Here’s a fun trick for parsing an ICE string attribute, identifying the letters and typing out the text with particles:

Download the sample scene here and read more about it below. (Soft 2011+ required.)

Taking this knowledge we can also do variations on the concept like turning a string into an array of booleans, for example:

Let me know in the comments if you make anything cool with this technique.

The classical way of doing symmetrical shapekeys (a.k.a. “blendshapes” if you’re in Maya or morphs if you’re in Max) is to make a symmetrical one then add it twice and paint off its influence with two weight maps, one for each half. In Maya you’d use the Paint Blend Shape Weights tool, but it’s basically the same deal.

In ICE, shapekeys have a .positions ICEattribute in them. This is an array of positions (vectors) representing the relative offset from the original mesh. In other words, it means you need to add them to the existing point positions to make said shape occur. That said, we won’t be using .positions in this post but full PointPosition’s instead.

Here’s what we’re gonna be working with in my example:

Normally you would make the 2 weightmaps, select one then Shape->Modulate Shape Key with Weight Map. The map looks kinda like this:

This involves making sure you have 100% of one half and 50% of the middle. You want 50% because you want to be able to add the shapes for both sides and get 100% of the deformation in the middle, else you’d get 200% and that’s no good.

Let’s see how we can use ICE to skip that step altogether by only deforming points in one half instead of relying on a map to define it, as pictured at the beginning of this post.

So as you can see we read the PointPosition, split out to scalars with the “3D Vector to Scalar“, then feed the X to different nodes to see if it’s bigger or equal to / bigger / smaller or equal to / smaller than zero. With the “Select Case” we use the correct one as defined from our dropdown menu input attribute “Type“. (If you didn’t know: to define a dropdown menu for an attribute in a compound just rightclick it and go to Properties, then fill in “Combo string” and “Combo value” then click “Add combo” as desired.)

The If node before the Linear Interpolate makes sure that if we’re not dealing with the correct half, we just let the positions pass through untouched. Otherwise, we check if the “Type” (mode) is set to one that includes the middle line, and if X is 0 it means we have a point in the perfect middle of the mesh, in which case we only affect it by 50%, else we let it go through. At the end we do one more Linear Interpolate between the affected result and the original mesh, so we can blend it gradually with a slider.

Lastly, if anyone’s curious what the word “Epsilon” means in regards to an “Equals” node, it’s basically the margin of error permitted in the comparison since vector values aren’t exact numbers most of the time in 3D. Thus an epsilon of 0.001 in this case means that a vector’s posX can be off from 0 by 0.001, so it could anywhere between -0.001 and 0.001 and still be considered to equal 0. You can increase the epsilon if you need to.

All you need to do is lock at the time.clock()…

# We need this for OS detection:
from platform import system as OStype
 
# Step 1: tick, tock...
from time import clock
start_time = clock()
 
 
# Step 2: ???
# (You do your procedures here.)
# You NEED to do SOMETHING. Don't leave this blank!!
 
# Here's a filler of nothingness:
from time import sleep
sleep(0.05)
 
 
# Step 3: calculate duration
timeTaken = clock() - start_time
 
# In Windows clock() returns seconds but in Linux it's milliseconds, so:
units = ["seconds" if OStype() is "Windows" else "milliseconds"][0]
 
msg = "It took "+str(timeTaken)+" "+units+" to process your code."
 
Application.LogMessage(msg) # if you're in Softimage,
# otherwise use print() or whatever.

I tried to make the snippet above as generic as possible, but if you’re using Python in Softimage, you can use XSIUtils.IsWindowsOS() for detecting Windows instead of my OStype stuff.

Fiddling with the ExtrudeOp options

Try this yourself:

1. Get a sphere. (My screenshot example was a half-sphere.)
2. Select all polys. (Press Y to enter poly mode then Ctrl+A to select all.)
3. Press Ctrl+D to Extrude.
4. In an Explorer open your object’s operator stack, find the ExtrudeOp and open its PPG.
5. Turn off Merge, then fiddle with Length, Inset Amount and Subdivs.
6. Then in the Transform tab, play with the sliders there.
   You can get some very interesting (and often abstract) results!

*UPDATE [21/05/10]*: A buddy of mine who uses Maya informs me that the mayan Extrude has options to do this as well if you peek in the channel box. Just so you know.

[CLICK TO SEE VIDEO]

BREAKDOWN:
1. Set an OK center position with "Move Center to Bounding Box" / "Move Center to Vertices".
2. Enter "Center" mode. (top right)
3. Right-click on "Ref" button (below Local) and choose "Pick Polygon/Edge/Point Reference".
Click an object to select it and highlight the desired components.
4. While still in both "Center" and "Ref" modes, reset rotation to 0,0,0 then go back to "Object" mode (top right), go "Local" mode and reset rotation to 0,0,0 again. — That’s it!

FORUM THREADS: [xsibase] [xsiforum.com]

** Download Example Scene (XSI 6.02+) ** — Raw Rotation & with post-blur [QT MP4]

Why?

The fast skinshader (mentalray) material that comes with XSI off the bat is pretty awesome, but it has one downfall which is the lack of a transparency input.

How?

A Refraction node combined with Binary Alchemy’s wonderful SSS shader, from their (freeware) "Essentials" shader collection, available for download on their site.

BA’s SSS shader doesn’t do transparency or refractions off the bat, and it won’t let you plug in a material, so that’s not an option. However, a Refraction node (or Transparency node, though that would look wrong) can be plugged into its "Replace Color" input no problem. Plug your transparency map to the weight input and you’re set.

The final rendertree looks like the following:

But why would you need skin to be transparent? Humans aren’t transparent, you crazy nut!

True, however… what about fish? Certain fish can be almost completely transparent and most are at least partially so.
Not only that, but in the areas that they are, they refract light, too. Behold some evidence below:

What is the refractive index of transparent skin?

That’s a good question…. and I’ve no idea. (If anyone knows, get in touch.) I’d guess it’s something around that of some sort of plastic or silicone.
(In my example scenefile I used refraction of 1.2 just to see if it was working and by no means whatsoever is that the correct refractive index for skin.)

Ok… it’s transparent, but shouldn’t it be a bit blurry too?

Absolutely! And that’s where the magic of post-production can kick in. One way to do it is to have a pass of your transparency as black on white, and use that to selectively blur the transparent areas to give the illusion of blurry refraction. [Another way, potentially slower to render, is to use an Architectural node instead of the Refraction one to get blurry refractions off the bat. -- Thanks ghonma for the tip.]

I’ve provided my simple approach to doing the effect in post using XSI’s own FXtree:

(Click on the picture to the right to download a QT .mov of the animated rotation after post-production.)

If you see any mistakes or feel the need to correct any of the methods described above, let me know so I can make this document more accurate.

[SEE VIDEO]

FORUM THREADS: [xsibase] [cgtalk] [xsiforum.com] [indocg.com] [xsiforum.de]

NOTE:
Sometimes, enabling “Sample Displacement Before Rendering” under the Optimization tab in the Renderer Options may drastically speed up your render even more.
Bare in mind disabling it means mentalray doesn’t get accurate bounding boxes for the displaced geo, which means BSP calculations can be affected.
This will not affect render quality though, only overall render times.

*UPDATE* [03/01/10] This tutorial was made in XSI 6 and you should know that the “sib_interp_linear” node is the “ChangeRange” node in present versions.

Here it is if you’re looking for it: (clicky clicky)