Help with cam.Start3D please

[amkoc]

This works but only from certain angles...

Trying to overlay a texture onto a playermodel. It works but only from certain angles, otherwise it just doesn't draw :/
[lua]

local matLight = Material( "models/spawn_effect" )

function FX:Render()
if !ValidEntity(self.ply) then return false end
self.ply:DrawModel()

cam.Start3D( EyePos() , EyeAngles() )
--if ValidEntity( self.ply ) then
SetMaterialOverride( matLight )
self.ply:DrawModel()
SetMaterialOverride( 0 )
--end
cam.End3D()

--self.ply.RenderOverride = nil
end
[/lua]