Modding, Mission Design, and Coding > Test Builds

GGX Lighting Model

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Hi, it's me, the dude who introduced physically-based rendering to Freespace. FSO 3.8 shipped with the Blinn-Phong specular model which looks pretty good. I adopted it because it was cheap and easy to implement.

However, a lot of commercial games are shipping with more complex specular lighting models. One notably is GGX, popularized by Disney's engineers (, now being used in Unity and Unreal.

GGX is a bit more expensive to calculate than Blinn-Phong but its specular reflectance behavior is closer to reality than that of Blinn-Phong.

Taken from, the first image shows a highlight from real world chrome values. The second image is GGX. The third image is the Beckmann reflection model (which produces values close to Blinn-Phong)

Here's what it looks like in Freespace:

As you can see, Blinn-Phong has a bit of a stronger falloff than GGX, almost making reflections seem glossier than they really are. GGX allows the reflections a chance to relax a bit allowing for a bit more material expression.

Try it out yourself (Win32 Build Only):

Great stuff, I'm gonna play around with this XD

Shiny! And this reflection model highlight all the scratches much more. I will try this with proper PBR stuff. Maybe it preserve all custom reflectivity settings better than current rendering engine. Good work, man :yes: !

I have some more comparison pics!

First a very rocky asteroid.
Blinn Phong


Your first reaction may be "huh, not as vibrant" which... it is, but the specular highlight on the asteroid is much less prominent which I think helps sell the "rockiness" of the asteroid.

Next SF Asteroth (I was experimenting with making new PBR textures for some Shivan fighters)
Blinn Phong


Again your first reaction may be "huh, normal map doesn't pop as much" which.. it doesn't, but if you look at the two rear panels, in Blinn Phong, one is well lit, and the other is just totally dark, only the environment reflection is doing anything. In GGX, both are well lit, and I think gives a better contrast with the rest of the hull.

Basically intensity of the lighting is a little bit less, but you get something more visually pleasing in my opinion. Everything isn't as harsh.

(Also here's a worst case shot of the Asteroth
Blinn Phong


Hm, I get error 0xc000007b when launch this.  :(

Nvm, copied files from nightly win32.


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