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Found 18 results

  1. RBD sim and orient

    Hello guys. Recently i have run into strange issue. I have my packed objects, that have some orient on it. I need to feed them into the Bullet sim, problem is that if i have orient as attribute on the packed objects, my sim explodes on first frame (no intersecting geo), if i remove my orient, sim behaves as expected. so i have run my sim without the orient coming to bullet (renamed orient to keep_orient) and i thought i will just substranct+add them at the end to get correct orient values for my instancing i do as next step. Problem i have is that i was not able to get correct orient from it. Would someone able to explain me what would be necessary to do to make it work, or why bullet explodes with orient values? sorry i cant share any scene at this point. my whole setup is: points in the space, that have @pscale and @orient (random nodes), that goes into the grain sim, to make sure i have no intersections, then i do copy bunch of rocks onto those points which goes as packed geo into the bullet sim.
  2. Hi everyone. I have a RBD sim that falling some geo's. And I wanted to copy some geo's to their centers. But theese geo's has no rotation data. How can I copy the rotation data of sim ? I tried to tranfer orient and w attributes and it doesnt work as well.
  3. Hey everyone, I'm looking for a little help on a pyro sim I'm doing. I've got a fuel and temperature source that move along a path, emitting flame. The goal is to make a look like the flame is propelling an object forward, like a jet engine. I'm able to achieve most of this easily enough, but my sim has a lot of wasted space because the sim container doesn't rotate with the movement of the source. This really slows everything down and it's driving me crazy. I've tried a few things that used to work in H16 (the "point position" node specifically), but H17 sources volumes differently and won't play nice (the sim will rotate the already rotated source volumes again). Most of this I learned here https://gumroad.com/l/TqUNR, which no longer works properly with H17's volume sourcing. Anyway, if anyone could help out with this it'd be great. inverse_transforms_6.hip
  4. I have a feeling this might be a dumb question, but I have been stuck on it for a few days now. Or maybe not so, as I've been looking countless treads here, but none really solved my problem. I've got a really simple setup, pop curve force guiding some rbd objects (I also tried doing it with points and copy stamping after sim to the same result). At a point in the sim the vectors start to point outwards: What I would need is for their direction to be always facing forward as they are at the start: I've had some luck with using pop torque, but still not what I need. I've attached an example file and the curve alembic. RBD_Directional_Vectors_Curve_Force.hip curve01.abc
  5. Hi, I'm facing a problem and I can't find a solution by myself so I'm asking for your help ! I want the object that come form the object merge (1) to be oriented relative to the normal from the pieces coming from the foreach (2). I hope I'm clear enough ! Thank you for your help !
  6. Hi guys, I'm very new to Houdini. I'm coming from a Softimage ICE background so my brain is still struggling with adapting to a new workflow so bear with me if you can! I was following this awesome tutorial from the Entagma guys (linked bwlow). In short, I replaced the spheres he uses at the end with the trusty ol' pig head and now I would like to figure out how to make these pigs heads turn in the direction they are moving as they slide around the surface. I've spend a long time googling and looking at previous posts related to particle orientation but I can't seem to find a way to adapt anything to this scenario. I'll attach the scene file if anyone has any advice? I think I would need to do something like finding the point position from the current and previous frames and subtract them to create the direction vector but I can't find a way to do that in any of the PopVops. I tried using a PopLookat and setting the target to look at the velocity but not luck. Any help would be appreciated. I'm not great at VEX, I come from ICE so Pop Vops etc work best in my brain if thats possible. Cheers (not sure how to reduce size of video in this post, apologies if it shows up giant!) Entagma_GrowthEvenOnSurface_V01a.hipnc
  7. Orient attribute

    Hello! I'm trying to create an @orient attribute on a simple circle (so the copies all point inwards towards the center of the circle) I laid down a polyframe & fed it's generated @N and @tangentu attributes into a quaternion VEX function but it's a no go. From what I gathered, I'm missing an "up" vector & a transform matrix & I'm not sure how to set this up with a wrangle... Orient_attribute.hipnc
  8. orientation not matching

    Hi guys. I have a simple sim with a tube which I steal the points from and want to instance another model onto those points. for some reason the orientation is not lining up. What am I overlooking here? shot_Coinery-Coinery_mod_Modeling_v0008_nocomment_jra_.hiplc
  9. Hi everyone, I would like to better understand matrices and how to use them to do what I want. I've prepared a hip file with screen shots of things I get and don't get. While writing this I'm almost making discoveries so please bare with me if it seems like a long thread First off, applying a matrix3 to rotate my points seems fine as long as my vector is normalized. Else, it affects scale as well. Why is that? 1. rotate around y matrix3 m = ident(); float angle = ch("angle") ; vector axis = {0, 1, 0} ; rotate(m, angle, axis); @P *= m; 2. rotate around {0,1,1}. Not good. matrix3 m = ident(); float angle = ch("angle") ; vector axis = {0, 1, 1} ; rotate(m, angle, axis); @P *= m; 3. rotate around normalize({0,1,1}) matrix3 m = ident(); float angle = ch("angle") ; vector axis = normalize({0, 1, 1}) ; rotate(m, angle, axis); @P *= m; Hence, we need to normalize the rotational axis vector to prevent scaling the geometry. Secondly, I'm having issues setting the pivot for my rotations. In the examples above this all works well if our pivot is set at the origin. So how do we set the pivot to be at the center if our geometry? Please take a look at rotate_not_at_origin object. To begin this little science experience, I've copy stamped boxes on a single box and used the normals from the orignal box as the rotation axis vector. So far so good. This all goes to shit if we move our original box from the origin. How do we solve this? The only way I've seen, and don't understand, is using @orient as follows before the copy stamp. Also, this no longer copies the geometry based on the normal direction of my points. matrix3 m = ident() ; float angle = ch("angle") ; vector axis = normalize(v@rot_axis); rotate(m, angle, axis); @orient = quaternion(m); So how do we solve this? I really need to wrap my head around this once and for all gahhhhh!! Thanks everyone! Maxime matrices.hipnc
  10. Polygon Jitter Orient Problem

    Hello everybody... I am working on a project and stuck on one point. Need a help so bad! lol In the hip file what i tried to do: Created a almost torus shape and and needed little bevel on the edges bla bla bla... In pointvop1 i am giving jitter animation to primitives and taking the animation from the sphere1's transforms. Through the animation, prmitives jittering/animating from object and they coming back to 0 poisition when sphere get far from the object. After that, in attribwrangle3 i am deleting primitives and using only points of primitive's center points. Ok here what i try to do! In attribvop6 i triend to use few attributes and the thing i need is. When points are far from the object i need to give them noise or turbulans or something that gives them motion and when pyramid shaped get close to zero position and create and object i need them not moving and just sit the 0 poition. In sum what i tried is they should rotate while they are going to 0 poisition and when they get close they should stop and just sit and stay. If you turn normal1's display flag you can see that they are not in real order. there are gaps and normals are not correct... I really stick in this part and cant move more. If any help would be amazing life saver lol Thank you for help! Lens_polygon_test.hip
  11. Hi everyone, I'm trying to do a school of fish with a particle system that would follow a curve. Basically I'm emitting some particles and they move along a curve with a popcurveforce. By default the particles orientation seem to go along with the curve but since I'm trying to do a school of fish, I would like my particles Z orientation to always be 0 so the fishes don't swim on the back. So far I've tried with this expression in a popwrangle : p@orient.z = 0; The thing is it seems to zero out the orientation of x and y as well.. And I still want the x and y to go along with the curve. I'v tried with a popattract instead of a popcurveforce and I'm still not able to constraint the Z orient.. Maybe it has to do with something else than the @orient attribute since I don't see it in my geometry spreadsheet..? There's something I don't get! (Needless to say that I'm new in Houdini :P) Thanks a lot! test_fish_school.hiplc
  12. Hello Guys, I have some issue with @orient values for particles on POP context after plugging POP torque / POP spin.When I plug one of this nodes my copied geo on particles start look like on ex_v01 gifBefore sim I randomize v@N for random look instanced geo after coping to points.When I bypass POP drag / torque all look fine randomized, because I think use Normal for adjust orientation, on randome direction gif you can see it.How I can randomize orientation value at the beginning of simulation particles?Thanks advance!
  13. Attribute Reorient Node Tutorial

    Hello community : i created this short tutorial on how to use the reorient attribute node in houdini and also i showed how it is work, it is some math matrix stuff, hope you find it helpful and hope you like it : Note : this training will give you nice idea of using the Matrix in Houdini , .
  14. I'm trying to mess around with orienting a particle's alignment to it's vector. Or a watered down version would be a cube on a path that follows it based on the particle's vector or velocity. Basically, orienting the particle to "speed space" if that makes sense? I tried mixing Normals and Velocity to possibly get them aligned but I'm pretty much lost. I took a look at @mestelahere to help me out, but I'm pretty much in over my head trying to do it in Houdini. I attached my file that is just a spinning circle with box's copied onto them. I was trying to make a simple scene where the boxes rotation matches it's vector. So nothing too out of the ordinary, but still kind of confusing. Thanks :)! velAlign.hipnc
  15. First of all, I want to tell you what end result I want so you can solve my scene file or suggest other easier way of doing it. I want to get the transformations of these rbd dominos to object level. My first approach was to simulate rbd fractured objects then use dynamics chop to get that data and export it to object level but it got some problems. My second approach was to "get point data" from dops and do some matrix magic in VOPSOP with points and import that data through geometry CHOP so it can get exported to object level grid's transformation. I have tried to use orient attribute to my advantage but objects behave weirdly. Their positions are wrong. This is good exercise for you to use SOPs, DOPs and CHOPs interconnectively. You can see my file with both approaches, check out these nodes and tell me what am I doing wrong? I just want to apply the boxes domino data to grids in object level. Thanks! dynamics orient.hip
  16. Hello, I have seen some really helpful examples of how to orient primitives along a curve with the CopySop but unfortunately in my setup I won't be able to use the CopySop (example scene is a quick mock up). How would you orient the individual layers along the guide curve? I have the tangent's from the guide curve and have tried to align the layers to this, but with now luck. I would really appreciate some ideas on this. Thanks orient_along_curve_101.hip
  17. Hi guys. I'm trying to get point rotation around local axis (around local Y axis) I need to export points in Maya later, so I can't use copy sop for stamping. If I use transorm sop with Copy Stamping I can rotate Objects along local axis, but if I'm trying to edit rot and orient point attributes points are rotating in worldspace (around world XYZ) not along local axis. If I use orient attribute points are aranged in worlspase, not along normal. Can sombody help with that, please? ps I found Make Instance Transofm Vex node, but 'Ive got no Idea how to use it >__> point_rotation_001.hip
  18. Hello! I am currently trying to wrap my head around being able to transform (rotate) instance objects for sop copy and instance rendering. Basic stuff, I know, but I'm stuck and my math suck. I have a hard time grasping dot product, cross product, matrices and quaternions -> 3D transforms There are, as far as I can see, a multitude of attributes and options to do this, and I am wondering what would be best suited for my use? Some use up, some use orient. Basically, I would like to have the rotation options of the transform sop (x, y, z rotate) to work on a point instance where the normal direction is the "up" direction (think teapots standing on a displaced ground plane, rotating planar to the ground when editing the y axis). I've been through a lot of examples but I just can't make them work for my scene. Either the objects are flipped or rotation is happening on the wrong axis or objects are not rotating smoothly, or I am not able to figure out how to "flip" to the right axis when using N and up (usually +-90 degrees in x) inside the vop. Most of all, it needs to be stable on deforming geometry. Any example of rotation working in this scenario would be most welcome! Also, if you have a link to a good (basic level) resource regarding this topic, that would be awesome! Thanks.
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