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Effect framework: Difference between revisions
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→Parameters
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Note that parameters can use the <use> tags to enable properties to specify the values. | Note that parameters can use the <use> tags to enable properties to specify the values. | ||
==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 : | |||
<syntaxhighlight lang="xml"> | |||
<generate> | |||
<tangent type="int">6</tangent> | |||
<binormal type="int">7</binormal> | |||
<normal type="int">8</normal> | |||
</generate> | |||
</syntaxhighlight> | |||
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 : | |||
<syntaxhighlight lang="xml"> | |||
<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> | |||
</syntaxhighlight> | |||
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. | |||
==Technique== | ==Technique== | ||