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4.10.5 Creating a Genmesh Mesh

This section describes how to create a Genmesh mesh.

What is Genmesh?

A `Genmesh' mesh object (see section Genmesh Mesh Object) is a generic triangle mesh object. Genmeshes also support animation (see section GenMesh Animation).

Genmeshes are very useful for static or semi-static geometry (chests, doors, candles, swords, etc.) which can sometimes require a lot of detail.

Genmeshes use vertex lighting (or stencil if you use a stencil lighting shader).

Genmesh objects always have to be created through a factory. So, first you create the actual geometry in a genmesh factory and then you create one or more instances from that factory. This is a great way to save memory. This does mean that it is not possible to HardTransform genmeshes. It is only possible to HardTransform Genmesh factories.

Creating a Genmesh in a Map

Here is an example of how to create a cube genmesh in a map file:

<meshfact name="cubeFact">
    <v x="-0.1" y="0.1" z="0.1" u="0" v="0" />
    <v x="-0.1" y="0.1" z="-0.1" u="1" v="0" />
    <v x="0.1" y="0.1" z="-0.1" u="0" v="1" />
    <v x="0.1" y="0.1" z="0.1" u="1" v="1" />
    <v x="-0.1" y="-0.1" z="0.1" u="1" v="0" />
    <v x="-0.1" y="-0.1" z="-0.1" u="0" v="1" />
    <v x="0.1" y="-0.1" z="-0.1" u="1" v="1" />
    <v x="0.1" y="-0.1" z="0.1" u="0" v="0" />
    <t v1="0" v2="3" v3="1" />
    <t v1="3" v2="2" v3="1" />
    <t v1="4" v2="5" v3="7" />
    <t v1="5" v2="6" v3="7" />
    <t v1="0" v2="4" v3="3" />
    <t v1="4" v2="7" v3="3" />
    <t v1="1" v2="6" v3="5" />
    <t v1="1" v2="2" v3="6" />
    <t v1="0" v2="1" v3="5" />
    <t v1="0" v2="5" v3="4" />
    <t v1="2" v2="3" v3="7" />
    <t v1="2" v2="7" v3="6" />
    <autonormals />
<sector name="bla">
  <meshobj name="cube">
      <v x="1" y="0" z="3" />

In this example we define a box by specifying the eight corner vertices and the twelve triangles. The <autonormals> tag specifies that normals will be created automatically (to give the box a smooth appearance). The normals are used for lighthing. It is also possible to specify normals manually. Note that with every vertex we also specify a texture coordinate (uv coordinate).

To create a genmesh box you can actually use a short-hand notation:

<meshfact name="cubeFact">
      <min x="-0.1" y="-0.1" z="-0.1" />
      <max x="0.1" y="0.1" z="0.1" />
    <autonormals />

This is a quick way to make boxes in a map file.

Creating a Genmesh Programmatically

Here we create the same genmesh programmatically:

// First create the factory:
csRef<iMeshFactoryWrapper> fact = engine->CreateMeshFactory (
  "crystalspace.mesh.object.genmesh", "cubeFact");
csRef<iGeneralFactoryState> factstate = scfQueryInterface<iGeneralFactoryState> (
  fact->GetMeshObjectFactory ());
factstate->SetVertexCount (8);
factstate->GetVertices ()[0].Set (-0.1, 0.1, 0.1);
factstate->GetTexels ()[0].Set (0, 0);
factstate->GetVertices ()[1].Set (-0.1, 0.1, -0.1);
factstate->GetTexels ()[1].Set (1, 0);
factstate->SetTriangleCount (12);
factstate->GetTriangles ()[0].Set (0, 3, 1);
factstate->GetTriangles ()[1].Set (3, 2, 1);
factstate->CalculateNormals ();

// Now create an instance:
csRef<iMeshWrapper> mesh =
  engine->CreateMeshWrapper (fact, "cube");
mesh->GetMeshObject ()->SetMaterialWrapper (myMaterial);
csRef<iGeneralMeshState> meshstate = scfQueryInterface<iGeneralMeshState> (
  mesh->GetMeshObject ());
meshstate->SetLighting (true);

This will basically create the same cube as in the map file example.

Include Files

The include files useful for this section are:

#include <imesh/genmesh.h>

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