This is a screenshot of Javier’s new version of the X-15 for X-Plane 10.  In this case I have hacked the rendering engine to show the specular channel* (the alpha channel) of Javier’s normal map as the texture of the airplane.  In other words, that is the per pixel shininess that Javier “drew into” the normal map.  there isn’t any lighting on the airplane; the bright edges are simply parts of the plane that are completely glossy.

Just look at how gnarly and detailed and full of goo it is!  When you look at the plane under normal lighting conditions you simply see the regular texture.  But when the sun reflects off of the plane, the reflection is messed up by this complex specularity pattern.  The fact that the sun reflections change unpredictably and dynamically is what sells the illusion.

I mention this because normal maps are expensive – they aren’t compressed and can chew up 4 or 16 MB of VRAM easily – they have to be at high resolution to get the subtle bump details.  As long as you’re going to have the resolution, make use of it by putting “texture” into the specular channel – it’ll make your materials seem a lot more complex.

X-Plane 10: X-Plane 10 will allow you to use a gray-scale PNG as a specular-only image, for this kind of “texture” at 1/4 of the VRAM cost, in case you don’t need the actual bump mapping.

* 3-d nerd: X-Plane’s terminology is different from what you’d see in a typical 3-d modeler materials editor.  What we call “shininess” is the specular level – that is, how bright specular hilights appear to be.  In a 3-d editor this is usually an RGB color, but X-Plane only gives you a single level control; the specular hilights take on the tint of the sun instead.

The “shininess ratio” or “specular exponent” you’d see in a 3-d editor isn’t available in X-Plane – it is set to a fixed exponent by the sim.  The unconventional names is a historical artifact.

About Ben Supnik

Ben is a software engineer who works on X-Plane; he spends most of his days drinking coffee and swearing at the computer -- sometimes at the same time.

8 comments on “Making Specularity Work For You”

  1. did you mean users can choose to fly with a “gray scale” colored aircraft vs the regular colored textured version? who would want to fly gray planes all the time?

    1. Not at all. In this picture I have temporarily hacked X-Plane to reveal an aspect of the authoring process for the education of third party authors. This is not something we will ship, it has no use to users. It just lets authors see how plane is built, sort of like an X-Ray.

  2. Mad detail on that X-15. Love the way X-Plane can crunch polys, and Javier knows how to sling ’em. Very, very happy that grayscale png’s will be used as specular maps in X-Plane 10. Fiddling with the alpha of a normal map is not for the faint of heart, even with a decent art proggie like Photoshop. What will the attribute command be, Ben? Has that been established?

  3. will xplane 10 have cubemap reflexions or is this considered too expensive? (specular-maps are a very oldschool way to fake “reflexions, while raytraced reflexions are a thing of the future, cubemap relexions that get generated every few seconds are a nice way to create great looks with reasonable computation)

    1. We will not have dynamic environmental reflections in 10.0.
      We _might_ have them in 10.x. It’s something we are interested in and it’s on the short list for the next set of ren features, but there’s no guarantees of course.

      I think they’ll be variably expensive based on ren settings…lots of ways to dial them up and down.

      I don’t think we’ll do static cube map reflections – what would you bake into the cube map?

      1. 6 renders from around the object of interest. i don’t think this would be needed to update often, could be done as a very low priority job. i have red that racing games do this,…e.g. 2003 project gotham 2 comes to mind.

  4. Maybe if you included a pikkie of the unhacked view plus both textures it would make more sense to the many unschooled in the finer points of specular maps. Otherwise what looks and shines like guano….

  5. More importantly, you need to do something about the constant ambient illumination that is haunting XP 9. Virtually all contours are lost in the parts not facing the sun. And I hazard the guess, normal maps are not going to show in these locations either.

    I read somewhere you already do lighting in linear space. Well then you could add some skylight no?

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