Additive Blendshapes 2003-11-24 - By Eric Kunzendorf
Back
Hi Kevin!
What is happening is that you are keying the sdk with the sphere in the center,
let's say at x0,y0 and moving the sphere to the upper right corner at x1,y1,
correct? The four corners from upper left moving counter clockwise would be:
x1,y1; x-1, y1; x-1,y-1; and x1,y-1. Correct also? The problem is that you
should only use one attribute to drive an SDK control.
So let's say you assign the upper right hand corner x1,y1 to smile and the
upper left hand corner x-1,y1 to frown. Trying to have both x and y drive the
blendshape is a mistake; it will cause problems because you have the same
blendshape assigned to different values at different times. But if you use just
x, then you will be okay with this instance, but the shape will mix with
whatever shape you assign to y. If you try this with y, you won't get any good
results because you will be assigning both smile and frown to y1, that won't
work. I believe I am correct here, but jump in anyone if I am not describing
this clearly.
Two suggestions: first, try assigning the blendshapes to the middle of the
sides, rather than the corners. These coordinates will be from the right hand
side moving counter clockwise: x1, y0; y1,x0; x-1,y0; and x0,y-1. That might
get you what you want. Keep in mind that the blendshapes will mix at the
corners. Or...
Jason Osipa's Stop Staring book covers exactly how to do what you are trying to
do with this type of interface. But he doesn't use SDK, he uses expressions
very elegantly. While I don't agree with doing EVERYTHING with blendshapes, as
he does; he very clearly explains how to use expressions with blendshapes to
create slider based interfaces. He also explains how to convert a range of
coordinate values to -1,0,1 for use in driving blendshapes. Also, check out his
use of the clamp function(procedure?) to clamp values to a particular range. I
found it to be clearly explained even to a math dunderhead such as myself! I
hope this helps, and good luck!
Excelsior!
Eric Kunzendorf
Computer Chair and Animation Instructor
The Atlanta College of Art
Kevin Chu wrote:
> Hi All,
> I have an interesting problem with some blendshapes. I'm trying to set up an
interface using set driven keys and blendshapes. I have an interface in the
shape of a square and a sphere in the middle of the square which I am using as
the driver in my set driven keys, to drive a series of blendshapes. Each of
the four corners of the squares represents a blendshape, and the center of the
square represents the starting shape.
>
> So here's what I did. First I made four blendshape targets, and ended up
with 4 blendshape sliders. Then I started making a driven key, setting up my
sphere in the center of the square as the driver, I then keyed all of the
blendshapes at zero when the sphere was at the center of the square. Then I
proceeded to move my sphere to the top right hand corner, and this time I
changed one blendshape slider to 1 and kept the other 3 at zero. I continued
this process for the other three corners. So theoretically, when I move my
sphere to the far corners of the square, I should have three of my four
blendshape sliders at zero and one of the sliders at 1. However, this is not
so, in fact, my results are quite strange, and I'm not sure how to solve this
problem. What I do know, is that I need to set this up so that the blendshapes
are some how additive to one another. Does anyone have any ideas?
>
> Thanks
>
> -Kevin
>
> -- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---
> List-help: <mailto:listar@(protected)?Subject=help>
> List-unsubscribe: <http://www.highend3d.com/maya/listserver/>
> List-subscribe: <http://www.highend3d.com/maya/listserver/>
> List-archive: <http://www.highend3d.com/maya/archive/>
-- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---
List-help: <mailto:listar@(protected)?Subject=help>
List-unsubscribe: <http://www.highend3d.com/maya/listserver/>
List-subscribe: <http://www.highend3d.com/maya/listserver/>
List-archive: <http://www.highend3d.com/maya/archive/>
|
|
