BetterSpace: Whitestar Tutorial

Lesson 5 part d:
Building the Upper Wings and Engine Pods:
Patching the wing spline cage.

With the spline cage for the upper wings and engine pods loaded into a fresh layer, cut out all the curves that are shown in black in the image below, and paste them into a layer for safe-keeping. All the curves that are not involved in defining the upper-surface of the wing are cut away.

leave only the curves needed for the upper-surface of the wing

The following image should be used as a key for the next few sections:

The curves are labelled, r(x) for a rail curve, p(x) for a profile curve and c(x) for an auxiliary curve.

key for the following sections

Select the following curves in this order:

Press ctrl+f to patch these curves, and enter values of Perpendicular: 10, Parallel 7. If you are making a lower of higher polygon version of the model, adjust these values accordingly, but beware, simply incrementing one of these values by +1 can result in a final model with several thousand more polygons than you may expect. Remember that the number of polygons created by a spline patch is determined by the number of parallel knots multiplied by the number of perpendicular knots. Therefore, whereas you may think that by deciding to use values of 10x10 instead of 5x5 for a particular patch, in order to get double the detail, you actually increase the number of polygons from 25 (5x5) to 100 (10x10). Keep this in mind.

Carefully deselect p1 by clicking on it, and then select p3 by holding down SHIFT and clicking on it. Patch this (ctrl+f) and leave the values as they are in the requestor.

Next, deselect p2 and select p4. Repeat the patching process. Finally, deselect p3 and select p5, repeat the patching procedure...

Did that last patch work as you had expected? Mine didn't. What I got was this:

eh? what's going on here then?

As you can see, the patching worked fine up until that last patch. So why did the last one go wrong?

Okay, you've got me, mine didn't go wrong, I just set it up like that so that I could explain what to do if something like this happens to you. Before I explain, let's clear up the screen. If you have a horrible mess like the image above, press u to undo the last operation. Now deselect everything, and then press w to view the Polygon Statistics. (If something other than polygon statistics pops-up when you press w, close the window and ensure that you are in Polygon Selection mode. then press w again.)

Press the + symbol next to Faces and Modeler will select alll the polygons in the current layer, leaving all the splines deselected. Cut (press c) these polygons out and Paste them into a fresh layer (press p). Now return to your spline cage and put the layer with the freshly-cut polygons into the background layer. Select the following curves in order:

If you study your spline cage, you can see that p5 joins r1 at two points. This is why the patch went wrong. in a case like this, Modeler uses the orientation of the curve to determine how to patch the surface. In this case, the curve is oriented the wrong way around: as you can see, the start of the curve is on the underside of the model. You can fix the problem by selecting p5 by itself and flipping its orientation (press f).

Now, reselect the curves in the order shown above and patch them as before. With any luck, you will be left with something like this:

ah, that's better.

If you are not left with something like that, or if any of your subsequent patches go wrong, simply undo them and search for splines which may be oriented incorrectly. Don't be afraid to flip a few curves here and there to see if you can fix the problems.

Using the Polygon Statistics Window, cut the new polygons out, making sure that you do NOT cut the splines out with them. Swap active layers by pressing the apostrophe (') key. Paste your polygons into this layer. You must now make sure that all of these polygons are facing the same way. refer back to Lesson 1 Section 6 for a reminder of how to do this. Once all the polygons are aligned, deselect everything and merge points (press m).

Swap layers again by pressing the apostrophe so that your spline cage is in the active layer. We will now patch the upper surface of the wing's leading edge.

Select the following curves in order, using the key given previously:

Patch these curves with values of Perpendicular: 5, Parallel 7. It is important not to have too many subdivisions in the perpendicular section, as this is really only a small section of the model, and any more would be wasteful.

Deselect c1 and select p3, then patch the resulting enclosure. Now deselect p2 and select p4... do you see a pattern emerging here? Continue in the same fashion as you did to make the previous set of patches, until you have patched the enclosure made by p4-r2-r3-p5. You should then have something resembling this:

patching the upper-leading-edge

Keeping the splines in the foreground layer, select a fresh layer to be the background layer. Now, deselect everything, cut all the polygons out, swap layers and paste the polygons into this layer. Ensure that all the polygons are aligned correctly, but DO NOT merge points. You will see why later. Swap layers back, select curve c1 and zoom in to it.

Select the following curves in order:

Patch these with values of 5 and 5. This is a three-sided patch, which, as you may remember, needs to have its points merged before it works properly. Deselect everything and the select a few of the new polygons. Press ] (closed square bracket) to select all connected polygons, then merge points. Cut these polygons out and paste them into the layer containing the other polygons forming the leading edge of the wing. Check to see that they are all aligned.

the small 3-sided patch made by r2-r3-c1

While you are still in this layer, cut out all the polygons and paste them into the layer which contains the polygons you created in step 17.

Select a few polygons roughly in the areas shown below. There is no need to be particularly accurate here.

select a few polygons

Now press ] to select all connected polygons. You should have something like this:

All the patches except the small three-sided one you just created, and the one formed by c1-r2-r3-p2 are selected.

you should have these polygons selected

With these polygons selected, merge points. Once this is done, deselect everything and select the two patches that were not selected in the image above. Merge points for these two. You should now have two separate groups of polygons. We'll leave these alone for now. Save the contents of this layer somewhere safe.

Return to the layer with the splines in it. You must now lose the curves p2, p3 and c1. Put them into the layer that contains all the curves which you cut away at the beginning of this lesson (section 17).

While you are in this layer, pick up the rail curve that defines the trailing edge of the wing and cut it out You will also need the small curve that you made in Lesson 5 ptc, Section 9 (labelled tiny profile curve on the trailing edge), and the first fix-it curve from section 14. Paste them back into the layer containing the splines that you have been working on, and merge points. You should be looking at a spline cage like this one:

addendum to key

This image also labels the new curves for easy identification. The curves that you should have just pasted-in are shown selected.

We will now patch the upper-trailing edge of the wing ion exactly the same way as be patched the upper-leading-edge.

Notice that in the above image, the curves c2 and f1 both have their start point on the underside of the wing. If yours do this, you must flip them before you continue to avoid the patch going horribly wrong for the reasons explained earlier. Select the following curves:

Patch these with values of Perpendicular: 4, Parallel: 7. Now deselect c2 and select p3. Patch this etc...

You will notice that if you try to patch p4-r1-r4-p5 Modeler will tell you where to stick it. This is what our fix-it curve f1 is for. The final patch for this section is not p4-r1-r4-p5, but rather it is p4-r1-r4-f1.

Once the patching is done, cut out the polygons and paste them into a new layer, doing the usual chechs to make sure that they are all aligned.

the trailing edge polygons

Finally, we will create the end-cap for the upper-trailing-edge, as we did for the leading edge in section 18.

Select the following curves:

p1-r4-c2

Make a patch with values of 4, 4. Remember the procedures that must be followed after creating a three-sided patch.

the trailing edge end-cap

After all this is done, cut the polygons out and paste them into the layer containing the rest of the polygons that form the upper-trailing-edge of the wing. Check the alignment of all these polygons, and then merge their points.

Cut all these polygons out of this layer and paste them into the layer containing the rest of the polygons that you have created for the upper wing in this lesson.

Merge together all the polygons, with the exception of the polygons shown to be selected in the image below. This image should give you a hint as to what these polygons will be used for: they will form the luminous strip on the front of the White Star's upper wings.

all non-selected polygons in this image have merged points

Select all the polygons shown to be deselected in the image above and press q to change their surface attributes.

Enter the name WS Upper Right Wing Skin and enter the following values.

Press Apply.

We now need to get some details from a previous object, so select a fresh layer and Load the object you made earlier called WS Lower Nose.lwo. This will import all the texture information which is applied to that object. What we are after is the texture for the luminous strip.

Once the object has loaded, return to the previous layer, with your wing polygons. Select the polygons which were selected in the image above, and press q to apply a surface. From the Surface pop-up menu, select Light Strips and press Apply.

applying the Light Strips texture

Once you have applied the surface to the necessary polygons, you can delete the lower nose object which you loaded previously.

Okay, let's turn on the OpenGL preview and have a look at what we've got.

OpenGL view of our polygons

Save these polygons as WS_Upperwing_uppersurface.lwo.

Put ALL the splines for the upper wings into one layer and select the curves c1, c2, f1 & p5. Flip these curves so that their start points are on the underside of the wing. Next, cut out the necessary polygons so that you are left with what is shown in the image below, and paste them into another layer.

leave only curves needed to define the lower surface of the wing

You have seen how to create the upper surface of the wing, and the underside is no different. Repeat all the steps above to build the lower surface of the wing, and you should be left with something resembling the image below.

This image shows the various polygon patches generated by this process. I have alternated their layers so that the different patches are apparent.

the patched lower surface

And now for a quick OpenGL view, so that you can see how it all fits together.

OpenGL view of the lower surface

Load up WS_Upperwing_uppersurface.lwo into the same layer as this object, and merge the points for the whole object.

If all goes to plan, you will be left with this: (This image has been modified to show the underlying polygon structure of the object, you should see a regular OpenGL view.)

OpenGL view of completed wing section

Save this object as WS_Upperwing_Right.lwo.

Do you have any comments of questions regarding this lesson?