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Home: Autodesk FBX SDK Progammer's Guide

 

Layers contain materials, textures, UV, and other layer elements

Using layers to control how a model is rendered

Creating layer elements for materials and textures

 

Applying Textures and Materials to Meshes > Using layers to control how a model is rendered > 

Using layer 0 to store a normal to each face

In this section of code, we will assign the normals that we created earlier in a layer element for normals, and we will assign that layer element to Layer 0 of the mesh.

We start by creating layer 0 if it does not already exist:

// Set the normals on Layer 0.

KFbxLayer* lLayer = lMesh->GetLayer(0);

if (lLayer == NULL)

{

    lMesh->CreateLayer();

    lLayer = lMesh->GetLayer(0);

}

Here we assign normals to each vertex of each polygon in our mesh. A normal is a vector that defines which way a face or vertex is pointing. The direction of the normal indicates the front, or outer surface of the face or vertex. Normals are (usually) perpendicular to a polygon.

Since our mesh is a cube:

• There are six faces.
• The faces of the cube are squares, i.e., four-sided polygons.
• Therefore, we assign normals to 24 vertices (control points).

A layer element is composed of two arrays, called DirectArray and IndexArray:

• DirectArray stores the actual pointers to the data. In this case, the data will be the normals: 24 vectors, one for each control point of each face.
• IndexArray stores index numbers to DirectArray. When used, IndexArray provides an additional level of indirection to the vectors.

We start by creating the layer element for the normals.

// We want to have one normal for each control point,

// so we set the mapping mode to eBY_CONTROL_POINT.

KFbxLayerElementNormal* lLayerElementNormal= KFbxLayerElementNormal::Create(lMesh, "");

lLayerElementNormal->SetMappingMode(KFbxLayerElement::eBY_CONTROL_POINT);

// Set the normal values for every control point.

lLayerElementNormal->SetReferenceMode(KFbxLayerElement::eDIRECT);

The normals for each face of the cube will face the same direction. Accordingly, the first four vertices, which refer to the first face, are assigned the same normal (lNormalZpos); the second four vectors, which refer to the second face, are assigned the same normal (lNormalXpos); etc.

GetDirectArray() returns a pointer to a DirectArray for normals. Add() appends a vector to the end of the array.

lLayerElementNormal->GetDirectArray().Add(lNormalZPos);

lLayerElementNormal->GetDirectArray().Add(lNormalZPos);

lLayerElementNormal->GetDirectArray().Add(lNormalZPos);

lLayerElementNormal->GetDirectArray().Add(lNormalZPos);

lLayerElementNormal->GetDirectArray().Add(lNormalXPos);

lLayerElementNormal->GetDirectArray().Add(lNormalXPos);

lLayerElementNormal->GetDirectArray().Add(lNormalXPos);

lLayerElementNormal->GetDirectArray().Add(lNormalXPos);

lLayerElementNormal->GetDirectArray().Add(lNormalZNeg);

lLayerElementNormal->GetDirectArray().Add(lNormalZNeg);

lLayerElementNormal->GetDirectArray().Add(lNormalZNeg);

lLayerElementNormal->GetDirectArray().Add(lNormalZNeg);

lLayerElementNormal->GetDirectArray().Add(lNormalXNeg);

lLayerElementNormal->GetDirectArray().Add(lNormalXNeg);

lLayerElementNormal->GetDirectArray().Add(lNormalXNeg);

lLayerElementNormal->GetDirectArray().Add(lNormalXNeg);

lLayerElementNormal->GetDirectArray().Add(lNormalYPos);

lLayerElementNormal->GetDirectArray().Add(lNormalYPos);

lLayerElementNormal->GetDirectArray().Add(lNormalYPos);

lLayerElementNormal->GetDirectArray().Add(lNormalYPos);

lLayerElementNormal->GetDirectArray().Add(lNormalYNeg);

lLayerElementNormal->GetDirectArray().Add(lNormalYNeg);

lLayerElementNormal->GetDirectArray().Add(lNormalYNeg);

lLayerElementNormal->GetDirectArray().Add(lNormalYNeg);

We’ve finished assigning normals to the DirectArray of normals. Now we assign the DirectArray to the layer (layer 0):

lLayer->SetNormals(lLayerElementNormal);

This completes the construction of the mesh for a cube.