160 lines
5.4 KiB
HTML
160 lines
5.4 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML>
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<HEAD>
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<TITLE>Interform Procedural Textures</TITLE>
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<LINK type="text/css" rel="stylesheet" href="../webdocs.css">
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</HEAD>
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<BODY>
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<H1>Interform Procedural Textures</H1>
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<P>The interform procedural texture generates a texture from
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two color index maps and a palette. The effect varies, but is
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usually used for bubbling or flowing effects. It is highly
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recommended that you play with the interform procedure explorer
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in Kai's Power Tools before trying to make interform textures
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of your own.</P>
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<PRE class="syntax">
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<B>ATD1</B>
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<B>type = interform</B>
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<B>width =</B> <I>integer</I>
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<B>height =</B> <I>integer</I>
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<B>palette =</B> <I>filename</I>
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<B>mother =</B> <I>filename</I>
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<B>mother_move =</B> <I>string</I> (optional)
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<B>mother_vx =</B> <I>float</I> (optional, for scrolling)
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<B>mother_vy =</B> <I>float</I> (optional, for scrolling)
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<B>mother_speed =</B> <I>float</I> (optional, for wander)
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<B>mother_rate =</B> <I>float</I> (optional, for wander)
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<B>mother_strength =</B> <I>float</I> (optional, for wander)
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<B>father =</B> <I>filename</I>
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<B>father_move =</B> <I>string</I> (optional)
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... (other options same as for mother image)
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</PRE>
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<H4>Parameters</H4>
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<DL>
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<DT><I>width</I></DT>
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<DD>Width of the texture, must be a power of two.</DD>
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<DT><I>height</I></DT>
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<DD>Height of the texture, must be a power of two.</DD>
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<DT><I>palette</I></DT>
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<DD>Filename of the image from which the color palette is
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derived. The image must be a 24-bit PNG file that is exactly
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256 pixels wide and at least one pixel high. This allows for
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easy creation of palettes using the gradient tool in
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Photoshop. The top line of the image becomes the interform
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palette.</DD>
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<DT><I>mother</I></DT>
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<DD>Filename of the first source color map, which must be an
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8-bit PNG file that is at least as large as the output size,
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but not necessarily a power of two. For your own convenience,
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it is recommended to be a greyscale file, rather than merely
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8-bit paletted, so you can more easily think of the file as a
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color MAP rather than having colors. See remarks section
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below.</DD>
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<DT><I>mother_move</I></DT>
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<DD>
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Determines how the mother image moves. Can be one of the
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following values (more can be added upon request):
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<TABLE summary="interform move types">
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<TR>
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<TH>string</TH>
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<TH>Description</TH>
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</TR>
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<TR>
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<TD><B>none</B></TD>
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<TD>No movement whatsoever. This is the default
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value.</TD>
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</TR>
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<TR>
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<TD><B>scroll</B></TD>
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<TD>Scroll the texture continuously with speeds
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specified by <B>mother_vx</B> and <B>mother_vy</B>.
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These values are in texture units per second. For
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example, if you have −1.0 for <B>mother_vx</B>
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and 0.5 for <B>mother_vy</B> then after one second, the
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mother will have scrolled its entire width to the left
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and half its height upwards.</TD>
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</TR>
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<TR>
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<TD><B>wander</B></TD>
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<TD>Scroll the texture in a random direction but change
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the direction of travel over time. The scrolling speed
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is controlled by <B>mother_speed</B>, the amount of
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change in direction is controlled by <B>
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mother_rate</B>, and the strength of the steering force
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is controlled by <B>mother_strength</B>. Note that
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these are all optional values and do not need to be
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specified.</TD>
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</TR>
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</TABLE>
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</DD>
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</DL>
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<H4>Remarks</H4>
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<P>The interform procedural texture takes two color maps, the
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mother and father, averages the values of corresponding pixels
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and uses that value as a lookup into a palette. By constantly
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moving the color maps around, very interesting effects can be
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created. Keep in mind that when you are creating the color
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maps, you are not creating two greyscale images that are going
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to be blended together in any normal way.</P>
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<P>It is recommended for the best interform effects that the
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mother and father textures are "smooth" textures where the
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index value does not vary too quickly between successive
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pixels. Interform textures sometimes have a tendency to look
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blocky and pixellated, otherwise.</P>
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<H4>Advanced OpenGL Parameters</H4>
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<DL>
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<DT><I>internal format</I></DT>
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<DD>GL_RGB</DD>
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<DT><I>GL_TEXTURE_MIN_FILTER</I></DT>
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<DD>GL_LINEAR (no mipmapping, bilinear interpolation)</DD>
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<DT><I>GL_TEXTURE_MAG_FILTER</I></DT>
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<DD>GL_LINEAR (bilinear interpolation)</DD>
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</DL>
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<H4>Examples</H4>
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<P>No examples are presented here because it is rather
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difficult to capture the interform effect without many frames
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in an animated GIF and I have a lot of tasks on my list to do.
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Please take a look around <B>map joeyproc</B> for a variety of
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example interform textures.</P>
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</BODY>
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</HTML>
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