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PBR - a speedy guide!

Updated: Jul 5, 2021

I'm sure evreyone has heard of PBR by now, for users of addons, it's a must have feature. For developers, well, we don't stop mentioning it! Most people probably know what PBR is and what difference it makes. So think of this as a 5 minute speedy guide to PBR.

What is it? PBR stands for Physically Based Renderring which, according to Wikipedia is "Feasible and quick approximations of the bidirectional reflectance distribution function and rendering equation". Ok so that actually sounds a scary, right? In English, that basically means a computer graphics approach where objects are rendered so that they realistically reflect the flow of light as they would in real life.

So... why do we use it? Well, in our work, PBR makes a massive difference. That's why no developer will let you forget when it's included! When we are modelling buildings, or even ground textures, we want to add depth and make them as realistic as possible.

For buildings, adding PBR brings out more subtle shadows and reflections which would be missed completely if it wasn't included. It also prevents that flat / cartoon look which some addons can have.

Here's an example...

See this texture? It's a nice photorealistic texture, this makes up a small part of the terminal building in our Shannon scenery.

When we load up in the Sim it looks like this!

It's still a nice looking building, but it doesn't reflect any light - and it looks pretty flat. So what do we do?

We make a 'Normal Map', it's very purple, and after a while it hurts your eyes. As you can see though, it really highlights the depth of the texture. You can easily tell which parts 'stick out'. The Normal Map can also control the reflection level, all at once. So the more purple it is, the more it reflects. So once we create this, we tone it down and constantly play around with different levels until it looks just right. In this instance, the darker purple represents a more reflective surface. So we use that to cover windows and glass.

The sim still doesn't know what this is though, so we tell it. For X-Plane, we open up the object as a text file and add the following lines:

GLOBAL_specular	1

These basically tell the Sim which texture to use, as well as giving it the metal properties it needs, then the level of 'shinyness' it will have.

When you load up the Object WITH PBR, the difference is easy to spot!

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