Qt3D Cube, No surface texture but with edges, how to?

Hi, all:

I'm trying to create a cube shape, without any texture on the surfaces, but it should still be able to show the edges. I tried:

Code:

---

QGLSceneNode *cube = builder.finalizedSceneNode();
QGLMaterial *mat = new QGLMaterial;
mat->setColor( Qt::transparent); 
cube->setMaterial(mat);

---

Nothing can be shown up.

If I try

Code:

---

QGLSceneNode *cube = builder.finalizedSceneNode();
QGLMaterial *mat = new QGLMaterial;
mat->setColor(QColor(255, 0, 0));
cube->setMaterial(mat);

---

This will show up a cube with texture on all surfaces.


Is there a method to show just the edges (maybe I can specify the edge width, or even emphasize the vertexes), but not the surfaces?



Cheers
Pei