Is there a way to preview forces/deformers on particles?

[magneto]

Max has a 3rd party plug-in called ForceViewer that's very useful. It shows how a force is affecting the space by using vectors and deforming them accordingly:

Is there something similar or a trick used by expert Houdini artists to do the same?

I am having a hard time visualizing for instance how a certain Noise in VOPs affect particles.

[zarti]

..

I am having a hard time visualizing ..

im not an expert , yet i need such a useful feature ( not for fields only but for attribites too ) .

imho , that can be build but wd require extra geometry , extra time , extra etc ..

at least even for visualising ( on / off ) attribites actually their controls are Too ' physically far from ' a quick workflow ..

so , often i Trust to my intuition or trial&error technique , because thats not easy .

imho , those should be packed inside a dedicated tab folder of each node ( visualise any attribite thats passing there ) , or if thats ' expensive ' .. a new node for each Context .

afair , i illustrated with XSIs ICE ability to view or hide attribs and asked the option to have UnCountable-Geometry to use only for visualisation purposes ..

( maybe that was @H12 Wishlist . time to copy-paste @13th one maybe )

.cheers

[magneto]

Thansk zarti. How does it work in XSI? I only saw their viewport display of values which was similar to Houdini's but more options for matrices, etc.

It would be massively useful to be able to visualize these in the viewport, but I am not sure of the best way to propose. ForceViewer is ok but if there can be a better way, it would be dream like.

[symek]

One option is to sample accel with additional particles. I suppose this way you capture all forces applied on particles, though I haven't checked this.

1) Create a bounding box of the size of your sim. Append PointFromVolumeSOP and plug into second input of your POPNet.

2) Then, inside the POPnet, add additional SourcePOP: Use second context geo/Emission: Points/ Impulse Activ.: $F==1, Birth rate: $NPT/ Constant Active. = 0 / Birth Group: say, "samplers".

3) Append StatePOP, and set Group to "samplers" and Stopped == 1.

4) Use CollectPOP to merge StatePOP with your main branch.

Now you have an additional set of particles, which have accel values from a spot of a sim they were born in, but they are not moving (you will have to exclude them from collisions, InteractPOP etc of course). You can visualize accel as usual in viewport, or convert accel to color, or copy some gizmos, whatever.

hth,

skk.

Edited March 26, 2012 by SYmek

[magneto]

Thanks Symek, genius method

I have a few questions about this.

1. How do you determine the size of your sim?

2. Can I use the box whose input is the popnet? If I do this, it doesn't work due to evaluation order I believe, so what if I use 2 popnets? This way I wouldn't have to worry about it interacting with the first popnet, right?

3. To sample values at a different time in the system, you just change where they are impulse born?

I guess your system can be made so that the visualization particles born and die every frame so you can see it as you play your animation, right?

Thanks again man

[bhaveshpandey]

also in H12 you can now use volume trail for some custom visualisations.

if your using it for particles, you'll need to create volume from them and then use these new sops..

or else just use fluid source sop (which creates this volumetric data along with many other things..just dive into

the sop and see how its done)

another work around would be to visualise these in dops..just attach these as a scalar/vector fields and use the scalar/vector visualisation dops

Edit: (which would of course require you to setup your pops inside dops).

there should be many other ways to do this and would need a bit of extra setup time..

cheers.

Edited March 26, 2012 by bhaveshpandey

[old school]

You can use Volumes to help in visualizing volume density data.

You can use the Source Volume SOP in H12 which builds a density and vel.* volume primitives from any incoming geometry including raw points, line segments (using minimum distance), open surfaces or manifold geometry.

The points being fed to the Source Voluem SOP are what drive the resulting density and volume data in the constructed volume primitives. The velocity shows up as curved tails that you can visualize in the viewport. Lots of control here.

This is the most straight-forward way to visualzie a velocity field.

You can use the Volume Trail SOP in H12 to visualize with curved tails as well.

Please look at the two attached files for a couple examples of various options and contortions. Is this what you guys are after?

volume_trail_on_curve_with_v_attributes.zip

volume_trail_on_particles.zip

[zarti]

Thansk zarti. How does it work in XSI? I only saw their viewport display of values which was similar to Houdini's but more options for matrices, etc.

..

well , ( iire ) i have seen its users rightClicking over network wires . a small window appears and they choose ' what they want to see ' .

oc , im talking about attributes here not fileds ..

it is not that i found it the best ' possible ' form of implementation , esp because i hate extra-poping-up-windows .

thats why im hopping more to have a special node which ' communicates ' directly with OGL ; its parameter's are on their own pane , only existing attribs are available , a node can be easily connected / disconnected ( shaking / dragging over any wire ) , could have multiple inputs which could take info from ' anywhere ' , pseudo-fields ( why not ?! ) , etc .. etc ..

sweet dreams ! .. no ??

[magneto]

@oldschool, amazing trick. I didn't know that was possible. This is of course much more flexible and powerful than the ForceViewer. I just have to explore all the possibilities

@zarti, I think I have seen what you are talking about in XSI. I am not sure of your implementation, but if you have any mockups, I would support it