Hi there
I'm trying to produce some nice cloud like text after doing a cmivfx tutorial on fractals.
There technique is to import i3d volumes - one as the basis of the volume and another as a slightly offset gradient volume to get the nice wisps around the edges.
I'm trying to animate the text but can't bring in time dependant files into the Vex Volume Vop (no text.$F.i3d allowed).
So I'm merging two animated volumes one density the other offset, into a volume vop. I need to create a gradient from the offset volume
but there isn't a handy node for doing that job.
Has anyone got a suggestion about a way to approach this?
thanks
John

I'm trying to animate the text but can't bring in time dependant files into the Vex Volume Vop (no text.$F.i3d allowed).

Are you sure that $F should be $F4 or so. As normally you would have frame padding with a sequence of frames

Rob

hi there rob
I had a go at putting the padding ($F4) in , but the vex nodes always say the same thing

//Cannot have channels that depend on time//

I guessed that's a limitation of using vex.

I'm doing a work around by bringing in my two volumes by renaming one and merging them.
I think this works but I'm having trouble calculating the offset volume as a gradient.
I know the gradient needs to calculates the distance of each point from the bounding box or centre as a vector. but I'm not sure how. any tips?
thanks again
John

You just create a parameter ie a string and then plug it into your vop node. The parameter is there for you to use at the top level , ie you add your path to your files. Unless we are talking about something else completely different

I'm doing a work around by bringing in my two volumes by renaming one and merging them.
I think this works but I'm having trouble calculating the offset volume as a gradient.
I know the gradient needs to calculates the distance of each point from the bounding box or centre as a vector. but I'm not sure how. any tips?
thanks again

Unfortunately I have no idea what you are doing. Often in cases like this its better to put up a simple scene file as it encourages others to take a quick look.

Rob

Thanks for that Rob
I'm having a go at promoting the string attribute now.

I've made a simplified version of my project.
Inside there are three different geo nodes.

the first exports the geometry

the second imports the i3d into a vex shader.

the third unsuccessfully attempts to copy the vex shader network in a vop volume.

I like the vop volume approach as it avoids the rendering out of geometry and avoids the time channel restriction in vex.
What you reckon ?
john

Hi >

Had a brief look at your scene. Not really sure what you are doing but the best way to debug something is to start replacing all those errors you are getting and lower the isooffset volume resolution to get faster feedback

cloud_surface_me_i3d > In the shop > vopcvex1.

Your fractal cevex embedded otl is broken I replaced with AA noise > Replaced P parameter with the globals vop > As your P parm didnt seem to be acting on anything.

volumevop1 > You have a volume coming in then it goes nowhere. I have droped the turb nose you have and added Noise to the volume over time. and then finally out put the the density.

The cloud_surface_me_i3d node now renders. as does or_cloud_surface_me_Vop_volumes

rob

Hi rob
thanks for going to the trouble of tweaking my project.

What I'm trying to do is animate a volume and still keep control of the cloud like form that the ‘cloud surface me ’ shopnet shader produces.

I'd like to be able to animate the volume object forming or dissolving or some such variant , from particles or whatever.

the vex shader way seems to limit you to only using one i3d saved volume from disk. no ‘$F’ allowed in it's channels for animation.
So I started trying a work around by manipulating the volume itself in the VexVop.

I'm only just getting my head around using volumes and shaders.
I can see now that's there's a difference between using an embedded shopnet shader and playing around with the vopvex to manipulate the densities of the volume , when I render the shopnet one it's quite high definition , but the vexvop one always looks blurred even when I upres it's sampling. so maybe it's not the best approach anyway.

what would people suggest?

Hi,
You can use a low res sim and convert it to i3d to render it with the volume procedural. You can use the $F if you promote the parameter. This way should work, even if not refreshed correctly on the viewport, try a quick render.

Another way off adding animation is to animate the noises in the shader.

Nice one,
I promoted the parameter and it will now use the $F. lovely.
I've got my animated i3d's in my procedural shader. cheers for that.

I'm still confused by the use of procedural shaders - materials and their hierarchy.
It's very clear in houdini when linking nodes to one another how things interconnect, but then there are other ways things connect that are not visible.

Can anyone suggest any tutorials that might get me going in the right direction?

Thanks again Rob and Parri

HUGHSPEERS
Nice one,
It's very clear in houdini when linking nodes to one another how things interconnect, but then there are other ways things connect that are not visible.

You can turn on the dependency wires and halos in the Network Pane to visualize other dependencies.

To do this, open the Display Options in the Network Pane by using the “d” hotkey or pressing on the eye icon. Go to the Dependency tab and enable all the options except for the last one for now that only displays dependency links and halos for selected nodes.

You can also RMB on any operator and form the menu, choose View Dependencies. This opens up a dialog that shows you the specific dependencies.

wow a whole world revealed

thanks Jeff

I've been nailing everyone within ear shot that is new to Houdini to always turn on dependencies. Heck I even use it to get a 10,000ft view of an existing scene that I didn't build.

And for the love of all things Houdini, switch to the Technical Desktop!

Build desktop sucks for everything but modeling imho. It makes me cry when I see a 14+ year Maya veteran spin their wheels in /ch for a good half hour before they close Houdini. If we're lucky, they may open up Houdini again, or not. With a Tree View up and centre all the time, it is easy to see exactly where you are and you start asking all the right questions. Not “where the f**k am I”?

This leads to the question: Why are most videos done with the Build Desktop? Because it is the default and in our infinite wisdom have left it that way since H9. Fear of the dark. Guess what I'm pushing for in H12… It's always the little things.

Now to get back on topic: Clouds.

I am hoping Mr Price or Mr. Ben Simmons will perk up here as they were instrumental in the Amelia Cloud tools at MrX. I know those two are always running at 120%.

It's not just in the volume data you generate. You also need to work on the lighting and rendering of the clouds. I know that MrX put a lot of effort in to the Mantra shader and their own model of light scattering inside clouds. You can use the Volume Scatter SOP to generate the Cd color fields that will be used by Mantra to simulate light scattering in clouds. It is not as efficient as doing it in Mantra with a custom shader, but it works, and it works well enough for single users and small one-offs. You can use multiple Volume Scatter SOPs to bake in sky and ground lights. Just use the Name SOP to rename the fields. Name the Sky scattering as Cd_sky and for the ground bounce, Cd_ground, etc. Then mod your volume surface shader to pick these up and mix them in to diffuse. You can merge these fields in with the density field (and others) in to a single .bgeo file saved on disk to archive your cloud with baked in scatter light fields.

Yes they used i3d files to hold the various modeled clouds on disk for later recall and placement in to the scenes. At the time they were using Houdini9 and 10. They didn't have the vast improvements to volumes in Houdini11.

These days I would investigate using the .bgeo format to hold the volume data on disk. The .bgeo format now supports compressed volumes. You can utilize the new Mantra Volume procedural to render your clouds. Then there are all the new Volume based SOPs to utilize in sculpting volumes.

following with some test at odforce on how to do clouds, and doing reserch, i was able to do some displacement in the material,

but how you call in the point clouds and how you color them to get the SSS effect?
this is my small test.