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Old 5th April 2021, 04:03 PM   #1
CraigSaunders
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Smile Exporting OBJ8 - Objects have different properties

Hi all,

I have recently created a scenery object for X-Plane 11 using AC3D. I have managed to apply textures to the whole object and export it to OBJ8 format for use in X-Plane 11.

Unfortunately, a few of the surfaces appear to have a darker appearance compared to the rest. I have tried to edit the material properties in AC3D, however the same properties are set for all objects. I can't for the life of me figure out why this is happening?

The culprit surfaces also have a 'bare metal' shine to them, whereas all others are just matte white with some shadow effects. Please could someone let me know how to fix this, as the textures I apply are being affected by this. I have even tried deleting the whole object and remodelling it to get the same result!

Please see attached picture. The textures have not yet been adjusted, this is just for the purposes of testing the model.

:?

Best regards,


Craig
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Old 6th April 2021, 12:41 PM   #2
humbug
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Default Re: Exporting OBJ8 - Objects have different properties

Well, I've never made any scenery object, just aircraft, but I'll throw out some guesses in the hope that I stumble across something helpful. It could be that you know all this, so forgive me if I say something obvious. . .

1) Are you texturing with AC3D textures or using a [myobject].png file? If the latter, then you will get different colors and shininess from your object's NORMAL_METALNESS setting (or not if commented out with # or deleted from the obj8 header) and the _NML.png file.

2) I have found that AC3D's export code will sometimes (often?) insert a code in the object file such as "ATTR_shiny_rat 0.200000" which impacts how shiny a portion of the object is. This is essentially manually changing the "GLOBAL_specular 1.0" value in the obj8 header from 1.0 to 0.2 for those triangles. Maybe this impacts how the portion of your object reflects light in X-P?

To get at this, open your *.obj file in a text editor and scroll down to the end or simply search for "ATTR_shiny_rat" and see if there are any in there. If you find one, the easy way to remove this is to simply comment out that line with "#", save and see what happens. If it's fouled up, you can just go in and remove the "#" easily.

3) I'm not seeing from your picture what's happening. Is the center portion clear? If so, you need to select those surfaces and "flip normal" (CONTROL-SHIFT_N or under the Surface menu). Surfaces have a direction. You *can* select one surface (only) and run "Unify Normals" under the Surface menu, but that doesn't always work for me. Maybe it will in this case though . . .

Well, let us know if any of this helps or show another pic or two and we can go from there.

Best,
Steve
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Old 6th April 2021, 03:06 PM   #3
CraigSaunders
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Default Re: Exporting OBJ8 - Objects have different properties

You've hit the nail on the head here I think. Thanks very much for your response. All of these have occurred to me, I tried changing the ATTR's in the OBJ8 code.

Turns out it was down to setting all surfaces to 'One Sided' within the X-Plane toolbar as part of the plugin. After doing this, the problem disappeared!

Thanks very much for taking the time to respond.


All the best,


Craig
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Old 6th April 2021, 06:40 PM   #4
humbug
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Default Re: Exporting OBJ8 - Objects have different properties

Great!

Perhaps you know this, but if you need two sided surfaces, the X-P plugin readme suggests not using 2 sided parts but two identical one-sided parts with switched normals for the "underside" part. I do this all this time. It's the "cull" "no_cull" calls in the obj8 file that slow things down apparently . . .



Steve
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