# Symbolic

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• Birthday 07/31/1978

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Orm
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1. ## Particle collisions with bounce and inherited velocity.

Thanks Macha.
2. ## Particle collisions with bounce and inherited velocity.

Hello Macha, thanks for the link. It is a good site in general, I am already using similar approaches, with some extra bits and pieces. The main question is, for example "How we calculate a relative velocity?" or "Is it called Relative Velocity?" at first place. For example in a case where we have a box travelling from A to B and a particle travelling from C to B. And when they collide at some point what exactly is happening? The aim is that the particle picks-up a bit of the velocity of the box and slightly change its direction... What is the maths behind that? Is it this? http://en.wikipedia.org/wiki/Relative_velocity Cause I am using it, and it works but I am not sure if it is the right thing. Thanks.
3. ## Particle collisions with bounce and inherited velocity.

Hello, Just to make it clear: I am more after the logic and the correct ways of calculating "Tagential" and "Normal" vectors, based on the particle's and the volume's velocity. And then I will be updating my ACCEL with the resulting vector. Thanks.
4. ## Particle collisions with bounce and inherited velocity.

Hi, For a while I have been trying to make my own particle collision system for POPs. I would like to manipulate the ACCEL instead of velocity and I am aware that updating ACCEL will give me softer results, meaning there will always be a bit of lag as the forces get updated. I have many bits and pieces already working, so I am already using the required building blocks, "volume samples", "volume gradients" and some other attribute stuff related to proximity to volumes etc. So technically I am at a good position, the main part that I can not get working (or at least I am not %100 that it is working) is the part where we put all the vectors together, this being: 1) The vector of the velocity of the volume. (Inherited velocity, relative velocity?) 2) The vector of the particle's current velocity. 3) The vector of the force that will keep the particle outside of the volume. (Push force.) etc. So I have all the data above, I just do not understand how I should be putting all of this together. Any ideas, suggestions? Thanks!
5. ## Flipbook sub-frames?

I see, well... thanks, that will kind of work. So I I would like to see what happens between f1 and f24, I will timewarp from 1-24 to 1-240. Not very elegant, but yeah, might do the job. Ehanks.
6. ## Flipbook sub-frames?

(Sorry, double post from the sidefx forum, since I got no reply there) Hi, H11.0.775 (linuix) here, I am not able to playback sub-frames in my flipbooks. I tried everything, all playback settings and flipbook options has 0.1 in there, and no matter what I do I can not view my subframe results in the flipbook. Well, I can see them as they cook, but then as soon as the flipbook starts to play, it only plays integer frames?! It was not like that on H10?! Am I the only one who needs this function? Any ideas? Thanks.
7. ## Variable checking.

Hello! Thank you very much! Yep, this is waht I am going to do, lookup to a set of strings. Cheers.
8. ## Variable checking.

Thanks AdamJ, However I still do not know how to check if \$MAPG is a wrong, well I can do that with some string by string checking. But it would have been nice to be able to check if a string is one of Houdini's own declared variables, like \$CR, \$PT, \$MAPU etc. Thanks.
9. ## Variable checking.

Hello AdamJ, Sorry for the multiple posts. I need to explain this in a better way. The problem is this: I have two string inputs on my OTL (1) Attribute to use: (2) Component: So if the user goes "foo" in section (1), then he may specify "FOO1" as the first component in section (2). I can check both of those conditions, I check if the attribute "foo" exists, then I guarantee that it is mapped and "FOO1, FOO2, FOO3" are valid. If "foo" does not exist, I flag and error. * * * However, lets have a look in a more complex situation as bellow, (Here I need an extra way of variable checking) So if the user goes "uv" in section (1), then he may specify "MAPU" as the component or "UV1" for the first component If he miss types MAPU as MAPG for example, the process will fail. So as you see, I need to check the native Houdini variables towards this. The "h" in there was for that, "ishvariable", is supposed to check the native Houdini variables (I guess?). Any ideas? Thanks for the help.
10. ## Variable checking.

Thanks! But I could not get it working: echo `ishvariable("MAPU")` will return 0 ? Any ideas?
11. ## Variable checking.

Hi, For a tool, I am trying to check if a specified variable is correct or not? Is there an expression to ruturn this check? ex: \$MAPU will return "ok", \$MAPG (if it does not exist) should return "error" Any ideas? Thanks.
12. ## A python expression aware of the channel name it lives in?

Great! Works perfectly. Thanks.
13. ## A python expression aware of the channel name it lives in?

Hi, For a python expression in a channel box, is there a way that this expression can query the name of the channel (parameter name) that it lives in? ex: a string channel has the following expression: hostChannel="some python methode to get the channel name" return str(hostChannel) So the string in the string box is the actual parameter name. Thanks,
14. ## Returning the frame for a value in a channel

Hi anim! Thanks for the help! Works perfectly. I was just starting to think that I will waste my entire Sunday trying to figure this out and there is no one around to help me. This was a real life saver. Thanks.
15. ## Returning the frame for a value in a channel

Hi, I have one single channel in CHOPs that goes between 270 and 362. There is a moment that I get the max value. I would like to be able to return the FRAME number at that particular moment as my value goes to its maximum level. Any ideas? Thanks. (In the attached image we can clearly see the moment the "value" (orange line) "hits" the max value (green line). I would like to be able to return the \$FF at that moment.)
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