context: 
  #region ================== Copyright (c) 2007 Pascal vd Heiden
  
  /*
   * Copyright (c) 2007 Pascal vd Heiden, www.codeimp.com
   * This program is released under GNU General Public License
   * 
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   * 
   */
  
  #endregion
  
  #region ================== Namespaces
  
  using System;
  using System.Collections;
  using System.Collections.Generic;
  using System.Globalization;
  using System.Text;
  using System.Windows.Forms;
  using System.IO;
  using System.Reflection;
  using System.Drawing;
  using System.ComponentModel;
  using CodeImp.DoomBuilder.Map;
  using CodeImp.DoomBuilder.Geometry;
  using System.Drawing.Imaging;
  using CodeImp.DoomBuilder.Data;
  using CodeImp.DoomBuilder.Editing;
  using CodeImp.DoomBuilder.IO;
  using CodeImp.DoomBuilder.Rendering;
  using CodeImp.DoomBuilder.Types;
  using CodeImp.DoomBuilder.VisualModes;
  
  #endregion
  
  namespace CodeImp.DoomBuilder.GZDoomEditing
  {
  	internal sealed class VisualLower : BaseVisualGeometrySidedef
  	{
  		#region ================== Constants
  
  		#endregion
  
  		#region ================== Variables
  		
  		#endregion
  
  		#region ================== Properties
  
  		#endregion
  
  		#region ================== Constructor / Setup
  
  		// Constructor
  		public VisualLower(BaseVisualMode mode, VisualSector vs, Sidedef s) : base(mode, vs, s)
  		{
  			// We have no destructor
  			GC.SuppressFinalize(this);
  		}
  		
  		// This builds the geometry. Returns false when no geometry created.
  		public override bool Setup()
  		{
  			Vector2D vl, vr;
  			
  			int lightvalue = Sidedef.Fields.GetValue("light", 0);
  			bool lightabsolute = Sidedef.Fields.GetValue("lightabsolute", false);
  			
  			Vector2D tscale = new Vector2D(Sidedef.Fields.GetValue("scalex_bottom", 1.0f),
  										   Sidedef.Fields.GetValue("scaley_bottom", 1.0f));
  			Vector2D toffset = new Vector2D(Sidedef.Fields.GetValue("offsetx_bottom", 0.0f),
  											Sidedef.Fields.GetValue("offsety_bottom", 0.0f));
  			
  			// Left and right vertices for this sidedef
  			if(Sidedef.IsFront)
  			{
  				vl = new Vector2D(Sidedef.Line.Start.Position.x, Sidedef.Line.Start.Position.y);
  				vr = new Vector2D(Sidedef.Line.End.Position.x, Sidedef.Line.End.Position.y);
  			}
  			else
  			{
  				vl = new Vector2D(Sidedef.Line.End.Position.x, Sidedef.Line.End.Position.y);
  				vr = new Vector2D(Sidedef.Line.Start.Position.x, Sidedef.Line.Start.Position.y);
  			}
  			
  			// Load sector data
  			SectorData sd = Sector.GetSectorData();
  			SectorData osd = mode.GetSectorData(Sidedef.Other.Sector);
  			if(!osd.Updated) osd.Update();
  			
  			// Texture given?
  			if((Sidedef.LowTexture.Length > 0) && (Sidedef.LowTexture[0] != '-'))
  			{
  				// Load texture
  				base.Texture = General.Map.Data.GetTextureImage(Sidedef.LongLowTexture);
  				if(base.Texture == null)
  				{
  					base.Texture = General.Map.Data.MissingTexture3D;
  					setuponloadedtexture = Sidedef.LongLowTexture;
  				}
  				else
  				{
  					if(!base.Texture.IsImageLoaded)
  						setuponloadedtexture = Sidedef.LongLowTexture;
  				}
  			}
  			else
  			{
  				// Use missing texture
  				base.Texture = General.Map.Data.MissingTexture3D;
  				setuponloadedtexture = 0;
  			}
  			
  			// Get texture scaled size
  			Vector2D tsz = new Vector2D(base.Texture.ScaledWidth, base.Texture.ScaledHeight);
  			tsz = tsz / tscale;
  			
  			// Get texture offsets
  			Vector2D tof = new Vector2D(Sidedef.OffsetX, Sidedef.OffsetY);
  			tof = tof + toffset;
  			tof = tof / tscale;
  			if(General.Map.Config.ScaledTextureOffsets && !base.Texture.WorldPanning)
  				tof = tof * base.Texture.Scale;
  			
  			// Determine texture coordinates plane as they would be in normal circumstances.
  			// We can then use this plane to find any texture coordinate we need.
  			// The logic here is the same as in the original VisualMiddleSingle (except that
  			// the values are stored in a TexturePlane)
  			// NOTE: I use a small bias for the floor height, because if the difference in
  			// height is 0 then the TexturePlane doesn't work!
  			TexturePlane tp = new TexturePlane();
  			float floorbias = (Sidedef.Other.Sector.FloorHeight == Sidedef.Sector.FloorHeight) ? 1.0f : 0.0f;
  			if(Sidedef.Line.IsFlagSet(General.Map.Config.LowerUnpeggedFlag))
  			{
  				// When lower unpegged is set, the lower texture is bound to the bottom
  				tp.tlt.y = (float)Sidedef.Sector.CeilHeight - (float)Sidedef.Other.Sector.FloorHeight;
  			}
  			tp.trb.x = tp.tlt.x + Sidedef.Line.Length;
  			tp.trb.y = tp.tlt.y + ((float)Sidedef.Other.Sector.FloorHeight - ((float)Sidedef.Sector.FloorHeight + floorbias));
  			
  			// Apply texture offset
  			tp.tlt += tof;
  			tp.trb += tof;
  			
  			// Transform pixel coordinates to texture coordinates
  			tp.tlt /= tsz;
  			tp.trb /= tsz;
  			
  			// Left top and right bottom of the geometry that
  			tp.vlt = new Vector3D(vl.x, vl.y, (float)Sidedef.Other.Sector.FloorHeight);
  			tp.vrb = new Vector3D(vr.x, vr.y, (float)Sidedef.Sector.FloorHeight + floorbias);
  			
  			// Make the right-top coordinates
  			tp.trt = new Vector2D(tp.trb.x, tp.tlt.y);
  			tp.vrt = new Vector3D(tp.vrb.x, tp.vrb.y, tp.vlt.z);
  			
  			// Create initial polygon, which is just a quad between floor and ceiling
  			WallPolygon poly = new WallPolygon();
  			poly.Add(new Vector3D(vl.x, vl.y, sd.Floor.plane.GetZ(vl)));
  			poly.Add(new Vector3D(vl.x, vl.y, sd.Ceiling.plane.GetZ(vl)));
  			poly.Add(new Vector3D(vr.x, vr.y, sd.Ceiling.plane.GetZ(vr)));
  			poly.Add(new Vector3D(vr.x, vr.y, sd.Floor.plane.GetZ(vr)));
  			
  			// Determine initial color
  			int lightlevel = lightabsolute ? lightvalue : sd.Ceiling.brightnessbelow + lightvalue;
  			PixelColor wallbrightness = PixelColor.FromInt(mode.CalculateBrightness(lightlevel));
  			PixelColor wallcolor = PixelColor.Modulate(sd.Ceiling.colorbelow, wallbrightness);
  			poly.color = wallcolor.WithAlpha(255).ToInt();
  			
  			// Cut off the part above the other floor
  			CropPoly(ref poly, osd.Floor.plane, false);
  			CropPoly(ref poly, osd.Ceiling.plane, true);
  			
  			if(poly.Count > 2)
  			{
  				// Keep top and bottom planes for intersection testing
  				top = osd.Floor.plane;
  				bottom = sd.Floor.plane;
  				
  				// Process the polygon and create vertices
  				List<WorldVertex> verts = CreatePolygonVertices(poly, tp, sd, lightvalue, lightabsolute);
  				if(verts.Count > 0)
  				{
  					base.SetVertices(verts);
  					return true;
  				}
  			}
  			
  			return false;
  		}
  		
  		#endregion
  
  		#region ================== Methods
  
  		// Return texture name
  		public override string GetTextureName()
  		{
  			return this.Sidedef.LowTexture;
  		}
  		
  		// This changes the texture
  		protected override void SetTexture(string texturename)
  		{
  			this.Sidedef.SetTextureLow(texturename);
  			General.Map.Data.UpdateUsedTextures();
  			this.Setup();
  		}
  
  		protected override void SetTextureOffsetX(int x)
  		{
  			Sidedef.Fields.BeforeFieldsChange();
  			Sidedef.Fields["offsetx_bottom"] = new UniValue(UniversalType.Float, (float)x);
  		}
  
  		protected override void SetTextureOffsetY(int y)
  		{
  			Sidedef.Fields.BeforeFieldsChange();
  			Sidedef.Fields["offsety_bottom"] = new UniValue(UniversalType.Float, (float)y);
  		}
  
  		protected override void MoveTextureOffset(Point xy)
  		{
  			Sidedef.Fields.BeforeFieldsChange();
  			float oldx = Sidedef.Fields.GetValue("offsetx_bottom", 0.0f);
  			float oldy = Sidedef.Fields.GetValue("offsety_bottom", 0.0f);
  			float scalex = Sidedef.Fields.GetValue("scalex_bottom", 1.0f);
  			float scaley = Sidedef.Fields.GetValue("scaley_bottom", 1.0f);
  			Sidedef.Fields["offsetx_bottom"] = new UniValue(UniversalType.Float, oldx + (float)xy.X * scalex);
  			Sidedef.Fields["offsety_bottom"] = new UniValue(UniversalType.Float, oldy + (float)xy.Y * scaley);
  		}
  
  		protected override Point GetTextureOffset()
  		{
  
gt: 			float oldx = Sidedef.Fields.GetValue("offsetx_bottom", 0.0f);