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Add generate documentation

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fredb 2010-03-28 16:30:38 +00:00
parent e7444434c5
commit 17f9563900
1 changed files with 45 additions and 3 deletions
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46
Docs/README.effects
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@ -79,7 +79,7 @@ Values are assigned to technique properties in several ways:
<uniform>
<name>ColorsTex</name>
<type>sampler-1d</type>
< value type="int">2</value>
<value type="int">2</value>
</uniform>
* The name of a property in the parameters section can be
referenced using a "use" clause. For example, in the technique
@ -151,6 +151,7 @@ polygon-mode - children: front, back
program
vertex-shader
fragment-shader
attribute
render-bin - (OSG) children: bin-number, bin-name
@ -209,8 +210,49 @@ those parameters in its "techniques" section. The derived effect
overrides any default values that might be in the base effect's
parameters section.
Generate
--------
Often shader effects need tangent vectors to work properly. These
tangent vectors, usually called tangent and binormal, are computed
on the CPU and given to the shader as vertex attributes. These
vectors are computed on demand on the geometry using the effect if
the 'generate' clause is present in the effect file. Exemple :
<generate>
<tangent type="int">6</tangent>
<binormal type="int">7</binormal>
<normal type="int">8</normal>
</generate>
Valid subnodes of 'generate' are 'tangent', 'binormal' or 'normal'.
The integer value of these subnode is the index of the attribute
that will hold the value of the vec3 vector.
The generate clause is located under PropertyList in the xml file.
In order to be available for the vertex shader, these data should
be bound to an attribute in the program clause, like this :
<program>
<vertex-shader>my_vertex_shader</vertex-shader>
<attribute>
<name>my_tangent_attribute</name>
<index>6</index>
</attribute>
<attribute>
<name>my_binormal_attribute</name>
<index>7</index>
</attribute>
</program>
attribute names are whatever the shader use. The index is the one
declared in the 'generate' clause. So because generate/tangent has
value 6 and my_tangent_attribute has index 6, my_tangent_attribute
holds the tangent value for the vertex.
Default Effects in Terrain Materials and Models
---------------------------------------
-----------------------------------------------
Effects for terrain work in this way: for each material type in
materials.xml an effect is created that inherits from a single default