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Bent and PRT Normals

Hello, I tested some maps rendered in Xnormal, and im intrested in Bent and PRT Normal maps. Can’t find information how can I use it and for what they were created.
I’m search way for stylized lighting(or smth like that) and i heard some tips with these normals, but there were not good explanation(and in UE Bent normals create very ugly seams and flip green channel dont work).
I hope you can tell me something about these intresting maps.(And maybe if you know any tips for creating baked albedo with these normal maps, can share with me too;p)

Common application of bent normals is for faster environmental texture sampling. While conventional normal map holds information about normal direction at specific point, bent normal map represents averaged direction that is to be used to sample environmental map, with AO accounted. It is called bent normal map because it sort of bends the normal away from occluded areas. Bent normal maps are created by taking large number of samples in a hemisphere and averaging them.

I believe bent normals are already being used in static lighting system of UE4. You are not meant to plug them into Normal material input pin.

You’ve heard tips about bent normals and stylized texturing most likely because it used to be common to overlay green channel of bent normal map into diffuse texture to give some sense of directional top down lighting. With PBS it became obsolete for most cases.

As for PRT maps, I faintly remember something like that in Xnormal. I believe that in the essence, they just store directional lighting and shadowing from 6 directions.

In the end, it is up to you how to use those maps in your texturing process, but alone, they have no use in default UE4 materials.

Hmm thanks, it was very helpful. You have bigger knowledge about normals so maybe do you know one another thing. I looked for some workflows, and in GTA5, Overwatch etc workflows normal maps was always without blue channel, maybe do you know why they dont use them.

I’m kinda new to Bent Normal maps, anyone got any tips of how they are actually used in UE4? The 4.17 release notes mention a lot of whats happening behind the scenes and the benefits in image quality, which have sparked my interest, but not much on authoring them of using them in materials.

I haven’t seen any other software other than xNormal capable of baking them either.

While I’m here I thought i’d answer this. :stuck_out_tongue:

This is common in some engines (including UE4 if I’m not mistaken) as a means to drastically improve image quality of normal map data at the cost of some extra memory: The blue channel is recreated in the engine at runtime, instead of being stored in the texture. A format such as BC5 DDS or similar is used for compression, which BC5 stores only two channels, R & G, but they contain twice the bit depth. So in other words you get much better normal map fidelity than you would using DXT1, for the same memory footprint of a DXT5, if I remember correctly.

I’m fairly certain in Maya, a bent normal map is the normal in object space rather than in tangent space. So going on that I’d imagine more software support it but under a similar name perhaps?

I’m quite interested in this too, b/c of the supposed reduction on light leaking. Here is the relevant trello card.

Btw handplane is now freeware, ie pay what you want on gumroad. can do object space normal’s and has ue4 options.
intro to handplane