
Imagine for an instant you are in a room and there is a 
book on the Woor beneath a cotfee table. Someone walks in 
and says "...could you put the book on u7e table, please...P". You 
would pick up the book off of the floor and put it on the 
coffee table. As simple as this sounds, it rarely works this 
way in 3D modeling programs. 

Generally, an implicit modeler who has these same objects 
represented in the LightWave3D Modeler, would select the 
object and drag it to the table, but chances are, it won't be 
sitfing exactly on the table (seeFigure 2.4.1). If you zoom in 
closer in the 3D interface to where the book and table meet. 
you'll see that the book is siightly above or below the 
surface of the table. 

An explicit modeler who has these same objects represented 
in the LightWave3D Modeler, would first determine the 
distance between the bottom of the book and the top of the 
table and use Modeler's numeric move tool to move the 
book that distance. It would be highly accurate but it's not 
natural. it takes time, and implicit modelers would probably 
not go through the trouble; It requires that you work out a 
mathematical problem. In real life we can rest the boftom of 
the book on the top of the table without using mathematics. 
ote that this has the "Obj" keyu!ord assigned to keep it locked 
to its parent object. Now, if you examine the animation, there are only three nulls that have 
more than one keyirame. Two fade nulls control the neon letters, making them brighten and 
dim appropriately. Finally, a tag null alternates between -21, -22, -23, and -24, creating the 
chasing eftect. NOTE: a negative tag value means that the surface effectors effect all 
surtaces except the one with that tag, hence. a tag of -21 will effect all surfaces except 
those tagged to 21, so as the tag is animated, the Surface Effector influences every surface 
but 21 , every one but 22, etc., giving a nice "chasing light" eftect. Again, aside from the setup 
of the various nulls, there are only three null objects animated during the entire animation. 

Tutorial #17 - Accident.lws - D namic Trail Effects 

There's nothing really complicated to this scene at all...that's the beauty of it. A car is 
keyiramed braking and spinning out. Attached to its four wheels via parenting are four Surface 
Effectors, three parented to one that controls the fade of all fcur. Now, the trick to this efrect is 
that the four efFectors have "Dynamic Trailing" turned on (i.e. the "DT=0" phrase, meaning 
Dynamic Trailing is set to fade out OQlo Per second...if it had said DT=1 , that means that the trail 
would fade out I OOOlo by I second, DT=2 means that it would fade out 200010 Per second, or 
100olo in half-a-second). So, at the point the car begins to skid, the Fade null is keyframed 
from I to O, turning it on. The path that each Surface Eftector takes then leaves properly 
registered skidmarks on the surface of the pavement. Now, try that with image mapping 
sequences! 

Tutorial #18 - Lasrburn.lws - Laser laser burnin bri ht - more D namicTrail Fun 

This scene demonstrates persistent trailing, along with faded-out trailing. Attached to the tip of 
a laser are several Surface Eftectors with Dynamic Trailing on. A path was traced generated 
using the Path2Motion plugin in Modeler. Now, the way Dynamic Trail Eftectors stack up is 
that the first one in the object list (i.e. the in-order list that comes up if you bring up the 
"Objects" panel and click on the multi-selector). So, we have the first and top-most SE (S_E 
Glo L=1 R=255 G=150 B=66 DT=2 TPF=4) creating the bright orange-ish glow following the 
laser. Notice that it has DT set to 2, meaning that it will fade out 200'/¥ in cne second, or 100'1-
in one-half second. Note, also, the "TPF=4" embedded in the object's name. What this means 
is that it will generate four in-between positions for the Surface EfFector...this is useful when 
the distance between frame positions becomes greater than the eftective radii of the Surface 
Effector. If this option weren't on, you would see spots lined up in a row, rather than one 
continuous trail. In any event, as the laser beam carves out the path made for it in Modeler, it 
leaves at first a glowing trail, fading to black one-half second after the laser passes by. 
Keyframe in some nifty camera moves, and we've got a nice animation. 
