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Search the Community: Showing results for tags 'matrix'.
Found 18 results

Hello everyone. Got a question about vex rotation for VDB objects. I've got a FLIP setup in which there is a model of a ship moving forward and rotating slightly. I created rotation control using VEX code. Very simple version of it looks like this: //Rotate object along X axis; this is just for an example matrix3 m = ident(); float angle_x = radians(ch('Angle')); rotate (m, angle_x, {1, 0, 0} ); @P *= m; This works for regular objects just fine. However, I want to use VDB version of the ship for collisions. When I apply this code to VDB object it doesn't work. I need VDB object to move and rotate as the original model exactly. So the question is  How can I transform this code or write a new one to rotate VDB object exactly as regular model?

Hi, I am trying to give little banking in my flying object.......so i have created a 3 by 3 matrix,gave an angle and an axis in the direction of velocity....and then used it in vex as a rotate matrix.... vector axis = normalize(@v); vector matx = cross(axis, {0,1,0}); vector maty = cross(axis, matx); matrix3 m = set(normalize(matx),axis,normalize(maty)); float angle = fit(sin(@Time * 0.5 + fit(random(@ptnum),0,1,0,360)),1,1,45,45); @angle = radians(@angle); rotate (m, @angle, axis); @orient = quaternion(m); i want to know is there any way to print the value of rotate matrix?? i did the same thing in vop sop and its working but here i face some issue. what's wrong i didn't understand.

 quaternion
 matrix

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Hi guys, I was wondering if any of you could help me solve the following issue: I have one animated object (polygons). I am trying to create a deformation on it's rest position and apply it back to the animated object so that I can have more control on that deformation. So far, I have tried two different approaches: 1. Calculate de point difference in the deformed rest position and transfer it to the animated object using an attribute reorient node. It kind of works but it changes the transfered deformation too much. 2.Using matrices to transfer the deformation. I have tried it without success. I know how to export the translation/rotation/scale but I don´t know exactly what to do with it. Does anyone knows any way of transfering the deformation from the deformed rest position to the animated position? Could anybody explain how to apply the matrix translation/rotation/scale into the animated object? I would appreciate some help on this issue because it´s beginning to drive me crazy!! Thanks!! transferDisplacement_01.hip
 3 replies

 matrix
 deformation

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Hello Everyone, http://www.hossamfx.org/mathinhoudinivol2/ Hello Everyone, Description: In volume two of Math in Houdini training. We will continue exploring the big role of math in creating visual effects and controlling the simulation behavior and this time we will move to more advanced concepts and provide cool projects. I will explain one of most important physical parameter: the gradient. And show you how to use it in rigging and collision and give you wide idea about using gradient in different operations in Houdini also We will go indepth with matrices and learn cool techniques using the matrix: it is the “Frame of Reference” you must know this magic secret about matrix. If you have many questions about Quaternion parameter, So we will dive into this concept and answer all questions with cool projects and we will see how to create quaternion field to effectparticles motion and if you don’t know what is the Vector 4, we will have cool project about using vector 4 inside the wire solver dynamics. And I will show you how it to build your own cloth simulation from scratch, this part will give wide idea about how the dynamic solvers work and what is the constraint , gravity , and how the collision is calculated ….. and many other math topics. Thank you. Lesson plan WHAT IS THE GRADIENT, AND FOR WHAT !!! all dynamic solvers use Gradient and normal and velocity and collision calculations, all this Physical Parameters use Gradient, you absolutely Know what is the Gradient !!! ? 1. Gradient & Slope Relationship– Are there any relationship between it? 2. It can create Normal – slope can create normal, how? 3. Speed and Velocity calculates –it is awesome how slope can calculates speed for everything. 4. Slope & Dot product in Rigging – No more tutorials about how to Rig the wheel. 5. Gradient of surface – Slope can create Gradient 2D field. MATRIX IN DEPTH !!! we will start by talking about for what we need matrix and next it will be more clear how it is easy to use matrix, and Frame of Reference is strong concept that you must have idea on how to use. 6. Why we created the Matrices – to understand matrices I must know for what it was created. 7. Recreating the Matrix – Now we will see how it is more easy with Matrices. 8. Frame of Reference – it is cool Concept you must know how to use with matrices. QUATERNION, NO MORE QUESTIONS ??? you don't know any thing about quaternion! you will know every thing about it, for what, when to use, how to control and how to build field of quaternion to advect particles. 9. What is the Quaternion – You will Have depth understand of this Scary parameter. 10. Quaternion Field part 1 – Quaternion inside Dynamics can create awesome animation in Particles. 11. Quaternion Field part 2 –How to Keep Particles inside defiened Volume using quaternion attribut VECTOR 4 IS A QUATERNION, ... !!! the orient attribute in the Wire solver is very important and you must know how it work, in this project we will manipulate this Attribute to create procedural dynamic animation. 12. Quaternion & Wire Solver – Big role of Quaternion in wire object. 13. Feelers & Quaternion part 1 –Feelers of insects moving around all the time, we will simulate this motion with quaternion. 14. Feelers & Quaternion part 2 –How to control the physical parameters of feelers to get nice real motion. SIMULATION CODE & COLLISION it is very important to get depth understand of how the Dynamic solvers work, we will see how we can build cloth simulation and add collision to this simulation using the Point VOP and Sop Solver. 15. Apply Gravity –Without any dynamics solvers, we will create our solver and start by adding gravity force to objects using the point vop and sop solver. 16. Create Cloth Force – Define the force spring between cloth object points and create pin constraint for new solver. 17. Gradient & Collision –Gradient of Volume is the way to create collision between objects. ِAll Content With Project Files . Full information Here
 13 replies

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Hello wizards! I have a question about point wrangle SOP. Is it possible create a matrix, and use that matrix in copy SOP as a transform ? In the file attached, i build all axis that i need for create a matrix, and rotate the copies with "roll_on_path" ramp parameter, but until now, no way. If someone have an idea... a big Thanks

Hi there, I have been trying to figure this out but probably don't know enough about transform/rotate matrices and how they work. What I got is a circle of flat boxes all orientated in Z. The flat side is always faced to the center of the circle. See attached image for better understanding. Now what I want is a rotation around the local X axis of each box. Attached is an example file to see what should happen and also what I have come up so far. To better illustrate what the end result should be there is the same setup built with a copy SOP and a transform node before to do the rotation. Now the solution I came up with kind of works. The main problem is that there seems to be some sort of scaling. You can see this when viewing the solution made in Houdini in template mode. Maybe someone can point me in the right direction. Also, my setup is not very elegant so if there are other or better solutions I would love to hear them. Thanks in advance! Dennis rotate_objects_local_v01.hiplc

Hi EVERYONE : Maybe this tutorial is not very short, watch it completely, i am sure that you find new stuff about matrix and you will learn new technique .Hope you find it useful !!! Hossam Aldin Alaliwi more training here : www.hossamfx.org

if you have some problems with matrix, how it work, how to use , HOPE this tutorial will help .Hossam Aldin Alaliwi full tutorial here : hossamfx.org/mathinhoudinivol2/ cheers!

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 , .

Hello, simple question: what's the proper syntax for matrices in VEX? Exemple: vector a = {0,0,1}; vector b = {0,1,0}; vector c = {1,0,0}; matrix3 X = {a, b, c}; I would imagined this would work, but it doesn't, nor does the expanded version ({{a.x, a.y, a.z}...), why is that? I have the impression I'm missing something basic, but anyway Thank you.

If I want to transform a velocity vector by a matrix4, do I just multiply it by the transpose(inverse(matrix4))? maybe I need to extract the scale from the matrix and multiply the velocity by that as well? Cross posting from https://www.sidefx.com/forum/topic/45863/ in case more people will see it here

Hi I am trying to rotate a volume so it aligns with the original geometry. (align along x axis  convert to volume  revert back to original place) I tried setting the primintrinsic, but the pivot point is shifted relative to the original geometry, there is a way to specify the desired pivot for the matrix? Any ideas? Thanks) volume_rotate_v01.hip

Hello folks I'm on my journey of switching from Maya to Houdini as a character rigging animation artist. I'v found it very facinating so far. I hope with your help I can find workout a few problems which I need to deal with at the moment. 1. Is there a way in houdini to tranform an object using 3 vectors at scene level (not at SOP level using Vex, Etc...) 2. Is there a way to control the effect of a Finite Element simulation by a weight map so the geometry stays intact in some parts? 3. How can I make a cloth simulation stick and slide on a colider so to be used as realistic skin effect? Any hints or tips or alternatives whould be greatly appreciated. Cheers Ramteen
 1 reply

 matrix
 finite elements

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A while ago I used some very simple Matrix multiplications to bring geometry, that is positioned anywhere in space, back to the origin and from there, back to its original position. Maybe anybody here can help me remember? I think I created a world space transformation Matrix, called it myMatrix, and then multiplied it by its reverse to transform geo to the origin. In order to translate the geo back, I just multiplied by myMatrix...is that possible or am I getting something wrong? (Not in fromt of a Houdini right now) Anyway, how do I get the world space transformation matrix for an object positioned anywhere in world space, for example for some geo that came into my scene as an ABC from Maya? Lookattransform in VOPSOPs? Thanks for your hints and patience.

Hi, we are turning some animated geometry (alembic, nondeforming animation) into clouds, but because we want the noise of the clouds to be in local space (not be affected by the animation), I am trying to work out how to apply the animation after the creating the clouds referencing the intrinsic transform of the alembic. Using an AttributeVOP, I've managed to copy the intrinsic:packedfulltransform of the animated alembic, on to the intrinsic:transform of the static alembic model. I am still trying to get my head around the difference between matrix3 and matrix4 for these transform. Is there a general rule to which matrix type is used in each case? intrinsic:packedfulltransform is matrix4, intrinsic:transform in packed primitives is matrix3, but intrinsic:transform in VDB is matrix4. So what I put together and works for packed geometry or simple volumes, doesn't work with VDBs unless if I pack them before hand. Also my understanding is that intrinsic:packedfulltransform and intrinsic:packedlocaltransform are not writable and I can only change intrinsic:transform . Is that right? thank you

Hello! Please tell me how to make a similar effect? Thank you!

Hi, How to find rotation angles between two vectors? Lets say Vector A = {0, 1, 0} and B = {1, 0, 0}, the angle between these vectors is 45. We can find this angle by using combination of dot product and inverse cosine. But I would like to know the rotation vector like {45, 0, 0} Thanks for your time
 10 replies

 Rotation matrix
 angle

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Is there any existing functions for extracting the final Transformation matrix that used for a copy or an instance. I am aware of the rules that create it : http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=6679 but are there any existing python functions (or easy methods) that allow you to extract this transformation matrix from a hou.Point() Object ? Thanks in advance,