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7 <title>Creating the Alphamap</title>
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13 <p align="center"><font size="5">Creating the Alphamap</font></p>
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15 <table border="1" cellspacing="1" width="100%" bordercolor="#808080" bgcolor="#000000" cellpadding="10">
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17 <td width="100%"><font FACE="Times New Roman">
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18 <p> The alphamap referenced by the alphamap key/value pair is an art file created
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19 specifically for the map. For non-digital artists, it may be one of the more
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20 technically and conceptually challenging things that need to be created to make
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21 the terrain map work.</p>
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22 <p> Simply put, the alpha map is the template that the compiler uses to assign
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23 textures to the terrain surface.</p>
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24 <p> To make the alphamap, you must have, or have access to, an art program that
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25 can save a file as an 8-bit BMP file with indexed color. I
\92ll discuss other
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26 file types later on, but the BMP file is probably the simplest solution, both
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27 technically and conceptually.</p>
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29 </font><b><font SIZE="4">
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31 </font></b><font FACE="Times New Roman">
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32 <p> First, you need to understand a couple vocabulary words
\85 jargon, if you
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35 <p>Indexed Color:</b> In essence, each color used in a piece of art is
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36 remembered by its location on the color table or palette (see below). There are
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37 256 colors available, numbered from 0 to 255. Each position on the palette has
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38 its own number. This number has nothing to do with the RGB values of a color in
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39 that position. If you change the actual color located at a particular location
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40 on the palette (say from red to blue), all the pixels that were formerly that
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41 shade of red (if painted using a color with that index number), will change to
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42 the new color of blue.</p>
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44 <p>Color Table:</b> This is what Photoshop calls the indexed color layout of 256
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45 colors. In Paint Shop Pro it
\92s a palette. This is a pop-up window that shows
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46 the colors in the palette and their arrangement. For making an alphamap for a
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47 terrain map, the colors you choose are not important, but their position on the
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50 <p>Palette:</b> This is what Paint Shop Pro calls a Color Table.</p>
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52 </font><b><font SIZE="4">
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53 <p>Making the Palette</p>
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54 </font></b><font FACE="Times New Roman">
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55 <p> The best way to start is to make a set of colors to use when painting
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56 alphamaps. If you want, you can do this once and save it out. In PSP edit the
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57 palette (in Photoshop, open the Color Table). Make sure the colors are sorted by
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58 index number (there may be a pull down menu that allows this). In PSP, the
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59 colors are indexed from the upper left (color 0 in the upper leftmost position
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60 and increasing in value to the right). In Photoshop, the positions are reversed.
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61 The color with value 0 is in the lower rightmost position and the index numbers
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62 increase to the right.</p>
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63 <p> Because there is a direct one-to-one relationship between colors in the
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64 palette and individual shaders that make of the metashader, you should select
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65 clearly distinct colors to represent each shader. You should have one color for
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66 each layer you intend to include in the map (see keys above), which means one
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67 color to represent each root shader. You may find it convenient to create more,
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68 so they are available for later use (if you save the palette).</p>
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69 <p> This method worked for me to make a 16-color palette in Paint Shop Pro.
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70 First, I reduced my palette size to 16 colors. I clicked on each palette
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71 position and created a color for it (don
\92t use black). Then, I increased my
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72 palette size back up to 256 colors, filling the rest with black. In Photoshop,
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73 it
\92s easier to select all the colors you don
\92t intend to use and make them
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74 black. Then, I save the palette out as a file for later use.</p>
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75 <p> Another thing you might try is to make a grayscale palette, then use only the
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76 first few positions for your color and leave the rest for grayscale (this allows
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77 you to import bmp height maps and use them as guidelines).</p>
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79 </font><b><font SIZE="4">
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80 <p>Alphamap File Data</p>
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81 </font></b><font FACE="Times New Roman"><b>
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82 <p>File type:</b> The alphamap is a BMP format file or a TGA file (see other
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83 file formats below). With BMP format, each color in your palette corresponds
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84 directly to a root shader used to create the smooth texture blends on the
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87 <p>File size:</b> The size of the alphamap should be one-to-one with the number
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88 of vertexes in the map. If you have 64 divisions x 32 divisions in your terrain
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89 mesh (65x33 vertexes), you should use a 65 by 33 alphamap. You can use an
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90 alphamap with a size that is not a one-to-one map with the number of map
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91 vertexes, but you can then expect a less precise interpretation of your texture
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94 <p>Colors linked to Shaders:</b> If an 8-bit texture is used (BMP), q3map links
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95 a color
\92s position on the palette to an identifying number in the name of a
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96 shader. The color in position 0 would reference a root shader named <metashadername>_0.
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97 The color in position 1 would reference a root shader named <metashadername>_1.
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98 <metashadername> refers to the value of the Shader key (see Key: Shader
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99 below). In theory, you could probably have 256 different root shaders assigned
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100 to the terrain entity. In practice, you
\92d probably want to bite your arm off
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101 at the elbow before doing something as complicated as that.</p>
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102 </font><b><font SIZE="4">
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103 <p>Other File Formats</p>
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104 </font></b><font FACE="Times New Roman">
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105 <p> It is possible to use a TGA file (a RGB color format) for an
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107 files are handled differently than indexed color files like BMP. Instead of
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108 looking for a position on the palette, q3map interprets the RGB value of actual
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109 color. With a 32-bit TGA file, only the color values in the red channel are
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110 used. The program assumes that a gray scale of equal values is being used. The
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111 program divides the colors by the number of levels into equal-sized ranges. When
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112 assigning textures, q3map looks at what range the color falls in and chooses the
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113 appropriate shader to place or blend.</p>
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114 </font><b><font SIZE="4">
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115 <p>Controlling Texture Blends</p>
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116 </font></b><font FACE="Times New Roman">
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117 <p> Each triangle on the mesh can only have two root shaders blending across it.
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118 Another way to say this is that there should be only two different colors on the
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119 three vertexes that form any given triangle in the mesh. Any more, and a sharp,
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120 unblended edge appears on the terrain surface. This can take some trial and
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121 error to correct. A bsp -switch command called -showseams can help the mapmaker
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122 find these errors. Create a new bsp command in your project file that includes
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123 this option. We recommend doing it with a novis only operation.</p>
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124 </font><font FACE="Times New Roman" SIZE="2">
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125 <p align="center"><img SRC="Image5.gif" WIDTH="266" HEIGHT="352">
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126 <img SRC="Image6.gif" WIDTH="264" HEIGHT="352"></p>
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127 </font><font FACE="Times New Roman">
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129 <p> In figure 3, the blue and white image on the left is a scaled up (4X) version
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130 of the alphamap used on Distant Screams. It shows three different root shaders
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131 in use. Compare that to the gray scale height map on the right and you can see
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132 how the artist chose to assign textures to the various heights and depths of the
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133 map. As long as the guidelines for texture placement are followed, a mapmaker
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134 should be able to work with more different root shaders than shown here.</p>
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135 </font><b><font SIZE="4">
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136 <p>Alphamap Creation Tips:</p>
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139 </font></b><font FACE="Symbol" SIZE="2">
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140 <p>· </font><font FACE="Times New Roman">The alphamaps for the team arena maps
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141 are included with this document, both as reference and as files that you can
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142 modify to work with your own maps. You may want to compare the alphamaps against
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143 the heightmaps for the same maps, just to see how id resolved mapping issues.</p>
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144 </font><font FACE="Symbol" SIZE="2">
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145 <p>· </font><font FACE="Times New Roman">You can create a quick (though not
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146 necessarily good) alphamap by saving your height map as a new file. Then use the
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147 \93posterize
\94 filter that can be found in some art tools. Reduce the number of
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148 colors in the art to equal the layers (number of unique root shaders) in the
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150 </font><font FACE="Symbol" SIZE="2">
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151 <p>· </font><font FACE="Times New Roman">If you are creating a new alphamap
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152 from scratch, use colors that are easily distinguished from each other.</p>
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153 </font><font FACE="Symbol" SIZE="2">
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154 <p>· </font><font FACE="Times New Roman">If you are making an alphamap for a
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155 team style map where both sides of the map are identical (mirrored or rotated),
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156 you only need to design the map for one side. Copy and position it as described
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157 above for the heightmap.</p>
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158 </font><font FACE="Symbol" SIZE="2">
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159 <p>· </font><font FACE="Times New Roman">The id maps used simple color schemes
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160 that were homogenous throughout the maps. That is not the only way of doing
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161 things. It would be quite reasonable to use many more terrain textures
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162 (particularly if you weren
\92t going to build complicated, multi-texture
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163 architecture on top of them). Consider a map where one part of the terrain used
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164 red-themed textures and the other side blue themed textures. Have them blend
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165 into a few simple neutral colors near the map center.</p>
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166 </font><font FACE="Symbol" SIZE="2">
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167 <p>· </font><font FACE="Times New Roman">Try doing terrain style texture
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168 mapping on non-terrain geometry. Results will definitely vary, but some could be
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173 <p>Samples:</b> The last height map and the alphamap used to create each of the
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174 terrain maps in Team Arena is included in the Mapping Support folder. Note that
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175 the designers made vertex manipulations to the final terrain meshes that are not
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176 reflected in these height maps. Also, the alphamaps are in PCX format, not BMP
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180 <p align="center"><a href="entity_keys_and_values.html">Back</a> - <a href="table_of_contents.html">Table
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181 of Contents</a> - <a href="terrain_texture.html">The Terrain Texture</a></p>
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188 <p align="center"> </p>
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189 <p align="center"> </p>
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190 <p align="center">-16-</p>
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projects / xonotic / netradiant.git / blob