well, I have a little question because I have often read about "artifact" on
sooth_triangle but I don't understand. It is very difficult for me to translate
technical language and figurative sayings. Now I have started translating the
include files of my PovRay library that I interface with CAD, triangle to
smooth_triangle.
This wheel has black corners (two), on the right. Are these common artifacts, or
can I fix them?
Thanx in advanced!
G.

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"GioSeregni" <gms### [at] hotmailcom> wrote:
> well, I have a little question because I have often read about "artifact" on
> sooth_triangle but I don't understand. It is very difficult for me to translate
> technical language and figurative sayings. Now I have started translating the
> include files of my PovRay library that I interface with CAD, triangle to
> smooth_triangle.
> This wheel has black corners (two), on the right. Are these common artifacts, or
> can I fix them?
> Thanx in advanced!
> G.

I think you might be seeing the same bug that I've been seeing.

instead of pigment, try using (_BOTH_)

texture {pigment {rgb 0.1} finish {specular 0.4}}
interior_texture {pigment {rgb x*0.2} finish {emission 1}}

And see if those "corners" turn red.
If so, we're seeing the underside of those triangles, when we shouldn't.

- BW

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"Bald Eagle" <cre### [at] netscapenet> wrote:
> "GioSeregni" <gms### [at] hotmailcom> wrote:
> > well, I have a little question because I have often read about "artifact" on
> > sooth_triangle but I don't understand. It is very difficult for me to translate
> > technical language and figurative sayings. Now I have started translating the
> > include files of my PovRay library that I interface with CAD, triangle to
> > smooth_triangle.
> > This wheel has black corners (two), on the right. Are these common artifacts, or
> > can I fix them?
> > Thanx in advanced!
> > G.
>
> I think you might be seeing the same bug that I've been seeing.
>
> instead of pigment, try using (_BOTH_)
>
> texture {pigment {rgb 0.1} finish {specular 0.4}}
> interior_texture {pigment {rgb x*0.2} finish {emission 1}}
>
> And see if those "corners" turn red.
> If so, we're seeing the underside of those triangles, when we shouldn't.
>
> - BW

THANKS! You are right, the red is here (elevated to see it better).
This knowledge is very useful! Many thanks again!
G.

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"GioSeregni" <gms### [at] hotmailcom> wrote:

> THANKS! You are right, the red is here (elevated to see it better).
> This knowledge is very useful! Many thanks again!
> G.

Well, you're _supposed to_ see _that_ red - those are the undersides of the open
mesh - the inside of the tire.

You were talking about the "corners" on the upper right of the tire, which
should be smooth, and the same color as the rest of the tire.

And if you DO see red there, then try moving the camera around, and viewing it
from different angles - because it may just disappear and pop up in different
areas.

- BW

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"Bald Eagle" <cre### [at] netscapenet> wrote:
> "GioSeregni" <gms### [at] hotmailcom> wrote:
>
> > THANKS! You are right, the red is here (elevated to see it better).
> > This knowledge is very useful! Many thanks again!
> > G.
>
> Well, you're _supposed to_ see _that_ red - those are the undersides of the open
> mesh - the inside of the tire.
>
> You were talking about the "corners" on the upper right of the tire, which
> should be smooth, and the same color as the rest of the tire.
>
> And if you DO see red there, then try moving the camera around, and viewing it
> from different angles - because it may just disappear and pop up in different
> areas.
>
> - BW

I think you are just looking at preview image. If you open it you will also see
the triangles of the right we are talking about. I kept about the same point of
view just to check on my first image. It seems that they always arise on the
perimeter of the volumes (in positions tangential to the cone of vision)...
However, the internal color makeup is useful, it can help mask a bit the bug.
I think you could mask it a bit with a generic "finish" using the outer color of
the face
Thanks!
G.

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"GioSeregni" <gms### [at] hotmailcom> wrote:
> "Bald Eagle" <cre### [at] netscapenet> wrote:
> >
> > And if you DO see red there, then try moving the camera around, and viewing it
> > from different angles - because it may just disappear and pop up in different
> > areas.
>
> It seems that they always arise on the
> perimeter of the volumes (in positions tangential to the cone of vision)...

Yes, that is where those artifacts sometimes appear on a smooth-triangle object.
I think it also depends on the lighting angle, and maybe even the size of the
triangles.

What you are seeing is a known effect of raytracing the smooth normals when they
are viewed at that raking angle. (I thought that there was a short technical
explanation of this in the documentation, but I cannot find it.) The camera is
picking up the unlighted (black) interior of the object.

If I make a low-rez height_field and add the 'smooth' keyword, the same thing
happens. The interior_texture trick is one way to try and make these artifacts
less noticable. Or try adding the 'double_illuminate' keyword to the object. If
I recall, this was a recommended 'fix' for the problem. It seems to work most of
the time, but not in every situation.

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"Kenneth" <kdw### [at] gmailcom> wrote:
> "GioSeregni" <gms### [at] hotmailcom> wrote:
> > "Bald Eagle" <cre### [at] netscapenet> wrote:
> > >
> > > And if you DO see red there, then try moving the camera around, and viewing it
> > > from different angles - because it may just disappear and pop up in different
> > > areas.
> >
> > It seems that they always arise on the
> > perimeter of the volumes (in positions tangential to the cone of vision)...
>
> Yes, that is where those artifacts sometimes appear on a smooth-triangle object.
> I think it also depends on the lighting angle, and maybe even the size of the
> triangles.
>
> What you are seeing is a known effect of raytracing the smooth normals when they
> are viewed at that raking angle. (I thought that there was a short technical
> explanation of this in the documentation, but I cannot find it.) The camera is
> picking up the unlighted (black) interior of the object.
>
> If I make a low-rez height_field and add the 'smooth' keyword, the same thing
> happens. The interior_texture trick is one way to try and make these artifacts
> less noticable. Or try adding the 'double_illuminate' keyword to the object. If
> I recall, this was a recommended 'fix' for the problem. It seems to work most of
> the time, but not in every situation.

Ok, thank! I am working on .. it does not seems by light position, but by the
angle between WP and smooth_triangle (s) ...
Many thanks again!
G.

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"GioSeregni" <gms### [at] hotmailcom> wrote:
> "Kenneth" <kdw### [at] gmailcom> wrote:
> > "GioSeregni" <gms### [at] hotmailcom> wrote:
> > > "Bald Eagle" <cre### [at] netscapenet> wrote:
> > > >
> > > > And if you DO see red there, then try moving the camera around, and viewing it
> > > > from different angles - because it may just disappear and pop up in different
> > > > areas.
> > >
> > > It seems that they always arise on the
> > > perimeter of the volumes (in positions tangential to the cone of vision)...
> >
> > Yes, that is where those artifacts sometimes appear on a smooth-triangle object.
> > I think it also depends on the lighting angle, and maybe even the size of the
> > triangles.
> >
> > What you are seeing is a known effect of raytracing the smooth normals when they
> > are viewed at that raking angle. (I thought that there was a short technical
> > explanation of this in the documentation, but I cannot find it.) The camera is
> > picking up the unlighted (black) interior of the object.
> >
> > If I make a low-rez height_field and add the 'smooth' keyword, the same thing
> > happens. The interior_texture trick is one way to try and make these artifacts
> > less noticable. Or try adding the 'double_illuminate' keyword to the object. If
> > I recall, this was a recommended 'fix' for the problem. It seems to work most of
> > the time, but not in every situation.
>
> Ok, thank! I am working on .. it does not seems by light position, but by the
> angle between WP and smooth_triangle (s) ...
> Many thanks again!
> G.
Bug hacked?
old sprites concept? I'm under no illusions, I'll do more tests, but in this way
I don't see the bug anymore

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Le 2023-11-24 à 16:19, GioSeregni a écrit :
> well, I have a little question because I have often read about "artifact" on
> sooth_triangle but I don't understand. It is very difficult for me to translate
> technical language and figurative sayings. Now I have started translating the
> include files of my PovRay library that I interface with CAD, triangle to
> smooth_triangle.
> This wheel has black corners (two), on the right. Are these common artifacts, or
> can I fix them?
> Thanx in advanced!
> G.
> 
That can happen when you can see the triangle but it's normal is 
pointing away from the camera.

Try rotating the tire along it's axis.

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"GioSeregni" <gms### [at] hotmailcom> wrote:
> "GioSeregni" <gms### [at] hotmailcom> wrote:
> > "Kenneth" <kdw### [at] gmailcom> wrote:
> > > "GioSeregni" <gms### [at] hotmailcom> wrote:
> > > > "Bald Eagle" <cre### [at] netscapenet> wrote:
> > > > >
> > > > > And if you DO see red there, then try moving the camera around, and viewing
it
> > > > > from different angles - because it may just disappear and pop up in
different
> > > > > areas.
> > > >
> > > > It seems that they always arise on the
> > > > perimeter of the volumes (in positions tangential to the cone of vision)...
> > >
> > > Yes, that is where those artifacts sometimes appear on a smooth-triangle object.
> > > I think it also depends on the lighting angle, and maybe even the size of the
> > > triangles.
> > >
> > > What you are seeing is a known effect of raytracing the smooth normals when they
> > > are viewed at that raking angle. (I thought that there was a short technical
> > > explanation of this in the documentation, but I cannot find it.) The camera is
> > > picking up the unlighted (black) interior of the object.
> > >
> > > If I make a low-rez height_field and add the 'smooth' keyword, the same thing
> > > happens. The interior_texture trick is one way to try and make these artifacts
> > > less noticable. Or try adding the 'double_illuminate' keyword to the object. If
> > > I recall, this was a recommended 'fix' for the problem. It seems to work most of
> > > the time, but not in every situation.
> >
> > Ok, thank! I am working on .. it does not seems by light position, but by the
> > angle between WP and smooth_triangle (s) ...
> > Many thanks again!
> > G.
> Bug hacked?
> old sprites concept? I'm under no illusions, I'll do more tests, but in this way
> I don't see the bug anymore


WOW!
right no trick
left the concept ... SHAPE-in-out XOR SWAPSHAPE-out-in

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