Coercing Assimp into reading OBJ PBR materials

Edit January, 4th 2022 : The Assimp maintainers merged just a few days ago a pull request that enables PBR support by Assimp’s OBJ importer. If you are able to use a recent version of Assimp, I would advise you to go get it and work with it the way Assimp expects it. See the pull request here.

These days, I’m trying to import 3D models exported as Wavefront OBJ files in my Vulkan renderer. In order to achieve that effortlessly (kinda), I’m using the very good Assimp (pun not intended) library.

It kinda works well if you stick to a « traditional Blinn-Phong » lighting pipeline (also known as « prehistoric lighting » 😉 ), with ambient/diffuse/specular components and so on. Everything is there. Things become trickier if you try to bring PBR into the mix, with roughness, metallic and ambient occlusion maps for example.

What parameters should you use in Assimp to read those values ? What texture type should be used in order to import those maps ? Turns out it’s not as easy as one would think, because support on both the Wavefront OBJ specification and Assimp is just not there.

So I had to cheat a little, let me explain how !

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Unreal Engine Tips – Bake a Material to Render Target

While working on the game Front Line Zero with the METATEK game developement studio, I’ve used the Unreal Engine 4 game engine for some years now.

I’d like to share some knowledge about the pitfalls and neat tricks I got to discover under the form of short, easily-readable blog posts.

Today’s topic : how to create an utility that draws the result of a material into a render target asset in the Unreal editor.

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