BetterSpace: Whitestar Tutorial

Lesson 7 part b:
Building the Spline Cage for the bridge bulge / windows

This part of the lesson will deal with building the small protrusion from the 'head' of the bridge which holds the bridge windows. As you can see from the image below, it is extremely simple, so it should be a welcome respite after building the splines for the rest of the bridge.

the goal of this lesson

The positioning of this object is very important, as it must sit with its lower edges just below the skin of the patched cage of the main bridge splines.

To achieve this, load the object ws_bridge_main_splines.lwo and place it in a background layer.

This image shows the position of the first curve in relation to ws_bridge_main_splines.lwo.

placement of rail curve r1 (left view)

Build the curve shown above in the left view. All points have x=0. As we will patch this separately from ws_bridge_main_splines.lwo, I have re-used names, so this curve is rail r1.

The next rail curve, r2, is the next to be placed. Draw the curve in the top view, then Drag the points into their correct positions in the left view.

placement of rail curve r2 (top & left view)

Next, toggle the End control point of the new curve, so that you are left with this:

r2 with End control point toggled

Our third rail curve's is due for creation now. The table below shows the point order, and as before, bold type indicates a point that already exists.

Note that the third point of this curve joins with the control point of curve r2. The image below shows this. I have left r2 selected for this image, as it shows the position of the control point r2p4.

creation of curve r3, joining r2

One more rail to build now, and this one requires no new points. Refer to the table below for which points to connect.

When the curve is built, toggle its Start control point (Ctrl+B) to achieve this:

creation of curve r4, using existing points

You may be wondering why the curve r1 is all in one piece, while curves r2 and r4 trace an almost identical path, and yet the path is made of two curves. The reason for this is that I want to avoid having a triangular patch between r2, r3 and the profile curve we will make next. By splitting the curve into two (r2 & r4) I can retain a four-sided patch. Clear as mud. Oh well...

With all four rails in place, you should be left with this:

all rails completed

We have now finished the rails (what, already?). It is time to build the profile curves.

Firstly, select the following points:

r2p1, r2p3, r2p4

... and mirror them in the x-axis to form the points r2*p1, r2*p3, r2*p4.

Now use the table below to build the three profile curves we need.

Finally, select all three profile curves and toggle their Start control points, to leave you with the completed cage.

profile curves pr1, pr2 & pr3

Save this completed cage as ws_bridge_bulge_splines.lwo.

We will now patch this simple cage. I am going to use a table to show you which curves to select, in which order and how many subdivisions to use in order to make this work.

So, did you end up with something like this? If you did, Merge Points and move on to the next step. If you've got something different, what did you do wrong?

patched mesh from ws_bridge_bulge_splines.lwo

When your mesh works properly, press Q to bring up the Surfaces requestor and enter the following values:

I'm afraid we have to lower ourselves to do a bit of basic polygon modelling at this point. In order to create the windows, we will use the trusty old Bevel tool to recess some of the polygons on the front of the mesh.

In order to do this, I will assume that your mesh is the same size as mine, so I'll give you a measurement now.

measurement at longest point: 5.28m

As you can see, at its longest point, my cage measures 5.28m. In order to have the bevels work properly, you should scale your object now so that it is the same size as this one.

Now for those bevels. Select the following polygons:

polygons selected for window-making

Press B to Bevel these polygons and enter these parameters:

bevel requester

This will leave you with something like this:

bevelled polygons

Leave these polygons selected and use the Drag tool to move their points around until they look like this:

altered polygons

Finally, press Q to apply a new surface to these two polygons, and enter the following values:

Now deselect all the polygons and mirror them across the X-axis before merging all points.

You will be left with this:

finished mesh

Save this object as ws_bridge_bulge.lwo.

Do you have any comments of questions regarding this lesson?