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Technical Discussion » Bullet physics implementation and other stuff


cybermax: 255 posts; Offline

May 10, 2011 08:48:10

niko3d
Hi Cybermax
Thanks for the great work on you bullet implementation. I tried this out a while ago on my old machine and it was working great. Ive recently had to replace my machine and i cant seem to get a working version of your bullet tools and example projects.

When we run with the latest win64 build, all we get is a single point falling down. So im guessing we need a new version of the plugins compiled. The single point seems to originate from the bulletProperties node.

Any chance you can compile for Houdini 11.0.737 win64bit? We would love todo some tests with your bullet setup :¬) Will the old example projects still work ok with the newer builds?
Cheers
Nick

I work on new version where all bullet code is on server side(exe file). But I dont support new version anymore, so maybe some other user can help you, or you need to install visual studio 2005 and compile for yourself :shock: . Your problem is not about old/new machine, but version of Houdini.

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Technical Discussion » Bullet physics implementation and other stuff


cybermax: 255 posts; Offline

May 8, 2011 21:24:03

oh_qxs
opppps,the problem has been solved temporarily, It is because the point's number in geometry, so I export the geometry first as obj file, then read from file and do convex decomposition then, It is ok, I will find the true reason :twisted:

If you use decompositon from bullet example files, be carefull. Its APPROXIMATE Convex Decomposition, so finall body(object) can be compress(deform) and If you have two or more pieces which are close, solver explode this objects. I am preparing new sop node for decomp, but I use my algorithm(I used this alg. some time, but in last few days, I worked on it, and its better), which create convex bodies, which is not deform!

Netvudu
Hi cybermax.
Autofreeze is a DOP node that checks the “energy” left on every “dobject” and if it is below the threshold given by the user it takes out that dobject from the simulation.
It´s very handy because as the pieces stop around the simulation gets faster and also you never have unwanted vibrations at the end.
I will also take the chance to thank you again for the bullet solver. I´m having a lot of fun playing with it. 8)
I would like to ask you a couple of questions. In case of an object that collapses slowly and gradually from one side to the other what is the best method to follow? Would it be using multijoints?
Also, regarding forces…The bullet_force looks like a directional force. Is it the only type of force available? (if it is, then ok…just asking).
Thanks.

Autofreeze: Yes, bullet include this function, I can implement.

Fracture X Constraints: like a default I recommend constraints which create better result, but If you have many thousand constraints, Its vibrate, so in this case, you can use fracture or combine!

bullet_force: Its point force, so You can have volume, where every voxel has one force and you can simulate for eg. wind.

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Technical Discussion » Polygon clipping with HDK


cybermax: 255 posts; Offline

May 6, 2011 19:44:47

same problem here:

http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=21258&highlight=clip [sidefx.com]

so, I think that Its Bug, so tomorrow I will start programming my clip function, because this “clip” is devil :evil:

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Technical Discussion » Polygon clipping with HDK


cybermax: 255 posts; Offline

May 6, 2011 15:33:24

In documentaion I found this two function:
00804 // Polygon clipping
00805 void clip(UT_Vector3 &normal, float d = 0, int normlize = 0,
00806 const GB_PrimitiveGroup *primGroup = 0);
00807
00808 //
00809 // Polygon creasing
00810 void crease(UT_Vector3 &normal, float d = 0,
00811 int normlize = 0, int outputGroups = 0,
00812 GB_PrimitiveGroup *above = 0,
00813 GB_PrimitiveGroup *below = 0,
00814 const GB_PrimitiveGroup *creaseGroup = 0);

My code is:

OP_ERROR SOP_test::cookMySop(OP_Context &context)
{
boss = UTgetInterrupt();

if (lockInputs(context) >= UT_ERROR_ABORT)
return error();

duplicateSource(0, context);

gdp->clip(UT_Vector3(1, 0, 0));

unlockInputs();
return error();
}

like input geometry I use just default box, but nothing happen, Why???

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Technical Discussion » Bullet physics implementation and other stuff


cybermax: 255 posts; Offline

May 1, 2011 20:25:31

wxaj0928
http://www.youtube.com/watch?v=4ufjeDdlYsE&hd=1 [youtube.com]

use cybermax's Bullet solver
I just increase the realtime fracture
but,Dop have “Autofreeze” node
How do I achieve the bullet SOLVER

Yeeh, nice work with real-time fracture.
You can describe “Autofreeze” function, I do not know DOP network much
:?

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Technical Discussion » Bullet physics implementation and other stuff


cybermax: 255 posts; Offline

May 1, 2011 12:40:58

Some news:

I start implementing RBD to client/server system and I dont know what I smoked(not real, I dont smoke :shock: ), but I find few very crazy things in plugin source code, which you can see.

So firstly:
Using input->getPointAttribute(“…”) in loop is very very slow, so right place is before loop and then in loop, you can use only setElement. This is problem with speed, so its not bug, but Its on many place in code, so be carefull with this.

Second:
If you want to delete array, dont use delete array but delete array. First code delete only pointer. I found this on few place too.

Next problem:
Sorry, I just forgot other problems, but It exists :?

Edited by - May 1, 2011 20:23:22

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Technical Discussion » Bullet physics implementation and other stuff


cybermax: 255 posts; Offline

May 1, 2011 12:31:32

wxaj0928: very nice, but this is your implementation, so with “my test” you mean “my solver”!!

oh_qxs: I can not load your page, Its loading over minute, but its still empty :?

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Technical Discussion » Bullet physics implementation and other stuff


cybermax: 255 posts; Offline

April 25, 2011 08:23:56

oh_qxs
“profiler”,you mean ??for example….

for example:
http://en.wikipedia.org/wiki/VTune [en.wikipedia.org]
http://www.codersnotes.com/sleepy/ [codersnotes.com]

oh_qxs
BTW, can you explain to me how to automatically test concave polygon? I can not understand the testConvex function in your bullet solver actually ops:

For every convex object is true, that If you compute normal for any polygon(normal direct from object), all other object points must place on back side. you can easily test this with “dot product of normal and test point”+d. If results for all planes are less that zero, object is convex.

note: plane is : ax+by+cz+d=0, where a,b,c is test point and x, y, z is normal.
note2: normal of plane you can get with cross product of two edge of polygon.

hope that you understand, its basic mathematic, which you need to know, If you want to program CG :?

edit: ouuu, I am not home, so I cannot see the code, but I think, my code has some toleration so its not “less that zero”, but “less that toler” :wink:
and maybe I have normals, which direct to the object, so its revers “more that -toler” :!:

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Technical Discussion » Plugin, C++, and python


cybermax: 255 posts; Offline

April 22, 2011 10:49:14

dulo
One BIG drawback with c++ is that you have to match the exact build and compiler. If you build against build 781 you plugin wount work with build 782.
It seems to quite impossible to create a plugin which could be sold somehow because you would have to provide hundreds of builds for each combination of plattform, compiler, distribution and build …

with python and inlined c++ you “just” have to match the compiler which is tedious enough because it prohibits the usage of prebuild python packages.

when i started developing for houdini i was quite shocked of the inflexibility.
plugins i built for lightwave 7 still work for lightwave 10 for example .. this is something i just can dream of with hdk / houdini ..

Yeeh, Its crazy :evil:
You have two options:
1) You can provide source code and users can compile for their version
2) You can hide Your secret code to DLL and provide only basic source code and SDK for your DLL. In DLL you can not use HDK, It can works or It can not works :-(

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Technical Discussion » Bullet physics implementation and other stuff


cybermax: 255 posts; Offline

April 21, 2011 11:33:02

oh_qxs
Finally,I finish my work!!!
For the easy use,my bullet solver is a simple color system,
red is active,blue is static,cracks with same green color are a big block,I use my compoundGroup to constrain the cracks,setting up constraint at contact point,It looks fine,
and in the simulation artist only need to control the color of groups they need to get move or stop,I like this style and is really easy to use, maybe I can make some demo someday!
but speed is not good enough,because I use piles of constraints just for effect and easy use ,speed or not,it is a question!

Interesting system, maybe create some video and inspire other users.
Try to use some “profiler”, which can allow you find your slow code. This limits dont sound like a “slow speed”, so I think that problem is somewhere else :?

Anyway, I work on new solver, which is design for solving fast fluid in sort time, so You keep fingers crossed, I think It will be really fast.

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Technical Discussion » HDK enable/disable parameters and switch to dimmed display


cybermax: 255 posts; Offline

April 18, 2011 18:17:58

yongningbrg
Hi,
I am using HDK, how can I enable/disable editability of my attributes? When it is disabled, I want it to be grayed out.
Thanks!

Easyyy …
unsigned SOP_class::disableParms()
{
unsigned changed = 0;

if(READ_ATTIBUTE(t)) //read some attibute
{
changed += enableParm(“name_of_attibute”, 1); //enable
}
else
{
changed += enableParm(“name_of_attibute”, 0); //disable
}

//again for other attributes …

return changed;
}

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Technical Discussion » Bullet physics implementation and other stuff


cybermax: 255 posts; Offline

April 3, 2011 07:54:25

oh_qxs
emm,yes it's not hard work actually,maya's API is as simple as his own script language named mel,so just as you mentioned the “client/server”, first do simulation in plugin,get the data,update display in maya,just as we do in houdini plugin,but it is more simpler,Do you want try?Because I have no time at the moment and have no idea of sim fluid using GPU , ops: ,but maya can give you more feeling of speed than houdini platform I think ,so ,what do u think? :wink:

ok, I love houdini, so I dont want to jump back to maya, BUT When I end this client/server version I can send you server.exe and source codes for plugins and you can try to rewrite code for maya. So What do you think?

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Technical Discussion » Bullet physics implementation and other stuff


cybermax: 255 posts; Offline

April 2, 2011 09:11:45

oh_qxs
thx man,just as you say, I CAN DO IT!!!
Although I am a maya user and starting learning houdini several months ago, but sure you are right, houdini is really a great tool expecially in VFX I think, it can give you powerful control and great freedom, yes I love this cool guy! hoho!

I think that since I am using client/server system is possible make GPU Fluids for Maya. Actualy Its very simple, because server(which is alot of code) is exe file and clients are few plugins, which have very simple code(connect to the server, send data or orders,download data back, update houdini - with my SDK is only few rows). SoI think is very simple rewrite this code and create maya plugins and make some waves in maya. I dont know maya SDK(I used maya before I jump to Houdini, but I didnt create plugins), but I think that its not too hard.

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Technical Discussion » Bullet physics implementation and other stuff


cybermax: 255 posts; Offline

April 1, 2011 08:39:01

oh_qxs
WOW! Amazing works! :shock: ,I like it!
At the moment I'm trying writing my own bullet SOP solver, and it's a hard work really, especially when I use btCompoundShape to get auto glue effect, I'm stuck in it, :x , and keep moving on very very very slowly :cry:

This is exactly whan I want. Inspire other to use HDK. Houdini is great tool, but If user working with HDK, Its a industry BOMB!!!So Glue effect its not simple, but you can do it!

Darric:
thx,
Yeeh, You right, I can render like points, but In this case, splashes are very massive( Its not only small pieces around). So I have plan to add some new features which allow me add more particles to main_simulation, then secondary splash sim can have very detail particles, so I can render like a points.

Ouu, new video: http://vimeo.com/21801118 [vimeo.com]

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Technical Discussion » Bullet physics implementation and other stuff


cybermax: 255 posts; Offline

March 31, 2011 20:57:21

I just start testing splashes. Its not bad, but It can be better :?

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Houdini Lounge » Cuda fluid solver plugin


cybermax: 255 posts; Offline

March 31, 2011 13:48:14

cklosters
You know what, most (big) studios don't use accelerated fluid solutions. A lot get's done with maya or houdini and by people knowing what they are doing.

Maybe today They dont use GPU, but according emails what I get, They have a great interest. So I think that for two years GPU will be use even in small studios.

cklosters
Next to that memory is a big issue and GPU clusters are fairly expensive and hard to code for

GPU clusters(I call clouds) is not hard to program, but offcourse, uploading and downloading data from/to GPU is time expensive, so Clouds will not be fast like a “all in one GPU” solution. :?

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Houdini Lounge » Cuda fluid solver plugin


cybermax: 255 posts; Offline

March 31, 2011 10:35:12

Ouu, finally some competition. Do you prepare liquid version, or do you have plan only for smoke???

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Technical Discussion » Bullet physics implementation and other stuff


cybermax: 255 posts; Offline

March 30, 2011 07:45:24

icarus551
lookin good, keep at it! i like your bullet implementation over the other main one

thx, I very love client/server implementation, so I will create server and client side for bullet too. With this new system you will not need to create loop(for more complex scene) with file nodes or feedback node(I get many emails from users and this is the bigest problem). Its more flexible and well-arranged!

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Technical Discussion » Bullet physics implementation and other stuff


cybermax: 255 posts; Offline

March 29, 2011 11:03:27

new video: http://vimeo.com/21648325 [vimeo.com]

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Technical Discussion » Bullet physics implementation and other stuff


cybermax: 255 posts; Offline

March 27, 2011 07:49:59

frogspasm_deux
Very cool!

thx.

I have facebook only in czech language, so If you want to know If I work, you can follow me on twitter … http://twitter.com/milansuk [twitter.com]

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