mesh with subset.

Other Standards COLLADA
1

hy.
I have a mesh with 2 subset with 2 different material .
My importer start to import from the scene graph.
But when i get a node of the scenegraph i have an istance with the 2 material

this is a piece of the xml collada file


<instance_geometry url="#Cube-Geometry">
					<bind_material>
						<technique_common>
							<instance_material symbol="Materialaer" target="#Materialaer">
								<bind_vertex_input input_semantic="TEXCOORD" input_set="1" semantic="CHANNEL1"/>
							</instance_material>
							<instance_material symbol="Material_ferr" target="#Material_ferr">
								<bind_vertex_input input_semantic="TEXCOORD" input_set="1" semantic="CHANNEL1"/>
							</instance_material>
						</technique_common>
					</bind_material>
				</instance_geometry>





now in the normal sequence i get the geometry 
const domInstance_geometry_Array pGeomAry = m_CurrentNode->getInstance_geometry_array()//current node is the current node //selected by the traverse the scene graph.

//i use this for get the geometry isnstance.
xsAnyURI puriGeom = pGeomAry.get(0)->getUrl();
puriGeom.resolveElement();

In a multiple mesh subset i get the group of triangles that have the current node material group of vertex,but with 2 instance of 2 different materials how i resolve the triangle group that i must process?(I have 2 triangle group in this case ) and start reading the geometry of the corrispondent subset(triangle group)?

thanks.

2

In your example, Your 2x <instance_material> is used only inside that <instance_geometry>.
Your <geometry> should be something like this.


<geometry id="Cube-Geometry">
   <mesh>
      ...
      <triangles material="Materialaer"> ... </triangles>
      <triangles material="Material_ferr"> ... </triangles>
   </mesh>
</geometry>

Your <bind_material> is trying to bind:
Materialaer with
Material_ferr with
The material group names in triangles happened to be the same as id of material. This is not neccessary required.

Here is a better example on how to resolve the material binding


<geometry id="geometry1">
   <mesh>
      ...
      <triangles material="group1"> ... </triangles>
      <triangles material="group2"> ... </triangles>
   </mesh>
</geometry>

<instance_geometry url="#geometry1">
   <bind_material>
      <technique_common>
         <instance_material symbol="group1" target="#blue"> ...
         <instance_material symbol="group2" target="#red"> ...
      </technique_common>
   </bind_material>
</instance_geometry>

<library_materials>
   <material id="blue">...</material>
   <material id="red">...</material>
</library_materials>

you can make another instance geometry that reference the of the same geometry that binds with different materials


<instance_geometry url="#geometry1">
   <bind_material>
      <technique_common>
         <instance_material symbol="group1" target="#green"> ...
         <instance_material symbol="group2" target="#yellow"> ...
      </technique_common>
   </bind_material>
</instance_geometry>
3

thanks.
And in collda dom(that i use)there is a method for get the relative materials group triangle?
Now I get the group of triangle by a numeric index (0,1,2)in succession.
How i get the group by the specific material?

4

The material group is a xml attribue in your triangles element.
If you use the COLLADA DOM, then check the below code


   domTriangles * triangles = mesh->getTriangles_array()[triangle_index];
   daeString * material_group = triangles->getMaterial();
   // lookup your binding table with key = material_group
   // you'll get result material ID from the binding table
   // That ID will be the material you use for that instance_geometry

Herbert