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Involuntary Transparency on HDA's

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Hi guys, 

I'm trying to learn how to make HDA's for games and specifically UE4 right now. 
I've made some simple assets with a varied level of success, but they've all had the same issue in common. 

All the assets I bring in have either a lower transparency on the surface closest to the camera/player (objects with thickness) or is being clipped in half from the point of view as if the near clipping plane is super high ( open objects without thickness f.e. a tube).

Any help on getting to the bottom of this issue would be greatly appreciated! 


Edited by Digistruct

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Hey Jack,

Because you're using a negative value in the polyextrude the resulting geometry has the normals facing inwards.  In unreal the default material only displays geo with normals facing the camera.

There's a couple things you could do.  In Houdini open up your display options by hovering your cursor over the viewport and hitting "D".  Under the optimize tab turn on "Remove Backfaces" to get an idea of the result you will see in UE4.

You could add a reverse node after the polyextrude in your hda but that would still cause problems if the polyextrude value was positive.

Maybe add a toggle to flip the normals.


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