Tutorial 4 in the Intermediate Twilight Render V2 Tutorial Series

With V2.4, Twilight Render provides a set of geometry editing tools.  In this tutorial we will look at how to use the Selection, Texture, Edge, and Face tools that come with Twilight Render Pro.


  tools context

All the Twilight Render Pro Tools can be found from the context menu (by right clicking in the scene) or from the Tools menu of the main SketchUp menubar.  Which tools are available is determined by what is selected in the scene.  Edge and Select tools require edges to be selected.  Texture and Face tools require faces to be selected.  Note that you must make your selection before activating any tool; you can not change the selection once the tool is activated.

Select Tools

As the name implies, Select Tools add new selection functions for selecting sets of edges.

  • Select Loop - A loop is a continuous train of edges connected end to end.  Select Loop starts at the first selected edge and finds a loop that starts and ends at this edge.
  • Select Loop Between - Like Select Loop, this tool selects a loop between two selected edges.
  • Select Ring - A ring is a set of 'opposite' edges.  Select Ring starts at the first selected edge and finds opposing edges in a ring starting and ending at the selected edge.
  • Select Ring Between - Like Select Ring, this tool selects a ring between two selected edges.

Like all tools, how you use them is up to you.  Here are some suggested uses.

select ring sm

 connect edges

  • Using Select Ring in combination with Connect Edges (see below), you can add a geometry subdivision.

select loop

scale loop

  • After Select Loop, you can scale or offset the loop to add detail to a cube, cylinder, sphere or any other mesh.

 Texture Tools

The Texture Tools can help you map a texture material to your surface.  By default, SketchUp will often map textures to a surface in a broken, faceted appearance.  The Texture Tools can help map images more smoothly.

 texture default

Here is how SketchUp mapped our texture to an extruded hexagon by default.  While we don't expect a perfect wrap, this isn't what we are looking for.  Wrapping the texture around the vertical surface can help us achieve a lot of different effects like curved signage, textured poles and beams, and more.

After selecting the faces we want to map, we can choose one of our texture tools from the Texture menu.

  • Cylinder - Maps the texture to the surface as if it were wrapped around a cylinder that encompassed the geometry.
  • Sphere - Maps the texture to the surface as if it were wrapped around a sphere that encompassed the geometry.
  • Camera - Maps the texture to the surface as if you were holding a square of the texture directly in front of you and projected it directly onto the geometry.

Cylinder Texture Mapping

cylinder map  cylinder texture 

As you can see, the texture is projected onto the surface as if it were wrapped around a cylinder.  Note that "horizontally" the texture is wrapped one time around and that vertically the texture is sized to fit the vertical extent of the geometry.*

Spherical Texture Mapping

sphere map  sphere texture 

Like Cylindrical Mapping, Spherical Mapping wraps the texture around the surface but this time as if wrapped around a sphere.  Like Cylindrical Mapping, the texture is "horizontally" wrapped one time around the surface.  Unlike Cylindrical Mapping, the "vertical" mapping is also a curved wrap.*

Camera Projection Texture Mapping

camera map a  camera map b 

Camera Projection Mapping projects the texture directly away from the camera view, onto the surfaces.  When viewed from the original angle, the texture seems perfectly flat.  When viewed from the side, you can see how the texture stretches out.

 Positioning and Scaling

Immediately after selecting your mapping method from the context menu, you will be able to position and scale the texture.  Left click in the scene and drag to position the texture.  Left-to-Right will slide the texture "horizontally".  Top-to-Bottom will slide the texture "vertically".  To scale, hold down shift while clicking and dragging.  Left-to-Right scales the texture horizontally; Up-to-Down scales the texture vertically.

*Advice on Texture Mapping

 Texture mapping works by "pinning" the texture image to a face at each corner.  All the space in between the corners, the texture is assumed to be a smooth transition from point A to point B.

texture pins

When the texture is aligned to the edges of the face, the texture mapping is smooth and faces line up easily.  However, if the texture mapping is not aligned to the edges of the face, we can run into problems.  As mentioned before, the texture is pinned at the face corners, and we can be sure that the textures will match at the corners.  But when the texture is not aligned to the face, the space in between the corners may not line up correctly.  This will give your texture mapping a broken appearance.

mismatch texture

How can we prevent this from occuring and get a nice smooth texture?

The first and best way is to understand that the Cylinder and Sphere mappings are Axis-Aligned.  If your geometry is axis-aligned when you map it, you will get the best results.  You can also create a group or component out of your geometry when it is axis-aligned, and texture it later in any orientation (because the geometry inside the group is still axis-aligned to the group's axes).

 axis aligned

Another option is to triangulate your geometry (break your faces into triangles).  The nature of texture mapping means that triangles will line up with each other better than other shapes.  This won't work all the time, but will work in many situations.

triangulate texture

It's important to note that the nature of Cylindrical and Spherical mapping means they may not generate good results on horizontal surfaces (like the top and bottom of our hexagon).  Manual mapping may be necessary for those faces.

Face Tools

Face Tools operate on selected faces and require at least one selected face.


The Subdivide Tool splits each selected face in half (one or more times).  How a face is split depends on the number of edges it has.  Generally a face will be split on it's longest edge across to the opposite edge or vertex (depending on the number of edges).

  • Select the faces you want to subdivide.  At least one face is required.
  • Right click and choose Subdivide from the Faces menu.

face tools

  • The Subdivide tool will open, set to 1 subdivision.  This is shown with green lines at the point of subdivision for each selected face

subdivide 1

  • Type your selected number of subdivision into the measurement box (1,2,3, etc) or left-click in the model, move the mouse, and click again to set the number of subdivisions based on the length of the specified line.

subdivide 2

  • When you have set the number of subdivisions, right click and choose 'Done'.

Note that you are limited to 10 subdivisions.  It is strongly recommended that you don't exceed 5.  If you need more, reselect the faces and subdivide again.  As iterations increase, a precision error can occur which can cause badly formed or missing faces.  If you use higher subdivision counts, it is recommended that you group and explode your faces after subdivision to help remove badly formed edges and faces.


The Triangulate Tool breaks faces up into triangles.  It uses SketchUp's built in triangulation mechanism, and is very simple to use.

  • Select your faces to triangulate
  • Right click and choose Triangulate from the context menu.
  • Your selected faces will be triangulated.

Note that any face that is already a triangle will not be further triangulated.  Use Subdivide if you wish to break triangles into smaller triangles.



The Greeble Tool adds small geometric details to meshes to give them a "complex" appearance.  It does this by randomly offsetting each selected face.

  • Select the faces to offset.
  • Right click and choose Greeble.
  • A preview of the offset faces will be shown in green.
  • Enter the maximum offset amount in the Measurement box.  Alternatively, click in the model, move the mouse, and click again to set the length of the maximum amount of offset.
  • The preview will update to show the change in face offset.
  • Right click and choose 'Done'.
greeble preview   greeble

Beside created interesting shapes, the Greeble Tool has great practical application for creating randomized brick, stone, and tile surfaces.

greeble brick

 Edge Tools

The Edge Tools provide a variety of tools to modify and create edges.  Some are very simple and others quite complex.

Hard Edges and Soft Edges

The Hard Edges and Soft Edges tools simply set all the selected edges to Hard & Unsmoothed or Soft & Smoothed.  This can be useful in conjuction with other tools to control smoothing.

soft edge

Connect Edges

The Connect Edges tool connects the mid-point of each selected edge.  Selected edges that share a face will be connected with a new edge.  This can be used in conjunction with Select Ring to create subdivisions.

connect edge

Combine Curves

The Combine Curves tool is available when the selected edges are curves, created using SketchUp's Arc Tool.  All connected, selected curves are combined into a single curve.

combine curves


The Bevel Tool creates 'rounded' or beveled corners from every selected edge.  The Bevel Tool is very flexible and can be used with nearly any combination of edges.  It looks best when used with regular, clean geometry.

  • Select the edges you wish to bevel.
  • Right click and choose Bevel Edges

bevel menu

  • The bevel preview will show a preview of the bevel cuts in green.
  • You can set the size of the bevel cut by entering a number into the Measurement box or by clicking in the model, moving the mouse, and clicking again.  The preview will update automatically to show the position of the bevel cuts.

bevel preview

  • Right click and choose 'Done'.  The bevel cuts will be made into the selected geometry.

bevel a

bevel b

As mentioned earlier, bevel works best with regular, clean geometry.  Extra edges, edges with more than 2 faces, and badly formed faces will often cause bad results including missing faces.  In some cases even clean geometry can create missing faces.  These are usually easily corrected by drawing over one of the edges bounding the misisng face with SketchUp's line tool.  The bevel preview will usually highlight problem areas in yellow or red to alert you to possible problems.

Friday, January 20, 2017

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