Difference between revisions of "Documentation Talk:Tutorial Section 3"

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<p>
 
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First, we would like to digress a moment to talk about the difference
 
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between a lathe and a surface of revolution object (SOR). The SOR object,
 
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described in a separate tutorial, may seem terribly similar to the lathe at
 
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first glance. It too declares a series of points and connects them with
 
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curving lines and then rotates them around the y-axis. The lathe has
 
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advantages, such as linear, quadratic, cubic and bezier spline support. </p>
 
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<p>
 
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Plus, the simpler mathematics used by a SOR does not allow the curve to double
 
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back over the same y-coordinates, thus, if using a SOR, any sudden twist
 
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which cuts back down over the same heights that the curve previously covered
 
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will trigger an error. For example, suppose we wanted a lathe to arc up from
 
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&lt;0,0&gt; to &lt;2,2&gt;, then to dip back down to &lt;4,0&gt;. Rotated
 
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around the y-axis, this would produce something like a gelatin mold - a
 
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rounded semi torus, hollow in the middle. But with the SOR, as soon as the
 
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curve doubled back on itself in the y-direction, it would become an illegal
 
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declaration.</p>
 
  
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* picked up suggested changes -- [[User:Jholsenback|jholsenback]]
+
* Jim, Thanks for making the earlier update. I noticed another place in the prism part of the tutorial where we should mention the bezier spline.
 +
 
 +
* Where we today have:
 +
 
 +
=====Teaching An Old Spline New Tricks=====
 +
<p>If we followed the section on splines covered under the lathe tutorial
 +
(see the section <!--<linkto "Understanding The Concept of Splines">Understanding The Concept of Splines</linkto>--->[[Documentation:Tutorial Section 3#Understanding The Concept of Splines|Understanding The Concept of Splines]]), we know that
 +
there are two additional kinds of splines besides linear: the quadratic and
 +
the cubic spline. Sure enough, we can use these with prisms to make a more
 +
free form, smoothly curving type of prism.</p>
 +
 
 +
* I think it should read:
 +
 
 +
=====Teaching An Old Spline New Tricks=====
 +
<p>If we followed the section on splines covered under the lathe tutorial
 +
(see the section <!--<linkto "Understanding The Concept of Splines">Understanding The Concept of Splines</linkto>--->[[Documentation:Tutorial Section 3#Understanding The Concept of Splines|Understanding The Concept of Splines]]), we know that
 +
there are three additional kinds of splines besides linear: the quadratic,
 +
the cubic and the bezier spline. Sure enough, we can use these with prisms to make a more
 +
free form, smoothly curving type of prism.</p>
 +
 
 +
 
 +
 
 +
* And one more which now reads:
 +
 
 +
====Prism Object====
 +
<p>The prism is essentially a polygon or closed curve which is swept along a
 +
linear path. We can imagine the shape so swept leaving a trail in space, and
 +
the surface of that trail is the surface of our prism. The curve or polygon
 +
making up a prism's face can be a composite of any number of sub-shapes,
 +
can use any kind of three different splines, and can either keep a constant
 +
width as it is swept, or slowly tapering off to a fine point on one end. But
 +
before this gets too confusing, let's start one step at a time with the
 +
simplest form of prism. We enter and render the following POV code (see file
 +
<code>prismdm1.pov</code>).</p>
 +
 
 +
* that I think should read:
 +
 
 +
====Prism Object====
 +
<p>The prism is essentially a polygon or closed curve which is swept along a
 +
linear path. We can imagine the shape so swept leaving a trail in space, and
 +
the surface of that trail is the surface of our prism. The curve or polygon
 +
making up a prism's face can be a composite of any number of sub-shapes,
 +
can use any kind of four different splines, and can either keep a constant
 +
width as it is swept, or slowly tapering off to a fine point on one end. But
 +
before this gets too confusing, let's start one step at a time with the
 +
simplest form of prism. We enter and render the following POV code (see file
 +
<code>prismdm1.pov</code>).</p>

Latest revision as of 16:05, 24 May 2016

  • Jim, Thanks for making the earlier update. I noticed another place in the prism part of the tutorial where we should mention the bezier spline.
  • Where we today have:
Teaching An Old Spline New Tricks

If we followed the section on splines covered under the lathe tutorial (see the section Understanding The Concept of Splines), we know that there are two additional kinds of splines besides linear: the quadratic and the cubic spline. Sure enough, we can use these with prisms to make a more free form, smoothly curving type of prism.

  • I think it should read:
Teaching An Old Spline New Tricks

If we followed the section on splines covered under the lathe tutorial (see the section Understanding The Concept of Splines), we know that there are three additional kinds of splines besides linear: the quadratic, the cubic and the bezier spline. Sure enough, we can use these with prisms to make a more free form, smoothly curving type of prism.


  • And one more which now reads:

Prism Object

The prism is essentially a polygon or closed curve which is swept along a linear path. We can imagine the shape so swept leaving a trail in space, and the surface of that trail is the surface of our prism. The curve or polygon making up a prism's face can be a composite of any number of sub-shapes, can use any kind of three different splines, and can either keep a constant width as it is swept, or slowly tapering off to a fine point on one end. But before this gets too confusing, let's start one step at a time with the simplest form of prism. We enter and render the following POV code (see file prismdm1.pov).

  • that I think should read:

Prism Object

The prism is essentially a polygon or closed curve which is swept along a linear path. We can imagine the shape so swept leaving a trail in space, and the surface of that trail is the surface of our prism. The curve or polygon making up a prism's face can be a composite of any number of sub-shapes, can use any kind of four different splines, and can either keep a constant width as it is swept, or slowly tapering off to a fine point on one end. But before this gets too confusing, let's start one step at a time with the simplest form of prism. We enter and render the following POV code (see file prismdm1.pov).

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