# SimplyMaya Forums

Welcome to the forum, feel free to ask questions here.

Home / forum / Lighting & Rendering, Dynamics & Effects, Texturing / Dynamics & Special Effects / Position Attribute in Expression Question (from Learning Maya Dynamics 5)
 Register FAQ Members List Calendar Mark Forums Read

 20-06-2004, 06:46 AM #1 Gun-Kata Registered User     Join Date: Jan 2004 Location: Los Angeles Posts: 68 Thanks: 0 Thanked 0 Times in 0 Posts Position Attribute in Expression Question (from Learning Maya Dynamics 5) float \$nz = 3* noise (nurbsPlane1ParticleShape.position*.1 + time); nurbsPlane1ParticleShape.position = nurbsPlane1ParticleShape.position0 + <<0,\$nz, 0>>; Hi, that expression is used to control the y value of each particle in a grid of particles that has been parented to a nurbs plane. The result looks kind of like cloth blowing in the wind. What I don't understand is how the part that is in red can possibly be used to assign each particle its own y coordinate. Isn't position a vector attribute? How then can it yield a scalar value for \$nz? And furthermore, how is it that it yields a different y value for each particle in the field? Last edited by Gun-Kata : 20-06-2004 at 06:49 AM.
 20-06-2004, 01:12 PM #2 kbrown Moderator     Join Date: Sep 2002 Location: London, UK Posts: 3,198 Thanks: 0 Thanked 8 Times in 8 Posts The answer lies in the second line. The scalar value is used in a vector <<0, \$nz, 0>>. Why does it yield to a different y value? Well, because the vector is added to the initial position of a given particle. __________________ Kari - My Website - My IMDB Do a lot, Fail a lot and Learn a lot!
 20-06-2004, 06:14 PM #3 Gun-Kata Registered User     Join Date: Jan 2004 Location: Los Angeles Posts: 68 Thanks: 0 Thanked 0 Times in 0 Posts Thanks! What I still don't understand though is how an equation that uses a vector quantity with three distinct numerical components (nurbsPlane1ParticleShape.position) can yield a single decimal numerical value (float \$nz). If, for example, nurbsPlane1ParticleShape.position is equal to <<2,3,4>> and that value is then inserted into the equation, then shouldn't the equation also yield a vector quantity? ps. Nice Quake III model btw.
 21-06-2004, 01:57 AM #4 kbrown Moderator     Join Date: Sep 2002 Location: London, UK Posts: 3,198 Thanks: 0 Thanked 8 Times in 8 Posts Ah... Now I see what you mean. It is because of automatic type conversion. In this case the .position vector is automatically converted to a float by calculating a magnitude (length) of it. These two will yield to the same result: float \$nz = <<1, 2, 3>>; float \$nz = mag(<<1, 2, 3>>); __________________ Kari - My Website - My IMDB Do a lot, Fail a lot and Learn a lot!
21-06-2004, 02:35 AM   #5
Gun-Kata
Registered User

Join Date: Jan 2004
Location: Los Angeles
Posts: 68
Thanks: 0
Thanked 0 Times in 0 Posts

Quote:
 Originally posted by kbrown Ah... Now I see what you mean. It is because of automatic type conversion. In this case the .position vector is automatically converted to a float by calculating a magnitude (length) of it. These two will yield to the same result: float \$nz = <<1, 2, 3>>; float \$nz = mag(<<1, 2, 3>>);
Now I get it. Thanks!

 21-06-2004, 07:06 AM #6 mind_raper Registered User   Join Date: Nov 2002 Location: Pakistan Posts: 57 Thanks: 0 Thanked 3 Times in 3 Posts kool explaination Kbrown... ...... __________________ Learn the Rules|Then| Burn the Rules Book

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts vB code is On Smilies are On [IMG] code is On HTML code is Off

 Similar Threads Thread Thread Starter Forum Replies Last Post Maya Hair/Polygon Error ingram_no.7 Members Lounge 13 10-12-2010 10:27 AM LayoutTools for Maya 2011 is here... ctbram Members Lounge 1 06-12-2010 10:32 PM Open a Lightwave file in Maya 2011 radiant777 Maya Basics & Newbie Lounge 2 04-12-2010 02:45 AM

## \$34

Month-to-month billing

## \$87

Billing every 3 months
 \$29/month Unlimited access to all videos Project files to download Easy to cancel at anytime Save \$5 per month or \$15 in total compared to monthly billing with this package.

## \$288

Billing every 12 months
 \$24/month Unlimited access to all videos Project files to download Easy to cancel at anytime Save \$10 per month or \$120 in total compared to monthly billing with this package.

Your plan will automatically renew. You can cancel at any time via your PayPal account to avoid being charged again.

You can view the FAQ on our video plans here. You can contact us directly here. By clicking one of the buttons above, you agree to our Terms and Privacy Policy.