How to !

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Just thought I would share some of my solutions to common issues that pop up for users. I have so many files now on my laptop it would be shame to throw them away without sharing the knowledge I have gained from asking questions and doing work.

Scene attached shows how to make a ID pass with instanced objects, use the inspection tool in Mplay to read the point number.

The scene also shows how to override the dif color per instance via the creation of an attribute based on the point colour. The overridden colour is then rendered as a image plane. Any questions feel free to ask.

Rob
Edited by - June 16, 2013 02:07:23

Attachments:
teapot.jpeg (63.2 KB)
idpass.hip (300.9 KB)

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Create an attribute > and blast away geometry points based on a colour component.

Attachments:
rse_blastaway.hip (63.3 KB)

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Technique . Create a rest attribute , which you can then use in VOPs to drive noise on points or on any other attribute.Very handy indeed !

Rob

Attachments:
noise.jpeg (21.3 KB)
rse_vopSop_restpostion.hip (93.1 KB)

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Thanks a lot, Rob!
I'll pin this thread in my bookmarks now…
Toronto - ON
My Houdini playground [renderfarm.tumblr.com]
“As technology advances, the rendering time remains constant.”
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No problem, dont feel the need to post a reply or anything. I just wanted to share those simple techniques I use all the time in production to get my shots over the line. The files are raw and not noted but work. My main interest is in VOPs for the average user like me !

Rob
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Technique :- Create a custom vector in vops and use it. to fire points at a moving target. 10 points to whom can figure out how you could have the points landing just infront of the predicted trajectory of the sphere !

Rob

Attachments:
rse_custom_vector.hip (153.8 KB)

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Arquestro gets the points . The scene shows how you can make the points hit the target !

Rob

Attachments:
rse_custom_vector_393_solution_136.hip (159.9 KB)

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Technique , Use a ramp in VOPs to out put an attribute which then can be remapped to the pscale attribute, to art direct the size of spheres

rob

Attachments:
rampvop.hip (90.1 KB)
Screen Shot 2013-05-20 at 3.34.57 AM.png (116.9 KB)

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Create useful vector attributes from point. You might get given a bunch of points with just velocity and then have a task to adjust them. That means needing some basic attributes this set up shows you how to generate. N , v , up , id and use a very simple vop sop to generate a new up vector that's perpendicular to N.

Attachments:
rse_crossproduct.hip (89.0 KB)
Screen Shot 2013-05-26 at 2.24.04 AM.png (141.6 KB)

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ah, the ol' double-crosser technique

thanks for posting these… honestly, I think handy VOPs workflows and tricks is one of the most exciting parts about learning Houdini. You apply the same concepts in so many different contexts… maybe as a minimalist piece / challenge to myself, I'll take one simple idea in VOPs and apply it again and again, in POPs, COPs, DOPs… variations on an algorithm for 8 contexts.
I'll have to give that some serious thought.

Well, thanks, it's been inspirational!

I'll see if I can post some handy-dandy, casual VOPs stuff too.
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Technique: - This scene shows you a smart way of getting the transform and rotations data from an asset > The point generated has N and up that matches your geometry asset. That asset could of come from maya or another dept in your pipeline> Very handy
Note the point is at world zero and I invert the transform on the object merge node.

Rob

Attachments:
rse_matchNandup.hip (102.3 KB)

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Technique :- Build a better volume for collisions. This example shows you how to build a volume from an attribute. Handy for those all over awkward, odd shaped geometry assets you get , that requires a better detailed volume to act as a collision..

Rob

Attachments:
rse_volumefromAttribute.hip (129.5 KB)

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Technique :- Object merge sop very handy but often you want to merge more than one stream of data and even better just plug your data in and merge. This scene shows how you can get the multi parm block from the object merge sop upto the top level of your tool , where you can just plug in your data and go.

/obj/`opinput(“.”,int(strreplace($CH,“objpath”,“”)-1))`/OUT

The above expression will evaluate the input and resolve a path. The “strreplace” part strips out the name of the parameter and leaves the number so you can count the inputs , 1 , 2 , 3 , 4 etc etc . The technique can be expanded to do all sorts of things.

Rob

Attachments:
sop_multiparm_readinputs.hip (86.2 KB)

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Very simple scene for someone new to the software. Shows how to use the render UV object parameter on the mantra node. You can render your paint sop brush artwork or render out that UV map to paint. Remember to keep your render image size square.

Attachments:
rse_example_rendermaps.hip (314.9 KB)

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Technique : - VOPS > Use a start and end time to act as a trigger on a value in vops. So over time the points change colour from Red to Blue.

Rob

Attachments:
rse_sop_vop_time.hip (130.6 KB)

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Thanks, dissecting vops nets is real helpful.

If you have the time , and feel inclined…

Post more vop stuff please. Some files with some inline coding would be awesome.
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You really want to watch this
http://www.sidefx.com/index.php?option=com_content&task=view&id=2512&Itemid=132 [sidefx.com]

Then maybe start a new thread with your questions.

Rob
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Good stuff from Ari, I'm working through that now, along with a vex fractal tutorial.

I found this as well: http://www.sidefx.com/index.php?option=com_content&task=view&id=1744&Itemid=166 [sidefx.com]

Your examples also helped me learn by studying the vops nets…just hoping you'll post more.

Thanks again!
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Technique:- Use a texture projection sop from the camera to drive points as members of a group using the following expression

$MAPU >= 0 && $MAPU <=1 && $MAPV >=0 && $MAPV <=1 && $MAPW = 0 && $MAPW <=1

Then in vops move the points to prove the group is working. Can be used for all sorts of things like to define the birth of points from geometry only when the camera is looking at the subject matter.

Rob

Attachments:
Screen-Shot-2013-07-06-at-8.07.58-AM.gif (40.8 KB)
rse_uv_group_displace.hip (88.2 KB)

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Excellent! Just want to know how to “Like” a threat in the forum and see them at one place
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