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freejonah

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About freejonah

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    Peon
  • Birthday 07/14/1971

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    http://www.jonahhall.com

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  • Name
    jonah
  • Location
    venice, ca

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  1. inflatable wind sock

    Hi everyone. I'm looking down the barrel at a very cool project that involves creating a CG wind sock and blowing it around in the air. After poking around in Dops for a while I decided it would be a good idea to involve the expert Houdini community. Essentially I need to create a wind sock that has air flowing through it, bending it, flapping it, etc. I also have to animate it like a character. My idea was to create a soft body simulation of some sort that uses a sop animated cage as a target. If anyone would like to prototype it I am attaching a hip file that sets an example scene up. My intention was to post an example of where I was at but my attempts have been so unsuccessful I didn't want to contaminate everyone's thinking. The sop "TARGET_FOR_DOPS" is just a stand in for the keyframed animation I will need to follow. Thanks in advance to anyone with any ideas they can share. I'm very grateful as we are a bit of a pickle here. wind_sock.hip
  2. 6 axis robot arm rig

    I'm looking for a good solution for creating an IK rig that behaves like a 6 axis robot arm like one would see in a modern car factory. This means each rotation axis would be heavily constrained to it's own rotation axis. My target that the rig will follow is a matchmove so it needs to follow it exactly. In theory a six degree robot should be able to follow any point in space, but the math escapes me right now. Have any of you done something like this? Curious to see what's been done in the community. Thanks in advance, Jonah
  3. Looking for floating object ideas

    Genius Houdini Community! I'm having a hard time wrapping my head around something so I thought it best to ask the experts out there. We're about to do a project where a rigid object ( like a box or a tea kettle ) is floating weightlessly in a room. It is being blown around by wind and bumping into objects as it goes. What we would like to do is loosely keyframe the object for basic choreography and timing but have the dynamic object "follow" it, like a target. This way you get the benefit of having keyframed motion influencing the dynamics. Would a sop solver be the right way to go here? Field force? It's been a while since I used dops so any advice or examples would be appreciated. I'm sure there's an elegant solution out there but I'm just not able to think of it. Thanks very much!
  4. altering scale with ODE objects

    In an attempt to simulate the way bubbles in a head of foam grow and push each other around, I'm trying to use the ODE solver. The problem is a lack of any kind of scale control on each individual sphere primitive. Toggling on "Use Deforming Geometry" seems to do nothing to the influencing radius as the simulation runs. The goal is to have lots of little spheres pushing against one another, but with some of them getting bigger and pushing the others out of the way as the simulation grows. I can't figure out how to do this, unfortunately. Advice, or better yet, example hip files are welcome! Thanks in advance Odforce community.
  5. Camera UV coordinates in a Shader

    HI there, Sometimes I find myself doing projects with lots and lots of prebaked geometry data that is a hassle to go back and recook. In these cases I really wish I could tell my surface shader to look up some coordinates from a projection camera ( OTHER than my rendering camera ) that I've set up without having to go back and bake in UV coordinates on the points or vertices. I see that you can do something in Light_NDC space, which is cool. I would like to do the same transform in a camera_NDC space.
  6. sculpting volumes

    Here is a quick demonstration of what sort of thing I'm building. In the hip file note that I've made a slightly modified version of "billowy_smoke" to properly utilize the uvw volume, plus it treats the noise a bit differently. If anyone has a better way of doing this uvw buffer stuffing thing I've doing, like in the volume vop, please share. Thanks! post.hip volume_test.mov
  7. sculpting volumes

    not sure. what am I looking at?
  8. sculpting volumes

    Super cool. thanks for this! It was well timed since I've just now started poking around into manipulating density fields in vops. I've had some luck trying to manipulate the values with expressions using the volumemix sop, but I can see that this is a much faster way to go. The particular problem I'm working on has to do with carrying uv coordinates through the volume system all the way to the renderer. Essentially I'm trying to get "P" out of my noise generating at the shader level by replacing it with something that deforms with the geometry. Imagine an animated guy walking across the scene. I'm trying to fill him with puffy cloud stuff without having the noise pass through him. I want the noise to move with his body, as if he he's made of big shaggy carpet stuff. I started experimenting with creating a "uvw" volume, and it's been really good! The tricky bit is stuffing coordinate values into a volume that doesn't really know that the stuff around it is moving. Currently I'm stuffing a block of points with uv values that relate to the geometry nearest to it, then source those uvw values from a volumemix node using nearpoint() followed by a point() expression. I then including these four volumes at render time: o: density 1: uv.x 2: uv.y 3: uv.z this does a nice job of "gluing" the coordinates the shader uses to the volume at render time. I would really like to use the volumevop to do this but I'm not sure how to use the pointcloud stuff yet. Those vop nodes don't have help cards, unfortunately ( RFE! ).
  9. sculpting volumes

    Hello Odforce community, I've begun really digging into the volume tools in Houdini and am looking for some tips on sculpting volumes. I've been playing with IsoOffset, metaballs and other things. The rendering aspects of volumes feel very nice, and I'm getting good results. The shader writing is simple enough, and I'm doing fine there too. It's actually modeling and animating them that seems to have me a bit stumped ( granted I've only been doing this for 1 day. ) What I'm trying to do is figure out how to really use sops to have good control over density modeling and managing the rest position that the shaders use to build noise and other rendertime attributes. Some basic questions: 1. How can you use a rest position with a metaball? Will it transform correctly? 2. How do you control density so that it falls off gradually towards the volume's boundary, rather than just butting up against the edge? 3. Can we use surface meshes to build volumes where the uv, rest or some other coordinate drives the look and feel of the volume? 4. Is it expected that we fill an empty volume with density values from points and other primitives? If so, how is this done? 5. Are there ways to offset density values in the volume primitive, rather than multiplying them? Dropping noise values down below 0 around the edges always gives you those nice wispy effects. I would love to have that option. Sorry if these questions are a bit broad. I'm used to being able to use sops to build very specific geometry but I'm feeling like the volumes are a bit of a black box right now. I'm willing to bet I just don't have an understanding of it yet. I, of course, would love to see some hip files that people have that demonstrate some of these abilities. Any help would be GREATLY appreciated. Many many thanks in advance, jonah
  10. PBR Glass

    Unfortunately doing that didn't seem to bring any of the specularity into the internal glass. It made it need a lot more sampling, as you said, but the results were still the same. This is kind of an unfortunate limitation to fake caustics. I'm probably going to resort to rendering the outer glass in a separate render and comping it on top. I've forwarded this thread to Sidefx to see if they have any suggestions. The one thing I don't know how to do is generate the caustics map. I haven't gotten quite that far. Can I get a quick explanation of how to do that? Many thanks for all this help, Jonah
  11. PBR Glass

    The double sided glass really solved the IOR questions. Thank you. The bigger issue is the type of lighting I get on the internal glass pieces when surrounded by a large, clear glass surface. I've included 2 images to help demonstrate the issue. The image "open.jpg" shows a bunch of red, glassy objects inside of an opaque half dome. The scene is lit with an HDR, giving the glass cubes lots of shiny, reflective lighting. All good there. The second image, "closed.jpg", has that same set of cubes surrounded by a clear glass outer structure. You can see that the cubes are getting some light, but not nearly the characteristic that they have in the open one. My Reflect_Limit is set to 14, so I'm getting all the bouncing I feel that I need. You can see that the HDR is not reflecting onto the cubes in the same way, only reflecting the diffuse component around between the cubes. I'm trying to figure out how to get the cubes to look like they do in the open.jpg image, but with clear glass around it.
  12. PBR Glass

    Great advice. Thank you. I'll try this next.
  13. PBR multithreading

    In case anyone is still interested, we have found the culprit. A "Multi_SSS" node was buried deep in my shader, unutilized. That node is causing all of my problems. Even though it is switched off, it is causing a lot of calculations that I do not want, and therefore it's killing my multithreading. This only occurs if my relevant Limit settings ( Reflect Limit, Diffuse Limit, Glossy Limit ) is set to higher than 1. Once it is, everything goes crazy at render time. Simply having that node in my shader, even if it's switched off, will cause the shader to run very poorly. I tried putting the switch outside of the subnet, but it didn't work. Seems like there isn't any way to shut that sucker down except by completely unwiring it from any output, which is unfortunate for micropoly rendering purposes. I told SideFX what I found and they said that this was indeed a bug. They said it was no big deal to fix it, but some of you out there should be aware of this in case you have this operator in any shaders that you support for both Micropoly and PBR.
  14. PBR Glass

    Interesting. I was assuming that Inside IOR was bending the reflection vector for the refraction, and Outside IOR was bending the reflection vector for the reflection. This is really helpful. Why, then, are these values being used to modify the surface reflections in these glass shaders? Shouldn't they be independent since the reflection vector is independent of both of these conditions ( glass and liquid )? To take advantage of both of these IOR settings, does the glass then have to have two sides that are spaced apart?
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