Contents page

Index

IX. A Mode for Every Season

                        IX. A Mode for Every Season

The basic commands to pick, move, and view the world and everything in it are very important, as they are used constantly. The actual work you perform in building objects depends on the user changing the view and manipulating the objects almost without thought.

No matter how good we are at manipulating objects and changing the view, using these commands will never BUILD an object for us. To do this, Imagine has different MODES that it performs different actions in. Some modes allow us to manipulate objects and groups, as we have been doing already. Other modes let us pick and manipulate not objects, but the POINTS of an object, or the edges, or the faces. Still other modes let us drag points around in different ways. Some let us add NEW points, edges, and faces. (Aha! So that's how we can build our own objects!)

These modes are easy to change; you can just pull down the Mode menu and select which mode you would like to be in. The current mode is always displayed in the status line at the top of the screen; this is often handy when you get confused about what you're doing. The keyboard equivalents for changing the current mode all use right-Amiga and a digit; this makes the keypad become a "mode selector" if you don't want to use the pull-down menus and have stuff it takes to remember which digit is which mode. Personally, I don't have the stuff, so I bear with the pulldown menu rather than strain my poor brain.

The default mode is "Pick Groups", which means that whenever you click on a group, it will be picked. (Simple!) If you want to pick individual objects, EVEN IF THEY ARE THE PARENT OF A GROUP, there is a mode called "Pick Objects." Just select it from the mode menu, and now when you click on any object (in a group or not, child or parent) it will be selected. You cal obviously multi-select it using the shift key. When you are dealing with ungrouped objects, "Pick groups" and "Pick objects" work identically.

Different modes let you deal with the different parts of an object. Up until this time, we've always dealt with entire objects at a time. We could rotate, scale, and move them, add them, group them, and delete them, though we could not affect their basic structure. The remaining modes all work on PARTS of objects, not objects themselves. One important note is that to even enter these other modes, you must have selected at least one object (or group) for the new modes to act apon.

You'll also find that I consistently lied to you in most of the previous sections. I always referred to picking objects as opposed to picking anything else. ALL of the pick and select commands except Find work equally well in picking faces, edges, or points as opposed to just objects or groups. Most other commands like Delete will work on the parts of an object as well.

One new mode is "Pick points." If you pick an object or group and enter the pick points" mode, the object will turn white (the object is NOT picked anymore!) and it's points will all become visible (they will show up as small squares.) Now you are in a different mode; you are no longer picking and selecting OBJECTS, you are dealing exclusively with points. You can then click on the points which will turn orange as you pick them. You can use the shift key to multi-pick, or the lasso and drag box to grab many points at once. You can also select points, and use all of the selection tools to help you get any subset of points you want. Selected points are green, picked points are orange, and picked and selected points are yellow.

When you're picking points, edges, or faces, Imagine will work ONLY with the points, edges, or faces in the object that was picked before you chose the "pick points (or edges or faces)" mode. This prevents you from confusing one object's points with another's. When you scroll around your view or redraw the screen, the other objects won't even be updated, so don't get scared if they seem to disappear. When you re-enter pick objects or pick groups mode, all of the objects will re-appear.

Just because you can pick something doesn't mean you can perform every command on them. In the case of points, you can delete your picked points, or use the transformation requester to translate them; interactive dragging is actually another mode of it's own, though. When you delete a point, you delete any edges and faces that that point help form. You cannot do things to selected points that make no sense (like grouping them, or saving them to a file)- that's just weird.

You can perform some other commands that aren't applicable to objects as a whole, however. For example, a very useful command is called "split." It takes the selected points, removes them from the original object, and gives them their own axis. In effect, the original object is split into two parts defined by the points you picked. Any connecting faces or edges are deleted (two objects do NOT share!). This might be very useful when you have a logo and want to pull one letter out of the object to do something special with it.

One command that is unique to pick points mode is "taut", which is found in the Functions menu. If you select three or more points and select "taut", the middle points will jump to the line segment defined by the first and last points. This command might be useful to line up a bunch of points in a straight line quickly. Taut does NOT work with anything other than picked points.

Picked points can be manipulated with the Transform command. The picked points can be translated, scaled, rotated, and positioned INDEPENDENTLY of the rest of the object. Rotations and scalings all use the object's axis as a reference point. Absolute positioning will move the FIRST point you pick to the location you choose, and the rest of the picked points will be translated an equal amount. Interactive dragging is accomplished using the "drag points" mode.

Picking edges is similar to picking points, except to specify an edge you just click on the two points that make it up, or lasso or drag box the entire edge. Just like points, you can't perform every command on them. You can delete them and split them.

You CANNOT translate edges or use taut on them. Deleted edges will delete any face they belong to, but the points in the edges will NOT be removed.

A new command you cannot perform on points but can use on faces is called "fracture." This command is in the Functions pull down menu, and is often very useful. The fracture command will take and break each edge into two edges, with an additional point added to the midpoint of each selected edge. This command is very useful when you need to increase the detail level at a certain area of an object; the extra edges that appear allow you to manipulate them to add finer details and structures.

Select Faces is again pretty straightforward. You must click on ALL THREE of the points that make up the face to select it. Fracture works very well on faces; it splits each face (one triangle) into four triangles defined by the midpoints of the face. The new faces can then be manipulated for higher object definition.

Deleting faces removes the faces, but not the edges or points that it was made up of.

Picked faces allow you to characterize an object's appearance in local areas. The attribute requester normally allows you to give the object overall color, reflection, and transparency values. You can actually set these for every single face, if you like. You can pick one or more faces, select "attributes" from the Object menu, and use the sliders to set the color, transparency, and filter values for the face or faces.

You will NOT see any change in the appearance of your object when you do this, but when you render, the faces you selected will all override the default object color with the attributes you selected. A danger is that face attributes are somewhat fragile. If you join or merge objects or start deleting or adding points to it, all face coloring is often lost. To keep this from happening, color individual faces LAST, just before saving your object.

A final note about face coloring; don't depend on it for coloring your objects in complex ways. Using grouped objects or brush maps is much more robust and allows better control. Coloring individual faces is useful mostly for quick and dirty attribute definition or for making small details that aren't worth the bother of a brushmap or extra object.

Both "pick edges" and "pick faces" will allow you to split off the selected parts of the object to create two new objects by using "split", just as split works with selected points.

Three additional modes are "add points", "add edges", and "add faces". Add points will add an additional point to your object in the location you click on. Add edges lets you click on TWO points and will add a new edge joining them. Add faces mode will let you add a new face to an object by clicking on the THREE points that make it up.

"Add lines" mode is a convenient combination of "add points" and "add edges". As you click, a new point is added in the location you point to, and further clicks will add additional points along with an edge joining the latest point to the one that was immediately preceding it. Thus, a few clicks around the border of a rough circle will make a set of points with the edges following the outline of that circle. Carefully clicking on the location of an existing point will cause the new line to connect to to that point, so making closed shapes is easier.

"Drag points" mode allows you to interactively drag individual points in your object around. If you select this mode, you can click on any point and drag it to a new location interactively. Any edges or faces that this point is connected to will follow the point to its new location.

Dragging multiple points is also easy- just use the shift key, multi-pick the points by clicking on each in turn, and when you want to start dragging them, just release the shift key.

AN IMPORTANT TECHNIQUE: What if you want to select a point or points in one view, and drag them in an orthogonal direction? For example, you have a plane defined by a horizontal 10 by 10 grid, and you want to select a bunch of points from the middle and pull them up. If you click on the points from the top view, you can easily select any of the points you're interested in, but you can only drag them left and right, forward and back. You want to be able to drag them UP.

Here's the method for doing this: it is invaluable, so remember it. Whether you want to move one point or a hundred, press the shift key to multi-pick the points. Click on the points you want to move in ANY view, keeping the shift key depressed. To move all of these points, KEEP THE SHIFT KEY DEPRESSED and move the mouse to the view where you want to move the points in. Press and hold the left button, then RELEASE the shift key. The picked points will move with your mouse for as long as you keep the button held down. Releasing the button will anchor the points.

In the example with the 10 by 10 horizontal grid, you would press shift, click on the points you want in the top view, move to the front (or right) view, release the shift key, move the points up, and release the mouse button. That's it!

Magnetism, a more complex way of dragging points will be covered in the "advanced" Detail tutorial.

One problem with manipulating points, edges, and faces is picking the RIGHT point. When the object is complex, the wireframe displays can get very cluttered. There is a convenient way of simplifying a view to get points out of your view- it is a mode called "hide points". In hide points mode, any points you select (with click, drag box, or lasso) will disappear from view- they will go away. They still exist, they just aren't displayed and can't be picked or manipulated. You can "hide" whatever points that get in the way of your work area, then change modes, and manipulate the non-hidden parts of your object. Selecting "pick objects" or "pick groups" will make the hidden points re-appear.

For example, if you're working on a helicopter model and you want to work on the rotor alone, you might select "hide points" mode, and use the lasso to indicate the main helicopter body. The rotor is left alone, and after changing into drag points or select faces mode, it is easy to indicate what portion of the rotor you want to deal with without accidentally modifying the helicopter body. Selecting "pick objects" mode makes the entire helicopter, with the rotor changes, reappear.

In theory, you can create any object by adding an axis, then adding points, edges and faces. In practice, these are very low level commands; you generally use the more powerful commands like "mold" and "slice" found in the Object editor. The low level select and add modes are built to give you the low level control that you sometimes need; however, they are more for defining basic outlines that are then used in the more powerful Object commands, or for touching up small details on nearly complete objects. The next Detail tutorial will talk about these commands.

This file and the text therein is Copyright 1991 by Steven P. Worley. All rights reserved. This file may be distributed freely in computer or paper form as long as 1) It is unchanged and unedited 2) is distributed in its entirely 3) gives proper credit to the author, Steven Worley.

                         -> Return to Alphabet <-