Only 3 faces of a standard cube adapt material color in Fast Preview

Hello,

I just start testing Blend4web.

I changed de color of a standard cube material.

But when I view this in Fast Preview only 3 faces of the cube show a color update.
The other faces are black… What am I doying wrong?

thnks to reply :-)

Select your cube, go to Edit mode, use A to make sure all faces are selected. Go to the materials tab (Little round icon), select the material you want then you will see a button that says "Assign"

I guess it's just lighting. If you change "Viewport Shading" option in Blender from Solid (default) to Material you will see those black faces as well.