as area lights in all situations.  This means that 
  every shadow ray test against an area light source is sampled across the area of the 
  light source.  This patch allows to specify a <tt class="function">max_trace_level</tt> for the area 
  light which turns off the soft shadows above the specified trace level. 
  </p><p>Syntax is:
    <a class="indexterm" name="id2528712"></a>
    </p><pre class="synopsis"><tt class="function">light_source</tt> {
  <i class="parameter"><tt>LOCATION</tt></i>, <i class="parameter"><tt>COLOR</tt></i>
  [LIGHT_MODIFIERS...]
  <tt class="function">max_trace_level</tt> <i class="parameter"><tt>INTEGER</tt></i>
}</pre><p>
  </p><p>
    If you for example specify:
    </p><pre class="programlisting"><tt class="function">light_source</tt> {
  &lt;1.0,2.0,2.0&gt;
  color rgb 1.0
  area_light 0.5*x 0.5*y 9,9 jitter adaptive 1 circular orient
  <tt class="function">max_trace_level</tt> 1
}</pre><p>

    this will only result in soft shadows on directly visible surfaces.  In reflections, 
    refractions and radiosity the light source will be treated as a point light.
  </p></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="camera.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="references.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="effects.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">2.3. Camera </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 2.5. Effects</td></tr></table></div></body></html>
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