//mxd. Alpha based picking
        public override bool PickAccurate(Vector3D from, Vector3D to, Vector3D dir, ref float u_ray)
        {
            if(!BuilderPlug.Me.AlphaBasedTextureHighlighting || !Texture.IsImageLoaded || (!Texture.IsTranslucent && !Texture.IsMasked)) return base.PickAccurate(from, to, dir, ref u_ray);

            float u;
            new Line2D(from, to).GetIntersection(Sidedef.Line.Line, out u);
            if(Sidedef != Sidedef.Line.Front) u = 1.0f - u;

            // Some textures (e.g. HiResImage) may lie about their size, so use bitmap size instead
            Bitmap image = Texture.GetBitmap();

            // Determine texture scale...
            Vector2D imgscale = new Vector2D((float)Texture.Width / image.Width, (float)Texture.Height / image.Height);
            Vector2D texscale = (Texture is HiResImage) ? imgscale * Texture.Scale : Texture.Scale;

            // Get correct offset to texture space...
            int ox = (int)Math.Floor((u * Sidedef.Line.Length * UniFields.GetFloat(Sidedef.Fields, "scalex_mid", 1.0f) / texscale.x
                + ((Sidedef.OffsetX + UniFields.GetFloat(Sidedef.Fields, "offsetx_mid")) / imgscale.x))
                % image.Width);

            int oy;
            if(repeatmidtex)
            {
                bool pegbottom = Sidedef.Line.IsFlagSet(General.Map.Config.LowerUnpeggedFlag);
                float zoffset = (pegbottom ? Sidedef.Sector.FloorHeight : Sidedef.Sector.CeilHeight);
                oy = (int)Math.Floor(((pickintersect.z - zoffset) * UniFields.GetFloat(Sidedef.Fields, "scaley_mid", 1.0f) / texscale.y
                    - ((Sidedef.OffsetY - UniFields.GetFloat(Sidedef.Fields, "offsety_mid")) / imgscale.y))
                    % image.Height);
            }
            else
            {
                float zoffset = bottomclipplane.GetZ(pickintersect);
                oy = (int)Math.Ceiling(((pickintersect.z - zoffset) * UniFields.GetFloat(Sidedef.Fields, "scaley_mid", 1.0f) / texscale.y) % image.Height);
            }

            // Make sure offsets are inside of texture dimensions...
            if(ox < 0) ox += image.Width;
            if(oy < 0) oy += image.Height;

            // Check pixel alpha
            Point pixelpos = new Point(General.Clamp(ox, 0, image.Width - 1), General.Clamp(image.Height - oy, 0, image.Height - 1));
            return (image.GetPixel(pixelpos.X, pixelpos.Y).A > 0 && base.PickAccurate(from, to, dir, ref u_ray));
        }