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Black stains in my rendering?


 
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arennuit
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Joined: 06 Dec 2013
Posts: 70

PostPosted: Tue Jan 23, 2018 12:44 pm    Post subject:
Black stains in my rendering?
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Dear forum,

I have a OSG app which I have been using for a while to display complex meshes, grids, widgets... Now I am displaying a NURBS surface (well it is also seen as a mesh to OSG) which is the result of a points cloud fitting and I observe dirty black stains on the normally smooth grey surface that is drawn. You can observe them on the image below.

[img]https://ibb.co/d55AWw[/img]

Now I have checked with the OSG default shading and with my own custom Phong shading and both methods return the same black stains.


[img]https://ibb.co/er5urw[/img]

I initially thought that it was due to my surface being slightly rippled itself (it should not be rippled but that could have been a bug explaining the behavior observed in my rendering), but it is actually not rippled at all, as seen on the normals rendering below and where all the normals are cleanly aligned (except in the bottom right where the geometry is no longer planar - which is expected according to the fitted points cloud).

Any idea of where these dirty black stains could come from?

Thanks a lot,

Antoine.[/img]
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arennuit
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Joined: 06 Dec 2013
Posts: 70

PostPosted: Tue Jan 23, 2018 3:43 pm    Post subject:
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Dear forum,

EDIT: It appears the images of my last message did not go through, so here is the same post including the images.

I have a OSG app which I have been using for a while to display complex meshes, grids, widgets... Now I am displaying a NURBS surface (well it is also seen as a mesh to OSG) which is the result of a points cloud fitting and I observe dirty black stains on the normally smooth grey surface that is drawn. You can observe them on the 1st image below.

Now I have checked with the OSG default shading and with my own custom Phong shading and both methods return the same black stains.

I initially thought that it was due to my surface being slightly rippled itself (it should not be rippled but that could have been a bug explaining the behavior observed in my rendering), but it is actually not rippled at all, as seen on the normals rendering below and where all the normals are cleanly aligned (except in the bottom right where the geometry is no longer planar - which is expected according to the fitted points cloud). The 2nd image below shows the normals are very clean.

Any idea of where these dirty black stains could come from?

Thanks a lot,

Antoine.
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robertosfield
OSG Project Lead


Joined: 18 Mar 2009
Posts: 11802

PostPosted: Tue Jan 23, 2018 5:23 pm    Post subject:
Black stains in my rendering?
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Hi Antoine.

My best guess is that some of your normal, color or textcoord data is
corrupted in some way resulting in the black areas around some
vertices.

Robert.

On 23 January 2018 at 15:43, Antoine Rennuit <> wrote:
Quote:
Dear forum,

EDIT: It appears the images of my last message did not go through, so here is the same post including the images.

I have a OSG app which I have been using for a while to display complex meshes, grids, widgets... Now I am displaying a NURBS surface (well it is also seen as a mesh to OSG) which is the result of a points cloud fitting and I observe dirty black stains on the normally smooth grey surface that is drawn. You can observe them on the 1st image below.

Now I have checked with the OSG default shading and with my own custom Phong shading and both methods return the same black stains.

I initially thought that it was due to my surface being slightly rippled itself (it should not be rippled but that could have been a bug explaining the behavior observed in my rendering), but it is actually not rippled at all, as seen on the normals rendering below and where all the normals are cleanly aligned (except in the bottom right where the geometry is no longer planar - which is expected according to the fitted points cloud). The 2nd image below shows the normals are very clean.

Any idea of where these dirty black stains could come from?

Thanks a lot,

Antoine.

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arennuit
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Joined: 06 Dec 2013
Posts: 70

PostPosted: Wed Jan 24, 2018 6:23 pm    Post subject:
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Robert,

You are a magician!

It was faulty normals.

Thanks a lot,

Antoine.
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