Hey all,
I have an hda that has geo and a principled shader assigned in a hda which is being loaded into unreal. According to the documentation a material property of "metallic" should transfer over when HE makes the materials on the unreal side of things. All other parameters seem to come over, but metallic does not. I started with a principled shader and then tried a material builder to make my own with a metallic property exposed. The later triggered a metallic parameter to be made in the unreal shader, but it was set to 1.0, no matter what I set the default of the parameter to be or on the outside of the shader. Is there something special I need to do to get it to listen to the metallic parameter? Or is it broken?

Hey all,

I was wondering if it's possible to control other environment variables (not houdini specific) in the unity_houdini.env. If your hda relies on a python library and you want to distribute it, it would be nice to be able to add they python paths to the unity_houdini.env. I tried PYTHONPATH which I use from my normal houdini.env, but houdini engine in unity didn't seem to read it. It got the hda search paths just fine.

The docs say “The environment file unity_houdini.env is in fact same as the traditional houdini.env file” but it doesn't seem to catch my PYTHONPATH adjustment. The same thing works fine in unity if I add it to the traditional houdini.env.

My unity_houdini.env looks like this:
PYTHONPATH = “W:/Work/PipeTest;&”
HEU_ENVPATH_ADD_HOUDINI_PATH = “W:/Work/Houdini;W:/Work/PipeTest;”

I tried adding the “HEU_ENVPATH_” on the beginning but that didn't change anything. Is there some syntax I have to use or is it just not possible? Any thoughts?

-bk

Congratulations!! Houdini is great about finding ways to achieve things and then building on each achievement for the next cool thing! I understand how you feel. A lot of my “microscopic achievement”s end up getting turned into tools that then get added to others.

Hey all,

Sorry for the “houdini engine for unity” noob question, but is there a way to display the helpcard from a hda in unity? It's not easy to search for and get relevant results.

-bk

@Ien Yeah that resembles some of the behavior I was seeing. It made me wonder why the initial cook on placement seemed to behave differently than subsequent cooks. It's been a while since I dealt with the issue, since that project ended and I have been doing raytracing on my current one.

* I tried a uv node in my shader set to a Precision of “Float”, but that didn't work.

Hey guys,

I am switching over from Unreal to Unity and have a voxel-ish game that uses pixelated unfiltered textures on geometry. I am seeing an issue where the texture isn't lining up exactly despite being correct in Houdini. I saw the same thing previously in Unreal but was able to fix it by using “full precision uv's” on the model. In Unreal you can tell the Houdini Engine Plug to favor them by default. Is there an equivalent on the Unity side?

-bk

@dpernuit Awesome. Thanks for following up!

@DASD Thanks for the reply, but I am not looking to -randomize- material assignments, I want to artistically -control- them hou side. I am setting up a system for doing level design on the houdini side. So imagine painting where a desert and a forest environment are and using material variants to reuse geometry but still show a transition between the two.

And as far as building it into the shader… I don't want to shift the heavy lifting into realtime. Even if it were easy to build a shader with multiple variants inside it (it's not a feasible workflow, we are talking several variants and lots of assets and sorta reinventing the wheel since unreal already has material instances) I wouldn't want to. It would be inefficient. I would rather do one of the workarounds that I mentioned.. but those also come with drawbacks as well.

And what I am talking about is only partially an unreal limitation. Yes, the HierarchicalInstancedStaticMesh component does have that limitation. But I am splitting the instances anyway, so they are actors once they are baked down to a bp and before that they are a HoudiniAssetComponent. So I assume that might be more flexible.

Seemed like a fair ask, given dpernuit was discussing per point uproperties anyway. I figured it wouldn't hurt to ask, I was part of the thread that spawned “unreal_material” as an attribute (as were you), just hoping to get that per instance point. Sidefx has always been awesome about taking feedback.

From what he said it's possible v2 would already make that possible as long as you change the material as a uproperty. I am currently implementing a workaround, so I thought I would ask. If it does I will just pause that part until v2 is available.

-bk

@dpernuit: Will the generic uproperty per instance on points in V2 you are talking about allow us to set a material for one of the materials (there might be multiple) on an instanced static mesh per point?

I currently have a situation where I have a car that has two main materials, a paint and a glass. I have created multiple variations of the paint material with different colors and graphics to have a decent set of car variations.

I can currently scatter a bunch of points on the hou side and instance the existing static mesh on them with the “unreal_instance” point attr, but I can't use the “unreal_material” attribute to change the material for each instance. I can't figure out an efficient way to control the material per point at the moment.

The only way I seem to be able to do it currently is making a duplicate static mesh with the other material on it and point at that with some of the instancing points, but that means the geo is duped for each variant. I also can make a bp with the static mesh, change to the material variant and point at that, but that changes how the instancing happens creating tons of actors and is much slower to create manually and in the editor to scatter. I am currently using the “unreal_split_instance” to force individual actors anyway, but I still can't affect which material is on them per point.

I would love to see the ability to change the material in each material slot per instance. In other words if the “unreal_material” worked per point when instancing and allowed you to specify which slot. That way I could just have one car mesh and several paint materials and set them appropriately on the points.

Sorry if I am missing some existing way to do it, but I tried several different ways without success. Let me know if you want more details or if I should submit a feature request.

-bk

Thanks Enivob! "@sourceprim == 1;" also works in pattern! Just glad to know that syntax works, I was pulling my hair out. I am not as familiar with VEX, I am python guy… but I am trying to learn to solve some my problems in vex and not always just fall back to python… trying to use vex for speed and the ability to compile it.

Feels like they should make it clearer visually which fields support VEX and which don't, like how python and hscript change the color. It makes an awesome piece of software feel less reliable. I should use wrangles more.

Anyone know if there is any collection/site of wrangle recipes besides what is in the wrangle nodes themselves?

Thanks for the help!

chrisgreb -

The workflow I was hoping for would be to make a bunch of instances on the houdini side, point at an unreal material with “unreal_material_instance” and change some parameters with “unreal_material_parameter_xxxx” and houdini engine would create material instances based on the parameter tweaks (like it does outside of this instance case) and then grouped the instances together into InstancedStaticMeshComponents on the unreal side based on which material they get assigned.

I will split it on the houdini side into separate instance nodes and unreal materials to achieve it, but would just save setup time and be more flexible with changes on the houdini side to have it happen dynamically.

Thanks chrisgreb!, but as I said at the end of my original post “unreal_split_instances” causes a huge perf hit. Which is why I was trying to come up with a different way.

Hey DASD!

Thanks for the reply, but I am not actually trying to put different vertex colors on the instances. I am just displaying that in houdini to visualize what is going into the “unreal_material_parameter_diffuse“ prim attribute that I am feeding into unreal.

But you are right about the material, I think I mistakenly thought you could apply a different material per instance via ”unreal_material". Seems not to be the case with some testing. I think I tested it before switching my geo to instances. So I thought I would be able to apply a bunch of different instance materials using the “unreal_material_instance” and “unreal_material_parameter_xxxx” methodology. But since it seems you can't have a different mat per instance… so that won't work.

Thanks again I will come up with a different workflow for it.

-bk

I feel stupid for not being able to get this figured out, but what is the proper syntax for accessing a single value from an attribute that is an array on some geo? I looked through a bunch of the docs other websites and it seems straightforward, but I can't get it to work.

My point attr of “sourceprim” has a value of "". Shouldn't I be able to do this in a parameter expression?:
@sourceprim

and get “1”?

so if I wanted to test for values on points with an expression to decide to delete I could do:
@sourceprim == 1

I can do it via a point() call but I would rather understand how to properly access it with the @ call.

Thanks for help ahead of time for anyone who schools me on this! Sample file below.

Hey guys,

I am trying to get a setup working with dynamic material instancing as described in this: http://www.sidefx.com/docs/unreal/_materials.html#MaterialsInstances [www.sidefx.com]

I setup a simple example scene with a grid and box copied onto the points. I want each box to have a different material instance with a different diffuse color. All the points have a “unreal_material_instance” parameter pointing at the same existing unreal base material. Each point has a different color value which I put into both “Cd” (to visualize in houdini) and “unreal_material_parameter_diffuse”. The boxes are packed and copied with a copy to point and the unreal values are moved to prim values on the final output.

I can't seem to get this to work properly in unreal. The first time I did it, it successfully made one instance material in “HoudiniEngine/Temp” that seemed to get the diffuse color from point 0, but it applied to all the boxes. I changed the color on all the boxes to red just to see if it was listening to the color and resaved my hda. Upon reloading it, it seems to have stopped listening all together and just assigns a default material. I deleted the hda and the temp instance material and reimported the hda, but that didn't change the behavior.

Is it supposed to work in the scenario I am showing? I am a little fuzzy on what logic might be happening with the prim attributes coming from the copy as the boxes are packed (packed so unreal sees them as instances). I tried a variation on this with the object level instancing node, but that had the same outcome and I wasn't sure if my unreal attrs were even making it on the instances.

Am I doing something wrong? Should my example be working? It would be great if I could get this to work!

I looked at: https://www.sidefx.com/forum/topic/53354/ [www.sidefx.com]
But that scenario is a bit different than mine (multiple materials on one object).

Thanks ahead of time for any help.

ps. I played with that new unreal_split_instances option. It's great and I know that gets the desired result, but splitting the instances on the scale I am working with causes a large perf hit. I basically I want the functionality the “unreal_material” parameter gives you with the added bonus of creating the instance materials automatically based on parameter changes the way the documentation describes “unreal_material_instance” and “unreal_material_parameter_xxxx” functioning.

Houdini Indie 16.5.496 and Unreal Engine 4.19.2

Thanks mark0s! Yeah I figured that out. I am gonna see if I can set it as a uproperty so I don't have to place and then recook it each time. Puts an unnecessary steps in the workflow.

Strangely when I baked the geo it stayed in the wrong state despite changing the "Distance Field Resolution Scale” to a proper value. But yeah, changing the value and recooking definitely fixes it.

Thanks again!

Hey guys,

I am working with Unreal 4.19 and Houdini Engine. I am trying to use dynamic lighting using mesh distance fields and am finding that houdini hda meshes don't show up in Unreal's mesh fields. This happens even when I bake the geo in unreal and place it in the scene from the content browser.

In Unreal, I tried setting the “Distance Field Resolution” to 1 on the hda actor and baked geometry, but it didn't help. On the baked geo I also tried checking on “Generate Mesh Distance Field” but that didn't help either.

I included the simple Box.hdalc for testing and a gif showing me placing a regular unreal box and then the hda and toggling on and off “Viewport>Show>Visualize>Mesh Distance Fields”

Funny enough, while first placing the hda, the houdini logo mesh shows up in the Mesh Distance Field before cooking to the box.

I am wondering if there is just a setting I am missing somewhere, or if this is a bug I should report.

-bk

Houdini 16.5.319 seems to fix the issue I was having.

Was there any resolution to this? I also have UE 4.18 installed and when I install Houdini 16.5.268 I only get an option for install Houdini Engine for 4.17. I was wondering if it might be because UE is installed in a non default location. My C: drive (I am on windows) is a small fast ssd, so I install things that take a lot of disk space on another drive. I have had this setup for a while and it has worked for quite a while before this.

Was there any fix to your issue? Or is houdini engine not out yet for 4.18?

-bk