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Assigning Texture Parameters to Material Instances using Houdini Engine


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Hi there, 

I've been hitting a wall with setting material instance texture parameters in unreal using an HDA. 

I've been referencing the documentation, this forum post and this forum post but none of the methods seem to work. 

I have stripped my testing down to just using the rubber toy test geo. I am only using one wrangle that I have tried running it over primitives and detail to set the unreal_material_instance string attribute to the unreal material path, and the unreal_material_parameter_* attribute (in my case unreal_material_parameter_basetex) to the material channel of the principled shader inside the rubber toy geo (I've tried both diffuse and basecolor). 

The material instance is correctly generated from the material, but nothing I have tried has successfully replaced the texture parameter on the material instance (called basetex here). 

In troubleshooting, I found that if the parameter is a float and I set "f@unreal_material_parameter_floatparam = 0.5", the material instance is overridden correctly. It also works correctly if I point s@unreal_material_parameter_basetex to an existing unreal texture by copying its reference path. 

The HDA exists in obj/geo1/HDA and the rubber toy geo is directly inside there (so from the squab example in the documentation I believe the path I want is testgeometry_rubbertoy1/shopnet1/ToyShader/diffuse)

I'm using Houdini 21.0.440, Houdini Engine 8.0.0, and Unreal Engine 5.6.1. 

I've attached some screenshots as well as the HDA I've been testing with. I did try the working HDA from here but that doesn't seem to work for me either so maybe I have a versioning issue...

Any help would be greatly appreciated!

Thanks! :)

Screenshot 2025-10-22 140112.png

Screenshot 2025-10-22 140237.png

Screenshot 2025-10-22 140249.png

unrealtest.hdalc

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