Hello,

I am a bit lost with the new POP Network. Several operators seem to have disappear and the replacing ones are not so easy to use.
Beside it seems the examples in the documentation are still based on the old POP Network, which is quite confusing.

So this is my problem: I try to generate new particles based on the collisions between particles from a given emitter and the ground. something quite similar to the BounceSplit example in the documentation.

When I created my particle system it went into the AutoDopNetwork. In this network the Split is not accessible. As far as I understand, and please correct me if I'm wrong, the Split has been replaced by the POP Replicate.

The thing is I don't manage to activate the replication when the hit occurs. I though I could use an expression based on the number of particles in the group from the hit, with npointsgroup, but it doesn't seem to work (I fact I don't know what to put in the Surface_Node parameter).

- Can someone tell me how to use npointsgroup within a POP please?

Here is an example scene.

Thank you very much


Thank

I played again with the scene and found that particles are bouncing as expected on other kind of objects such as spheres and boxes.
It may be due to the fact that these primitives define volumes and not surfaces.

I thet tried to thicken the surface of the grid in its Static Object DOP, and tweaks some other settings too, but nothing changed.

At lead I have an alternative to my issue by using a box instead of a grid but I still have no idea how to make a grid work in that case.

Hello Rabiee,

Thank you for your answer.
I checked all the points you mentionned and everything seem to be ok and though I keep having the particles going through the grid.

This is, step by step, what I did (and I did it again to be sure):

• - I created a grid
  - I droped a Static Object DOP from the toolbar on it. It then created an AutoDopNetwork with the solver in this network. The Static Object get connected to a Static Solver.
  - I dropped a Location Particle Emitter into the scene
  - I then dropped a Collision Detect Particles in the scene, once again from the toolbar, and selected the grid. The Collision Detect is added into the AutoDopNetwork and my particles get red when going through the grid.
  
  
  … and them what?
  Particles are still not bouncing on the grid and, well, I really don't see where to change that.
  
  I've attached the described scene to the post.
  
  Thank you once again for your help,
  
  Best regards

Hello,

I come back to Houdini after a little while and some things have changed, especially with the dynamic objects, and I have troubles to find my marks again.

So I try to make a simple bouncing particle on a grid.
The thing is I can make it stop, slide, stick… but not bounce. As mentionned on the node it is because the collider is not a static or dynamic object.. I then converted it to a static object and added it in the CollisionDetection DOP but I still cannot make my particle bounce.

Can someone explain how to make that work, and where to set up the bouncing behavior?

Thank you very much

Hello guys,


Although not so newbie with Houdini I still sometimes bump into something harder than usual to understand in the Houdini way of use.
I must admit this one put me into despair…
Once again, a few tips from you would be greatly appreciated

So what I would like to do is quite simple:
- There is a camera camA in my scene, connected, or not, to a SubNet
- I have a Font, nearby on the screenshot but on another network in my real case
- I would like to put an expression in the Font Text field so that if the camera camA is connected to a SubNet its name is displayed, if not something else is displayed.

The thing is, whether I use Expression, HScript or Python, I don't manage to get a code accepting the condition (and I spent quite a lot of time on it). I would then be delighted if you could provide me an answer for each langage so that I get a better understanding of them.

So here is what I did:

Expression:
I expected that line to work in the Text field:
`if('subnet'==optype(opoutputpath(“/obj/camA/”,0)),“1”,“0”)`
… but the node says: Bad data for function or operation (text). It doesn't work either with ifs

An expression such as
`1 + 1` works correctly and the Font displays “2”.
An expression such as
`ifs(1==2,1,0)` works correctly and the Font displays “0”.
An expression such as
`optype(opoutputpath(“/obj/camA/”,0))` works correctly and the Font displays “subnet”.
Any expression such as
`ifs('subnet'==optype(opoutputpath(“/obj/camA/”,0)),1,0)` doesn't work, whatever quotes I put around subnet…


HScript:

I expected that block to work in the Text field:
`if ('subnet'==optype(opoutputpath(“/obj/camA/”,0)) then
“1”
else
“0”
endif`
… but the Expression editor says: Syntax error - extra tokens detected in expression (text)

Anyway such an example doesn't even work, although it seems to be Hscript code:
`if (1==2) then
“1”
else
“0”
endif`

In the Hscript Textport the code works:
/ -> set toto = `(optype(opoutputpath(“/obj/camA/”,0)))`
/ -> echo $toto
subnet

So does this one:
if (1==2) then
echo 1
else
echo 0
endif


Python:

Python seems to be the recommanded langage to use nowadays in Houdini. It is a bit heavier than Hscript for quick expression though.
Nevertheless, here are my tries here:

Fisrt of course I set the Font node to Python (in fact I even started froma new one).
I expected such block to work:
if ('subnet' == (((hou.node('/obj/camA/').outputs())).type()).name()):
1
else:
0
…but the whole block is displayed and not interpreted

This block is also completely displayed:
if (1==2):
“1”
else:
“0”

In the Python shell we have:
'subnet' == (((hou.node('/obj/camA/').outputs())).type()).name()
works and return True

and
if (1==2):
1
else:
0
works and return 0

I guess some basic understanding of the way these language work in Houdini would be needed, but honestly the documentation is not clear at all and i didn't manage to get a clearer overview than the one I have now with it.


Thanks again for any tips, guides or solutions…

werwack

Hello,

I tried to use Notepad++ instead of Notepad for script editing, but I could't manage to make it work correctly. Some help would be greatly appreciated

I edited my houdini.env file and added an entry like this:
EDITOR = CPROGRA~1/Notepad++/notepad++.exe

This works, I can open and edit a script in notepad++ when I press Alt + 0 in the Edit Expression window, but modifications are not taken in account.
According to this thread, it would require that the editor works under the current houdini process (the ‘nofork’ parameter in the thread):
http://forums.odforce.net/index.php?/topic/8758-external-text-editor-for-scripting/ [forums.odforce.net]

Do you know how I have to set the EDITOR env param so that the given editor works?

Thank you,


Werwack

Nice, it looks like a real API

I am still transitionning frm HScript to Python, but the more it goes the more Python convinces me!

Thanks a lot!!

Hello,

I would like to know if there is a way to change the content of a list in a camera switcher.
It the cameras list accessible in Hscript or Python? Can we reorder it and change its content?

I also would like to know if it is possible to add a custom input to a node.

Thank you very much

Well, thanks for the tip, but unless I missed something it doesn't really help because I know where the backtick is on my keyboard. :cry:

Indeed it is not a matter of where the backtick key is mapped, it is just that Houdini seems to prevent it to be entered if you are not using a QWERTY…
The backtick is taken in account if I call the external text editor, but is is not otherwise, neither in the expression fields not in the consoles. Event the Alt + 96 (ASCI shortcut) isn't taken in account…

This thread is quite old but still seem to be applicable:
http://www.3dbuzz.com/vbforum/showthread.php?48273-backtick [3dbuzz.com]

Are you able to use the backtick on your side?


Regards

Hi Tomas,

Thank you very much for the code line. It really help

I progressively acquire the Houdini philosophy and this tip seem to me to be very consistent with it.


By the way I also discovered that the backtick character ( ` ) cannot be entered in Houdini with a AZERTY keyboard (I didn't had to use it so much so far).


Best

Hello,

I would like to know which camera is currently activated by a camera switcher, this without having to do an index check in the camera list of this switcher.

In other words, how could I get the name of the current camera of a switcher with and expression?

Thanks a lot for any help

Hi again Bollili,

In spite of many tries I still have troubles with the nodes you suggested

- I failed to make the Render COP node work:

• Whatever I do the node says that it cannot read the input files.
  
  Here is a basic scene. Could you please have a look at it and tell me if I do something wrong?
  
  As the documentation says: “This node currently only works with output drivers that produce .pic format files.”
  I start wondering if it supports .picnc files…
  
  
  - Unfortunately I also failed to make the ‘op’ function work. (I know it sounds a lot at the same time, but honestly I would have expected Houdini to be more intuitive and documented sometimes…).
  I used a File node in the Img network to get the 3D renderings (with the expression opout/mantra1 to get the output) and plugged it into a composite. Here the File node says 'Cannot find file opout/mantra1.
  … Although I followed the documentation samples. :?
  
  I also provided a sample file here.
  
  
  
  Thank you very much for your help.
  
  
  Best

Thanks a lot, Bollili, those topics really help!

By browsing in the documentation from them i aslo found this interesting page: Mantra render node (http://www.sidefx.com/docs/houdini12.0/nodes/out/ifd [sidefx.com]), with several examples including one called Rop_Fetch_Example1 (Fetch example), which is quite simple and nice to start with.

Things are still a bit tricking though and I still have troubles to understand with I sometimes don't get a visual result.
I'll play some more and come back with a scene if I still have some troubles.


Best

Hello,

I am desperately looking for a basic scene or tutorial to better understand the relationship between composting and 3D.

Practically I would like:
- to apply basic filters on an image and to be able to use it as a background image when rendering a 3D scene
- to be able to use this filtered image as a texture

In the other way I would like to get the output of a camera (the real output, not a generated images sequence) into the compositor and to apply some filters on it.

It may sound basic but I have a hard time to find tutorials on that.

Thank you very much for any help

The carve sop + remove duplicates setup works very well

Now I will have to iterate through every primitive as if they were curves. I guess a ForEach sop will do the trick (I have to learn how to use it but I saw some very good tutos from Peter Quint on it).

As I use a function to manipulate the curves, do you think it would be possible to integrate the look into it? How can I specify the primitive into it? It will probably involve $PR and $NPR, but I don't know exactly how.

Thank you

Hi Jeff,

exactly what I was looking for


Thanks a lot, pclaes. I tried the carve sop and the result is visually correct and fast, but indeed it creates some duplicates, which are not easy to remove.
Your other suggestion is also interesting but will very likely not be suitable for quite big objects…

I'm going to try the Remove Duplicate.

Hello,

how can I explode, or separate, an object into a set of curves?

For example, a cube primitive would give an object compound of 12 curves (or 12 groups).
So far, some curves I get from a cube correspond to several edges. I would like each edge to become a single curve.


Thank you

Thank you for the confirmation I was at the right place.

Did you press “Apply” at the bottom of the Preferences Dialog?

Of course, I tried this. But I hope pressing “Accept” without pressing “Apply” leads to the same result (which seem to be the case, btw), otherwise it's very confusing.

I found why I still had trouble after setting the 80's value: the vertical axis is not reset to the Y axis and the one used is based on a vector which is vertical at the moment of the parameter change. In other words, if the scene is upside down when the 80's parameter is applied, a rotation of the viewport will not put the Y axis at the expected orientation, so we think the parameter change has not been taken in account.

To really see the difference, the parameter change has to be done in a completely new scene.

Hello,

I moved to Houdini 11 recently and I face this problem: when I do a point of view rotation in the 3D viewport (by pressing the left mouse button), the Y axis is not vertical anymore… The view is quickly upside down and it is very disturbing.

I tried to change the Tumbling method in the Preferences, but it didn't change anything.

How can I go back to the rotation style where the vertical axis stays vertical?


Thx a lot

It appears that Blizzard is also using Houdini… Well, for cinematics, but still, its a game company.

It was recently used on the cinematic of Cataclysm, the last add-on for World of Warcraft. We can see a quick screenshot in the quick making of (at 1'24''):

http://www.youtube.com/watch?v=k7Fq5gx2dmA [youtube.com]