Cookbook  »  Snippets  »  Geometry  »  Vertex and Index Buffers  »  Generating A Mesh

This creates a mesh? named "ColourCube" with one submesh in resource group "General", a coloured cube of size 200.

void createColourCube()
    {
    /// Create the mesh via the MeshManager
    Ogre::MeshPtr msh = MeshManager::getSingleton().createManual("ColourCube", "General");
 
    /// Create one submesh
    SubMesh* sub = msh->createSubMesh();
 
    const float sqrt13 = 0.577350269f; /* sqrt(1/3) */
 
    /// Define the vertices (8 vertices, each consisting of 2 groups of 3 floats
    const size_t nVertices = 8;
    const size_t vbufCount = 3*2*nVertices;
    float vertices[vbufCount] = {
            -100.0,100.0,-100.0,        //0 position
            -sqrt13,sqrt13,-sqrt13,     //0 normal
            100.0,100.0,-100.0,         //1 position
            sqrt13,sqrt13,-sqrt13,      //1 normal
            100.0,-100.0,-100.0,        //2 position
            sqrt13,-sqrt13,-sqrt13,     //2 normal
            -100.0,-100.0,-100.0,       //3 position
            -sqrt13,-sqrt13,-sqrt13,    //3 normal
            -100.0,100.0,100.0,         //4 position
            -sqrt13,sqrt13,sqrt13,      //4 normal
            100.0,100.0,100.0,          //5 position
            sqrt13,sqrt13,sqrt13,       //5 normal
            100.0,-100.0,100.0,         //6 position
            sqrt13,-sqrt13,sqrt13,      //6 normal
            -100.0,-100.0,100.0,        //7 position
            -sqrt13,-sqrt13,sqrt13,     //7 normal
    };
 
    RenderSystem* rs = Root::getSingleton().getRenderSystem();
    RGBA colours[nVertices];
    RGBA *pColour = colours;
    // Use render system to convert colour value since colour packing varies
    rs->convertColourValue(ColourValue(1.0,0.0,0.0), pColour++); //0 colour
    rs->convertColourValue(ColourValue(1.0,1.0,0.0), pColour++); //1 colour
    rs->convertColourValue(ColourValue(0.0,1.0,0.0), pColour++); //2 colour
    rs->convertColourValue(ColourValue(0.0,0.0,0.0), pColour++); //3 colour
    rs->convertColourValue(ColourValue(1.0,0.0,1.0), pColour++); //4 colour
    rs->convertColourValue(ColourValue(1.0,1.0,1.0), pColour++); //5 colour
    rs->convertColourValue(ColourValue(0.0,1.0,1.0), pColour++); //6 colour
    rs->convertColourValue(ColourValue(0.0,0.0,1.0), pColour++); //7 colour
 
    /// Define 12 triangles (two triangles per cube face)
    /// The values in this table refer to vertices in the above table
    const size_t ibufCount = 36;
    unsigned short faces[ibufCount] = {
            0,2,3,
            0,1,2,
            1,6,2,
            1,5,6,
            4,6,5,
            4,7,6,
            0,7,4,
            0,3,7,
            0,5,1,
            0,4,5,
            2,7,3,
            2,6,7
    };
 
    /// Create vertex data structure for 8 vertices shared between submeshes
    msh->sharedVertexData = new VertexData();
    msh->sharedVertexData->vertexCount = nVertices;
 
    /// Create declaration (memory format) of vertex data
    VertexDeclaration* decl = msh->sharedVertexData->vertexDeclaration;
    size_t offset = 0;
    // 1st buffer
    decl->addElement(0, offset, VET_FLOAT3, VES_POSITION);
    offset += VertexElement::getTypeSize(VET_FLOAT3);
    decl->addElement(0, offset, VET_FLOAT3, VES_NORMAL);
    offset += VertexElement::getTypeSize(VET_FLOAT3);
    /// Allocate vertex buffer of the requested number of vertices (vertexCount) 
    /// and bytes per vertex (offset)
    HardwareVertexBufferSharedPtr vbuf = 
        HardwareBufferManager::getSingleton().createVertexBuffer(
        offset, msh->sharedVertexData->vertexCount, HardwareBuffer::HBU_STATIC_WRITE_ONLY);
    /// Upload the vertex data to the card
    vbuf->writeData(0, vbuf->getSizeInBytes(), vertices, true);
 
    /// Set vertex buffer binding so buffer 0 is bound to our vertex buffer
    VertexBufferBinding* bind = msh->sharedVertexData->vertexBufferBinding; 
    bind->setBinding(0, vbuf);
 
    // 2nd buffer
    offset = 0;
    decl->addElement(1, offset, VET_COLOUR, VES_DIFFUSE);
    offset += VertexElement::getTypeSize(VET_COLOUR);
    /// Allocate vertex buffer of the requested number of vertices (vertexCount) 
    /// and bytes per vertex (offset)
    vbuf = HardwareBufferManager::getSingleton().createVertexBuffer(
        offset, msh->sharedVertexData->vertexCount, HardwareBuffer::HBU_STATIC_WRITE_ONLY);
    /// Upload the vertex data to the card
    vbuf->writeData(0, vbuf->getSizeInBytes(), colours, true);
 
    /// Set vertex buffer binding so buffer 1 is bound to our colour buffer
    bind->setBinding(1, vbuf);
 
    /// Allocate index buffer of the requested number of vertices (ibufCount) 
    HardwareIndexBufferSharedPtr ibuf = HardwareBufferManager::getSingleton().
        createIndexBuffer(
        HardwareIndexBuffer::IT_16BIT, 
        ibufCount, 
        HardwareBuffer::HBU_STATIC_WRITE_ONLY);
 
    /// Upload the index data to the card
    ibuf->writeData(0, ibuf->getSizeInBytes(), faces, true);
 
    /// Set parameters of the submesh
    sub->useSharedVertices = true;
    sub->indexData->indexBuffer = ibuf;
    sub->indexData->indexCount = ibufCount;
    sub->indexData->indexStart = 0;
 
    /// Set bounding information (for culling)
    msh->_setBounds(AxisAlignedBox(-100,-100,-100,100,100,100));
    msh->_setBoundingSphereRadius(Math::Sqrt(3*100*100));
 
    /// Notify -Mesh object that it has been loaded
    msh->load();
    }

To display this cube within your Ogre application, you'll need to set up a material definition that looks like:

material Test/ColourTest
{
    technique
    {
        pass
        {
            ambient vertexcolour
        }
    }
}

Alternatively, the material can be created directly in C++:

MaterialPtr material = MaterialManager::getSingleton().create(
      "Test/ColourTest", ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME);
    material->getTechnique(0)->getPass(0)->setVertexColourTracking(TVC_AMBIENT);

And to insert the mesh into a scene:

Entity* thisEntity = sceneManager->createEntity("cc", "ColourCube");
    thisEntity->setMaterialName("Test/ColourTest");
    SceneNode* thisSceneNode = sceneManager->getRootSceneNode()->createChildSceneNode();
    thisSceneNode->setPosition(-35, 0, 0);
    thisSceneNode->attachObject(thisEntity);

Alias: GeneratingAMesh