Now that Metahuman licensing allows rendering in any DCC, the once strictly Houdini-to-Unreal character pipeline could become bidirectional. Does anyone know if SideFX or SideFX Labs is working on an Unreal-to-Houdini Metahuman workflow?

In my latest project, I rendered most of the scene with Karma XPU, then switched to Karma CPU when ultimate quality mattered or speed wasn’t a priority. A similar hybrid approach could apply here: render some sequences entirely in Unreal, then refine others with heavy VFX, such as FLIP or pyro, in Houdini with Karma.

Also, I’ve noticed that the Metahuman Grooming HDA is tailored to Unreal’s groom system, yet Unreal still doesn’t offer a native way to export groom strands to other DCCs without a paid third-party plugin.
By other side, it seems that Unreal has made huge leaps in many shot-related areas like custom aovs, OCIO, overall rendering consistency, USD support and fluids support, since its initial release, and holds a strong position in areas where Houdini is less present, including previs, virtual production, geometry-heavy environments, sound, live performances and character building.
Of course USD is key to tying all software together, but it still feels that bringing high-quality characters into Houdini will require close collaboration between dev teams (for example interchanging transparent materials is still great pain, and character not only have transparent eyes, but also sss skin and hair shaders).
Any insights would be greatly appreciated.

sabudimir
There is a nice example in the content library that you might find helpful. If I understand correctly what you wish to do, I think that example shows exactly that workflow (scene animate > sops/kinefx > scene animate).

https://www.sidefx.com/contentlibrary/kinefxapex-workflow/ [www.sidefx.com]

I've checked the example, and that's exactly what I'm looking for! Thank you for pointing it out!

I've read through animation workflow [www.sidefx.com] documentation and see that I can do APEX Control Extract [www.sidefx.com] to mix KineFX animation to APEX. The problem I have is that it returns controls at their rest position. Is there any way to extract the rig with controls while being animated? I've extracted the animated rig without controls using Scene Invoke and potentially can use it for retargeting. However, it feels overcomplicated since I think I have the data in the Scene Animate SOP and don't know how to extract it.

The problem context is that I have two APEX rigs: a motorcycle and a driver. I want to seat the driver onto the motorcycle using all the ik magic of Animation State, then extract the pose and procedurally animate characters driving along curves in SOPs and pass it back to APEX for final manual tweaking like tilting and knee direction.

You can hide them using the Configure controls node. Set the mask to asterisks * and control’s shape to an empty field.

You probably have the UV Coords toggle enabled in the viewport's Display Options.

octavio.halo
Any chance for a Python 3.11 version?

https://github.com/shycats/PyVirtuCamera/releases [github.com]

I would love to update it, but the latest version of the available API is still 3.10 https://github.com/shycats/PyVirtuCamera/releases [github.com]

If you'd like to use just kelvins without luminance, you can apply them using Color Picker.

If you have Kelvins + Luminance Chart [physicallybased.info], you can make a VEX wrangle to convert Temperature + Luminance to XYZ universal color space and then to linear sRGB;

The first screenshot shows that you're using XPU with Principle Shader. Karma CPU works with both Principal Shader and MaterialX, while Karma XPU works with MaterialX only. Houdini is doing some basic conversion from Principal Shader to MaterialX in the background, but you shouldn't rely on it, as it leads to unexpected results.

HristoVelev
Any chance to get it to work with a full commercial license and not just indie?

I can try to upload it on orbolt because I don't have a full commercial license. Or maybe I could connect to you and rebuild it on your license if needed. The asset isn't very complex; it's mostly a Python module with an interface.

I forgot to say the plugin only works with the Python 3.10 build of Houdini due to API restrictions.

Hi, Hristo.
I have just updated the bridge plugin between Houdini 20.5 and the VirtuCamera app for iOS. The plugin might be even clunkier than Unreal due to how the screen is captured and the lengthy post-recording of transformations to the camera keyframes. I have some ideas/tests on how to make a recording of transformation faster, but other projects are currently a priority.
You can read more about it and watch a video here in the topic [www.sidefx.com].
And download the latest version here on GitHub [github.com]
Feel free to contact me if you need help with testing this out.

VirtuCamera plugin: Update to Houdini 20.5
HDA Version 1.3, VirtuCamera API version 2.1.2

Works only with the Python 3.10 version of Houdini due to API compatibility.
Added a Display Preset dropdown menu for 4K and Full HD displays.

Download it from my GitHub repository: VirtuCameraHoudini-api-2.1.2-version-1.3-py310 [github.com]

Tested on Windows 11, Houdini 20.5.278 Py310, Iphone 11

DirtyVibeMedia
any chance we can get this for Mac? would be super sick! thank you in advance

Sorry, I can't do this; I don't have a Mac.

It looks very natural and realistic! The APEX tree is impressive as well. Is it intended that brunches disappear during growth?

I guess modern engines with PBR shaders have deliberately moved away from calculating the complex IOR with an imaginary part (k) for non-metals because the values for non-metals are too small to make a significant difference. When comparing the imaginary refractive indices of metals and glass, the range for metals can vary from 1 to 14, while for glass, it ranges from 2.8607E-06 to 8.1300E-06 (0.0000028607 to 0.0000081300). These are incredibly small values, and I doubt whether rendering engines even calculate to such precision, as these minuscule differences likely don’t have a noticeable impact on the final render.

In the Physically Based Rendering book [pbr-book.org], it is clear that the Fresnel function for conductors (metals) uses the complex refractive index, including the imaginary part k, which accounts for light absorption.
In contrast, FresnelDielectric function is not using it.
So, this likely applies to all engines that implement similar technology, as using the imaginary part for dielectrics does not provide significant benefits and only increases computational overhead.

art3mis
Thanks for sharing!
Minor corrections I believe are needed on the MtlxImage node signatures in the example .hip. For Roughness and Height maps I believe you should change the Signature to Float from Color.

And if using a Normal map, use Vector instead of Color.

Thank you! I fixed this in the updated example file.

Hakobus
Hey FaitelTech,

The node pack looks extremely useful, but it doesn't seem to work with Houdini 20.5. Any chance you might look at updating the pack for 20.5?

The quick update to run MaterialX Essentials Nodes on Houdini 20.5

Note: To see custom nodes inside Material Builder subnet, add "FaitelTech*" at the beginning of Tab Menu Mask parameter on Karma Material node or MaterialX Builder



https://github.com/Faitel/MaterialXEssentials [github.com]

Yeah, that sometimes happens to me, too.

Those utility tools are awesome; they look like they should be part of the standard Apex toolkit.

You guys are rock; keep it up! As much as I'd like to test the foliage with delayed evaluation, I'd like to see tutorials and examples of APEX usage in a non-rigging environment.

A way to do it is by baking color with a render engine like Karma CPU. COPs-based maps baker only supports transferring texture color, not the component color of the high-poly model.
I'm attaching an example of baking points scattered on a 'Rubber Toy' onto a UV-unwrapped Rubber Toy model.
The example based on the hip from the post [www.sidefx.com] by pablo_lukaszewicz [www.sidefx.com]:

ivanmalek
Hi,
I'm struggling a bit with a larger scene, where I'm using the Instancer to scatter grass.

Try to use point instances instead of native instances.