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Found 31 results

  1. Geodesics in Heat

    Hi everyone! I've made an illustration video-tutorial about the Heat Method application to point clouds by Keenan Crane et al, Yang Liu et al and others.
  2. Hello everyone, I have created few videos to introduce vectors and matrices in a fun way, with lots of real-world examples. Please go through them and I would love to get a feedback. Intro to Vectors | An Idiot's Guide to Vectors and Matrices, Part 1 Intro to Matrices | An Idiot's Guide to Vectors and Matrices, Part 2 Advance Operations | An Idiot's Guide to Vectors and Matrices, Part 3 Depending on the feedback, I am planning to create few Houdini specific videos as well.
  3. UV from vector file

    Hey. My idea is to create a uv in Illustrator and transfer same uv on geometry object. I try to solve it myself, but now i need your help/some idea. My problem is wrong rotation island on target uv model. I try sort points, primitives and my other idea didnt work. (ofc I dont want fix uv islands by hand) I cleaned my mad project for you and attached project files here (project, vector uv file and texture for experiments) Thanks for your answers. //add The main problem i think wrong sorting vertices i cant solve it. If you unlock "sort" node in my project you see primitives was sorted fine (i hope) I think new map will be more useful (testUV_02.jpg) //new HoudiniTestUV.hipnc testUV_01.ai
  4. Hi there. I am struggling with setting up the following: I have 2 points and I need to create a position/rotation vector from them to attach a new geometry onto the vector. I have got to the point where I have the new object aligned with the vector and I get a correct position and rotation, however I also get a random rotation along the object's own axis. (in an attached file it's the tube which is randomly rotating around it's own X axis. Any help would be appreciated, see the attached set up in the file. Many thanks! Adrianna vector_01.hipnc
  5. magnet force on two directions

    hello! I am having trouble making gravity work in two directions. Basically the world is a tube and I want objects to magnet/have a gravity like force along the Z and Y axis but not on the X axis. I attached my hip file and a picture. Any help would be great! Thank you! tube_attractor.hip
  6. Hi, I compute the velocity on an animated point and I copy a geometry on it which inherits the velocity but of course is not correct as every point now has the exact same vector. How can I realign the existing velocity in the geometry using vex without having to recompute it? I have attached an example hip. orientvelocity.hipnc
  7. How to Calculate @w to Aim RBD Object

    As I'm just starting to understand quaternions and orientation in Houdini, I'm not sure how complicated this is to achieve. I could be completely over thinking it. Ultimately I would like to create a force in dops to rotate the packed object to its current direction of motion, or it's velocity. Modifying @w seems to be the best way to do that. For a first step, I'm trying to make a setup that takes a rbd packed object and rotate it back to it's original orientation. While it technically does that, it doesn't do it logically. It flips around its axis in bizarre ways. As I understand, it's behaving erratically because it's trying to rotate around all of its axes at the same time. This is the code I'm using in a pop wrangle node: vector qToE(vector4 q_value){ float q_0 = q_value.w ; float q_1 = q_value.x ; float q_2 = q_value.y ; float q_3 = q_value.z ; vector out = {0,0,0} ; out.x = atan2(2*(q_0*q_1+q_2*q_3), (1-2*(q_1*q_1+q_2*q_2))) ; out.y = asin(2*(q_0*q_2-q_3*q_1)) ; out.z = atan2(2*(q_0*q_3+q_1*q_2), (1-2*(q_2*q_2+q_3*q_3))) ; return out ; } v@euler = qToE(@orient); @w = -v@euler*1*{1,1,1}; This is where I got the quaternion to euler function: I've attached my houdini file to this post. If anyone has any tips, I'd be very happy to hear them! Thanks! orient_rotate_v01.hip
  8. FGA Sequence Export....

    FGA Sequence Export.... I am using "GitHub Game Development Toolset" for FGA output. However, the included "rop_vector_field" can output only one frame. I want to know export FGA sequence. For example, how to output from 1f to 100f. Thanks...
  9. Hi all ! I'm struggling with an addpoint function, I'd like to use a variable to declare a point but it seems that's not allowed… What is the proper way to do this ? My code in a pointwrangle : float height = fit(rand(@seed, @ptnum), 0, 1, 0.4, 0.55); addpoint(0, {0,height,0}); if I put a 1 instead of "height" it creates the point perfectly well :/ Thank you for your help !
  10. In Vex, I'm trying to find a signed angle between two vectors i.e. an angle which treats one vector as a "base" and the other as a rotating "clock hand", so that I get positive angle for a concave angle between the two (0-180 deg) and a negative angle for a convex angle between the two (180-360 deg). The dot product on normalized vectors gives me the angle, but it's symmetric. Is there a trick that gets me the sign?
  11. I'm trying to control the normal of a single point. I want to use normals to visualize vectors that i will convert to velocity later. I've reduced my experiment to a single point to hopefully simplify things. I'm trying to make the normal point in a truly random direction for each frame. I tried this: float x = fit01(rand(ch("seed1")),-1,1); float y = fit01(rand(ch("seed2")),-1,1); float z = fit01(rand(ch("seed3")),-1,1); @N = set(x,y,z); which gave me a random direction with in a disk. If i substitute @N for @v and feed this into a popnet that uses inherited vel i get particles in a plane. see attached image. If I control each component of the vector leaving two at 0 and setting the third between -1 and 1 i can point the normal in any direction. I can't figure out how to get houdini to randomly set the normals direction in all directions. Help appreciated.
  12. (Novice) Align a selection to point

    Very simple operation required: I need to align all points to the vertical axis occupied by a single point. (align points to the vertical axis of the point highlighted) There has to be a simple method for this. Thanks in advance
  13. Hello!, Let's say I have a rotating cube, a grid floor and a direct light projecting the shadow of the cube into the floor.. how can I get the motion vector of this projected shadow? , I already know how to get the vectors of the cube but it's shadow is a mistery.
  14. Hello, Trying to read a vector array from another point at a certain index. From my understanding of Houdini something like this should work. vector tempArray[] = point(0,"vectorArrayAttrib",pointToReadFrom); vector v = tempArray[index]; Unfortunately this method is returning an empty array from the point() function. If this is not the right way to go about doing this please let me know. Any help welcomed. Thanks.
  15. Hello,I'm attempting to create the slitscan/timeshift effect. I'm creating a vector array in a for loop, each loop has an attrib from map and a wrangle that appends Cd to a vector array. It works when the attrib from map is always reading from the same file. When I change the attrib from map file read expression to anything that has to do with $F or the meta nodes iteration Houdini crashes. I have a test scene that has documentation and even nodes setup to create test frames to work with.If it is a matter of the way that multiple files cannot be read at once please let me know. If someone knows of a better way to read from multiple files at once and/or achieve this effect please let me know. I'm aware that after effects has this effect and uses gradients to determine which frame to look up color from. While that method is great, I'd like to be able to write the gradients/lookups in vex to achieve results. Any help greatly appreciated. -T concept_025_slitScan_v001.hiplc
  16. retarget or recompute vector

    Hi everyone, I try to figure out how to retarget a vector (v in that case) in particle trails. I explain: i got master particles who trail other particles in space, i inherit the master "v" to achieve a motion blur at render time, to avoid to much substep that way i got smooth line at low calculation cost. but i need to slightly noise the trails to achieve a "moving tentacles" look. Here is the problem when i apply the noise, obviously my "fake" v vector is not aligned anymore, it's stepped... i tried to recompute the vector with the help of id, but since my emission is not constant ( i shot on frame 5, frame10, frame15 etc..)the incrementation of the id in not constant to...I tried basic vector arithmetic, but i don't get results i need...I join a hip file, does anyone got an idea??? thanks by advance. Best H PS:excuse my english, I'm French... RecomputVelTest.hip
  17. Hi So basically I have a vector and an obj, how can I make the obj face the vector by specifiyng the front axis of the obj? (front, side, up) Is there a traditional way to do this? Because Im trying to do this myself through Vex and some transforming operations.. Example:
  18. Is it possible to access a single component of a vector in a stamp expression? Or is it just limited to single numbers? I've searched and haven't found anything specific to copy stamping and vectors. For example, if I had a vector attribute called size and I wanted to just get the second component. I've tried: stamp('../copy1', 'size.y', 0) stamp('../copy1', 'sizey', 0) stamp('../copy1', 'size[1]', 0) I know it would be easy enough to create an extra attribute with just the second component to stamp instead. But it seems like this should be unnecessary.
  19. NEW TUTORIAL: Alembic Vector Motion Blur Tutorial- A Houdini, Maya, Arnold and Fusion or Nuke Workflow Thanks for watching and Sharing! If you have any suggestion, please come them in! Thanks
  20. Whitewater workflow for Maya

    Hello, I think I've just blown my head trying to figure out a solution for this but I hope you can help me I made a simulation of water and whitewater in Houdini and then used alembic to send the mesh to Maya for rendering. The whitewater particles were sent via the Realflow connectivity plugin in .bin format. Maya had no problem opening both the water mesh and the whitewater particles, but my problem is that Maya can't compute any motion blur, I think this is because the files I exported do not have any motion vector information in them. Is there any way I can export this information and use it in Maya? To export the water mesh, I created the simulation and then I exported it to .bgeo sequence from the import node, then I re imported the .bgeo sequence in a new geometry file and created the mesh using the "particle fluid surface node" and from there I connected a ROP alembic output node. To export the white water I got into the whitewater source node and in that level I created the RF Particle Export node and in it's properties I referenced whitewatersource.cache in the SOP Path Also, I saw a video where v-ray proxy import is used to generate motion blur with some realflow mesh with the same problem, I don't know if I can do the same in Arnold, which is what I'm using for rendering. I'm quite new to the software but I'm loving it, if you can help me I'll appreciate it. Thanks.
  21. Hey, I have time seeking any motion vector pass somewhere in odforce, nothing work as fine for now, so any know the method of get motion vector pass from mantra pbr using all scene animation as alembic, camera moving, etc with houdini 14 ? thanks in advance Carlos
  22. Hi I'm actually trying to export a motion vectors pass with arnold for a pyro simulation baked into a VDB. I understand the concept behind the theory, which consist of getting pyro velocity matrix, camera inverted matrix, and multiplying them, but till now, I can't get to make it work. There's an example involving Mantra who work quite well : http://forums.odforce.net/topic/14831-motion-vector-for-volume/?hl=%2Bvolume+%2Bmotion+%2Bvector+%2Bpass The problem with this example is that the nodes used (GetBlurP) doesn't have their equivalent in the Arnold shader. I'm pretty sure I can do it with user data passed to the shader, but I can't figure it out. Does anyone here have ever achieved this? I would be very happy to hear about. Thanks Maxime
  23. Copy SOP and Rotations

    Hi everyone. I'm hoping one of you clever people will be able to help me with this little problem I'm having. When copy-stamping objects onto some animated points, the copied objects are transformed along with the points, but they do not fully respect the rotations. I have a feeling the solution will require a vopsop, with some kind of vector math to get Y normal rotations, but my knowledge of vector math is very limited and I'm struggling to find an elegant solution. I've created a simple scene to demonstrate the issue. You'll see that the teapots do not rotate along with the grid that they are copied onto. Any help would be much appreciated! rotNotWorking.hip
  24. VEX supports array function?

    Hi, this is my first post here. I've been trying to call a vector array function in VEX, but it either returned "Internal Compiler Error" or "Syntax error, unexpected identifier, expecting ';'". I also checked Array help file and the example as below didn't work at all: To specify a literal array, use curly braces, with the array members separated by commas: vector[] rgb_array() { return { {1, , }, {, 1, }, {, , 1} }; } Here is the simple code I tried to compile, but it returned an error message "Syntax error, unexpected identifier, expecting ';'." vector an_array[] = {{1,1,1}, {2,2,2}}; vector a[]; vector[] testFunction(vector[] a){ return a; } a=testFunction[an_array]; Does anyone know if VEX supports array function? Thank you very much!
  25. Hey Guys! I've been experimenting with the refract node in vopsop context as well as the refract() function in vex. I'm curious if anyone has been able to break that node down to it's raw form? I would essentially like to know how it actually evaluates it's inputs. Can anyone shed some light on that? I would like to know the math behind it. The refract function takes three inputs, a direction vector, a normalized normal and an index of refraction. thanks!
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