D3D Animation Basis(8)

D3D Animation Basis(8)

Drawing Meshes

Now that you have your meshes loaded and you've updated those skinned meshes that needed updating, it is time to throw some pixels at the display and show off those meshes! In total, I have created four mesh−rendering functions to help you in your projects.

HRESULT draw_mesh(D3DXMESHCONTAINER_EX *  mesh_container)
{
     //  error checking

     if (mesh_container  ==  NULL)
         return  E_FAIL;

     if (mesh_container -> MeshData.pMesh  ==  NULL)
         return  E_FAIL;

     if (mesh_container -> NumMaterials  ==   0   ||  mesh_container -> pMaterials  ==  NULL)
         return  E_FAIL;

     //  get the device interface
    IDirect3DDevice9 *  device;
    mesh_container -> MeshData.pMesh -> GetDevice( & device);

     //  release vertex shader if being used
    device -> SetVertexShader(NULL);
    device -> SetVertexDeclaration(NULL);

    DWORD last_alpha_blend, old_alpha_blend, old_src_blend, old_dest_blend;

     //  save render states
    device -> GetRenderState(D3DRS_ALPHABLENDENABLE,     & old_alpha_blend);
    device -> GetRenderState(D3DRS_SRCBLEND,             & old_src_blend);
    device -> GetRenderState(D3DRS_DESTBLEND,             & old_dest_blend);
    last_alpha_blend  =  old_alpha_blend;

     //  setup pointer for mesh to draw, either regular or skinned.
    ID3DXMesh *  mesh_to_draw  =  (mesh_container -> skin_mesh  ==  NULL)  ?  
                              mesh_container -> MeshData.pMesh : mesh_container -> skin_mesh;

     //  look through all subsets
     for (DWORD i  =   0 ; i  <  mesh_container -> NumMaterials; i ++ )
    {
         //  set material and texture
        device -> SetMaterial( & mesh_container -> pMaterials[i].MatD3D);
        device -> SetTexture( 0 , mesh_container -> textures[i]);

         //  enable or disable alpha blending per material
         if (mesh_container -> pMaterials[i].MatD3D.Diffuse.a  !=   1.0f )
        {
             if (last_alpha_blend  !=  TRUE)
            {
                last_alpha_blend  =  TRUE;

                device -> SetRenderState(D3DRS_ALPHABLENDENABLE,    TRUE);
                device -> SetRenderState(D3DRS_SRCBLEND,            D3DBLEND_ONE);     //  src color
                device -> SetRenderState(D3DRS_DESTBLEND,            D3DBLEND_DESTCOLOR);
            }
        }
         else
        {
             if (last_alpha_blend  !=  FALSE)
            {
                last_alpha_blend  =  FALSE;
                device -> SetRenderState(D3DRS_ALPHABLENDENABLE, FALSE);
            }
        }

        mesh_to_draw -> DrawSubset(i);
    }

     //  restore alpha blending states
     if (last_alpha_blend  !=  old_alpha_blend)
    {
        device -> SetRenderState(D3DRS_ALPHABLENDENABLE, old_alpha_blend);
        device -> SetRenderState(D3DRS_SRCBLEND,           old_src_blend);
        device -> SetRenderState(D3DRS_DESTBLEND,           old_dest_blend);
    }
    
     //  make sure to release the device object!
    device -> Release();

     return  S_OK;
}

 

If a material being used specifies an alpha value other than 1, then alpha blending is enabled. This way, you can specify portions of a mesh to use alpha blending by merely changing the material information. Also, if a D3DXMESHCONTAINER_EX object contains a skinned mesh, that mesh is rendered instead of the regular mesh.