Never ending melting object

[Korben]

Hello everyone,

 

I'm kind of new to Houdini and am facing a little problem...

I would like an object to melt indefinitely.

 

Here is my workflow ( hip file attached ) :

- create an animated ( mountain ) object

- add particles flowing on the object

- delete non needed particles then convert to VDB -> to poly.

 

My problem is that I have a "flowingparticles" group in which particles are added when they meet the surface of a volume ( volume sample < 0 )

When I convert this particles to vdb then to mesh, the mesh is "poping" at the place where particles are added. I think this is a normal behaviour.

 

My question is :

- Can I add some attributes that can be used as something like "if the particle has just been added to the group, it's influence to the meshing is 0 and slowy increase its influence...

 

I don't know if I'm clear about that. 

Please If you can just do a flipbook of the joined hip scene, you will see the poping at the top of the melting object.

 

Thanks a lot !

neverEndingMeltingObject.002.hip

Edited December 7, 2014 by Korben

[loopyllama]

After your pop vop, throw down a pop wrangle with this:

float frameduration = 30;
float maxscale = 1;

if (abs(@v.x)+abs(@v.z)<.01)
{
    @startframe = @Frame;
    @endframe = @Frame + frameduration;
    @pscale = 0;
}
else
{
    @pscale = fit(@Frame,@startframe,@endframe,0,maxscale);
}
  

now that you are using pscale, place a point wrangle above the "peak2" node with this:

@pscale = 1;

[Korben]

Yes perfect ! Thx !

 

Just a few others questions for curiosity purpose :

 

- Is it possible to achieve the same thing with only nodes ? ( no vex )

- I don't know VEX :

- what is @v.x ? and @v.z ? I think you test if the velocityX and velocityY are zero but I don't understand the @.

- frameduration is the duration (in frames) in which pscale go from 0 to 1, right ?

 

Thanks a lot.

[loopyllama]

You can mimic this behavior with a pop vop, which turns into compiled vex code anyways. Embrace vex, it is your future friend.

the @ symbol says that the variable will be an attribute. normally you write i@myInt; @myInt = 42; and myInt becomes an integer attribute. For a temp variable you can write int myTempInt; myTempInt = 99; myInt will appear in the node spreadsheet, myTempInt will not. Since velocity already exists as an attribute v we can directly access it with @v = myVector; or @v.z = myTempInt;

you can view the generated vex code of your vop nets with a right click. the docs are great for learning and sesi has a free video about the pop wrangle from Ari. Check it out and send him a thank you!

I just keep setting the start frame to the current frame as long as there is no x or z velocity. Once there is some x or z velocity, your particles are flowing down your object, so I stop setting the start frame. If you did this in sops the start frame would get set back to 0, and it wouldn't work.

You are correct about the v and frameduration.

Cheers

[Korben]

Thanks !

 

I will check the pop wrangle video asap