Alpha shouldn't be normalized or inversed?

[RongLiu-Leo]

When I check this default alpha map, it looks quite counterintuitive. It means all my primitives are transparent.

I check the code and find that the alpha map is affected by depth normalize and inverse check boxes. Per their hints, I think they should only affect the depth maps, not rgb and alpha.

This PR

• Makes normalize and inverse check boxes enabled only when it's depth rendering.
• Switches Inverse to off by default, since having it on by default feels counterintuitive.