View Full Version : Help with bouncing ball tutorial from the "Learning Maya" book
11-23-2004, 04:41 AM
I am up to the point of adding an expression for scaling in X and it tells me to:
From the Window menu, select
In this window, the ballScale node is
In the Expression Name field, enter
Click in the Expression: field at the
bottom and enter the following:
sx = 1/sy
This expression uses the inverse of
scaling along Y as the value for
scaling along X. So, if the Y scale
stretches by 2, then the X scale
squashes inward by 1/2, or 0.5.
Click on the Create button.
When I do that it gives me this error :
Error: Attribute already controlled by an expression, keyframe, or other connection: sx
What did I do wrong and how do I fix it? Thanks guys and girls.
11-23-2004, 06:54 AM
ok when you get this error, the first thing to look at is the attributes you are trying to control by the expression. select your ballScale node and look in the channel box to see if either scale X or scale Y is colored. if it is orange that means it has key frames on it. If it is purple, that means it is being controled by an expression. If it is yellow that means it is directly connected to another attribute. basicly if either of these things have any coloring then you need to break those connections before setting up the expression. To break the connections select the text for the attribute in the channel box and then right click on the attribute (you should get a hole list of options) then choose break connections. once both scaleX and scaleY are colorless then when you create your expression it will conncet fine.
11-23-2004, 02:36 PM
Are you talking about the color text box to the right of ScaleY?
I highlighted 0.52 right clicked on ballScale and click on Break Connections and tried to do the expression again and its still giving me the same error.
11-23-2004, 03:11 PM
personally, for maya begginers i would suggest getting maya fundamentals. Theyre are some typo errors and what not, but there are videos that go through doing the projects in the book as well. Also you will learn a lot more than you will in alias' book.
another tip is to do several projects with the new things you've learned. Try to do different things. Your going to run into problems, and if you mess around with using the new stuff on several projects, you'll really know how to use that tool.
11-23-2004, 03:52 PM
yes, I am talking about that coloring. What you have there is a key frame somewhere on that attribute. You need to check both scaleX and scaleY for keys. One other thing I just thought about is maybe the break connections doesnt work on key frames. Try this:
select the ballScale node and go to window/animation/graph editor. on the left there is a list of the keyable attributes. select the scaleX and scaleY on the left. THen hit "f" with your mouse over the graph window (this will frame the animation curves for the selected attribute). drag a selection box around all of those keys and then delete them.
You know you are ready for the expression when the attributes are not colored.
Also, I am not sure if this is correct, but the image you posted of the channel box only shows the scaleY node. if by chance you have hidden or locked the scaleX attribute then that cal also cause problems. If it is gone, you want to go to Window/General/cannel control. From there make sure the scaleX and scaleY attributes are both keyable and not locked.
hope this helps
11-23-2004, 09:42 PM
Hey, thanks Brad. I fix the problem. I just did what you said:
select the ballScale node and go to window/animation/graph editor. on the left there is a list of the keyable attributes. select the scaleX and scaleY on the left. THen hit "f" with your mouse over the graph window (this will frame the animation curves for the selected attribute). drag a selection box around all of those keys and then delete them. The stupid thing is the next step is to do sz = 1/sy and it gave me that stupid error again. So I just selected ScaleZ and did what you told me to do with the other two and it worked. So thanks.
01-20-2006, 12:00 AM
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