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+<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
+<html>
+<head>
+   <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
+   <meta name="Author" content="Mark Danks">
+   <meta name="Author" content="IOhannes m zmölnig">
+   <title>Texture mapping</title>
+</head>
+<body>
+
+<center>
+<h2>
+<u>Texture Mapping</u></h2></center>
+<a href="Gloss.html#Texture">Texture mapping</a> is the act of applying
+pixel data to a geometric object.  In GEM, this is achieved with the
+<i>[pix_texture]</i>
+object.  It is important to understand that the
+<i>[pix_texture]</i>
+object merely sets the pix as the current texture.  It does not do
+any rendering!  You need to use a geo object which does texture mapping. 
+All of the basic geo objects can texture map, such as <i>[square]</i> or
+<i>[sphere]</i>.
+<p><img SRC="tribar.gif" height=13 width=561>
+<p>A simple example of texture mapping is the following patch:
+<center>
+<p><img SRC="texture.jpg" BORDER=1 height=182 width=160></center>
+
+<p>This patch can be found at 07.texture/01.texture.pd.  Change
+the number box connected to the rotate object to see what a texture map
+on a cube looks like.
+<p>The <i>[pix_image]</i> object loads in the fractal image file.  The
+<i>[pix_texture]</i>
+object says that the pix data should be used as a texture map.  Notice
+that this is different than the previous manual section when we used the
+<i>[pix_draw]</i> object.  The final object in the chain is the <i>[cube]</i>
+object.  Because we have enabled texture mapping with the <i>[pix_texture]</i>
+object, the cube takes the pix data and applies it to the geometry.
+<p><img SRC="tribar.gif" height=13 width=561>
+<p>Texture mapping can be used with any GEM object.  In the previous
+manual section, you saw how to load in pix data with a variety of objects,
+including <i>[pix_multiimage]</i> and <i>[pix_video]</i>.  All of these
+objects can be used with the <i>[pix_texture]</i> object.
+<p>Because the pix data is applied to geometry, you can move, rotate, and
+scale the image.  This is extremely useful on the <i>[square]</i> object. 
+Instead of doing a one-to-one pixel mapping as occurs with the <i>[pix_draw]</i>
+object, you can resize and reshape the image.
+<p>OpenGL originally required that images must have dimensions that are power-of-2, such as 64, 128, or 256. This restriction has been released with recent gfx-cards
+(like some radeon/nvidia products).
+However, if the width or height of an image is not a power of two,
+then the <i>[pix_texture]</i> object will take care of this, 
+and still render it (depending on you hardware with some tricks).
+You can thus texture images of any size, but since this is based on tricking 
+the texture-coordinates, <i>[pix_coordinate]</i> might not give the wanted result any more.
+<p><img SRC="tribar.gif" height=13 width=561>
+<p>The example patch 07.texture/02.moveImages.pd is a much more complex
+patch which uses alpha blending to create a transparent object, in this
+case, the dancer.  Make sure to turn on the rotation with the <i>[metro]</i>
+object.
+<p><img SRC="tribar.gif" height=13 width=561><a href="index.html"></a>
+<p>People have been asking how textures are handled in GEM.  Here
+is a long explanation from an email which I wrote.
+<p><tt>  Here is how textures are dealt with under OpenGL and hardware
+accelerators.  This can obviously change in the future, but right
+now, I am fairly certain that the info is correct (I make games in my day
+job, so I have vested interest in this :-)</tt><tt></tt>
+<p><tt>  The amount of memory (VRAM) on the card (12mb for Voodoo2,
+16mb for TNT, 64mb for GeForce2, etc) is used for both textures (TRAM)
+and frame buffer space.  If you have a large rendering window, like
+1600x1200, it will take up 1600x1200x4x3 in 32-bit mode with double buffering
+and a Z buffer (or 23mb).  Most people run at TV resolution, like
+NTSC, so it takes 640x480x4x3 = 3.7mb   All of the space left
+is for textures onboard the card (FYI, if you have heard that people are
+having problems with the PlayStation2, notice that it only has 4mb of VRAM...not
+much onboard texture space, huh? :-)  Thankfully it has an <i>extremely</i>
+fast DMA bus)</tt><tt></tt>
+<p><tt>  Sooo, when GEM "creates" a texture, it immediately tries
+to send the texture to the card, which uses some of the left over space
+in the VRAM.  If you had a 640x480 window on a Voodoo2, you have ~8mb
+of texture space left over.  On a GeForce2, ~60mb.  The problem
+is what happens if you want more textures than can fit into TRAM. 
+OpenGL requires that the video drivers deal with the problem, so GEM doesn't
+care too much (more about this later).</tt><tt></tt>
+<p><tt>  In most cases, the drivers cache the textures in main memory
+and if a texture is requested for rendering and it isn't resident on the
+card, it will download it.  If you have AGP, then this is pretty quick,
+although none of 3dfx cards really take advantage of this (ie, those cards
+are about the same speed as the PCI bus).  So depending on the number
+of textures, and how complex the scene is, you might be able to display
+more textures than you have TRAM.</tt><tt></tt>
+<p><tt>  One slowdown that can happen with GEM is that it makes a
+copy of the image before sending it down the chain of objects.  If
+you are constantly changing images with a pix_multiimage, this can be a
+performance hit, but you can modify the actual pixel data with the pix
+objects.  The pixels aren't sent to the graphics card until the pix_texture
+object is reached.</tt><tt></tt>
+<p><tt>  GEM tries to help with this with a few objects.  pix_imageInPlace
+acts much the same as pix_multiimage, but it downloads _every_ image in
+the sequence to the card when a download message is recieved.  It
+also immediately turns on texturing, instead of making a copy (ie, you
+don't need a pix_texture object).  Much faster, but not as flexible. 
+pix_movie does much the same thing.  It sends the pixel data without
+copying it if there is a new frame to display.</tt><tt></tt>
+<p><tt>  The entire pix system uses a caching system so that the copying
+and processing only occurs if something actually changes.  For example,
+if you had a pix_threshold object, it would only process when rendering
+started...and every time that the values actually changed.  You can
+use pix_buf to isolate parts which don't change from those that do, but
+it involves another copy.</tt><tt></tt>
+<p><tt>  On the Voodoo2, the hardware itself limits textures to 256x256...this
+will never change.  The newest Voodoo5 boards have a higher texture
+size.</tt><tt></tt>
+<p><tt>  If you load the _exact_ same image (this means the exact
+same file/path name), then the pix_image has a cache system which means
+that it is only loaded into the</tt>
+<br><tt>computers memory once.  However, each pix_image still sends
+its own copy down to the gfx card.</tt><tt></tt>
+<p><tt>  You could use a single [pix_image]/[pix_texture] with [separator]
+to do this...I have done it a lot in the past.</tt><tt></tt>
+<p><tt>  The reason that [pix_image] doesn't share the actual texture
+data is that you can modify the pixel data with other pix objects...[pix_image]
+doesn't actually send the texture data to the gfx card, [pix_texture] does.</tt>
+<p><img SRC="tribar.gif" height=13 width=561><a href="index.html"></a>
+<p><a href="index.html">[return]</a>
+<br> 
+</body>
+</html>