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29. A Human Skull - Modeling the Jaw 1 |
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 MODELER, THE JAW Load 'SkullTutorial6.lwo'. Do a 'File->Save Object As...' and bump the number by one to 'SkullTutorial7.lwo'. Next comes the jaw. People seem to stay away from doing the jaw for some reason, but a skull is never complete without the bottom jaw. Most people haven't probably thought of it much as they generally see a skull with the jaw intact. But, just as in the wild with wild animal skulls, the only thing that holds a human skull to the jaw are muscles. The jaw is a separate object! Now, some people are going, "Well, OF COURSE the jaw is a separate object!" but others are going, "Hey, I thought that Brazil was a type of nut." So, lets start. We'll build the jaw in Layer 3. Some of you may have the upper teeth in Layer 2, while others might have pasted them directly into Layer 1, but Layer 3 is definitely free. So, click on the upper diagonal of Layer 3. Also, as usual, press 'd', choose the 'Backdrop' tab and under 'Presets' do a 'Load Backdrop' to load in the skull images. We'll be starting in the 'Right' viewport. I turn on 'Symmetry' mode to ensure the points will appear at the zero X axis. I analyze the jaw, determining what my plan will be. As usual, I want to use as few polygons as possible to arrive at the best quality model. I press '+' to select the 'Add Points' tool and start sketching as symetrically as I can the major contour lines.  I turn off 'Symmetry'. In the 'Back' viewport after pressing CTRL-g to enter the 'Select Points' mode, I corral every point with the right mouse button. I press 't' to enter the 'Move' tool and move the entire line of points to the right until it lines up with what I'll call a 'pivot point' where it will soon be swung around to aim at where the joint of the jaw meets the skull.  I press 'y' to use the 'Rotate' tool, point to the bottom-most point in the 'Top' viewport where the red dot is, and clicking the left mouse button and and moving to the left I rotate the row of points counterclockwise...  ... until the 'Back' viewport shows that the dots touch the edge of the back of the jaw.  Because of the angle that it was swung, the points by the jaw's hinge will no longer line up with the edges of the jaw in the 'Right' viewport. I highlight these points.  I press 't' to move the points and line them back up so they are in correlation with the edges of the jaw again. Press CTRL-t to move particular points until they all line up perfectly again. Pay no attention to the fact that the bottom of the back of the jaw in the 'Back' viewport doesn't line up at all with those points. Perspective skews them. The thing we basically needed from that image was where to stop the rotation. Any vertical line would be proper, it would just be lines that went from that point to our eye that would be a problem. Now, I start to create polygons in the same manner we've been doing. I select a poly, clockwise, pressing 'p'. As I move down the jaw from the top of the joint downward, I see that there are points missing, if I wish to make only 4-sided polygons. I stop, press '+' and add some more where I think they might be appropriate.  Remember that it is a fluid medium. You don't have to keep what you make at any time, and if one method doesn't seem to be working, delete those polygons and make new ones. As I reach the area where the two foramen holes are, I decide to change the diamond shaped points that I had placed, and move them so they're in a square formation, instead. I add two points which will join with the lower foramen hole.  After placing new points, I always have to check in the 'Back' viewport to ensure they are placed correctly on the X axis, as well. Sometimes in difficult areas, I have to add or subtract one point at a time. Once I've figured out that area, the rest sometimes becomes evident. In this case, I place one point that will match up with the other three points.  I still don't know what will have to be done around the leftmost of the foramen holes, but it's best to work around that for the time being and, with hope, it may resolve itself. I extend the wavy set of polygons which comprise the gumline (you are familiar with that one) as that might tell me something. I decide to use one triangle and three 4-sided polygons as the triangle shouldn't cause problems, it being flat there. The top part of the top foramen hole has already been resolved.  And, I throw darts with my eyes closed for a second, but I have a pretty firm feeling about most of those dots - at least. Sometimes you just have to whing it and see what you get. In difficult choice situations, it's best not to lay down too many points at once.  I will do a 'k' on the two polygons below the dots and will redraw them as more standard rectangles. I choose to cop-out on a decision for a while. I don't wish to lose any detail yet, and there's a huge flat jaw where I can lose points one by one as I cross it. I'll just have to 'k' (kill) some of those huge simple polygons to the right.  I now have to go from five dots, to two dots. It's always best to do that in stages, so let me do the old five little four little three little... First I'll kill those two big polygons on the right though. And, I kill a couple more polygons for a moment to see what things look like, and I decide to add more more point here...  Now I can see the pattern. If I add these red dots (or move existing dots to conform to them) I can eliminate a lot of triangles.  And, to eliminate the confusion where the jaw turns at the lower-right corner, I add more rows and kill some polygons. I extend the thin area on the left all the way up to the point at the top, and do the same with the right-hand side.  When I start connecting them, though, I am left with one triangle down by where the jaw turns sharply. When I count, I find that I left out a row. I move those rows out of the way to give it room, I select the six points which comprise the row, press 'c' and 'v'. Nothing will seem to have occurred, but if you were in 'Point Select' mode when you did the copy and paste, and points were selected, there are now two sets of points sitting on top of each other. This is a very dangerous position to be in and you MUST move those points before you do anything else or they will be empty points stuck in the same location which will cause problems later, so... press 't' to move them. Move them so they are equidistant from each other.  And, if this were a mathematical formula, it would only be finished if we get rid of that last triangle in the same manner. I highlight the row of points...  I do a 'c' to copy them, a 'v' to paste them, a 't' to move them, and another set of points appears. However, it appears UNDERNEATH the points that were there before and the points that were there before, which are connected to the polygons, are the ones which move. So, the copy/paste in succession only works well when the points aren't already part of polygons. If they are part of polygons, the newly pasted points will not be the ones which move when you wish them to, the connected ones will move. This is why I copy them, I change to a new blank layer, I paste the points, I move them, I cut them to the clipboard with an 'x', I switch back to the original layer, pasting them with a 'v'.  I choose the 'Smooth Wireframe' view type, and enter 'Polygon Select' mode by pressing CTRL-h. I highlight all polygons which seem to need flipping.  I press 'f' to flip them. When I go to the 'Perspective' viewport, I find that the reason some are black, some are dark gray, and some light gray is it looks like a crumpled piece of aluminum foil.  Because I did so many revisions on the points, LightWave guessed wrong where I'd like my X coordinate too often, and I just figured I'd worry about it later. Well, it's now later. I throw the image into a very steep angle, and press CTRL-t, flattening the high ones and raising the low points. I lay it down as if it were a roadway. I move each line so it is smooth as it runs down the line, and I make sure each vertice is equal distant from the ones around it.  Once I've flattened part of the roadway, I zoom in with the '.' key, or rotate it with ALT and do it in the other direction. After flattening them manually for a while, I decide to reverse the rotation I did, flattening them by putting a number in. I return to the 'Top' viewport, and I press 'y' to pivot the points around the same pivot point I pivoted them outwards before.  I enter 'Point Select' mode by pressing CTRL-g. I highlight just one point that I think best represents the X axis of the line and press 'i' to bring up the 'Point Info' requester. I copy down the X position value (18 mm). I highlight all points in the jaw, pressing 'i' again. This time I put 18 mm as the value where it says X (mixed)', when I click OK, it flattens in the X direction.  I press press 'y' to rotate the line and pivot it to the left around the bottom-most point until the edge lines up with the back of the jaw again like it did last time. I enter 'Polygon Select' mode by pressing CTRL-h, highlight all polygons in the jaw, press 'q' to bring up the 'Change Surface' requester, and put in 'Jaw' as a new Surface Name. I click on 'Smoothing' and give it a greenish color to distinguish it from the other colors. Just to check on progress I press SHIFT-v to mirror, 'n' for numeric requester, and OK. I press CTRL-F3 to bring up the 'Surface Editor', I choose 'Jaw' as the surface name and checkmark 'Double-Sided' so I can see the inside of the flat plane on the other side. And, just for this image, I change the color to white to see what it looks like so far.  Now, lets get back to what this representation means. The points that I've highlit in the next image should actually be in the center of the front of the chin, not where they currently are.  You can tell this if you look at the side view. That's what a side/front view means. Thus, the points to the right of those points actually curve around the edge of the front of the chin. So, lets start doing that. I press 'i' to bring up the 'Point Info' requester and put zero in the X gadget. Those six points snap to the centerline.  When I compare which tooth this highlit line of points is on, it corresponds with this tooth. Therefore, I need to create new lines in the front that ripple for those teeth as well.  When I draw the wavy polygons which pass along the gum line, it creates four points between the two lines of points. Too many for such a small space. When I create the points which will be polygons, I drop it from 4 to 3 to 2 so there will be a few triangles, but less congestion.  I highlight the outside points on the side, but not the front, of the jaw. I turn it so its edge is towards me. I press 't' to enter 'Move' tool, and pull all points inward (away from the outside of the jaw) to give it a slight rounded edge  When I make sure all polygons are turned off, pressing TAB to enter SubSurface mode, it is starting to look like a jaw.  I will now create the inside surface of the jaw. Enter 'Polygon Select' mode, CTRL-h, and right-click draw a cyan selection circle around these polygons.  I press 'c' to copy these polygons to the clipboard, pick a blank layer and 'v' to paste them there. From the 'Top' viewport, select 't' to move the polygons and drag them inside the other set of polygons by the thickness you think the jaw would be. A jaw is thinner at the back where the hinge is, and thicker where the front teeth are, so I pivot it around the red dot with 'y' from the 'Top' view.  While in 'Wireframe Shade' view type and 'Point Select' mode, I select every point on the top edge of the inside of the jaw, press 't' to move the points and drag them toward the outside jaw surface until they're about half-way across.  Again I create a bevel on all four foramen holes using the 'Extender' tool.  I extend it from both sides to create a tube between each side just as I did with the eye socket foramen hole.  After creating one internal foramen tube, I copied it to another layer, pasted it, moved it, pasted it back, welding the two ends to the other hole. Press 's' to save the object. Click for a Rotating 3D Version of the skull done using the Blaxxun3D Applet |
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