Move A Point Along A Vector

[nier]

Hi!!

I have a point and a vector... how to move this point along this vector using the vector's magnitude as the amount to move? I need only to know how to use the vector as the direction of the movement....

should be easy, no??

thanks!!
Daniel

[joojaa]

QUOTE(NiER @ 07/10/08, 02:09 PM) [snapback]288145[/snapback]
should be easy, no??

yes literary point=point+vector.

Anyway there is some considerations on point moving in general in maya as mal is nbot the tool for doing things in mmaya in general. Its the tool for coordinating the end move. So do you want to animate, move a group, transform cluster, multiple points or what.

(so dont loop over points for example to move them do it in particle expression on a softbody, if its a comand issue then do it in mel, if its not then bind it to something that does the job)

[nier]

thanks Jooja

I had already kinda figured it out... I knew it was easy...
What I am doing is getting velocity information of the voxels from a 2D fluid and using these vectors to move points in a grid... it is working ok by now

CODE
######## PYTHON CODE ###########

import maya.cmds as cmds

def movePoints():
    #to run this, select the locators
    locs = cmds.filterExpand(sm=22)
    fluid = "fluid_2DShape" #name of the fluid container

    for l in locs:
        #position of locator
        pos = cmds.pointPosition(l)
        #find out on which voxel the locator is located
        cmds.select(fluid, r=1)
        vx = cmds.fluidVoxelInfo(voxel=pos)
        #get the velocity vector of this voxel
        d = cmds.getFluidAttr(at="velocity", xi=vx[0], yi=vx[1], zi=vx[2])
        #get the magnitude of this vector
        magCmd = "mag <>;" %(d[0], d[1], d[2])
        mag = mm.eval(magCmd)
        #unitVector = [d[0]/mag, d[1]/mag, d[2]/mag]
        #move point along vector
        f = 20 #reducing factor
        cmds.move(d[0]/f, d[1]/f,d[2]/f, l, r=1)        
        #draw a line to see where it went
        pos1 = cmds.pointPosition(l)
        cPoints = [pos, pos1]
        cmds.curve(p=cPoints,  d=1)

The locators above are place in each of the grid points....
Nothing fancy, but it is working the way I wanted....

Thanks!
lg,
Daniel

[joojaa]

Yes however you dont want to be doing this in mel, but in particle ecpressions instead. Because maya cannot run mel on the fly teh expression node is designed to do tat and for points use a particle expression as it auto loops the points and is meant for this kind of thing.

This is just a illustrative way peopel think maya works and it does not. You never do anything drectly in mel if you can help it.

This si whty people think mel is inneficient, and they want to use python instead (however this does not solve anything you still have the same indirect interface). But ist rather how maya works. If you need runtime things you pack them unside nodes and nodes have some dfesign constraints that seem wierd but make your code much more resuable,.

[nier]

I always read you writing this comment, and lately I've been very curious to learn the API... I have absolutely no idea how it works and what I could accomplish with it, but I guess it would solve lots of problems I usually have with memory running out, for example...

I'll take a look at that...
thanks again!

[ewerybody]

hehe :] once I came across this problem as well and broke my head about it. And yes it was that simple!