orient and copy

[sschoellhammer]

Hello,

another beginner question ahead..

I want to scatter curves on the surface of my hippo so they conform to the surface. I'm creating the orient attribute like this:

float randomRotationScale = ch("randomRotation");
float randomRotation = rand(@ptnum) * 3.14 * randomRotationScale;
@orient = quaternion(randomRotation, @N);

but it's not really doing what I want. I've attached an image and the hip file. 

It's something so straightforward I feel I miss something pretty basic 

seb

felt.hiplc

[Atom]

Here is a variation on Matt's solution posted here.

It randomly rotates along the Z-Axis only while maintaining alignment with the primitive normal.

ap_me_random_align_to_primitives_centroid.hipnc

[galagast]

Is this what you were after?

I added two approaches.. one is using the orient attribute, and the other one is using an N and Up for orientation, with the addition of a custom randrot for randomly stamped rotations similar to what Atom has posted above.

I hope this helps!

H15.5.607 Indie

felt_v2.hiplc

[Iskander]

I am a newbie,but know,you can also grow hair by pop.
And i have a question,why you did't use volume trail?
Is this heavyweight variant?

 

felt_v2.hiplc

Edited October 16, 2016 by Iskander

[sschoellhammer]

Hello all,

thanks so much for the many, quick replies! The pop way is interesting too Iskander

It seems stamping the rotation seems to be the way to go for me!

galagast: I actually wanted to have them sit parallel to the surface. That's also why I don't use fur, I want it to look like lots of hairs layered ontop of each other like this:

When I lay them flat I get those funny patterns like in the attachment, I don't quiet understand why they are so visible as there is random rotation on the curves..

I might just layer another shell ontop but still curious!

seb

 

[sschoellhammer]

I have one more question..

@N = @N;

why is this needed? Most confusing behavior ever..

[acey195]

its just a way to initialize Normals, from vertice positions relative to its neighbours.
Alternatively, you could put down a "Facet" node and enable "post compute normals"

You can also say

@N = {0,0,1};

This will assign normals, but all facing the same way.

 

also note that if the object already has normals, @N = @N will just keep the normals as they are, rather than re-initializing them.

[galagast]

You could probably do a couple of things:

• Add a bit more randomness to the randrot seeding.. currently it is set to only range from 0 to 360, instead of maybe -360 to 360.
• Stamp in a couple of other random values, maybe for other rotation axes.
• You could also add other strand curve variations, just use a Switch SOP to randomly pick one for the Copy.

@N = @N; // Yep, as Twan mentioned, it's for initializing the normals

[sschoellhammer]

Thanks!!

OK, I was confused because there is a normal sop and also a normal attribute coming from it - and yet if I comment out that line @N=@N the result is different (as in wrong). 
AHA my normal sop was working on vertices.. got it!

Now I have another problem  I created a for loop to create a number of different curve shells and I'm using the iteration detail attribute to modify them. 

I'm using it it in the peak node like this (for the height):
detail('../foreach_begin1_metadata1', 'iteration', 0) * 0.2  + 0.2
to offset each shell a little and that seems to work just fine.

but when I use it in the wrangle like so:

int it = detail('../foreach_begin1_metadata1', 'iteration', 0);
@randrot = random(@ptnum + ch("seed") + it*10000 ) * 360;

but now it seems to be just 0 all the time.. 

By the way I'm now randomizing the up vector which brings some joy but I think I still need the layers..

Added the file again, thanks so much for looking!

seb

 

 

felt2.hiplc

[galagast]

Cool, glad you got the randomization going

I'm not sure why that doesn't work.. I usually add a spare parameter to the Wrangle Sop and place the detail function there..

Here's a link to other methods for dealing with that problem.

 

[sschoellhammer]

ahhhh - the op: thing makes it work.. THANKS!!

 

 

[sschoellhammer]

Getting somewhere :))

Sadly blue screen of death while rendering, haven't saved the scene for 2 hours and my otl doesn't seem to load anymore, sigh.
( I had created an asset for the felt/fur and had been saving it continuously) 
Does anybody know what the problem there might be? User error?

Next thing I'll do is this I guess:

 

 

Here is the error I get when loading the library:

Edited October 17, 2016 by sschoellhammer

[galagast]

Looking great Sebastian! I like it a lot.

Autosave: Ah yes, I have that turned on by default as well. A life-saver indeed.

OTL Error: Sadly, I haven't encountered that error yet.. Have you checked the actual folder where your otl is saved? Is it really there?

[sschoellhammer]

Glad you like  

this is the file, maybe it's corrupted? It just saved normally without problems. I saw that usually houdini makes a backup but there are no backups for a while so maybe something was off... mh

Well, doing it again I'll remember better I suppose

Sebastian_felthair.hdalc

[galagast]

Just letting you know, I'm also unable to install the hdalc.. It must be corrupted.

 

[sschoellhammer]

Hello! I just wanted to give an update on my houdini project

I redid my lost felt, got the rest of the model and I did some shading with mantra.

I used substance painter to make the maps and I really like how easy it was to integrate them into houdini!

There's a bunch of udims but the whole thing just uses one shader which is awesomely easy!

Well..  some more work to be done... !

[rbowden]

The felt looks great! You mentioned that you redid it, did your workflow for creating it change at all?

[galagast]

@Sebastian: That is really awesome! Can't wait to see the final!

[sschoellhammer]

Thanks!!!

@rbowden: I think I didn't change too much but I will upload the felt otl here once I'm all done with this image!