Awful artifacts (GLSL)

Just created another framework & just for a test threw a simple shader in. I don’t know am I lucky or what, but banding is very well noticable and annoying, like it would be fp16 or smthn. I am runing on 6800GT, 32 bit should be default… How it’ll look on R with 24 bit then???

http://lapas.dau.lv/salitis/img.PNG

vp

varying vec3 VertexPos;

void main(void)
{
	gl_Position = ftransform();
	VertexPos = (gl_ModelViewMatrix * gl_Vertex).xyz;
}

fp

varying vec3 VertexPos;

void main ()
{
	gl_FragColor.rgb = length(VertexPos)*.25.xxx;
	gl_FragColor.a = 1.0;
}

I don’t see what you are talking about. That screenshot doesn’t appear to have any banding.