Knowledgebase:Language Questions and Tips - Revision history

Warp at 12:16, 3 January 2012

2012-01-03T12:16:48Z

Warp: Changed reference to the obsolete targa averager to ImageMagick.

2012-01-03T12:14:47Z

Changed reference to the obsolete targa averager to ImageMagick.

Jholsenback: wording and addition

2011-02-24T00:28:28Z

wording and addition

Jholsenback: who cares

2010-06-04T10:21:55Z

who cares

Jholsenback: addition

2010-06-03T21:00:04Z

addition

StephenS: scaned for dead links

2010-04-28T01:12:55Z

scaned for dead links

Jholsenback: fixed typo as well

2010-04-09T11:14:25Z

fixed typo as well

Jholsenback: fixed html tag error

2010-04-09T11:12:29Z

fixed html tag error

StephenS: Update megapov web site, topic 6

2010-03-23T02:44:27Z

Update megapov web site, topic 6

Jholsenback: fixed tag typo

2010-03-21T11:07:42Z

fixed tag typo

@@ Line 92: / Line 92: @@
 <p class="Question">How can I simulate motion blur in POV-Ray?</p>
 <p>The official POV-Ray 3.7 doesn't support motion blur calculations, but there are some patched versions which do. (eg. the so-called MegaPov, which at the time of writing this documentation was still based on POV-Ray 3.5 code). See the [http://megapov.inetart.net MegaPov] site.</p>
-<p>You can also use other tools to make this. One way to simulate motion blur is calculating a small animation and then averaging the images together. This averaging of several images can be made with third party programs, such as [http://en.wikipedia.org/wiki/Imagemagick ImageMagick]. (<code>convert -average *.png output.png</code>)</p>
+<p>You can also use other tools to make this. One way to simulate motion blur is calculating a small animation and then averaging the images together. This averaging of several images can be made with third party programs, such as [http://en.wikipedia.org/wiki/Imagemagick ImageMagick]. (<code>convert -average frame*.png output.png</code>)</p>
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 <p class="QTNavBar">End of Topic: [[KB:POV-Ray Questions and Tips#Tips and tricks to achieve useful things:|Go Back to the Table of Contents]]</p>

@@ Line 92: / Line 92: @@
 <p class="Question">How can I simulate motion blur in POV-Ray?</p>
 <p>The official POV-Ray 3.7 doesn't support motion blur calculations, but there are some patched versions which do. (eg. the so-called MegaPov, which at the time of writing this documentation was still based on POV-Ray 3.5 code). See the [http://megapov.inetart.net MegaPov] site.</p>
-<p>You can also use other tools to make this. One way to simulate motion blur is calculating a small animation and then averaging the images together. This averaging of several images can be made with third party programs, such as the [http://iki.fi/warp/PovUtils/average/ Targa Averager] program.</p>
+<p>You can also use other tools to make this. One way to simulate motion blur is calculating a small animation and then averaging the images together. This averaging of several images can be made with third party programs, such as [http://en.wikipedia.org/wiki/Imagemagick ImageMagick]. (<code>convert -average *.png output.png</code>)</p>
 <p class="QTSpacer"></p>
 <p class="QTNavBar">End of Topic: [[KB:POV-Ray Questions and Tips#Tips and tricks to achieve useful things:|Go Back to the Table of Contents]]</p>

@@ Line 398: / Line 398: @@
 </pre>
 <p>The top surface of the first box is coincident with the top surface of the second box. When a ray hits this area, POV-Ray has to decide which surface is closest. It can't, since they are exactly in the same place. Which one it actually chooses depends on the float number calculations, rounding error, initial parameters, position of the camera, etc, and varies from pixel to pixel, causing those seemingly ''random'' pixels.</p>
-<p>The solution to the problem is to decide which surface you want to be on top and translate that surface just a bit, so it protrudes past the unwanted surface. In the example above, if we want, for example, that the second box is at the top, we will type something like:</p>
+<p>One solution to the problem is to decide which surface you want to be on top and translate that surface just a bit, so it extends slightly past the unwanted surface. For example, if the second box should be the top surface:</p>
 <pre>
 union
@@ Line 405: / Line 405: @@
+}
 </pre>
-<p class="Note">'''Note:''' that a similar problem appears when a light source is exactly on a surface: POV-Ray can't calculate accurately if it's actually inside or outside the surface, so dark (shadowed) pixels appear on every surface that is illuminated by this light.</p>
+<p>Scaling an object by a small amount using either <code>scale 1.0001</code> or <code>scale 0.9999</code> also works in certain situations.</p>
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 <p class="QTNavBar">End of Topic: [[KB:POV-Ray Questions and Tips#Things that don't work as one expects:|Go Back to the Table of Contents]]</p>

@@ Line 586: / Line 586: @@
 <p>The vector given as parameter to this keyword defines a direction. In theory any (non-zero) vector is ok. What POV-Ray does is that when it needs to know whether a certain point is inside the mesh or not, it shoots a ray from this point to the direction defined by this vector and then counts how many triangles of the mesh the ray hits. If the ray hits an odd number of triangles, POV-Ray assumes the point is inside the mesh, else outside.</p>
 <p>In theory it wouldn't be necessary for the user to give a specific vector. POV-Ray could just internally create some random vector. However, the reason why the user is given the option of defining the vector himself is that this algorithm might not be absolutely flawless in all cases. For example, if the vector happens to have the exact same direction as the tangent of a triangle, or if the rays happen to hit lots of edges of the mesh, the CSG operation might suffer from some jittering at some places due to the limited accuracy of floating point numbers (not asimilar to what happens with the infamous coincident-surfaces problem). If this would happen, changing the direction of the <code>inside_vector</code> a bit may well fix the problem.</p>
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@@ Line 587: / Line 587: @@
 <p>In theory it wouldn't be necessary for the user to give a specific vector. POV-Ray could just internally create some random vector. However, the reason why the user is given the option of defining the vector himself is that this algorithm might not be absolutely flawless in all cases. For example, if the vector happens to have the exact same direction as the tangent of a triangle, or if the rays happen to hit lots of edges of the mesh, the CSG operation might suffer from some jittering at some places due to the limited accuracy of floating point numbers (not asimilar to what happens with the infamous coincident-surfaces problem). If this would happen, changing the direction of the <code>inside_vector</code> a bit may well fix the problem.</p>
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--scaned for dead links [[User:StephenS|StephenS]] 01:12, 28 April 2010 (UTC)
+<p class="QTNavBar">End of Topic: [[KB:POV-Ray Questions and Tips#Other related things:|Go Back to the Table of Contents]]</p>
 <p class="QTNavBar">End of Section: [[KB:POV-Ray Questions and Tips#Other related things:|Go Back to the Table of Contents]]</p>

@@ Line 239: / Line 239: @@
 <p>Also note that this exact same trick can be used to get blurred refraction. It's also possible to get uneven blur, eg. the reflection is blurred more in the x-axis direction than in the other directions (this is achieved by scaling the normals unevenly), and countless variations of this (eg. the amount and direction of the blur may vary throughout the surface of the object) which makes this trick even more powerful than the reflection blur in MegaPov.
 </p>
-<p>If you also want to use a normal modifier in the object in addition to the blurred reflection, you can add it to the <code>normal</code>-block as an averaged normal map or similar, for example like this:</p>
+<p>If you also want to use a normal modifier in the object in addition to the blurred reflection, you can add it to the <code>normal</code> block as an averaged normal map or similar, for example like this:</p>
 <pre>
     normal

@@ Line 370: / Line 370: @@
 </pre>
 <p>This keyword can also be used to change the handedness of POV-Ray (see the question about [[KB:Moray#Topic 1|Moray and POV-Ray handedness]] for more details).</p>
-<p class="Note">'''Note:''' One could think "Why doesn't POV-Ray always set automatically the aspect ratio of the camera according to the resolution&nbsp;of&nbsp;the&nbspimage?".</p>
+<p class="Note">'''Note:''' One could think "Why doesn't POV-Ray always set automatically the aspect ratio of the camera according to the resolution&nbsp;of&nbsp;the&nbsp;image?".</p>
 <p>It is actually not a good idea to automatically set the aspect ratio of the camera (assuming square pixels) for reasons described below. Note, however, that it would be possible to automatize this using the <code>image_width</code> and <code>image_height</code> keywords, like this:</p>
 <pre>camera