mirror of
https://github.com/dhewm/iddevnet.git
synced 2024-11-21 12:01:18 +00:00
244 lines
10 KiB
HTML
244 lines
10 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN">
|
||
<!-- saved from url=(0043)https://www.iddevnet.com/doom3/bumpmaps.php -->
|
||
<html><head><meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
|
||
<title>id.sdk [Bump Maps]</title>
|
||
<link rel="stylesheet" href="style.css">
|
||
</head>
|
||
|
||
|
||
<body marginwidth="0" marginheight="0" topmargin="0" leftmargin="0">
|
||
|
||
<table border=0 cellpadding=0 cellspacing=0 style="width: 100%; height: 99px">
|
||
<tr>
|
||
<td style="width: 171px"><img src="images/doom.jpg" style="width: 171px; height: 99px" alt=""></td>
|
||
<td style="background: url(images/tile.gif)">
|
||
<table border=0 cellpadding=0 cellspacing=0 width=600>
|
||
<tr>
|
||
<td style="height: 19px; background: url(images/sdk.gif) no-repeat"></td>
|
||
<td rowspan=4 align=right><img src="images/id.gif" style="width: 42px; height: 99px" alt=""></td>
|
||
</tr>
|
||
<tr><td style="height: 29px; background: url(images/top.jpg) no-repeat"></td></tr>
|
||
<tr><td style="height: 27px; background: url(images/middle.gif)" class="title"> Making DOOM 3 Mods : Bump Maps</td></tr>
|
||
<tr><td style="height: 24px; background: url(images/bottom.jpg) no-repeat"></td></tr>
|
||
</table>
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
<table border=0 cellpadding=0 cellspacing=0 style="width: 770px">
|
||
<tr>
|
||
<td colspan=2 style="background: url(images/boxtop.gif);"><img src="images/span.jpg" style="width: 397px; height: 20px; float: left" alt=""></td>
|
||
</tr>
|
||
<tr>
|
||
<td style="vertical-align: top; width: 152px; background: url(images/tileleft.gif)">
|
||
<div class="leftMenu">
|
||
<script src="menu.js"></script>
|
||
</div>
|
||
</td>
|
||
<td class="mainContent">
|
||
|
||
Most of this was taken from a document written by John Carmack some time ago,
|
||
it was so good I decided to just copy it in here verbatim -- Brian
|
||
|
||
<div class="subsection">Bump Mapping in DOOM</div>
|
||
|
||
<p>
|
||
Virtually all geometric surface detail should be represented
|
||
in bump maps instead of drawn into the diffuse maps in the conventional
|
||
style. This allows a single texture to take on different characteristics
|
||
based on it<69>s interaction with lights.
|
||
|
||
</p><p>
|
||
Two types of images can be used for bump mapping: height maps and normal maps.
|
||
|
||
</p><p>
|
||
A height map is a gray scale image, with black being the
|
||
farthest distance away and white being the closest. An addition scale parameter
|
||
is required when using height maps to determine how deep the image is supposed to be.
|
||
You can<61>t properly cut and paste image fragments between height maps with different
|
||
scale values without distorting the shading. You can add, subtract, airbrush, or
|
||
smooth gray values by hand on a height map with predictable results.
|
||
|
||
</p><p>
|
||
</p><center><img src="images/bumpmaps_a.png" title="techpanel"></center>
|
||
|
||
<p>
|
||
A local normal map encodes the actual perturbation angle of the surface at each point
|
||
in the RGB color, so it is complete by itself without any scaling parameters. You can
|
||
cut and paste between any normal maps without problems, but you can<61>t reasonably modify
|
||
the angles of normal map surfaces by hand, or create one from scratch. Smoothing a
|
||
normal map works reasonably well in practice, although it does result in denormalized
|
||
pixel values.
|
||
|
||
</p><p>
|
||
The normal vector is encoded as <span class="">( ( R-128 ) / 128, ( G-128 ) / 128, ( B-128 ) / 128 )</span>,
|
||
so a normal pointing straight up ( 0, 0, 1 ) would be encoded as ( 128, 128, 255 ) in the image.
|
||
Most local normal maps will be primarily bluish, because most of the vectors will be pointing
|
||
up more strongly than any other direction.
|
||
|
||
</p><p>
|
||
</p><center><img src="images/bumpmaps_b.png" title="technormal"></center>
|
||
|
||
<p>
|
||
Renderbump is also capable of generating "global normal maps", which encode an absolute direction
|
||
in object space, instead of in local surface space, but global maps cannot be deformed or
|
||
used on different wall orientations in the same object. They have some minor quality and performance
|
||
benefits, so we might wind up using them for some static objects later, but the
|
||
support has been disabled for a while.
|
||
|
||
</p><p>
|
||
Height maps must be converted to normal maps at load time,
|
||
so it is usually superior to use normal maps unless you need to manually create
|
||
or manipulate the image in a way that is easier with height maps.
|
||
|
||
</p><p>
|
||
You can<61>t make a perfectly smooth slope in a height map because of the limited precision
|
||
in the gray scale image. This results in shaded streaks along the slope, especially with
|
||
higher resolution height maps. You may be able to hide that by adding some waviness to
|
||
the surface manually.
|
||
|
||
</p><div class="subsection">Using Bump Maps</div>
|
||
|
||
<p>
|
||
Every surface that interacts with light will have a normal map.If one isn<73>t specified,
|
||
it will default to "_flat", an internally generated normal map with no changes. There
|
||
is currently no speed benefit to not having a normal map, although it might be possible
|
||
to add a fast path for that in the future.
|
||
|
||
</p><p>
|
||
Most materials can be specified in the "shortcut" form, where you specify the diffusemap,
|
||
specularmap, and bumpmap, and let the engine generate the full stages for it.
|
||
|
||
</p><pre class="code">textures/doom/techpanel
|
||
{
|
||
qer_editorimage ase/techpanel.tga
|
||
diffusemap ase/techpanel_diffuse.tga
|
||
specularmap ase/techpanel_specular.tga
|
||
bumpmap ase/techpanel_local.tga
|
||
}
|
||
</pre>
|
||
|
||
<p>
|
||
If diffusemap<span class="GramE"> is nor specified, it defaults to a solid white image.<span style="mso-spacerun:yes"> If specularmap is
|
||
not specified, specular lighting will be disabled for
|
||
that surface, giving a speedup.
|
||
|
||
</span></span></p><p>If you need to perform any shader
|
||
system operations, like animation or scrolling, you will have to write the
|
||
stages out separately:
|
||
|
||
|
||
|
||
</p><p>
|
||
"Testbump <image name>" Uses the specified normal map on every surface in
|
||
the world. If you want to test a heightmap, you must use an image program
|
||
and scale factor to convert it to a normal map: "TestBump heightmap( bumpmaps/squiggle.tga, 4 )"
|
||
|
||
</p><p>You can modify the lighting calculations to examine the bump
|
||
mapping under different conditions:
|
||
|
||
</p><p>
|
||
"r_skipSpecular <0 or 1>"<br>
|
||
"r_skipDiffuse <0 or 1>"<br>
|
||
|
||
</p><div class="subsection">Renderbump</div>
|
||
|
||
<p>
|
||
The renderbump tools generate normal maps directly from detailed polygonal geometry.
|
||
The high poly count models will be tens of thousands to hundreds of thousands of
|
||
triangles, while the geometry that will use the normal maps can be either simple flat
|
||
brush sides, or game character level geometry of around two thousand triangles.
|
||
|
||
</p><p>
|
||
The alpha channel of the normal map will contain a mask if there were areas in the
|
||
map that did not directly map to geometry. This can be copied to a diffuse map to use
|
||
with the alpha test option for per-pixel opacity. Note that if you use the normal map as
|
||
a template for the specular map, you should explicitly clear or remove the alpha channel,
|
||
because it will prevent more efficient compression forms from being used.
|
||
|
||
</p><p>
|
||
The generated image will be saved to the game basepath.
|
||
|
||
</p><p>
|
||
There are two forms, both integrated in the main DOOM executable.
|
||
|
||
</p><p>
|
||
<b>Flat RenderBump</b>
|
||
|
||
</p><p>
|
||
</p><pre class="code">RenderBumpFlat [-size <width> <height>] <modelfile></pre>
|
||
|
||
<p>
|
||
Size defaults to 256 by 256 if not specified.
|
||
|
||
This version generates normal maps suitable for mapping on surfaces like standard textures.
|
||
The modelfile should hold a set of triangles that make a generally 2D surface in the XZ plane,
|
||
with the front side facing down negative Z. The modelFile does not need to have texture
|
||
coordinates, but you should save it with normals if you don<6F>t want the entire thing smooth shaded.
|
||
|
||
</p><p>
|
||
The generated normal map will be saved to "<modelFile>_local.tga".
|
||
|
||
</p><p>
|
||
RenderBumpFlat uses the graphics accelerator to draw the normal maps, which makes it very fast,
|
||
but imposes a couple restrictions. You cannot create an image of higher resolution than the screen,
|
||
and you shouldn<64>t drag another window over the working window while it is rendering.
|
||
|
||
</p><p>
|
||
RenderBumpFlat automatically performs 16x oversampling, so the resulting image should be sufficiently anti-aliased.
|
||
|
||
</p><p>
|
||
<b>General RenderBump</b>
|
||
|
||
</p><p>
|
||
</p><pre class="code">renderBump <lowPolyModel></pre>
|
||
|
||
The renderbump command is used to generate a normal map for a non-flat surface like the surface of a character model in the game.
|
||
<p>
|
||
The parameters for renderbump are specified in the materials applied to the surfaces of the low detail model
|
||
|
||
</p><p>
|
||
</p><pre class="code">renderBump [-size <width> <height>] [-aa <0/1/2>]<br> [-trace <0.01 - 1.0>] <normalMapImage> <highPolyModel></pre>
|
||
|
||
<p>
|
||
Size defaults to 256 by 256 if not specified.
|
||
|
||
</p><p>
|
||
AA defaults to 1 if not specified.
|
||
|
||
</p><p>
|
||
Trace defaults to 0.05 if not specified.
|
||
|
||
</p><p>
|
||
The AA setting determines how much anti-aliasing will be done. The default level
|
||
of one gives 4x anti-aliasing, while level 2 gives 16x and level 0 gives 1x.
|
||
|
||
</p><p>
|
||
The trace setting determines how far off of the low poly
|
||
surface that a ray cast will look for triangles in the high poly surface.
|
||
It is expressed in fractions of the largest bounding axis. Tracing speed goes down
|
||
rapidly as this is increased, but if your high poly geometry isn<73>t showing up
|
||
in the normal map, you may need to increase this to 0.1 or more. The best solution is
|
||
to try very hard to have the low poly version be a very close match to the high poly version.
|
||
|
||
</p><p>
|
||
The lowPolyModel must have texture coordinates on it, and care should be taken to make
|
||
sure the mapping is as good as possible. Before doing a RenderBump, test the model in
|
||
the game with "r_showTexturePolarity 1" and "r_showEdges 1". Make sure that there aren<65>t any
|
||
texture seams that aren<65>t absolutely necessary, and that there are no overlapped texture projections.
|
||
|
||
<br>
|
||
</p></td>
|
||
</tr>
|
||
<tr>
|
||
<td colspan="2" bgcolor="#CCCCCC"><img src="images/span2.gif" style="width: 397px; height: 8px; float: left;"></td>
|
||
</tr>
|
||
</tbody></table>
|
||
|
||
<table border="0" cellpadding="0" cellspacing="0" width="770">
|
||
<tbody><tr>
|
||
<td align="left" class="legalese">Copyright <20> 2004 <a href="http://www.idsoftware.com/">id software</a></td>
|
||
</tr>
|
||
</tbody></table>
|
||
|
||
|
||
</body></html>
|