point cloud issue with color attribute in Vop

Forums Houdini Indie and Apprentice point cloud issue with color attribute in Vop

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vbk!!!: Member; 383 posts; Joined:; Offline

July 13, 2011 1:53 p.m.

I am trying to use point cloud to color points of a mesh.
A lot of artefacts appear during the iteration.
The point cloud is created on the fly with particles.

check the.hip file attached.

Thanks for your help.

Attachments:
pcloudtest.hip (99.1 KB)

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symek: Member; 1390 posts; Joined: July 2005; Offline

July 13, 2011 3:21 p.m.

vbk!!!
I am trying to use point cloud to color points of a mesh.
A lot of artefacts appear during the iteration.
The point cloud is created on the fly with particles.

check the.hip file attached.

Thanks for your help.

What was a second pciterateVOP inside a while loop for? Anyway, with a single one at the front of a while loop works better…

hth,
skk.


tamte: Member; 8555 posts; Joined: July 2007; Offline

July 13, 2011 4:51 p.m.

that pointcloud setup is not correct because:
1. pciterate inside while loop may not execute after pcimport as required
2. only last point is taken into account since nothing is accumulating value inside the loop
3. pcimport imports distance 0-n and in smooth1 you are taking into account only 0-1 range, you need to normalize distance to maxradius first

here is correct(I hope) usage of point cloud for that case
it is currently doing just what attribtransfer can do so I included attribtransfer method too

Attachments:
pcloudtest_fix.hipnc (116.1 KB)

Tomas Slancik
FX Supervisor
Method Studios, NY


vbk!!!: Member; 383 posts; Joined:; Offline

July 18, 2011 4:44 a.m.

ok I understand better now
thx for your time Tamte

ps :I was using Attribute transfert first but I would like to try point cloud …

About the pcimport node : Is it possible to import age of particle with it ?
How could I made age based radius varation during the point cloud iteration ?

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tamte: Member; 8555 posts; Joined: July 2007; Offline

July 18, 2011 5:18 p.m.

sure, but you need to import vector attribute “life” not float “age” since if you look at particles no “age” attribute exists, just “life”
age is first component of life attribute

Attachments:
pcloudtest_age_fix.hipnc (129.0 KB)

Tomas Slancik
FX Supervisor
Method Studios, NY


vbk!!!: Member; 383 posts; Joined:; Offline

July 19, 2011 5:10 a.m.

thanks a lot Tamte.
I understand better the point cloud now and how you can use it.

++

Vincent

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zarti: Member; 330 posts; Joined: July 2007; Offline

July 20, 2011 9:10 a.m.

just wanted to say “ thanks ! ” to tamte,

i too , understood ‘some’ things better after looking at your latest example .

absolutely helpful .. ( this file should be dropped inside official docs , imho )

.cheers

except the things that cannot be seen , nothing is like it seems .


vbk!!!: Member; 383 posts; Joined:; Offline

July 27, 2011 11:52 a.m.

yep,

a new little question …
I would like to use the pcloud inside a vopsurface node.
I replaced the
op:`opinputpath('.',1)`
by
opobj/grid_object1/popnet2

but it seems it's not enough to make this surface node to work …
Is it the good of op: ?

Thanks

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tamte: Member; 8555 posts; Joined: July 2007; Offline

July 27, 2011 2:17 p.m.

you cannot refer to object geometry from shader since when it is run the scene is already translated for mantra so the nodes don't exist anymore

you have to write your pcloud files to disk then reference disk files in that parameter, as you do with textures

Tomas Slancik
FX Supervisor
Method Studios, NY


vbk!!!: Member; 383 posts; Joined:; Offline

Oct. 3, 2011 9:18 a.m.

Hello again,

My problem with point cloud shading is still here.
I write .bgeo files on disk and link it to “file” parameter node …
but nothing happens.
It works perfectly in opengl

I joint a file. I wiil be more than happy if someone can take a look at it.

++

Vincent

Attachments:
pcloudtest_age-shading.zip (608.2 KB)

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claudio_101: Member; 121 posts; Joined: July 2008; Offline

Oct. 4, 2011 4:38 p.m.

Hi Vincent,
I had a look and I see that your render flag is on the grid SOP while your display flag is on the pointcloud null.
If you set your render flag to the null it renders fine.
Cheers

Attachments:
Screen shot 2011-10-04 at 22.36.14.png (12.6 KB)
Screen shot 2011-10-04 at 22.36.02.png (297.3 KB)

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vbk!!!: Member; 383 posts; Joined:; Offline

Oct. 5, 2011 3:13 a.m.

hmm no …
the goal is to render the SHADER not the vopsop.
The vopsop is for the display and a surface shader is linked to the grid object.
This shader is built the same way the vopsop is but I am not able to render anything with it. Tamte suggested me to render the pointcloud on disk, what I did. But there is still a problem with this pointcloud shader.

Thanks anyway Claudio.

++

Vincent

http://vimeo.com/vbkstudio [vimeo.com]


tamte: Member; 8555 posts; Joined: July 2007; Offline

Oct. 5, 2011 5:08 a.m.

1. use P instead of Cf for pointcloud lookup in shader
2. transfer that P to object space before usage (with Transform VOP)

Tomas Slancik
FX Supervisor
Method Studios, NY


vbk!!!: Member; 383 posts; Joined:; Offline

Oct. 5, 2011 6:12 a.m.

thanks tamte

I found the first point finally but was stuck with the space coord.
Is the default coord space for shaders, the camera space ?

WHy this choice ?

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claudio_101: Member; 121 posts; Joined: July 2008; Offline

Oct. 5, 2011 6:21 a.m.

Hey Vincent, I didn't! Where can you change the lookup?

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vbk!!!: Member; 383 posts; Joined:; Offline

Oct. 5, 2011 7:11 a.m.

I use a little laptop for this test. I copy paste the network of the vopsop to the shader without to check the output of the global variables node …
Houdini keep in memory the order of the input and output of the node, not the name of the variable you link at. In the vopsop the first output of the global variable node in the Position but, in shop context, the first output of the global node is color. The Position output is the fourth one.

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claudio_101: Member; 121 posts; Joined: July 2008; Offline

Oct. 5, 2011 7:23 a.m.

Okay…that is one I'll never forget!

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