Found 20 posts.
Search results Show results as topic list.
Technical Discussion » Velocity Orient in RBD simulation by using poplookat
- ILIAZHAO
- 20 posts
- Offline
Hello guys, I'd like to have the orientation of each packed object in my simulation follow my attribute "v" (align the z-axis and velocity of each piece). Therefore, I wrote "target=@v;" in the poplookat's vex setting, but I found that if I randomize the orientation of my packed objects before simulating, the previous "target=@v;"setup cannot make each piece's z-axis follow my v. It seems that the poppookat will only work when the z-direction of each piece align with the z-axis of the world coordinate. I'd like to ask how to use the randomized orientation attribute I set in the initial state to align the orientation with velocity of each piece in Poplookat.
Edited by ILIAZHAO - Nov. 24, 2023 09:44:48
Houdini Indie and Apprentice » Question about the remaining points after using Dissolve
- ILIAZHAO
- 20 posts
- Offline
Hi everyone, I am trying out a workflow that turns a triangular surface into a quad one. When I use the dissolve node to remove an edge, it's logical that if I turn on “Remove Inline Points”, it will remove the extra points after the edge dissolved. But in practice it seems to just delete points where the point number are discontinuous with its neighboring points. As shown in the figure. I want to know if my understanding is right there ?
Technical Discussion » Question about the remaining points after using Dissolve
- ILIAZHAO
- 20 posts
- Offline
Hi everyone, I am trying out a workflow that turns a triangular surface into a quad one. When I use the dissolve node to remove an edge, it's logical that if I turn on “Remove Inline Points”, it will remove the extra points after the edge dissolved. But in practice it seems to just delete points where the point number are discontinuous with its neighboring points. As shown in the figure. I want to know if my understanding is right there ?
Houdini Indie and Apprentice » What does each component of the Orient attribute represent?
- ILIAZHAO
- 20 posts
- Offline
Houdini Indie and Apprentice » What does each component of the Orient attribute represent?
- ILIAZHAO
- 20 posts
- Offline
I found that the conversion of quaternion to Euler angles in Houdini seems to be different from the definition in mathematics. In mathematics (1, 0, 0, 0), (0, 1, 0, 0), (0, 0, 1, 0), and (0, 0, 0, 1) represent Identity quantization, rotating 180 degrees around the x-axis, y-axis, and Z-axis, respectively. However, in Houdini, we use (0, 0, 0, 1) to indicate no rotation, and if we use the quaterniontoeuler function with XFORM_XYZ, we will find that (0, 0, 0, 1) corresponds to a rotation of 0 degrees on the X, Y, and Z axes.
Can someone please kindly explain to me why this is? Or is there something wrong with my understanding?
Thanks
Can someone please kindly explain to me why this is? Or is there something wrong with my understanding?
Thanks
Houdini Indie and Apprentice » How does the VEX function "sample_sphere_uniform" work?
- ILIAZHAO
- 20 posts
- Offline
When I explore the function "sample_sphere_uniform", I don't understand how it works behind its parameter "vector u". It doesn't seem to correspond to x, y, z in normal situations. Could anyone explain what the three components of vector u here mean? I have seen people in some cases control the rotation of a point on the sphere by controlling this vector type parameter. I want to know the logic behind it.
Thanks
Thanks
Houdini Indie and Apprentice » Question about @TimeInc in Houdini dynamics.
- ILIAZHAO
- 20 posts
- Offline
@ifree
Thank you for your reply. I confused some concepts before. The initial velocity is constant in every frame or second, unless I want it to affect the position, I need to divide it by 24. I multiplied the initial velocity by @timeinc, which means that I mistakenly took the initial velocity as the initial acceleration, so I thought I would get its value at each frame.
Thank you for your reply. I confused some concepts before. The initial velocity is constant in every frame or second, unless I want it to affect the position, I need to divide it by 24. I multiplied the initial velocity by @timeinc, which means that I mistakenly took the initial velocity as the initial acceleration, so I thought I would get its value at each frame.
Houdini Indie and Apprentice » Question about @TimeInc in Houdini dynamics.
- ILIAZHAO
- 20 posts
- Offline
@ifree At the beginning, I wanted to multiply the initial velocity by @TimeInc because I thought the initial velocity was based on seconds rather than frames, so I wanted to change that to frame Initial velocity.
Houdini Indie and Apprentice » Question about @TimeInc in Houdini dynamics.
- ILIAZHAO
- 20 posts
- Offline
Oh, Sorry. You are right (3, 0, 0) I accidentally typed the wrong number.
And I finally understood my mistake.
The reason why I write (velocity * @TimeInc + force * @TimeInc) is that I regard the force here as a constant velocity rather than an acceleration.
This will cause my solver to produce a uniform motion rather than a quadratic function trajectory. I didn't wrap my mind about this at that time.
Thank you for your help.
And I finally understood my mistake.
The reason why I write (velocity * @TimeInc + force * @TimeInc) is that I regard the force here as a constant velocity rather than an acceleration.
This will cause my solver to produce a uniform motion rather than a quadratic function trajectory. I didn't wrap my mind about this at that time.
Thank you for your help.
Houdini Indie and Apprentice » Question about @TimeInc in Houdini dynamics.
- ILIAZHAO
- 20 posts
- Offline
Thank you Tomas.
Sorry, but I just want to make it clear that according to your code, it won't be the result that should be expected mathematically. Is that right? For example, suppose v= (3, 1, 0), force= (0, -1, 0) should theoretically get (1, 0, 0) after one second, but according to your algorithm, this is not the case.
On the contrary, if we multiply V by @TimeInc at the beginning to get frame based V, and then use frame based force to affect frame based V,like(velocity * @TimeInc + force * @TimeInc) we will get the expected value.
Sorry, but I just want to make it clear that according to your code, it won't be the result that should be expected mathematically. Is that right? For example, suppose v= (3, 1, 0), force= (0, -1, 0) should theoretically get (1, 0, 0) after one second, but according to your algorithm, this is not the case.
On the contrary, if we multiply V by @TimeInc at the beginning to get frame based V, and then use frame based force to affect frame based V,like(velocity * @TimeInc + force * @TimeInc) we will get the expected value.
Houdini Indie and Apprentice » Question about @TimeInc in Houdini dynamics.
- ILIAZHAO
- 20 posts
- Offline
When I'm trying to understand the simulation process of DOP network, and try to write it from scratch in the SOP solver. I find that the calculation order of DOP network is like e.g.
But my question is why can't it be written like this?
Why not just multiply velocity by @TimeInc at the beginning and then add the force multiplied by @TimeInc?
Wouldn't that beif we followed the first way. So we multiplied force by @TimeInc twice? Isn't it OK to just use the frame velocity add the frame force directly?
Thanks
vector velocity = set(3, 1, 0); vector force = set(0,-1,0); v@finalvel = velocity + force * @TimeInc; //Add the S velocity to the frame force? v@framevel = v@finalvel * @TimeInc ;
But my question is why can't it be written like this?
vector velocity = set(3, 1, 0); vector force = set(0,-1,0); v@finalvel = velocity * @TimeInc + force * @TimeInc; v@framevel = v@finalvel ;
Why not just multiply velocity by @TimeInc at the beginning and then add the force multiplied by @TimeInc?
Wouldn't that be
v@framevel = velocity * @TimeInc + force * @TimeInc * @TimeInc
Thanks
Edited by ILIAZHAO - June 26, 2022 13:00:51
Houdini Indie and Apprentice » Question about the normal of points and vertices in Houdini.
- ILIAZHAO
- 20 posts
- Offline
Houdini Indie and Apprentice » Question about the normal of points and vertices in Houdini.
- ILIAZHAO
- 20 posts
- Offline
Hey folks.
When I create a box, although there is no @N of points or vertices in the spreadsheet, according to the result of the viewport, Houdini performs shading according to its default vertices normal. After this step, if I add a point normal to the box, it will be based on point normal shading. If I add vertices normal to the box, it will be based on vertices normal shading. Does this mean that Houdini will detect whether the last normal in the network is points or vertices, and then use it to override the original default selection.
In addition, my problem is that after I create a point normal for this box, if I then create vertices normal for it, I find that the point normal I created before will disappear in the spreadsheet. And vice versa. Point normal will replace my previous vertices normal. Does this mean that vertices normal and point normal cannot exist at the same time?
Thanks
When I create a box, although there is no @N of points or vertices in the spreadsheet, according to the result of the viewport, Houdini performs shading according to its default vertices normal. After this step, if I add a point normal to the box, it will be based on point normal shading. If I add vertices normal to the box, it will be based on vertices normal shading. Does this mean that Houdini will detect whether the last normal in the network is points or vertices, and then use it to override the original default selection.
In addition, my problem is that after I create a point normal for this box, if I then create vertices normal for it, I find that the point normal I created before will disappear in the spreadsheet. And vice versa. Point normal will replace my previous vertices normal. Does this mean that vertices normal and point normal cannot exist at the same time?
Thanks
Work in Progress » Problems in "particlefluidmask" output
- ILIAZHAO
- 20 posts
- Offline
Hi, everyone. During my wave simulation, I was stuck by another problem. In the "particlefluidmask" phase, whenever I want to export the ocean spectrum, my program will get frozen. I wonder if it is because my spectrum is too heavy. I did merge several layers of spectrum together in previous part. But up to this point, my process was very smooth and I didn't feel stuck at all, so I don't know if there is any other knock to solve this problem. Has anyone encountered similar problems?
Thanks
Thanks
Houdini Indie and Apprentice » About HDA installation in Houdini.
- ILIAZHAO
- 20 posts
- Offline
Hi guys. I encountered some problems when installing HDA. Specifically, I downloaded some HDAS from GitHub, and then I installed them into Houdini as required, but when I loaded them, it showed that the HDA was a non-commercial version, and then I put the downloaded license file into Houdini's License folder, but it didn't seem to work. Houdini still showed that it was a non-commercial version. I think there may be a problem with the placement of my license. I simply drag it into the license folder in the Houdini folder directory.
So I want to ask what is the normal process of installing HDA licenses.
So I want to ask what is the normal process of installing HDA licenses.
Houdini Indie and Apprentice » Questions about parallel transport in Houdini rollercoaster
- ILIAZHAO
- 20 posts
- Offline
Hi, guys, I'm making a procedural modeling of a roller coaster. It looks very common, but I'm stuck in a problem.
After I create a curve, I want to use the parallel transport method to get a smooth orientation, but I find that I do get smooth normal, tangent and bitangent, but I can't smooth them where the ends of the curve are connected.
I mean, if I rotate and translate to the last point based on the normal of the first point, I will not get a smooth orientation where the last point meets the first point (I find that almost all the situations discussed in the tutorial are based on an unclosed curve, and I want to make a closed curve here, I wonder if there is a solution.)
As shown in the figure below, there is a smooth orientation in other parts of the curve, except where the curve is connected end to end.
After I create a curve, I want to use the parallel transport method to get a smooth orientation, but I find that I do get smooth normal, tangent and bitangent, but I can't smooth them where the ends of the curve are connected.
I mean, if I rotate and translate to the last point based on the normal of the first point, I will not get a smooth orientation where the last point meets the first point (I find that almost all the situations discussed in the tutorial are based on an unclosed curve, and I want to make a closed curve here, I wonder if there is a solution.)
As shown in the figure below, there is a smooth orientation in other parts of the curve, except where the curve is connected end to end.
Houdini Indie and Apprentice » Question about the number of points after fuse.
- ILIAZHAO
- 20 posts
- Offline
Houdini Indie and Apprentice » Question about the number of points after fuse.
- ILIAZHAO
- 20 posts
- Offline
I just encountered a very basic problem, but I haven't figured it out. I hope to get some detailed explanations. When I use the ‘fuse‘ function to connect a curve end to end in Houdini, I find that the number of points in my viewport and spreadsheet has changed. However, when I try to store these points in a list with the primtpoints() function, I access the len of the list. I find that the len here is still the number of points before ’fuse‘. Why is this?
I’ll appreciate any suggestion.
I’ll appreciate any suggestion.
Houdini Indie and Apprentice » Understanding of environment variable in Houdini.
- ILIAZHAO
- 20 posts
- Offline
Oh, thank you so much for your explanation. After some twists and turns, I finally got it.
I was misled to a large extent by the default path '$HIP/geo...' provided by 'file cache'node.
Because it makes me think that under $HIP are "geo", "flip", "cache"... these folders, so $HIP somehow becomes the location of project folder.
Thanks,
Ilya
I was misled to a large extent by the default path '$HIP/geo...' provided by 'file cache'node.
Because it makes me think that under $HIP are "geo", "flip", "cache"... these folders, so $HIP somehow becomes the location of project folder.
Thanks,
Ilya
Houdini Indie and Apprentice » Understanding of environment variable in Houdini.
- ILIAZHAO
- 20 posts
- Offline
Sorry to bother everyone, I know this is a very basic question, but it stuck me for a long time, so that every time it would give me trouble in mine mind. That is a clear explanation of the two environment variables of $HIP and $JOB.
I've read a lot of tutorials and explanations. I basically know that $HIP represents the parent path of my current scene file, and $JOB represents the parent path of my current project folder. Is that right?
But in my Houdini practice, this is confusing. When I create a new project, I can clearly see what my $JOB means. But that doesn't explain where the $HIP points to. When I create a 'file cache' node, it is obvious that $HIP, which is my project folder, is displayed on the upper level of the geo folder. Isn't that a same path with my $job?
I have attached my screenshot below, which shows my directory structure. I use the default folder structure generated when Houdini creates a new project. I made a little change, but it should be the same basically.
I hope someone could give me some advice.
Thanks
I've read a lot of tutorials and explanations. I basically know that $HIP represents the parent path of my current scene file, and $JOB represents the parent path of my current project folder. Is that right?
But in my Houdini practice, this is confusing. When I create a new project, I can clearly see what my $JOB means. But that doesn't explain where the $HIP points to. When I create a 'file cache' node, it is obvious that $HIP, which is my project folder, is displayed on the upper level of the geo folder. Isn't that a same path with my $job?
I have attached my screenshot below, which shows my directory structure. I use the default folder structure generated when Houdini creates a new project. I made a little change, but it should be the same basically.
I hope someone could give me some advice.
Thanks
-
- Quick Links