Here's the best result I could get with modifying the shaders:
Some sides are perfect, like
the top, but
some sides have dark parts. There are less dark parts if only the front sides are drawn, so I guess the 3D model has some overlapping polygons. I don't really know, I'm a noob at modelling.
Here's the shader definition:
mtl_haybale_
{
qer_editorimage models\mapobjects\haybale\haybale_side.tga
q3map_forcemeta
q3map_nonplanar
cull front
{
map models\mapobjects\haybale\haybale_side.tga
rgbGen identity
alphaFunc GE128
depthWrite
}
{
map models\mapobjects\haybale\_haybale_side_nrml-gggr.tga
rgbGen identity
blendFunc filter
depthFunc equal
}
{
map $lightmap
rgbGen identity
blendFunc filter
depthFunc equal
}
}