How to render front and back the same? (Render Face = both)

I have a generated mesh from a CAE analysis result I'm rendering that is made up of sheet metal that I'd like to render both back and front faces the same (as I have done with OpenGL in the past by enabling two-sided lighting and disabling backface culling).

I was hopeful that specifying "Render Face = both" would do the trick, but the appearance of the back face is darker and not what I expected. My goal is to have both the front and back faces render the same.

I'm using URP/Lit mesh material, and the images below show the model with Render Face set to both, front, then back. I am hoping that I can somehow find the setting that will allow me to show all polygons as seen in the front image, regardless of their facing direction.

Thanks, Dennis

Here's the screenshots:

Both:


Front:


Back:

 

Have you found a solution for this in URP?
It seems to me HDRP does is correctly but not URP.

 

I ended up writing a shader to flip back-facing normals in URP. I made a FFNormal subgraph:



I used it in my shader as follows:



If you find a better way, please let me know!

Thanks, Dennis

 

Sorry for the late reply - had no notification on.
Thanks for that, that is at least some help although does not solve all my problems, since I need a transparent object as well and not just a hard surface.
I am really confused how this is a problem at all. Is it so uncommon to use double sided stuff? Or are we doing something completely wrong?

Thanks again,

Alex

 

No problem. I was able to also do alpha, but used a variation of this shader (Surface="transparent") and set the alpha value. Other than that, the graph was pretty much the same.

 

Can someone help me fix this for the "SimpleLit" shader adapting the shader code. My attempt so far is to split the "ForwardLit" pass inside

SimpleLit.shader

into 2 passes: "ForwardLitFront" with

Cull Back

and "ForwardLitBack" with

Cull Front

. For the back pass I then set

#pragma vertex LitPassVertexSimpleFlipNormal

. I copied

LitPassVertexSimple

inside

SimpleLitForwardPass.hlsl

as

LitPassVertexSimpleFlipNormal

and added

input.normalOS = -input.normalOS;

at the top.

The result is unfortunately that the backface isn't rendered at all now. But it does seem to work in principle. If I remove the front pass the backface is rendered and lit properly. What am I missing so that both passes work at the same time?

 

Looks like URP is not rendering passes unless they have a different LightMode tag. I used "SRPDefaultUnlit" for one of them as the linked thread suggests and now it works.