pseudo fresnel effects

1. Unretouched rendering in Imagine using Fakely.ITX for glancing reflections. The Reflective Side Color on the Glass is 153, and the Front color is 10, with Threshold set to 0.

2. In this image the Reflective Side Color was raised to 255 and Front Color to 25 on the glass.

how issues of relative brightness could possibly fool you into thinking reflections are primarily additive

3. For the example below, I added some bright panels to the scene above, arranged as you see.

4. In the image on the left, the main light source, ambient and sky colors were all reduced to 1/4 of what they were in image #1. However, all the attributes on the objects are identical to image #1. The rendering at left was then taken into Photoshop, and the palette was stretched back out to match image #1, by lowering the high clip Levels 75%, and this resulted in the image at right. The reflections of the panels appear alot brighter (and seem primarily additive), because they were simply 4 times lighter than anything else in the original rendering.

Incidentally, there are probably better ways of expanding the palette in an image like this (than simply clipping off the high values) which could result in a less harsh, more attractive filmic look, so experiment.

And reducing the light to 1/4 the original was just a totally arbitrary, and convenient way of illustrating my point.

Q: Is this really the way reflections work? A: I don't really know, but it's an interesting theory. :)

gadgets for mesh editing

(These examples apply mainly to DOS Imagine 4.0 and earlier, but it may give you a few ideas on how to organize commands in later versions as well.)

An organized approach to configuring gadgets for basic mesh editing in the Detail editor.

Notice that there aren't any gadgets for obvious things like Load, Save and Attributes, because these are the few commands that have hot keys I can actually remember.

• Pick Methods

• Perspective View Adjustments

• Mesh Editing Modes

Rather than lumping the Pick and Add modes together (as in the MODE menu), I've grouped together modes that operate on the same aspect of geometry. For example, the basic Pick Point mode (PTS) is followed by Add Points, Drag Points, and Hide Points. This seems like a more logical way to break things down, and it helps me locate the modes I want faster. The gadgets are also organized in descending order from greatest complexity to least: Groups, Objects, Faces, Edges and Points.

• Subgroup Editing

• Other Frequently Used Functions

Make Quick Edges in conjunction with the Attributes/Quick Edges, allows you to rotate a model in realtime wireframe perspective. Otherwise the model will simply turn into a bounding box.

Gadgets are configured in Imagine's Preferences editor.

bones rules

44 caveats for avoiding problems with bones. Although numbered, they aren't necessarily in any particular order. (These were originally compiled for DOS Imagine 4.0, so they may not be as applicable to later releases. You'll see references to versions 3.0 & 3.1 below, these refer to the old DOS version not IFW.)

If you find the info on this page helpful, a small token of your esteem would be welcome at the following address: Tim Wilson, P.O. Box 4691, Crestline, CA 92325 USA.

• 1. Design your Geometry and Bones to work together. You can't do either your modeling or your boning totally independently of one another. You will have to go back and forth between the two, until you come up with an optimum design for the geometry, and figure out the appropriate layout of the bones. Drawings will help, especially to locate articulation points in the model, and will make the job of building the skeleton easier.

• 2. Geometry should be built to accommodate interpolation around a joint. It's not necessary to use regular cross-sections at joints but this may help you when defining the Big and Small Bone Subgroups.

• 3. Design your geometry to look as good as possibly through the widest range of motion.

• 4. If possible Bone the object with the limbs bent halfway through there normal range of motion. For example model your knee or elbow slightly bent rather than straight, and bone them that way. This way when you bend the joint it will look acceptable through a wider range of motion.

• 5. If it's too difficult to bone the limbs with them partially bent, then design the geometry the way you think you can bone the figure most easily or logically. You may find it easier if the limbs are aligned at more logical angles. For example, if you model a hand with the fingers bent in a natural position you may find it very difficult to get the bones set up right. The fingers can be more easily boned if they are aligned at more regular angles to the world axes. Then once they are boned you can bend the fingers into a more relaxed shape. Realize however that by designing your geometry with the limbs set at regular angles you may sacrifice some of the aesthetics of the model.

• 6. Put in enough points or cross-sections at the joints so when the limb is bent it won't start to look faceted. If you need to increase the detail, try Fracturing the area around the joint, and then running the new Smoothing Tool in 4.0 over it.

• 7. Realize that polygon geometry is not infinitely flexible, and that the range of movement in joints is going to be somewhat limited. Even though you may try to design your geometry for the widest possible range of motion as described above, when you bend the limbs into extreme positions, it will be hard to avoid ``crimping''. However, remember that your design does not have to be 100% perfect, because you can tweak the geometry in some poses and use a little morphing in combination with the bone deformation to get the bent joint to look better.

• 8. Once you've got your basic modeling done, layout your bones in the positions where you want them, before you begin to define the Bones Subgroups. Bones are good not just for limb joints but also spinal, tail and neck articulations especially if these are modelled with cross-sections.

• 9. All boned objects need at least 2 Bones. At the bare minimum, you need one bone to anchor the basic geometry parented to a second bone where you want the object to bend.

• 10. A BONE is simply a naked AXIS linked to your geometry.

• 11. When possible, each Bone should have its Z axis pointed toward the child below it in the hierarchy. This is more of a guideline than a rule. Obviously if you are branching out from a back bone into two arms, you can't have the parent back bone pointing towards the next articulation in the spine, AND the shoulder joints as well.

• 12. Group Bones Serially. Do not group all of the bones to a single parent axis. You must go down through the hierarchy progressively grouping each child object to its parent. If you use the basic GROUP command, every parent and child pair must be grouped individually. PICK THE PARENT OBJECT FIRST such as the Elbow, then Multi-Pick the child object such as the Wrist, and execute the Group command. You cannot simply PICK ALL the bones and then GROUP them at once. Serial grouping establishes the hierarchy. You know the old song... the hip joint is connected to the knee joint, which is connected to the foot joint. The shoulder joint is connected it to the elbow, which is connected to the wrist, etc.

• 13. The new CASCADE GROUP command in 4.0 States menu will be a tremendous help on this. It's more sophisticated than the old GROUP command. It will automatically group objects serially, in the order they've been selected. For example, if you select the Chest, Shoulder, Upper Arm, Forearm, and Hand, in that order, and then execute the Cascade Group command the objects will all be serially linked in a chain, rather than all grouped to the Chest. This is just what you need when setting up hierarchies of bones, particularly vertebral articulations.

• 14. Once your skeleton is built, Group the skeleton to your geometry by Picking your GEOMETRY FIRST and then the master parent bone in your skeleton, and then performing the GROUP command. This will make the Geometry the main parent of everything. The Geometry's axis is not used to manipulate any part of the figure. It is used to translate and rotate the WHOLE figure through space in the Stage. So you might want to position the Geometry's axis strategically for that purpose, either near the feet or in the middle of the Pelvis or Center of Gravity.

• 15. The geometry must always be the master parent in the hierarchy, when using bones.

• 16. Movement of the master parent cannot be incorporated into a State, so you will need to use the first bone in the hierarchy to get the whole geometry to move as part of a State. This first bone should be placed strategically for manipulating the whole model, in the center of the figure's pelvis for example, or as anchor on the ground.

• 17. The first bone in the hierarchy must have ALL faces in the geometry selected for both its Big and Small Subgroups. Then when you move the bone the whole geometry will follow it. (You can of course also move your whole figure in the Stage by tweening position. Sometimes you may wish to do both. For example, you might want to have an up and down motion as part of the States, but a forward motion as a change of Position in the Stage.)

• 18. Assign a Big and Small Subgroup to each Bone. This may seem obvious, but each bone MUST have subgroups defined otherwise the model will not work AT ALL.

• 19. Every Bone linked to the geometry must have Big and Small Bone Subgroups defined.

• 20. The Small Bone Subgroup represents the area of the limb's geometry that you want to rotate TOTALLY when the joint is moved. (Just a note of clarification. What the term `Small Bone Subgroup' ACTUALLY means is the *small subgroup* for the bone, NOT, I REPEAT, NOT the *subgroup* for the small bone.... There are no *small* and *big* bones...... What you are defining is a *small subgroup* and a *big subgroup*, to GO WITH each particular bone.)

• 21. The Big Bone Subgroup includes the area of the limb that you want to rotate totally, PLUS the area of geometry that will bend when the joint is moved.

• 22. Just so you know, the Big Bone Subgroup MINUS the Small Bone Subgroup is the area where the geometry will bend, stretch or interpolate around the joint. Your bone should be roughly centered inside this area of interpolation.

• 23. Knowing how large to make the bending area for a particular joint is something that comes through experimentation. A good rule of thumb is to make the bending area roughly as long as the object is wide. But this does not apply in all cases.

• 24. Never make a Small Subgroup BIGGER than the Big Subgroup though. Imagine will choke on this.

• 25. Assigning Subgroups to Bones can be done in two different ways. In 3.0, you must MAKE the SUBGROUPS first in PICK FACE mode, then pick your bone and use the BONES SUBGRPS command in the STATES menu to assign them to the Bones.

• 26. In 4.0, you can use `Quick Bones' to assign the Subgroups. Again when you go into PICK FACE mode, outline your Subgroups and then in the FUNCTIONS menu select either the MAKE/SML BONE SUBGRP, or MAKE/BIG BONE SUBGRP command, and then simply click the mouse on the axis you want the subgroups assigned to. It might be advisable to create Gadgets for these commands. It speeds things up considerably.

• 27. (3.1 USERS ONLY- DANGER ALERT! If you are using Quick Bones in Version 3.1 the MAKE SML BONE SUBGRP and MAKE BIG BONE SUBGRP commands' names are reversed [at least in my copy they are]. You can rectify this by assigning GADGETS to both commands and simply reversing the names.)

• 28. If you put the first bone in your hierarchy at the same position as the geometry's axis, you may have trouble selecting it with Quick Bones. In this case just make a Subgroup for all the faces in the geometry, and assign them to the Bone using the BONES SUBGRPS requestor.

• 29. If you are using 3.0 name your Bones Subgroups logically when you create them, otherwise you won't remember which subgroup goes with which bone; And also so they'll be easy to sort out later, if you have to make changes. If you are using the Quick Bones in 4.0, the naming of Subgroups will be taken care of automatically, and will be derived from the Bone's name. So make sure to name your Bones logically, before you begin making the Subgroups

• 30. Check to see if your Bone subgroups are correctly assigned. Once you've made your assignments you can check to see if they're set up right by going into the STATES pull down menu and selecting BONES SUBGRPS. See what names are shown for the BIG SUBGROUP and the SMALL SUBGROUP. Then hit BROWSE and locate the names and compare the number of faces for each. Obviously the BIG subgroup should have more faces than the SMALL subgroup. In the final analysis, it doesn't really make any difference what method you use to assign the bones. The only thing that matters is what's shown in the BONES SUBGRPS requestor.

• 31. The CHECK OBJECT command will also tell you if there are any errors in the basic structure of the Bones and Subgroups. So be sure to perform this command when you're finished.

• 32. Don't create your Default State until you've set up all the bones and done the subgroup assignments.

• 33. The DEFAULT STATE MUST HAVE SHAPE AND GROUPING STATES DEFINED to lock the geometry to the orientation of the bones. The Properties are optional but in most cases probably should also be selected.

• 34. Lock your textures to the DEFAULT State. Please note that Locked Altitude Brushes do not work correctly with Boned objects in Imagine versions 3.0 - 3.11.

• 35. You may find that the Default State you created for boning is not suitable for applying Brushes (and Textures which have a regular pattern). For example you might want the limbs to be straight instead of bent so you can apply a cylindrical map to them. If this is the case, then straighten out the limbs and CREATE a new STATE, and lock your textures to it instead.

• 36. Create new poses for your figure by ROTATING joints in PICK GROUP mode around their LOCAL axes. This will maintain the hierarchical relationships and allow you to create more realistic poses.

• 37. The order in which bone deformations are applied to the geometry is the the order objects are listed in the FIND REQUESTOR, from parent down to child. The child bones lowest in the hierarchy are applied last.

• 38. Be sure to SAVE your whole group after creating new States in the Detail Editor, otherwise the object file will not be updated with the new States. Select the master parent in Pick Group mode, and then SAVE it.

• 39. Bone States other than the Default, only need GROUPING defined. The exception is when the geometry is also deformed with morphing to cleanup a joint in an odd position, or change a facial expression. Then you would need SHAPE defined as well.

• 40. Although you can define States at any level in the hierarchy, the only States you can call up in the Action editor are the ones defined for the master parent in the hierarchy. You may for example want to make a bunch of different arm poses, and store theses States just for the Shoulder and its children. But you will need to make these part of an overall body State, before they can be used in animation in the Stage. When you have a pose constructed that you want to include in your animation, select the master parent in Pick Group mode, and then CREATE your State.

• 41. There are two ways to see if the geometry is deforming correctly after you've built a pose with bones. First you can simply pick the master parent axis in Pick Group mode, and then use BONES UPDATE. (Please Note: You don't need to do a BONES UPDATE each time you create a new state with Bones. It's there mainly to check the deformation of the geometry. However you won't hurt anything by doing it.) The other way to see the deformation is after you've created a State, you can just SET TO it again, and you will now see the geometry deformed.

• 42. Clean up problems with the geometry around joints using a SHAPE State. This can be a useful trick in getting bones to work better. Sometimes when you bend a limb into an extreme posture the geometry just won't bend correctly around the joint. You will usually see these problems after you perform BONES UPDATE or SET TO a State that's already been created. Just move the few points that are out of wack, and add a SHAPE state to this pose, in addition to the GROUPING. The SHAPE State can be added by going into INFO for that State. Then when you stage animation that uses this pose, morphing will correct problems with the geometry. (The new Smoothing Tool in 4.0 may be helpful for this. You should be able to select a problem area where the points are out of wack and then just run this tool over it to smooth it out.)

(NOTE: At the risk of causing unnecessary confusion, I probably should mention [for the nitpickers] :) that the relationship between boned objects and SHAPE States is actually a little more complex than described here. Technically, in Imagine, the morphing produced by a SHAPE State will completely override the deformations of bones. However, this is something you may not notice in your actual animation, because the spline interpolation in Imagine's tweening will still cause morphed points to more or less arc from position to position [though not as gracefully as bones will].

Some Imagine users deliberately employ a hybrid bone/morphing approach. IOW, they use bones primarily just to rough out their initial poses, then tweak the geometry extensively and end up using primarily morphing for all their final animation. However, this approach requires more intermediate keyframes for good results, and takes more work than using just GROUPING-only states to animate the bones.

At this point, I can't see any reason why a few SHAPE/GROUPING states cannot be mixed with largely GROUPING-only bone States, if you only need to tweak the geometry on a few particular keyframes. It could possibly cause some anamolous behavior though, and it depends on how picky you are about the end result.)

• 43. NEVER use a DEFAULT state in your animation, because it will not interpolate with other key states. Default states should be reserved for creating a base shape for Locked textures and brushes. Get into the habit of making a duplicate copy of the Default as your first NEW state, so you can include that pose in you animation when needed.

• 44. To animate a boned figure, set up a series of keyframes for it in the Action editor, by ADDING new bars to the ACTOR channel, and calling up the various poses with the STATES BROWSE menu in the ACTOR requestor.