disabled culling and normals in shader

[Thomas.]

I have problem with objects without culling. I'm using shader for calculating per-pixel lighting. When I disable culling, normals are still same, so lighting is "bad" from other side. Is there any simple and fast solution? or is better to use two triangle for each side?

[EgonOlsen]

Is there any simple and fast solution? or is better to use two triangle for each side?

None that i know of. You could invert the normal in the shader, but i've no idea how to detect if this is needed.

[Thomas.]

OK, so I will copy triangles to both side, that will be the simplest solution for me

[Thomas.]

I solved the problem. For calculating dot product of normal and light direction is using max from dot and 0 for "dark to light" shading

Code Select Expand

max(dot(normal, lightVector), 0.0);

If you replace above mentioned by this one, lighting is good from both side... get "light - dark - light" shading

Code Select Expand

abs(dot(normal, lightVector));

EDIT: this of course not working in camera - plane - light case. In theory, it will probably needs camera-vertex dot and check it with normal-light dot...?