[Houdini 15] PyroFX explosion render question

[Wurglor]

Hi guys,

I'm quite new at this stuff and my English is awful so please go easy on me D: 

I've been following This tutorial trying to figure out how to make an explosion in Houdini and I've got pretty far but once he got to the rendering part i got lost. Can't for the life of me find out why all the tabs, options and other stuff are different and how to gain similar results.

Can someone please explain to me how i could replicate his steps for rendering in 15th version since everything's different , also can someone explain why do i have to use volume visualization node in order to gain similar results in the scene view and does it affect render results in any way?

Thanks

Edited April 21, 2016 by Wurglor

[fathom]

yeah, pyro shader 3.0 is different than pyro 2.0.  you might be able to "opunhide" a pyro v2 shader, tho.  in hscript textport type "opunhide" and it'll list everything hidden.  you can see if there's a pyro v2 in there... not at a workstation at the moment or i'd look myself.

that said, pyro 3.0 is way better.  generally speaking, the idea in the pyro shader is to take 2 or 3 volume fields and use them to make your explosion look nice.  the density field is pretty much the "smoke" portion of your explosion.  the fire is usually a combo of heat and temperature, but i've often found heat by itself suffices.

the underlying theory is to have one field drive the color of the flames and another field drive the intensity.  like i said, i usually use heat for both.  then it's just a matter of finding good multipliers for each.  you can use the "physically accurate" color mapping or use the "artistic" color ramp (you'll have to generate the ramp yourself).  the trick is that your shader has to be tuned for the sim that's generating it.  there are not really any units on density or temperature or heat... they could be 0-1 or 0-100000 depending on how you set things up in your sim.

there's also a "fireball" material you can drop down that will fill in some default values...

edit: oh and the volume viz sop is really a simplified version of the same idea.  it just affects the display, not rendering.

Edited April 21, 2016 by fathom

[Wurglor]

23 minutes ago, fathom said:

yeah, pyro shader 3.0 is different than pyro 2.0.  you might be able to "opunhide" a pyro v2 shader, tho.  in hscript textport type "opunhide" and it'll list everything hidden.  you can see if there's a pyro v2 in there... not at a workstation at the moment or i'd look myself.

that said, pyro 3.0 is way better.  generally speaking, the idea in the pyro shader is to take 2 or 3 volume fields and use them to make your explosion look nice.  the density field is pretty much the "smoke" portion of your explosion.  the fire is usually a combo of heat and temperature, but i've often found heat by itself suffices.

the underlying theory is to have one field drive the color of the flames and another field drive the intensity.  like i said, i usually use heat for both.  then it's just a matter of finding good multipliers for each.  you can use the "physically accurate" color mapping or use the "artistic" color ramp (you'll have to generate the ramp yourself).  the trick is that your shader has to be tuned for the sim that's generating it.  there are not really any units on density or temperature or heat... they could be 0-1 or 0-100000 depending on how you set things up in your sim.

there's also a "fireball" material you can drop down that will fill in some default values...

edit: oh and the volume viz sop is really a simplified version of the same idea.  it just affects the display, not rendering.

Oh, thanks man!

Don't really understand what volume viz sop means though, are you talking about the volume node?

And one more question - Is there any way that i can make the quality of the smoke in the scene view higher?

[narbuckl]

49 minutes ago, Wurglor said:

Oh, thanks man!

Don't really understand what volume viz sop means though, are you talking about the volume node?

And one more question - Is there any way that i can make the quality of the smoke in the scene view higher?

The Volume Visualization Sop is literally a node in sops called just that, it acts just like your guide settings within dops, it lets you visualize your fields and color them in the viewport and transfer back and forth from the pyro shader and the visualization node. That being said I would strongly recommend setting up fire and explosions with a physical blackbody model, rather than a hand picked color ramp, for several reasons. Consistency across shots and setups being number one, number two being that the physical model will have a much better color range when you get to your low and high values. 

 

But Yeah, as mentioned above that video is pyro 2 and if you are using houdini 15, you are using pyro 3 :-/

 

-N

 

[Wurglor]

Alright, thanks guys!

I'll experiment a bit more tomorrow, yet to figure out how to stop my simulation from turning into a big wall of smoke after about 40 frames. 

I add vortex confinement node, change turbulence and other stuff but there's no real swirls to be seen :/

[fathom]

you can use the volume viz sop (or even just a volume mix) to drop the opacity way down (try .1, .01, .001, etc).  from there you can either adjust your sources or your sim to generate less density (if that's the problem) or just reduce the density in the shader.

 

[Wurglor]

Um, so I've been experimenting and have run into something weird.

When i try to cash the simulation with the OpenCL turned on it gives me these errosr somewhere around 56th frame:

OpenCL Exception: clEnqueueNDRangeKernel (-4)
OpenCL Context error: CL_MEM_OBJECT_ALLOCATION_FAILURE error executing CL_COMMAND_NDRANGE_KERNEL on GeForce GTX 770 (Device 0).

OpenCL Exception: clEnqueueNDRangeKernel (-4)


I assume it must mean that i don't have enough ram for this? Can't really find any info about this on the forums

Edited April 22, 2016 by Wurglor

[narbuckl]

31 minutes ago, Wurglor said:

Um, so I've been experimenting and have run into something weird.

When i try to cash the simulation with the OpenCL turned on it gives me these errosr somewhere around 56th frame:

OpenCL Exception: clEnqueueNDRangeKernel (-4)
OpenCL Context error: CL_MEM_OBJECT_ALLOCATION_FAILURE error executing CL_COMMAND_NDRANGE_KERNEL on GeForce GTX 770 (Device 0).

OpenCL Exception: clEnqueueNDRangeKernel (-4)


I assume it must mean that i don't have enough ram for this? Can't really find any info about this on the forums

That means you hit your video card ram limit and if you want to simulate at that size as is, you need to disable opencl acceleration. 

 

-N

[Wurglor]

Got it, thank you!

[fathom]

be careful.  some nodes will have opencl on by default in an "advanced" tab (i'm looking at you gas shred).