It's a common misconception that back face culling is done using normals.
Backface culling is based on the "winding" of the vertices. I think the
confusion comes when you auto build your normals and because the vertices
are wound the wrong way, the normal is opposite of what you are expecting.
But it is winding that controls backface culling.
Your object will be black if there are no normals only if the material has
setLighting(true) AND the emmissive component is (0,0,0). It will also be
black if the it is lit but there are no lights defined. This is a common
issue when you mix objects which are mapped with REPLACE and objects that
are mapped MODULATE. Because lighting only effects the vertex colors,
REPLACE mode is completely untouched by lighting, while modulate IS
effected. So when you mix two in the scene oftimes people do not consider
the lighting issues when they see some shapes clearly, but observe others to
be black. But shapes textured with REPLACE can be seen in a totally dark
scene.
Another way this can happen is if the vertices colored with black, or in the
absence of vertex colors your coloring attributes are black.
Dave Yazel
-----Original Message-----
From: Joachim Diepstraten
[mailto:[EMAIL PROTECTED]]
Sent: Friday, July 20, 2001 12:30 PM
To: [EMAIL PROTECTED]
Subject: Re: [JAVA3D] the object disappear if i set a material.
Hi Bob
> In case you're interested, normals are used for calculating lighting. A
> shape without normals means that no lighting can be applied, so it appears
> completely black.
Well that's only right when the material of the Shape has no
emitting. Another problem is that it might fall through the backface
removal without a normal.
EOF,
J.D.
--
Jmark2k+1 (http://www.antiflash.net/jmark)
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