# noumiere

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21

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• Rank
Peon

• Name
noumiere
• Location
New Zealand
1. ## Rotations using Orient attribute and Cross Product

Hi all i'm going over some concepts such as rotation and the orient attribute by doing some simple examples. I would appreciate if someone could clear up the confusion I'm having or point out where I've gone wrong Simply put - I have an Arrowthat i'm copying to points that are on 1) a line with @N = {0,0,1}; 2) a noise deformed grid The line is pointing in the Z axis before it is passed on to the copy to points sop. Here is what i'm trying to understand: I have an point wrangle on the Line and the Grid with the following where @up is set to {0,1,0} and the Angle channel is animated using @Frame; v@up = chv("up_vector"); vector nCrossUp = normalize(cross(@N,@up)); // Commenting out this line and the one below gives weird rotations v@up = normalize(cross(nCrossUp,@N)); matrix3 m = maketransform(@N, v@up); float angleRad = radians(chf("Angle")); vector axis = normalize(@N); rotate(m, angleRad, axis); p@orient = quaternion(m); This results in the arrows rotating on their @N axis on both the line and grid. My understanding is that: We have two approaches when dealing with orientations: 1) Using the cross product of the N and the Up and then crossing the resultant vector again by the @N to get proper @up vectors. 2) We can use the @orient to stabilise the rotation when the template points are deforming. Furthermore, in the line example above, the Normals of the template points are pointing in the Z-Axis. When I change the normals to be pointing in @N = {0,1,0} it breaks (because the N and the Y are both in the same direction?) How would I go about doing this properly and is there a need to use the cross product approach when using the @orient method? I have attached the hip file to this post if you want to look at what I've done. Thanks in advance! orient_Arrows_v01.hiplc
2. ## Flip Repel/Attract help

Thanks a lot Diego.It had to be something frustrating that I failed to see. I appreciate the help, it works now!
3. ## Erode / Rock tool I'm building

Great work! The breakdown you posted provided a lot of insight to the process
4. ## Flip Repel/Attract help

I think the issue is because the velocity is not coming in to the simulation from the sourcing.. however any insight would be welcome as I still haven't gotten it to work
5. ## Flip Repel/Attract help

Hi all, I'm trying to replicate an effect that involves sourcing Red and Blue particles on a Sphere that have an @attract attribute which determines if they repel or attract. I have run into a problem that I assume is quite simple but I have gone over the whole thing a few times without any success. I suspect the issue is in my DOP network where I have a Sop Solver that updates the Velocity through a Volume VOP using a Gradient and Volume Sample and outputs it to a bind export 'v', however I have tried to bind export it to 'vel' but it still doesn't work. There's a Gas Surface Tension that tries to keep the Red and Blue particles together. I have attached the file and would appreciate if someone could point out what I am doing wrong as I'm trying to learn this effect by breaking it down. Thanks and appreciate any insight! FLIP_zero_gravity_v01.hip
6. ## Orient of a point in a line

Hey Joachim, your explanation made a lot of sense! I implemented your suggestions and removed the second point, instead I merged in the initial point. The issue arises with the Normals for the merged point, or maybe I'm not sure of where in the stream I should resample? line_Orient_Vector.hip
7. ## Orient of a point in a line

Thanks a lot for the reply, Joachim. I have tried to implement what you said in a Point Vop and have attached it to the file. For some reason , the second point in the line does not seem to be oriented. Do you have any idea why? Could I be that my VOPs is incorrect? Thanks line_Orient_v04.hip
8. ## Orient of a point in a line

I have a snippet that scatters points on a grid and for each point, creates a unit vector Line comprised of two points that point at an object (in this case, a point). Everything works fine until I add the 'orient' attribute to the system. For some reason, it treats the rotation of all points as one and the axis is at the scene center. What I'm trying to do is have each point have it's own local rotation so that if I copy a geo to these points, they will aim at that object instead of staying upright. I've attached the scene file Thanks! line_Orient_v03.hip
9. ## SOP Solver first frame

Thanks a lot vic that makes a whole lot of sense now! I should add this to the comments of their video to let others know. Appreciate the help!
10. ## SOP Solver first frame

After multiple attempts and adding a switch node to Input one with condition \$F==1 and switching to the previous frame it still doesn't work.. volumeGradient_v02.hipnc
11. ## SOP Solver first frame

Hi there I was following some of the Entagma tutorials on SOP solvers and I came across a minor problem shown above. How do I get the SOP solver to function on the first frame? Currently it is saying that Vdbadvect1 requires a vector, it seems to work every now and then when I disconnect it and hook it up. I remember there was a way to add a switch node on the first frame, any ideas? Thanks!
12. ## Explosion 'shockwave' on rigid bodies

Update - There is no solution except to open the file up in 3DS Max and export the contents to an alembic file - they won't crash if you import this in Maya. Thread is resolved.
13. ## Explosion 'shockwave' on rigid bodies

Hi all, I managed to find a solution by using a Magnet Force SOP. Now I am having an issue where my alembic exports are crashing Maya - I have read that the solution is the change the animation speed to something slower but I am not sure how to go about this so Maya doesn't crash when I load the alembics. I have attached the updated files, Thanks and Best Regards, blast_shockwave_v02.hipnc explosion_test.zip
14. ## Explosion 'shockwave' on rigid bodies

Hi there all! I have what I think is a relatively simple concept but I'm having a hard time pulling it off. Simply put, I have some objects on a desk that will be exploded outwards as if there was a shockwave from an explosion behind it. Currently I've gone the route of using a Fan and Wind but for some reason I'm not getting the proper results. The idea is to have the objects 'thrown' forward so I can get a freeze frame later on. Any input or suggestions to improve from the current implementation would be greatly appreciated as I'm currently starting my dynamics adventures in Houdini. The scene file as well as objects used have been attached, thanks and best regards! blast_shockwave.hipnc explosion_test.zip
15. ## Cutting geometry driven by wire solver using another object?

Thanks again for your time, I have attached the script and the objects. What I am trying to achieve is to cut the strip while it is moving downwards so that after it is cut, we see some of the strip that is still moving downwards. Basically like a projector film strip, if you cut it, the film strip will keep piling up a little bit I have attached the scene file For now what I have done is the extend the strip so that it is longer (to act like it is a long film strip) and I have keyframed transforms in the SOP. This doesn't seem to work, as you can see in the attached file. I have another problem where it isn't properly interacting with static objects. I appreciate your help cutting_wire_Test_v02.hipnc cutter.abc plate_1.abc plate_2.abc projector.abc spool_B.abc spool_L.abc spool_R.abc
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