Question about chrome and spec layers

[Boeing_Driver 76]

Hi there,

 

I'm working on a repaint of the PMDG J41 and the last thing left is the spinners, which I want to make chrome (all other repaints I have seen have black spinners).

 

So there are two texture sheets to consider, the fuselage and the fuselage Spec texture. Both have black spinners and both alpha channels are black. I thought it would be sufficient to change the spinner color on the main fuselage sheet from black to light grey and leave everything else the same but that didn't work. Since then, I've experimented with a lot of different combinations but the best I can come up with is a grey when viewed in the direct light--not a shiny silver. There is plenty of reflectivity on the other side of the plane (opposite from the sun), but the sun side looks non-glossy to me.

 

I confess, I don't have a great grasp of how the Spec texture affects this function in the sim.

 

Can someone point me in the right direction to get that true chrome look?

[EagleSkinner 36]

Apart from posting the same message three times in quick succession, I think you are in the right place here - I only hope the moderators don't delete the wrong thread and make you lose your answers, so if I were you, I'd delete the other two post haste.

 

Do you have the FSX SDK installed? It is on the "Gold" or "Acceleration" versions of the FSX discs.

 

Now, about the speculars - this is what the FSX SDK has to say about them:

 

Specular Map and Specular Alpha channel (Falloff map)

 

The specular map controls the specular characteristics on a model’s surface. There are two components to the map; the RGB and the Alpha. The RGB component defines the color and brightness of the specular highlights and the Alpha channel defines the falloff for those specular highlights.

 

Falloff refers to the sharpness of the highlight. A light value in the specular Alpha channel will result in a sharper highlight, where a dark value results in a broader, softer-edged highlight. Combining the RGB and Alpha values in various ways will result in a wide range of surface specular characteristics.

 

 

 

Being able to control the specular characteristics in a texture allows for much more freedom and control when defining the differing specular qualities of various types of surfaces. Before the inclusion of Specular maps, one would have had to define specular characteristics on a per-material basis; the increased flexibility of being able to define values in a texture should allow painters to create some very exciting effects. That’s the hope anyway.

 

Note that this map will need to be specified in the map slot referred to in the 3ds max Material Editor as the Specular Color slot. Click the slot and define the path for the map.

 

There are a lot more words about reflection and chrome effects but these two paragraphs should describe the basic essence:

 

There are two ways Reflection map values can be displayed. The material settings in 3ds max allow users to define whether those Alpha channel values are used to generate either a “gloss” or a “chrome” effect. The “gloss” algorithm takes the per-pixel values of the diffuse and environment maps and adds them to generate an end result pixel value which always ends up being lighter than the original value. This is useful for painted surfaces which would look less like chrome and more like a shiny surface.

 

The “chrome” algorithm takes the value from the Alpha channel and, depending on how reflective that pixel should be (defined by the grayscale value in the Alpha channel at that pixel), replaces the diffuse value with the environment map value. So, for a black area on the Alpha channel (fully reflective), the display engine would completely replace what is painted in the diffuse texture with what is in the environment map. This is not the same as adding the two values. The result will not move towards the white end of the spectrum; it will move towards a replacement of the Diffuse texture with what is in the environment map.

 

So basically, if the model maker has chosen to set the chrome effect on the 3D model, it is going to stay that way forever - you, the user, can't alter the model surface settings.

 

If he hase defined chrome effect to be a function of alpha channels, then you can text the level of chrome-ness by painting the diffuse texture of the spinner a 50% grey and paint exactly the same area on the alpha channel a 50% grey (very rarely do you need a full black to maximise your reflectivity (in fact, this is normally used to make transparencies transparent... and in FS9 you could make parts of the fuselage (like unwanted bombs) disappear - not in X though)

 

You really need to have the SDK to read. That way xou can also read the long chapters about how textures, cubic environment maps, speculars and alphas all interact. The chapter "FSX Materials" is especially interesting and shows you all the different ways speculars, diffuse and bump texture interact. What makes painting so fraught is the fact that each model maker has a different set of favourite values for how he sets and defines his materials in his 3D software (GMax, 3DS Max, FSDS etc.)

 

Sorry I can't give you a single definitive answer here.

[Leen3131cs 107]

Thanks for this excellent explanation Chris.

 

 

 

 

BTW, I removed the two previous posts about the same question.

[Boeing_Driver 76]

Hello Gents, I posted this before I went on vacation (once) and wasn't aware that it had posted 3 times. Thanks to Leen for removing the duplicates. :o)

 

Stormpup, to be sure, this is complicated business. I read and re-read your quotes and the instructions you provided but I still have a number of questions;

 

1. Does the alpha channel for the SPEC texture supercede the alpha for the main texture? In other words, does the effect of the alpha that is combined with the SPEC texture have a greater control on the overall reflectivity than the alpha that is on the main texture?

 

2. If I understand the information you provided, I would want to make the alpha for the SPEC pretty dark in order to get the reflectivity of chrome. But does the alpha from the main texture also influence the reflectivity?

 

3. Which texture determines the final color seen on the plane? The main one or the SPEC? Or do they combine to make a cumulative effect?

 

4. Lastly, I'm not sure which texture you are referring to when you suggest the 50/50% combination (main or SPEC).

 

Thanks for any help you can provide.

[EagleSkinner 36]

Real World has kept me busy (too busy) so sorry for the delay in responding...

 

1. The 'main' texture is called the diffuse texture. The alphas do not inter-mix between diffuse, spec, bump or emissive (that last means the textures with an '_l' in the name - lower case L) So although they don't directly affect each other, there is an indirect effect. The shinier (darker) the diffuse alpha is, then you will see more detail from the cubic environment textures.

 

These cubic environment maps are a totally different thing - they are a "six part" image (imagine the six faces of a cube) that depict the world around the aircraft. It would be possible to have a "live" environment map, but ACES decided not to at the time because of the hardware load, so they made a static image to save processing power. You can find these textures in the FSX/Texture folder - there's a series of them all starting with "GlobalEnv*****.dds" - open one in DXTBmp and you will see.

 

Back to the comment - you can make your own Global Environment maps - the more contrasty, the more pronounced the reflection. Some models come with their own Global Env textures. So depending on the modellers setting in the 3DS Max export (or GMax / FSDS) the diffuse alpha channel mixes the env-map with the diffuse image to give the model its reflectivity. The MS basic envmap is fairly neutral so a dark alpha still doesn't "reflect" too much. If you have the Ikarus Gold Pitts, as an example where the modeller has included his own envmaps, then this new envmap is a high contrasty image so the aircraft looks glossier.

 

So basically for (1) - the diffuse alpha works primarily with the environment map and the developer's settings for reflectivity.

 

2 The spec's alpha channel on the other hand, does all sorts of wierd and wonderful things that I haven't fully sorted out in my own head yet. You really have to see the SDK and read all about texturing aircraft models, because there are so many different ways that this alpha seems to affect the spec texture. But basically the prime function of the spec alpha is to control the "falloff" values.

 

What the hell is "falloff"? And well you may ask... Well, for one thing, this appears to also take an information feed from the Fresnel Ramp dds texture, so depending on the gradient of this texture, the falloff is either brighter or darker and the spec alpha makes the falloff wider or narrower. How the hell do I describe this?

 

Oh yes - try this. Normally the spec is merely a 180° colour rotaion of the diffuse map texture which has reduced saturation and increased brightness. You won't really spot much effect. BUT if you create a chromalusion effect - mercedes cars sometimes have this paint - for instance the main colour might be metallic blue, but as you change viewing angles, the colour appears to change to green or purple. To do this in a repaint you simply start with a blue diffuse and a strong green specular... So... when you observe the model in sim, you will see the blue diffuse paint and depending where the sunlight is, you will see a green sheen from the specular. Hang on - I have an image somewhere...

 

OK, it is a purple diffuse with a blue specular, but you can see what I mean:

 

 

 

 

 

Falloff is the ammount you can see of the specular depending upon the angle of the FS "Sun's" position relative to your plane and your viewing angle - so... if you have a darker spec alpha, you will get a wider amount of the spec colour over your diffuse colour.

 

Another fun feature of the specular is that whatever you paint here is only visible from the right lighting angle in sim. Here:

 

 

 

The diffuse texture is plain orange. The specular is actually the specular from Patty Wagstaff's paint (the Cirrus logos) - as you roll this particular paint round the sky, the Cirrus logo will come into sight and disappear as the sunlight's angle changes.

 

So to sum up (2) - the spec alpha controls how much of the spec is visible as the "sunlight" falls on the model. This is REALLY great for cool trick paint jobs. Some of my paints have "secret" Eagleskinner hints in the spec...

 

3. It's the diffuse that defines the final primary colour appearance of the airplane. The Spec controls the reflection's colours.

 

4. Sorry - I was referring to the diffuse texture. 50% grey on the texture and 50% on the alpha is merely a stating point - it just depends on the modeller's export settings how much grey you need on the texture and how much on the alpha - thus "trial and error". You can, of course, look at chrome bits on the modeller's model textures. Open them in DXTBmp and compare the colour and alpha channels. A great chrome example is the acceleration pack P51D Mustang - there are a couple of really nice chrome / polished aluminium textures - use these as a guide.

 

Have fun!

[EagleSkinner 36]

A quick postscript...

 

I should remind all of you reading my previous post - I am no expert on Microsoft and ACES usage of texturing aircraft models and the FSX SDK. I hardly understand some of the words they use, let alone how they interpret their own words. :Monkey:

 

If you really want to understand what I have written, you also really need the SDK on your PC so that you can see the examples that ACES made for us to see.

 

Oh yes - and here's a fun trick:

 

Make your own fresnel ramp - use a rainbow coloured flood fill. Try it on any aircraft model (don't forget to save the original fresnel ramp image). Be prepared for a surprise lesson in a "1960's suspicious substances" new perception of the world...

[EagleSkinner 36]

Oh yes, I just found another example of how a spec affects what you see. These images are taken from my current project - Texan T6 "Thumper 12" - and a test texture I used previously. I have only started painting the diffuse textures on "Thumper" so far. The specs are still from a "playaround" paint I was working on to test the paintkit.

 

On the shot below, you can see some stars on the nose cowling of the test paint:

 

 

 

On this next shot, you can see the current paint project (Thumper 12) and how the specular (which was simply left in when I created a new texture folder in "sim objects") shows through onto the "Thumper" paint:

 

 

[Boeing_Driver 76]

That's some really great information. Unfortunately. some of it is over my paygrade. :o(

 

Now, one of the things I don't know, is whether the modeller placed a limitation on the reflectivity as you mentioned in your first response. I'm proceeding on the assumption that they didn't.

So after getting your clarification about the diffuse texture determining the actual final color, I went and did a 50/50% like you recommended. That effort resulted in a darker than desired color so I lightened the diffuse grey of the spinner somewhat. Here is the latest result--below is how it looks in the shade side of the sun;

 

 

All in all, not too bad except for some small bit of weirdness on the tip.

 

And here is the other side, under direct sunlight;

 

 

As you can see, while the color looks more or less correct in the other pic, in this one, it looks too white. But worse than that, there's no reflectivity.

 

I'm going to mess around with the Spec and its alpha channel some more, because from you've told me already, I think the color is correct but the alpha needs to be changed.

 

Please feel free to correct me, if you see an obvious solution.

[Boeing_Driver 76]

Okay, so I changed the alpha channel on the Spec sheet to white and here's what I came up with:

 

 

Much better overall. The color isn't exactly perfect but I'm not sure which of the four variables would be best to tinker with at this point....

[EagleSkinner 36]

Not knowing what the modeller did is the fun part of the equation

 

Now I am assuming you want chrome spinners?

 

Like I say - the default P51 racer has a very nice looking polished metal finish. Maybe the Beech King Air spinners would help you too? Or the Baron? As for the fuzziness at the tip of the spinner... Have you painted enough area? Take a look at all of these models' diffuse and specular sheets to get a clue.

 

If I do some polished Aluminium soon, I'll post pictures of my progress... in fact... the next paint is a bare metal T6 Texan. My current one is a silver painted and polished version. look:

 

 

 

AHHH Found the examples I wanted to show! The best polished metal spinner effect I can offer is this one of P51 "Eleen and Jerry" - a friend of mine owns the real one and I have re-created her for FSX. Here with the default cubic environment:

 

 

 

Here are diffuse and alpha to show the levels of grey I used:

 

 

 

 

 

 

 

As you can see - I really do use a darker alpha... At its present stage of progress, this model is still using the default speculars from the Acceleration Mustang.

[Boeing_Driver 76]

Thanks for posting the textures themselves--you're right, that spinner is really nice. That's the chrome look I'm trying to achieve. Can you tell me which part of the texture sheet is the actual spinner? It's not apparent to me just from looking at the sheet.

 

Also, can you post the Spec and its alpha?

[EagleSkinner 36]

I'm sort of half way certain that the spinner texture is taken off the light grey bit to the right of the pilot's face. Obviously the alpha values are corresponding.

 

Here's another spinner:

 

 

 

This one has 60% black as the diffuse colour and 70% black as the alpha value. As you can see - two different planes with shiny spinners. On the Mustang the diffuse uses a lighter grey and on the T6 a darker grey as base colour. That is what I mean, when I say developers set their own values for reflectivity. Painting is a frustrating process all the way... just as you get used to one model, you have to learn a new technique for the next one...