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Old 17th August 2006, 02:08 PM   #1
Reino
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Default Surface texturing

I make an irregular surface which will be extruded and the front should get a texture. Do I a polygon it is black and does not show the texture. If I do a polyline there is no surface to texture.
What am I not grasping?

Thanks, Reino.
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Old 17th August 2006, 03:27 PM   #2
Dennis
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Default Re: Surface texturing

What version of AC3D are you using? In pre 6.0 versions, this could be caused by the way vertices line up on your surface --- I don't remember if this was an issue in v5 or not?

In any case, I could see where this may also happen in v6 for certain polygon shapes. Can you post a screen shot of the polygon?
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Old 17th August 2006, 03:43 PM   #3
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Default Re: Surface texturing

I am using version 6. Here a screenshot to get an idea. Thanks for looking into it.

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Old 19th August 2006, 04:32 AM   #4
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Default Re: Surface texturing

Hi Reino,

I'm assuming the problem is with the "steeple"?

The angle of the screenshot isn't ideal --- it seems like from the angle it is at now, it would probably appear black-ish regardless of what it looked like from the side, based on how the headlight would hit it.

Can we get a more side-view of the problem (so we can see the problem polygons head-on)? Also, posting a wireframe + solid render would probably help too, so we can see how the polygons are arranged.

Dennis
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Old 19th August 2006, 12:01 PM   #5
Reino
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Unhappy Re: Surface texturing

Hi Dennis,
I see my screenshot is misleading in fact. The inner surfaces of the "steeple" are in fact not black and it appears only like that with the choosen perspective. However what I want to do is to texture the front side of this "steeple". It is an extruded polyline that does not have a surface in front and in the back.

The main building is now made from a box and can therefore be textured. Initially I wanted to make the whole thing out of one extruded polygon. Then I get a black front and backside which does not allow a texture.

I can not explain better at the moment.
Reino.
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Old 19th August 2006, 04:39 PM   #6
Dennis
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Default Re: Surface texturing

Quote:
Originally Posted by Reino
I can not explain better at the moment.
Fortunately, there's no need to --- I think I've reproduced the issue.

The best way to avoid these "black polygon" issues is to make sure all of your polygons are convex ( http://mathworld.wolfram.com/ConvexPolygon.html ). I think the concave parts of the polygons can sometimes confuse the normal calculations on complex shapes like this one, and you end up with a polygon that's sometimes black, sometimes not. Also, it makes things easier if you end up exporting your models to have all-convex polygons.

I've attached a shot that shows a couple of methods for creating the surfaces for the steeple front:

The model on the left was surfaced using "Create Ordered Surface". I basically just selected a set of 3 or 4 vertices at a time in counter-clockwise order and perform a Vertex -> Create Ordered Surface. Repeat until the polygon is filled.

A faster method is to select all the front vertices and perform a Vertex -> Create Mesh -> ....

The model on the right used this method. The only caveat is that it creates surfaces across the concave parts that you have to delete, but that's generally easy to do in one of the 2D views.

Hope that helps.

Dennis
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Old 19th August 2006, 04:53 PM   #7
Reino
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Default Re: Surface texturing

Thanks denis, I will try along your explanation.

Ed.: Your solutions work, are a bit labour intensive, depending on the complexity of the model. Found another way around. Doing a polygon with Vertex selected and going from the bottom right clockwise results in a white surface which can be textured easily. Just one of the solutions probably.

Last edited by Reino; 20th August 2006 at 03:47 PM.
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