DOS pCNJg @ hpNup`dos.libraryMvtarm' 9-3 ------------------------------------------------------------------------------- HIERARCHIES begets 'upper', 'lower' and 'hand', and 'hand' produces five offspring in the fourth generation, including 'thumb'. A drawback of this organization is that here may be combinations that we wish to select, like both thumbs, or all fingers and all toes, that are not accessible with a single Nvcommand. When you plan your hierarchical structure, you should bear in mind what combinations are going to be used most often, and design the hierarchy accordingly. Another major factor in the design of the hierarchy is motion. Although we have only touched on the subject so far, the primary use for a scene's hierarchy will probably be to animate objects. In later chapters, you will learn how motion fits into the hierarchy, but first you have to learn how to construcObst the hierarchy itself! Building a hierarchy As you have probably guessed, there is a facility in Sculpt Animate for building a hierarchy of names. To see it, execute the menu command EDIT NAME SELECTED VERTICES. Although this command is designed to supply a name to a group of selected vertices, it also lets you build a hierarchy of names. The requester that pops up has a column of 9 slots. This represents the 'current' generation of the hierarchy. Ps; Because we have not entered any names, all the slots are empty. To the left of the current generations is a long horizontal box titled 'Parentage', which is also empty. When the requester comes up, the box titled 'Add name:' will have a cursor in it, which means that it is ready for you to begin typing in the first name of the current generation. For starters, type in 'Bill'. When you press RETURN, the name will be transferred to the center of the current generation. Q5| 9-4 ------------------------------------------------------------------------------- HIERARCHIES Now type in 'Fred', 'Joe', etc. As you type in more names, you will notice that they are entered into the current generation in alphabetical order, and the name is always entered into the center slot. You may wonder just what it is that you are naming. As of now, nothing. You are simply enteriRJܔng names into the hierarchy. You may enter a number of names all at once, then go back at your leisure and assign them to vertices. +------------------------------------------------------------+ |============================================================| +------------------------------------------------------------| | NAME SELECTED VERTICES | | S V | | +------------+ +--+ +--------------+ | | Add name:| | |/\| | | | | +------------+ +--+ +--------------+ | | | | | | | | +---+ +----+ +-----+ | | +--------------+ | | |CUT| |COPY| |PASTE| |==| | | | | +---+ +----+ +-----+ | | +-T 8-------------+ | | Parentage | | |Bill | | | +---------------------+ | | +--------------+ +---------+ | | | | | | |Etc | |OFFSPRING| | | +---------------------+ | | +--------------+ +---------+ | | | | |Fred | | | +------+ |==| +--------------+ | | |RENAME| U8 | | |Joe | | | +------+ | | +--------------+ | | +----------+ | | | | | | |ERASE NAME| | | +--------------+ | | +----------+ | | | | | | +------+ +--+ +--------------+ +--------+ | | |CANCEL| |\/| | OK | | | B E CHAPTER 9 WHEELS WITHIN WHEELS Whenever you must deal with a complicated system, it is always easier to break down the larger problems into a number of smaller, simpler ones. As we saw in chapter 6, it can be very convenient to think of a complex object as a collection of simpler parts. When the object is completed, you can connect the parts together and forget about them, dealing with the object as a single item again. But wC ""hat if we want to deal with an object as a whole at some times, and as a collection of parts at others? As we begin to animate objects in subsequent chapters, you will see ample need for this ability. Sculpt Animate allows you to organize the objects of a scene, the parts of the objects, the parts of the parts, and so forth, into a hierarchy. At any given time you can deal with the level in the hierarchy that suits your needs. In later chapters you will see that, as DUAwith objects, object motions may also be placed in the hierarchy. Hierarchies of objects A hierarchy is a structure in which each member has a well defined level. Except for the uppermost level of the hierarchy, each member is subordinate to one superior member. On the other hand, each member may directly control one or more members at the next lower level. This ordering is similar to that of a branch of the armed services, or a large corporation. The Eexception is that in these 'real world' hierarchies, lower members are often subordinate to any superior, not just one. 9-1 ------------------------------------------------------------------------------- HIERARCHIES Another everyday structure that takes the form of a hierarchy is a family tree. We will borrow some familiar terms like 'parentage' and 'offspring' when we describe the hierarcFK Khial structure used in Sculpt Animate. The object structure of Sculpt Animate is imposed by giving names to groups of vertices. The names form a hierarchy. For the time being we will be discussing this hierarchical structure 'on paper'. The next section will discuss the mechanics of constructing and using such a structure. Suppose that we have constructed models of several people, Fred, Joe and Bill for example. It would be convenient to be able to treat the G&W*model of each person as a single entity, even though each may be constructed from several unconnect elements. It is as though we could issue the command 'SELECT Bill', and have all the vertices of the model Bill be selected. Bill could now be grabbed and moved to a new location, or rotated and expanded. For many cases, this is quite enough. If, for instance, Bill were not a human figure, but actually one of three red regions on the hull of a flying saucer, then havinHjX%g a name tagged onto Bill's vertices permits you to select them independently, without having to care what they're connected to. This sort of ad hoc, piecemeal, naming of things can be very helpful if you are just modeling objects. More complex organization may not be needed. But, as its name suggests, a big part of Sculpt Animate is animation. Bill, is more than likely, a human figure; or at least something that moves. If simple naming were all there was to the sceItRne's hierarchy, Bill would be like a mannequin with no moving parts. In the hierarchy, though, we can arrange his parts into a series of levels, with the whole lot being named 'Bill'. The idea is to be able to select some of Bill's parts independently, or select Bill all at once. Lets say we want to be able to select just Bill's left arm. It wouldn't be enough just to rename those vertices as 'leftarm,' because they would no longer be selected when J 9-2 ------------------------------------------------------------------------------- HIERARCHIES we select Bill. We need to have a way to name the vertices 'Bill's left arm.' In Sculpt Animate parlance, this can be done by naming the vertices 'Bill+leftarm.' Assuming that we had deselected all vertices, the command "SELECT Bill+leftarm" would then cause all the vertices of Bill's left arm to be selected. BK wy placing the cursor at Bill's left shoulder, the rotate gadgets could be used to raise Bill's hand, the first step in an animated salute, for example. This suggests that we could decompose Bill into several elements, such as Bill+leftarm Bill+rightarm Bill+head Bill+torso Bill+leftleg Bill+rightleg Each element could be further decomposed, for example Bill+leftarm+upper Bill+leftarm+loLJ3wer Bill+leftarm+hand The only limit in our subdivision is the amount of detail in the model of Bill. We can continue. Bill+leftarm+hand+finger1 Bill+leftarm+hand+finger2 Bill+leftarm+hand+finger3 Bill+leftarm+hand+finger4 Bill+leftarm+hand+thumb If we compare the structure of Bill to a family tree, we can regard the name 'Bill' as the founding father with offspring 'head', 'leftarm', etc. The name 'left7/$ne, point the cursor at any vertex on the spline, and execute the command EDIT SELECT INDICATED SPLINE and each knot on the spline will be selected. After you have built the curve that you need, it is a good idea to erase the underlying spline. Just move the cursor to one of the vertices of a spline and execute the command EDIT ERASE INDICATED SPLINE. The spline will be removed, but its vertices will remain. The vertices can now be manipulated in any of the usual wa8)ys. A spline uses up a certain amount of memory and it also slows down the refresh speed of the Tri-View, so once you are through manipulating the spline, it should be erased. Splines can also be made that are closed loops. Create them in the usual way. For example, draw a square with the curve tool. Then use the EDIT DO SUBDIVIDE menu command a few times so that you have several vertices along each side. Deselect all the vertices, and select only the corner verti9YVtces as knots. Then execute the EDIT DO MAKE 8-8 ------------------------------------------------------------------------------- SPLINES SPLINE command and you should have a fairly tolerable approximation to a circle. Experiment with the speed parameters, and you will find that you can make the circle slowly revert to a square again. An example: a gearwheel Suppose you wished to :Rmake a convincing model of a gearwheel, you could use splines to make the job much simpler. First clear the Tri-View, and make the Tri-View windows large with the command EDIT DO MAKE TRI- VIEW BIG. We are going to make a twelve tooth gear wheel, using eight vertices per tooth. In the west window add a circle with 96 subdivisions. Carefully select every fourth vertex of the circle. As a check, make sure there are three unselected vertices between every two selected;@= ones, especially between the last and first vertices that you selected. Execute the command EDIT DO MAKE SPLINE. You now have a 96 vertex circular spline, with 24 knots (all the knots are selected). Now deselect every other knot, so only twelve vertices remain selected. Execute the command EDIT DO EXPAND and make sure that the center of expansion is either CENTER or CENTROID. Move the upper slider a small distance to the left and watch a gearwheel shape emerg<Oe. When you are satisfied with the shape, leave the requester by clicking OK. Move the cursor to any vertex and execute the command EDIT ERASE INDICATED SPLINE, because we no longer need to use the properties of the spline. You now have the profile outline of a gearwheel. Save this outline to disk--you will need an unfilled copy later. Now the gear wheel profile may be filled with triangles, to make it a visible surface. If you were to select the gearwheel's =Rprofile and use the EDIT DO FILL command, the time to fill in a 96 vertex curve would be about half an 8-9 ------------------------------------------------------------------------------- SPLINES hour, so it might be quicker to use the edge maker tool. Alternatively, and perhaps less tedious, you can make a number of edges manually, to divide the outline into a dozen or so regions, the select eac>P1Ķh region in turn and use the FILL command on it. In any case, once you have filled the profile, save the filled version to a separate disk file, being sure not to overwrite the unfilled copy. You could now simply extrude the filled outline to create a solid gearwheel, but this step has two disadvantages. First, this will leave the back side of the gearwheel open. This is actually an advantage if it will never be seen, since it saves memory and speeds calculation,?̭ but it could be annoying if the back side needs to be there. The second disadvantage only arises if you intend to use smoothing. There are two things that can confuse the Phong smoothing algorithm: flat surfaces made up of many faces, and right-angle corners (see chapter 4). If you envision our extruded gearwheel, you'll see that it has both of these problems! If you wish to use smoothing on the curved portions of the teeth, you must somehow separate the gearwheel's @ dpedge from its flat surfaces. One way to do this is to form the gear wheel from three unconnected parts: the two flat faces and the curved portion that joins them along the edge. This allows you to turn smoothing on only for the curved portion. To do this, first clear the Tri-View and load the gearwheel profile that you saved earlier. Use MODIFY FACES to turn on smoothing, then extrude the profile. Add a copy of the gearwheel's filled surface with the PROJECT A lLOAD OBJECT command. Use the Grabber to move the face into place at the front of the gear wheel. Load a second copy of the filled outline and position is as the back surface. Select the flat surfaces and use MODIFY FACES to turn their smoothing OFF. The gearwheel is complete! 8-10 ------------------------------------------------------------------------------- ,"x[gadget to accept its new settings, or click the CANCEL gadget to undo your manipulations. In either case, the requester will vanish, and the rotate gadgets will resume their normal operation. If you make a spline with several knots and set the speed parameter for each knot to zero (the leftmost position for each slider). Then the non-knot vertices will move to lie on straight line segments between the knots. Try it. Although splines are usually thought of as smooth -#}curves, they can be made quite angular. Now go back and set the speed for each knot to its maximum value, and you will see that the spline shoots away from each knot with such force that it may even perform a loop before returning to the next knot. Quite baroque curves can be constructed in this way. Remember what they look like, you never know when they might be needed. We can compute this operation to the use of a wooden spline. Increasing the speed at a kn.$z)ot is like making the spline stiffer at that point, while reducing the speed softens the spline locally. Our simulated spline has far outstripped the abilities of any real spline. Although it is tempting to scatter many knots throughout a curve, the power of Sculpt Animate's splines is best realized if you use very few knots. If you go back to the example spline with only two knots, you will find that many very graceful curves can be created simply by adjusting their /%i/ speeds and slopes. In chapter 10 we will see how any 3D curve, including spline curves, may be used as a path to describe motion. In this use, each vertex of the curve represents a location in time and space. The 'speed' of an object following the curve will be directly proportional to the distance between vertices. You should remember that this interpretation of the word 'speed' differs slightly from the 'speed' of a knot. While it is true that increasing a k0&not's speed generally moves the 8-6 ------------------------------------------------------------------------------- SPLINES adjacent vertices apart, the effect is local. The distance between vertices also depends on the speed of adjacent knots, and on the number of non-knot vertices between knots. Each of these factors will figure into the perceived velocity of the animated object. Cusp1'[*s In mathematics, a cusp is a point where two curves meet with equal and opposite slopes, as in the horns of a crescent moon. In general usage, a cusp can refer to anything pointy looking. In Sculpt Animate, we will use a looser definition and apply the word to a place where two curves meet, but do not share a tangent. To see how this applies to splines, create a spline with at least three knots, set the cursor on one of the interior knots, then call up the M2(]ODIFY KNOT requester. Look at the gadget labeled 'Knot type:'. As you may have noticed on other knots we have worked with, this knot's type is REGULAR. The 'type' gadget is a toggle gadget which toggles between REGULAR and CUSP -- set it to CUSP. When the knot is made a cusp, the gadget labeled 'Side:' will become effective. This is another toggle gadget that has two states, INWARD and OUTWARD. These states refer to the two arrows that mark the knot. One points in3)1Hward, towards the knot, and the other outward, away from the knot. By toggling the Side gadget you can pick the side you want to manipulate. The side of the slope arrow that you can manipulate will be shown in yellow, the side that is shown in purple will not move. When a knot is made into a cusp, it is split in two, so to speak. Each side of the knot affects the non-knot vertices on that side, but has no effect on the other side. This means that the knot suddenly 4*jhas two slopes and two speeds, one set for each side. A cusp is like a point where the draftsman's wooden spline has been snapped and joined by a hinge. Use a cusp when you need to break up an otherwise smooth curve with an angle or corner. 8-7 ------------------------------------------------------------------------------- SPLINES Using splines By now you have probably thought of seve5+-Vral uses for splines. If you need to build an object with smooth curves, a spline will ensure that the vertices are placed along a convincingly smooth shape. If your hand hobbles while you use the Curve Tool, the wobbles will find their way into objects that you Spin or Extrude from the curve. Picking a few strategically placed knots and creating a spline will even out all the wobbles. If you want to modify a curve, it's much easier to grab a knot or two and move th6[mem, rather than have to individually move a dozen or more vertices and try to make them represent a smooth curve. Of course, the trade off is that non-knot vertices of a spline can only be moved by moving the knots. If all the knots of a spline are selected, then the grabber will move the spline all at once, without changing its shape. The rotate gadgets may also be used freely on splines, and on sections of splines. If you ever need to locate the knots of a spli!-:+vr of parameters is called the slope and the other pair is called the speed. The slope at the knot is just the direction of the 8-3 ------------------------------------------------------------------------------- SPLINES curve in the vicinity of the knot, in mathematics, this direction is called the tangent. Unless you take special action, Sculpt Animate calculates a reasonable slope based on t".dhe positions of the knots on either side To see how this works, do an ERASE ALL to clear the Tri-View, and draw a curve with a dozen or so vertices. Deselect them all and then select the two end vertices. Make a spline, as described above. All the non-knot vertices will align themselves uniformly between the knots. With only two knots, there is no information about the shape of the curve that you would like, so Sculpt Animate generates the simplest possible curve bet#/ xween the knots--a straight line. +--------------------------------------+ |======================================| +--------------------------------------| | MODIFY KNOT | | | | +----------+ | | Knot type: | REGULAR | | | +----------+ | | +----------+ |$0F | Side: | INWARD | | | +----------+ | | +----------+ | | Slope: |CALCULATED| | | +----------+ | | | | | | SPEED | | +----------------------------------+ | | | || %1 EDIT MODIFY INDICATED KNOT. A requester with the title MODIFY KNOT will pop up. The requester has a drag bar, so you can move it out of the way if it hides the spline you are working on. In the requester, you should see a gadget marked CALCULATED, beside the title 'Slope:'. Click on this gadget, and it will toggle 8-4 ------------------------------------------------------------------------------- '3~> SPLINES between CALCULATED and SPECIFIED. Leave the gadget in the SPECIFIED state, and notice that a yellow arrow has now been drawn at the position of the knot. The rotate gadgets in each window now have a special purpose. Instead of rotating selected vertices, they rotate the yellow arrow, which represents the slope of the knot. Rotate the arrow and notice that the curve between the knots deforms so that its tangent always matches the slope of the knot. (4 By switching to another Tri-View window, and using the rotate gadgets, you can point the slope in any direction and the curve will follow. If you click the slope gadget, so that it is in the CALCULATED state, the curve will snap back to correspond to the slope calculated from the positions of the nearby knots. The slope that you constructed is still remembered for the time being, in case you wish to return the knot to its SPECIFIED state later in this session. Only SPEC)5IIFIED knot states are saved with the scene, though. When we manipulate a knot's slope, it is as though we were twisting a draftsman's wooden spline at one of the knots. Real splines would not long survive such treatment, nor do real draftsmen have surplus hands to apple torque at each knot, so our mathematical spline has creative advantages over its real-world counterpart. The other control that you have over a knot is its 'speed'. This is set by the slider contr*6m\ol near the bottom of the MODIFY KNOT requester. To best understand how this parameter works, specify the slope of the knot you've been working with so it's at an angle of about 45 degrees to the line between the knots. Now just move the speed slider and see what happens. Each time you release the slider knob, the spline will be re-drawn. With large values of speed, the spline will seem to shoot out a long way before being influenced by the other knot. Small values +!3ãof speed will cause the spline to quickly forget about its initial slope and move towards the other knot. Also notice that the non-knot vertices get farther apart as the speed increases, and closer together as it decreases. 8-5 ------------------------------------------------------------------------------- SPLINES When you have finished manipulating the knot, you can either click on the OK 8I1designer wished to generate a smooth curve, he used a thin strip of wood (or metal or plastic) and bent it to produce the desired shape. The strip was called a spline. Usually, the designer would mark a few points, called knots, on his paper, and bend the spline so that it passed through the knots. The spline defines the shape of the curve between the knots. A mathematical simulation of a spline requires a little calculus, but all the messy details can be left to the9)^ computer. Sculpt Animate only needs three commands to work with splines: one command to make splines, one to modify them, and one to erase them. Although splines are very simple to use, there are some rules that must be followed, and since they are not at all obvious, you should study the next section quite carefully. As we have seen, a curve may be represented by a sequence of vertices that are joined by edges. They are not really curved at all, they are just a se:-b0quence of straight lines segments. If you use many segments, the approximation to a true curve becomes quite good. The curve tool can be 8-1 ------------------------------------------------------------------------------- SPLINES used to construct a sequence of edges, or the sequence can be built in a number of other ways using facilities we have already seen. Having constructed a curve,;j you can make it a spline, but first you must tell Sculpt Animate which vertices are to become knots. To do this, be sure that all other vertices in the scene are deselected, then select a few vertices along the curve you are working with. The vertices you select will usually be key locations along the curve--points that you either don't want to move, or that you want adjacent vertices to follow. Make sure that you have several unselected vertices between adjacent se<‚Ulected vertices. When the selected vertices become knots, the unselected ones will 'snap' into a smooth curve, and afterwards follow the knots wherever they go. Now execute the EDIT DO MAKE SPLINE command. If you have done everything correctly, the command will subtly alter the curve you have laid out. If a warning message appears, you have probably selected vertices that do not all lie on a single, unbroken curve. If this happens no other actions will be taken, so =hyou can try again. If the spline command succeeds, the unselected vertices on the spline curve will be re-aligned so they lie on a smooth curve which passes through the knots, which should not move. Each knot will have a small arrow drawn on the edges that connect to it. This identifies the vertex as a knot, even if it is not selected. By making the curve a spline, you have given it a property of smoothness. Until the spline is erased, anything that you do wit>h this curve will result in a smooth, flowing transition from one knot to the next. There is more than one way to draw a curve through a set of points, so the spline command picks one that follows a simple mathematical formula. You can exert quite a lot of influence over the curve, though, if you do not like the one that was chosen for you. 8-2 -------------------------------------------------------?3------------------------ SPLINES Let's try manipulating the spline some. Deselect all but one knot and use the grabber gadget to move the knot. If you watch closely, you will notice that the other knots do not move, but the non-knot vertices between the moving knot and the adjacent knots move so as to always lie on a smooth curve. Deselect the knot and select a non-knot vertex. Now try to move the vertex with the grabber tool and you will see that the grabber h@Sas no effect on a non-knot vertex of a spline. This is because the position of a non-knot vertex is solely determined by the positions of neighboring knots. This is one of the exceptions to the rule that only selected vertices may be manipulated in Sculpt Animate. In this case, non-knot vertices, selected or not, may only be manipulated by working with adjacent knots. Moving knots is the most fundamental way to manipulate a spline. Note that the spline does notAB0 have to lie in one plane. To see this, go to another Tri-View window and move a knot. you will see the spline twist into a third dimension. In Sculpt Animate, a spline is more like a piece of wire than a curve drawn on a flat surface. By moving the knots, the spline can be bent into almost any shape. There is one tricky part to manipulating a spline this way. If the spline is very smooth (that is, if it has a lot of non-knot vertices), then it may be hard to sele ,ct a knot by itself without contracting the Tri-View to 'zoom in' on it. Fortunately, this isn't necessary. As long as you've selected the one knot you want, selected non-knot vertices will just follow along as usual. This means you can use the Selector tool to 'shotgun select' several vertices in the neighborhood of the knot you want. Slope and speed The exact shape of the spline between two knots is determined by four parameters, two for each knot. One pai C6NH | G | |> | | | +------------------------------+ | | +------------------------------+ | | B | |> | | | +------------------------------+ | | +------------------------------+ | | H ||> | | | +------------------------------+ | | +-------- D U----------------------+ | | S ||> | | | +------------------------------+ | | +------------------------------+ | | V | |> | | | +------------------------------+ | | | | +-------+ | | | |  E)L | | | | | | | | | | | | | | +--------+ | | +--------+ | | | CANCEL | | | | OK | | | +--------+ +-------+ +--------+ | | | +---------------------------------------+ Fط The GROUND Requester If you select a SOLID ground, then it will be uniformly colored and you can use the sliders to pick a color. If you select CHECKERED, then the swatch divides into two and you can select two colors, just as you did for the sky. A checkered ground plane is one where alternate squares on the ground are different colors, like the squares on a chess 7-G!ڿ7 ------------------------------------------------------------------------------- THE WORLD board. The ground will only be checkered in the HAM imaging modes. In the other solid modeling modes, the ground will be the color of the top-half of the color swatch. The size of the square can be specified by clicking on the small checkered icon just to the right of the word CHECKERED. This sets the size of each square to be the same as the maximum dimension of the cuHrrent Tri-View 'box'. For instance, if you click this gadget when the Tri- view is sized so that only a small portion of your object is visible, then the checkers will be small in comparison to your object. If the object looks small in the Tri-View when you click the gadget, then the checkers will be very large relative to your object. In case you need to know, the center four-square of the checker pattern will always be centered on the Origin. The top half of the cIdolor swatch will be used for the northwest and southeast squares of this center block, the bottom half for the northeast and southwest squares. Although a checkered ground plane has become something of a cliche in computer generated images, it does give the image more depth, and enhances the illusion that the ground extends to infinity. In addition, it adds interest to scenes that contain mirrored objects, for the reflections of the checkered ground make it easier for J{O#the eye an brain to perceive the shape of a mirrored object. You can stretch the usefulness of a checkered ground with a little creativity. A red-and white checkerboard with fairly small squares can look like a tablecloth, especially if the observer is looking downwards. Enormous squares done in two earth-tone colors can suggest an agrarian plain. Additional features, such as hills, etc., can be added as objects placed in the background. When you use a checkerbK-oard, it is often best to keep the lamps fairly close to the subject, not much farther than the observer. This tends to darken the ground in the distance, reducing odd effects that can occur where the checker squares become very small. On the other hand, sometimes it 7-8 ------------------------------------------------------------------------------- THE WORLD can add balance and interest to anLٙ image to place an extra lamp off in the background, illuminating a patch of the checkerboard where there would otherwise be an unbalanced empty space. 7-9 ------------------------------------------------------------------------------- CHAPTER 8 SPLINES Earlier we showed you how to create basic curves in Sculpt Animate7 by placing individual vertices. This chapter describes a way by which you can take such a curve, roughly sketched, and easily transform it into smooth, sweeping curves. With a few mouse clicks you will be able to construct convincing profiles for aircraft and boats. Curves generated this way can be modified and controlled interactively. Splines and knots Splines provide a way of creating and manipulating smooth curves. In the days before computers, when a Nr1]-------------------------------------- THE WORLD The illumination setting can sometimes be used in place of fill lighting, but if the illumination value is set too high, images will seem flat and lifeless. Too small a value will make shaded faces look unnaturally dark. The default value that is set at program start-up is a good all-around value. The sky You will have noticed a blue background in the images you have created so far. This background, Oalthough it is called the sky, need not be blue. Execute the menu command WORLD SKY and you will see a color requester pop up. The SKY requester is similar to the ILLUMINATION requester, but it has a couple of extra gadgets. Unless it has been changed, the topmost gadget will contain the word GRADUATED. This gadget is a three-way toggle. Click on it a few times and watch it change from GRADUATED to NONE, then to SOLID, repeating the cycle as you continue to click.Pf If you leave this gadget set to NONE, there will be no sky, and the background will be black. Notice that the color swatch shows black, despite the settings of the sliders. Now select SOLID, and see that the swatch now reflects the color set by the sliders. If the sliders are moved, the swatch changes color normally. If you click OK and make an image, then the background color will be the one that you have selected. Now select GRADUATED, and notice that an exQJtra border is added around part of the swatch's perimeter. If the border surrounds the top half of the swatch, the sliders only change the color in that half. Now click anywhere on the swatch. The border should jump from the top of the swatch to the bottom, then vice versa if you click again. This is a special kind of toggle gadget. By selecting which half of the swatch is highlighted by the border, you can set up two entirely different colors. The upper color representR,zs the sky 7-5 ------------------------------------------------------------------------------- THE WORLD color at the zenith, or directly overhead. The lower color represents the color at the horizon. If you make a picture with a GRADUATED sky and use SNAPSHOT or PHOTO mode, the sky color will blend smoothly between the ones that you have selected. In PAINTING and SKETCH mode, the color S18of the sky will be the zenith color. As we have said, a GRADUATED sky blends the two selected colors into each other. In fact, some blending might actually occur if you were to set the two colors to the same value. This is because the color sliders are more accurate than the color resolution of the Amiga. If the slider setting falls between two usable values, Sculpt Animate 'dithers' the colors to simulate the correct shade. Because a GRADUATED sky must be ditTmhered anyway, this should cause no problem. If you select SOLID sky, however, it will be assumed that you want no dithering, and the closest available 'pure' color will be used for the whole sky. The ground If you wish to depict a scene in which objects are not floating freely in space, but are sitting on or suspended near the ground, then you must make a model of the ground. If the ground is to be flat, then a single triangular face could be employed. U:j If it is a few hundred times bigger than the scale of the other objects, it will seem to stretch off to infinity. This sort of ground has some disadvantages: for one thing, there is the bother of constructing and placing the ground; for another, this type of ground will often obscure your objects in the SKETCH rendering mode (see imaging modes, chapter 3). As a simpler alternative, you can use the ground plane that is built into Sculpt Animate. To use it, execute theVY command WORLD GROUND. A color requester will be 7-6 ------------------------------------------------------------------------------- THE WORLD invoked. Like the sky color requester, it has a ground type gadget near the top right. By clicking on it, it can be toggled between NONE, SOLID and CHECKERED. If NONE is selected, then no ground is produced. Otherwise an infinite ground plane is W9 generated that passes through the Origin. The Origin is the center of the Sculpt Animate universe, and it is where the observer target is initially placed. If ground exists and it passes through the Tri-View, it is displayed as a horizontal line in two of the windows. If you enable the ground but can't see it in a Tri- View window, it is because the Tri-View 'box' is too far above or below ground level. Try expanding the Tri-View until the ground comes into view.  B9 +---------------------------------------+ | +-----------+ +-----+ | | GROUND TYPE: | CHECKERED | |.:.:.| | | +-----------+ +-----+ | | +------------------------------+ | | R | |> | | | +------------------------------+ | | +------------------------------+ | Ysq* 7-2 ------------------------------------------------------------------------------- THE WORLD use the OBSERVER EXPOSURE MANUAL setting to brighten it. To see the effect of various lighting arrangements, try rendering a few SKETCH mode images of a test subject. A one-subdivision white sphere does nicely. Start with a single lamp at or near the observer's location, then render a few images, moving the lamp around towards one side a litZtle each time, until the subject is entirely side-lit. You will see that the shading of the sphere becomes deeper and more dramatic as the lighting becomes more oblique. It is usually good also to raise the main light up above the level of the subject, raising its highlights. As the obliqueness of the main light source increases, so does the need for a second light--otherwise the shading becomes too deep. The second lamp, called a 'fill' light, will usually be placed[Kq to the other side of the observer, perhaps a little closer to the line of sight. The fill light needs to be dimmer. While it is all right to reduce its 'wattage' with the brightness setting, it may be easier to simply place it a little farther away from the subject so you can see at a glance which light has more effect. When you are using PHOTO mode, you will often want dramatic shadows to be cast on the ground (the 'ground' is explained later in this chapter). If t\p4ݼhe subject is on the ground, this can often be achieved by placing a third light source relatively high, and somewhat behind the subject. This 'backlight' should usually be as bright as, or brighter than, the main light. If the subject is above the ground or the main light is far enough to the side, then the shadows cast by the main and fill lights may be enough. In some cases the 'main' light may be discarded, and only a backlight and fill used. These are not rules,] by the way, just basic suggestions to get you started. The only rules when it comes to lighting are use your imagination, try things out, and remember the arrangements that please you. 7-3 ------------------------------------------------------------------------------- THE WORLD Illumination Sculpt Animate employs a technique called low albedo approximation when it generates an image. ^`Y* This means that any part of an object that is hidden from all light sources will be totally dark. Such objects will not pick up reflected light from nearby illuminated objects. In order to soften the shadows, Sculpt Animate allows you to specify a diffuse ambient illumination that is independent of the lamps that you create. +---------------------------------------+ | | | BACKG_!ROUND ILLUMINATION | | | | +------------------------------+ | | R | |> | | | +------------------------------+ | | +------------------------------+ | | G | |> | | | +------------------------------+ | | +-----------------------`6jE-------+ | | B | |> | | | +------------------------------+ | | +------------------------------+ | | H ||> | | | +------------------------------+ | | +------------------------------+ | | S ||> | | | +------------------------------+ | aumc | +------------------------------+ | | V | |> | | | +------------------------------+ | | | | +-------+ | | | | | | | | | | | | | | bC9 | | | | +--------+ | | +--------+ | | | CANCEL | | | | OK | | | +--------+ +-------+ +--------+ | | | +---------------------------------------+ The Illumination Requester You can change the amount of the illumination with the command WORLD ILLUMINATION. ThiM9s brings up an illumination color requester that you operate in the same way as other color requesters. Unlike the lamps, there is no separate brightness facility for controlling the intensity of the ambient illumination, so you must do this entirely with the value (V) slider. Usually the V slider should be set about one quarter of the way from the left. 7-4 -----------------------------------------d Et have to, that's what DUPLICATE and REFLECT are for. By thinking of a scene in terms of parts, you can dispense with the 'easy' parts quickly, and concentrate on the parts that aren't so easy. 6-17 ------------------------------------------------------------------------------- MORE TOOLS Most of the time, you'll find that the 'hard' parts aren't that hard after all. The primary reason theUat a new shape looks hard is that you haven't done anything like it before. The best defense against this is to thoroughly familiarize yourself with the tools and commands that we have discussed, and the kind of shapes they can create. Remember that once you have achieved a basic shape, there are still any number of ways to transform it into the object you want, by adding and deleting vertices, resizing, spinning, etc. Every new object you create will open up a whole f;[new range of possibilities. 6-18 ------------------------------------------------------------------------------- CHAPTER 7 THE WORLD This chapter discusses the world in which Sculpt Animate objects reside. Facilities are described for lighting a scene and providing a ground and sky. Creating lamps The shag