Monthly Archives: November 2007

Knuckle Coupler

I’m used to making chain link couplings for UK Steam rolling stock, but with the tutorial I thought I’d do a bit of research and experiment with a knuckle coupler.
I found some good drawings of an ARA ‘D’ type in a 1920’s cyclopedia of US steam (CD Rom from PI Engineering)
What an awkward shape! I’ve been working on and off for several days using boolean intersections and subtractions. Welding points where 3DC was not totally accurate, consolidating and optimizing.
I finally ended up with about 400 polys of coupler (Will probably aim for less in the final version) I suspect that’s not too bad considering some chain couplings I’ve made were similar poly counts.
It is probably worth the detail as that is part of the model that people tend to watch very closely.
I’m quite pleased with the result.
I can now add this to my library of parts….

Tutorial 3a – Deck and Chassis

On with a bit more model making. This time the decking and chassis.
First – study the plan and photos. Mike managed to get photos of the real thing, I also have a source of original photos for this particular model, including a few good colour (color Open-mouthed) schemes.
Looking at the plan it seems I need a central rectangle. I can then extrude out the sides of this rectangle twice to get the side decks and extrude the ends
to give me the front/rear platforms by the steps.
From the photos and plan, it looks like there is a chassis extending down to just above the wheels. The decking is probably very thin and there is a small (about 4") side plate around the edge.
For the decking I start by dragging a cube primitive onto the scene.
Check the hierarchy and may sure the new cube group is a child of the main group – this will help with accurate positioning later.
I right mouse click on the cube. Select "Scale -> To Size" and scale it to the size I need.
Right click again and select Properties. Change the X and Z coordinates for the group to 0. This should make the primitive central on the model if the hierarchy is correct.
Now in the perspective view, right mouse drag the decking to the correct vertical position (watch the side view pane)
To start the series of extrusions, hold down the Ctrl Key and select both sides of the box.
Click on the Extrude Operation button on the left menu
If you have the 3DC main panel set up to show the object history, you should now see a parameter adjustment panel for the extrude just below the operation buttons.
Make sure both option boxes are checked and adjust the extrude size by looking at the plan view pane.
Repeat the same procedure for the second width extrude.
Now with the 2 sides selects, hold down the Z key (to restrict movement) and use the scale tool in the side orthographic view (bottom right of the viewport) to add the angle by the steps.
Repeat the 2 extrudes for the ends of the cube.
Now I’m going to delete the vertical sides where the steps go down (8 faces in total) and all of the underside faces.
By running the DoubleSide operation on the whole object, I end up with a deck with 4" side sheets.
I now select a few of the underside faces. This can sometimes be difficult after running the double side operation (3DC bug) – an invert operation usually lets you select them.
We then extrude down about 0.5m (1.7ft) and there we have a very nicely shaped chassis and deck.
(A Consolidate operation will then reduce the polygon count a little)
The Cab comes next …..

Tutorial 2 – The hood

Catching up with Mike – without the video. This is going to be a long blog….
It was a bit hard to see exactly what Mike did on his video, but here is my interpretation.
1. Starting with the Extrude object tool – use the mouse to drag this onto the scene.


2. This starts up a new window with 4 panes. Click on the little vehicle icon and select the side elevation plan.
This tool is not the easiest thing to use, but the general idea is to draw the outline. Don’t worry if the image you’re using isn’t square, it will be scaled correctly afterwards.
I start with a click in the bottom left corner and click to add the first point above it.
The square at the end of the line appears white.
Click on the end of the square again so it turns blue – otherwise the extrude tool will do a bezier spline between all the points.
Basically just work your way around the section, making sure all the points are blue and that the X and Y coordinates match for vertical and horizontal lines. The points can be dragged around the scene and you can zoom in for fine adjustments.
The last point doesn’t need to be blue, it just needs to be placed exactly over the first point (the green one)
Finally add a horizontal line in one of the other panels to give the object some thickness.
Click on the save button and close the window to return to the main screen.
3. First I selected a 30% transparent blue material and used the fill tool.
The new object needs to be positioned and scaled – I select the face that is going to be along the centre line and run my shift centre operation (square with blue X button)
Note – the Extruded object was created in a group that is a child of the Main group.
I then set X value of the object position property to zero. (right click object/properties)
This should centre the edge of the object relative to the main object.
I can now change to 2 or 4 views (menu View/Selection). Using the orthogonal side view, use the position and scaling tool on the lower right of the window to make the object fit over the plan.
4. Switching to 4 view I can now select the outside face in the perspective view. With the "X" key held down, to restrict the movement to the X axis, I can now use the front/rear view drag tool (bottom right) to make the object the correct width. (My plan isn’t cropped correctly)
5. Next I select the 3 top outside edges (Hold down the ctrl key, use edge select tool on right) and drag down the Y axis of the object modify widget to put a slope on the engine hood.
6. I select the front vertical edge of the lights, I can hold down the Z key and use the top view to shift the edge back a bit to add the front angle over the headlights.
7. With the same 3 edges selected from 5, I run the chamfer operation. You need to watch this one – sometimes in 3DC, the points need adjusting. I had to move the highlighted point in the image below down a bit.
8. With more "modern" models I would probably select the 2 new edges and chamfer them again to give an even smoother curve.
9. Ditto with the front vertical edge. I had a similar problem with points after the chamfer and had to make a few adjustments (I can feel a new plugin coming on, possible with multiple chamfer options!)
10. Finally I had to flip the object on the X axis before mirroring it on the X axis as the mirror only works one way. (This also removes the internal face)
I also ran the consolidate operation to remove a few extra polys from the flat faces.
And here it is with a solid texture applied. Canvas does not use smoothing groups – instead, for an object, angles over a set value are smoothed automatically.

New 3D Canvas version

Forgot to add there’s a new version available from
Big performance enhancements in several areas.

The 3D Canvas User Interface

Before I start the next part of the tutorial I think I’ll write a bit about the 3D canvas user interface as it is quite
different to the other tools out there and takes a bit of getting used to.
A lot of people coming from other tools generally have a hard time controlling the view and objects.
The type of item selected is controlled by the top two tools on the right hand menu bar object mode or face/edge/point mode
Multiple selection can be achieved for face/edge/point mode by holding down the ctrl key.
The next thing to mention are the "widgets".
In the perspective view these appear as 3 coloured axes with shaded triangles and as 2 axes in the orthogonal view.
The widget on the bottom left left controls the view point in the scene.
Dragging the mouse over the triangle on the left widget adjusts the view position.
Dragging the mouse over one of the axes on the left widget changes the view angle.
There is also a rectangular "zoom" area next to this widget.
Another (simpler) way to control the view is to drag an object with the middle mouse button (or mouse wheel) held down. This
rotates about the selected object axis. Middle mouse dragging over the base grid zooms the view.
The widget on the bottom right or the viewport applies operations to selected objects/faces/edges/points.
This widget has 2 triangles per pair of axes.
The triangles nearest the axes join/centre controls the position of the selected object/face/edge/point in the selected plane.
Similar move operations can be applied to the selected item using the left mouse button drag on the scene for the X/Z plane
and the right mouse button drag for the Y plane.
e.g. select the top face of a cube and right mouse drag to move it up.
The outer triangle controls the scale of the selected o/f/e/p in the selected plane.
Dragging the mouse on one of the right widget axes, rotates the selected item.
It really takes a bit of time to get used to these widgets and they are also affected by the orientation mode (buttons on the top menu) so it is worth taking a bit of time to practice these on simple objects to see what they all do.


…in Seattle!
It was good to meet up with Mike and some of the other Aces team this week.
However it dos mean I’m going to be a bit behind on the tutorial until I get back to the UK on Tuesday.
An interesting Devcon, pity I’m not allowed to say anything about it.
I now have much more detailed plans for the switcher and Tim C gave me some close up photos of a real one, so hopefully I’ll be able to make a reasonably detailed model now.