When my local City Manager's office wanted an interesting animated open for their public access broadcast of our City Council Meetings, I won the bid. They liked my previous work as well as my idea for this animation. They use three cameras in the chambers. Two on tripods at either side and one "monkey cam" on the back wall set for a wide cover shot. The meeting usually just starts from the wide shot when the mayor strikes the gavel and goes from there. I proposed to do a photo-realistic fly through the room. The viewer would start from the entry as the doors opened, panning back while traveling across the room to highlight the furniture including the podium, the dais, the tables and old time wooden arm chairs. The camera would finally stop in the rear at the same POV as the monkey cam shot holding there as the director dissolves to live from the back wall camera. The people would appear to dissolve into the animation.I used a freeze frame of the wide shot from an actual broadcast to match my animation's final view. I measured the real camera's lens height and position from an arbitrary 0,0,0 point in the room. Then, I set LightWave's camera to those coordinates and set the focal length so the walls and furniture matched the freeze of the live. This way the CG integrated well into the live shot.
All of the furniture in this scene presented modeling challenges especially the old time wooden office chairs. They were important to the clients because they were from the original Chambers and were so sweet. When I first looked at them I thought they were common so a 3D object would be out there in the public domain. After a bit of surfing around, I soon realized that I would have to create them as well as all the furniture and walls the camera would see. They had curved wooden backs that flowed into arms. You could see where the wood had been glued up from smaller pieces and then fashioned to shape.
The right tool for the job
I use LightWave 3D for all my animation work right now. There usually are a number of ways to model things in LightWave. The MetaNURBS modeling tool is generally though of as a character animation tool. I have used it for logo work before when I needed smooth shapes with rounded edges. Now I could see that it was the way to make the chair back piece as well as the seat and red leather seat cushions.Preliminaries
I spent a morning in the actual room taking measurements and pictures. I shot the chairs from the top, front, and side as well as on an angled 3/4-side view that gave me a good template for the curve used for the back rails. I scanned them into my computer. I cleaned them up a bit, accentuating the contrast of the shapes, so I could use them as background templates for the pieces I had to duplicate. My approach was to first make the shapes of the parts and their relationship to each other accurate. The pictures were all to different scales but the shapes were there. Afterwards I would adjust the height, width and depth of the chair globally to make it the right size in the scene. That way I didn't have to worry about the absolute sizes when modeling over the scanned views, just their relationship. After loading the three views of the chair into modeler as background templates I put down 4 points to help align and scale the templates to each other in the backdrop settings. They might not be absolutely the right scales and size but they are now in the proper relationship to each other. (Pic 1)
Modeling the back piece
Remove the alignment points. Because of the chair's symmetry, only half must be created from scratch. MetaNURBS require a pre-nurbed object made up of quad polys which, when MetaNURBS is activated (tab key), will display in preview what the smoothed object will look like when metaformed or frozen. This preview patch view is the cool part because you can make adjustments to the pre-nurbed object and see what it looks like when smoothed in real time. Also you can add geometry with tools like bevel and smooth shift to primitive shapes for more complex models interactively.For this back piece, because of the compound bends and shape changes, I decided to do a rail extrusion on a cross sectional object to give a rough pre-NURB object. Then, after turning on metaNURBS, points could be moved to give it some extra detail that was missing like the wider part for the armrest.
To make the rails put down points, starting at x = 0, across the top edges, forward and down the arm support. Make them into a spline. Use as few points as needed to have the spline follow the curve of the part as viewed in the three views. Turn off grid snap to tweak the spline's points to the right shape with the drag tool. Repeat for the bottom edges. Make sure the points at the start of each curve in the center of the chair back are at 0 with set val.
In another layer, make a 3 by 3 box that is flat in front view (X high and low are 0) Size and position it to be like a cross section of the chair back in the center of the piece. Select the two center rows of point in the y direction and then use the stretch tool to push them towards the top and bottom edges. Repeat in the Z direction. You should end up with a 3 by 3 rectangle in the side view that when NURBS is activated, looks like a rectangle with rounded edges. Experiment with moving the interior points to give a more or less sharp curve to the corners. Without moving the points, the shape of the cross section would be too oval. Finally rotate it to allow for the offset of the top and bottom of the actual cross section of the back piece. Make sure it is positioned right for the rail extrude by moving it in the side view and setting its points to X =0. (Pic 2)
Ride the rails
With the cross sectional template in the foreground layer, put the splines into the background layer. Run rail extrude, default settings with lengths and uniform selected. This will produce an object that starts to resemble the back piece especially when you turn on MetaNURBS with the tab key. There will be 20 more cross sections created and skinned guided by the rails. (Pic 3)
Now comes the part where MetaNURBS shines. In the side view select groups of points from each cross section on the lower arm rest part. Move and rotate them so the patch model conforms more closely to the template. You will notice that there is a common technique to moving the points in a NURB patch model and moving points in a spline curve. To have tighter radiuses move the cross sections closer. To match the side view of the part better move groups of points that defines the surface there. In a few minutes you will be comfortable with modeling this way. (Pic 4)
Add detail with more geometry
In the top view you can see that there needs to be a widening for the armrest. In order to make the outline fit the piece in this area, more geometry must be added. Hide all the polys except this area for clarity. Go to another layer with the model in the background. Make two 2-point polys that will intersect the piece in the top view in the places where additional cross sections are needed to make the additional curves. Switch layers with the comma key. Use Drill to slice to add the needed geometry. (Pic 5) Now there should be enough points from cross sections to model the shape just right. (Pic 6) Unhide the hidden polys.
Now the mirror tool is used at X=0 to create the right half. The NURBS patch view will show an error at the centerline. To correct it first merge points. Then select the 18 polys that were the ends of the two halves of the mirrored sections and delete them. The back section should be contiguous and smooth now. Freezing it with a patch division of 2 should give enough detail for a close camera. (Pic 7)
Surfaces
The piece is really made up of three wood pieces glued together. Each part has the wood grain in a different direction. The glue joint boundaries must be made in order to define the different wood grain surfaces. Slicing the part in the proper areas so the back, the arm rests and the vertical front parts can be assigned different surfaces sets them up. I set up a number of wood grain surfaces for this whole project made from wood images. Some were vertical and some were horizontal. The back section needs a wood surface that has the grain running in the X direction. The armrests need a vertical wood grain surface and so on.Final thoughts
After modeling this part, the rest of the chair was all downhill. The seat was similar but easier. The red leather seat pad was a small challenge because it wraps around the front and under the seat. I found that I could take a copy of the top, front and bottom surfaces of the seat and slice the shape of the base of the seat pad into them. The unsliced polys were deleted and the sliced polys were smooth shifted to create the pre-NURBED object. Some more tweaking of points and I had the seat and Seat pad. The rest of the chair used more conventional modeling.
As you can see from the animation frame, this project was a large detailed job. I feel as if I turned a corner in my career doing it. Every step of the way I had to push my personal modeling envelope. Photo-realism is a lot more work than logos but waaaay more fun.
Isle of Imago - vidjunk@complink.net
