fsx plane textures and fresnell

[crowbar2k]

I ve recently got the nemeth ec135 and downloaded the gfees texture that can be found on this sites downloads. In dx 10 this makes for a seriously reflective & shiny and jazzy looking heli but having had a look at the dds files the one difference seemed to be having a fresnell dds file included (though this looks to be a greyscale from white to black only 4 pixels wide)

I was expecting the spec map to be really extreme but it isnt - just a green shade

can anyone explain what the fresnell shader does for fsx? and whether it would be applicable to all aircraft ie if you put a fresnell.dds into another aircrafts texture folder could you have a similar increase in reflectivity?

[n4gix]

No. All textures used must be defined in the model prior to compilation. Without the actual source file(s), the end user cannot make any changes.

[crowbar2k]

so would the only way of telling be to look for some sort of white to black ramp among the dds files to know fresnell maps were usable?

do you know of many other aircraft that do have it specified?

[n4gix]

No, I'm not aware of any specific models that make use of the FSX fresnel ramp texture option. In fact, they don't even need to have a frenel ramp .dds file in the aircraft's ..\texture folder!

With the fallback options available via the texture.cfg file, it is quite possible that a model might use one of the several stock fresnel ramp .dds textures from the sim's default ..\Scenery\texture or ..\Texture folders.

[CBris]

There is a very good chapter on textures and fresnel ramps in the FSX SDK that comes with the Acceleration pack. Very much worth reading.

As you will see, the fresnel does need to be activated by the modeller.

And if you "mess around" with the fresnel ramp, you can often find some "interesting results... Try making a rainbow shade.

There are some 300 copies of the fresnel_ramp.dds on my PC - all in the respective sim objects folder, mostly in the aircraft, helicopter or boat's fallback folder.

Oh... DX10 is still not really a working proposition. Not even ACES supported its use really. Turn it off - it's a waste of resources And when DX11 comes, you can forget it for the sim anyway - unless MS surprise us all and make a patch. Or the graphics cards makers do something...

[crowbar2k]

the nemeth ec 135 is a well above average model but I can see why plane makers havent leapt at using fresnell much - having so much reflectivity on the surfaces really scrutinises the 3d model - any area where points or polygons have been reduced show up very strongly. I should think most fs 9 gen and even some fs 10 gen models would look terrible with it turned up as high as the gfees example


- I wouldnt like to guess how high model polygon numbers would have to jump before it is usable

[n4gix]

You won't find any real explanation in the SDK, unfortunately.

Fresnel ramps are used to affect a material or texture based on the angle of incidence between your view and the direction each polygon in the object faces. If you're looking at a ball then a fresnel ramp could be used to change how the part of the ball directly facing you looks versus how its edges that are facing away from you are shaded. So you could have the parts of the ball facing away from you tinted blue, and the rest red for instance. They can also control translucency in the same way. You can achieve some really amazing effects with them.

Specular maps on aircraft models basically control the shininess of of things, but they allow control on a per pixel basis rather than a global setting in a material like FS9 had. So with a specular map you can have say a black nose hood be a lot less shiny and 'glinty' than say a polished aluminum part. They can also be used to change the colour of the hotspot where the sun actually hits an object, making it slightly yellow or blue or whatever. In a specular map the RGB colour channels control the colour and intensity of the hotspot highlights and the alpha channel controls how sharp or broad the hotspot is. As an example both an orange and an apple are specular but an orange has a broader and lower intensity hotspot whereas the polished apple is much more 'specular' with a brighter smaller hotspot. Specular maps are great because unlike bump maps they cause very little performance hit.

The above explanations for frenel ramp and specular maps was provided by Mike Johnson (Lotus) in a thread from last year at AVSIM:
http://forums1.avsim.net/index.php?showtopic=242823