"jr" <cre### [at] gmailcom> wrote:
> hi,
>
> "tmelram" <taj### [at] yahoocom> wrote:
> > Hi, I am using Blender to model and wanted to use POV ray to render my scenes.
> > But, I'm getting serious shadow issues. There seem to be triangles near wherever
> > there are shadows!
> >
> > A picture of the problem:
> > https://i.imgur.com/z6Ftxv6.png
> >
> > How can I remedy this??
>
> I guess it would be helpful to see the (generated) scene code.
>
>
> regards, jr.

Here's what happened when I  tried to use the code you posted:

https://i.imgur.com/vEm5hnZ.png

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hi,

"tmelram" <taj### [at] yahoocom> wrote:
> "jr" <cre### [at] gmailcom> wrote:
> > "tmelram" <taj### [at] yahoocom> wrote:
> > > "jr" <cre### [at] gmailcom> wrote:
> > > > "tmelram" <taj### [at] yahoocom> wrote:
> > > > > Hi, I am using Blender to model and wanted to use POV ray to render my
scenes.
> > > > > But, I'm getting serious shadow issues. There seem to be triangles near
wherever
> > > > > there are shadows!
> > > > >
> > > > > A picture of the problem:
> > > > > https://i.imgur.com/z6Ftxv6.png
> > > > >
> > > > > How can I remedy this??
> > > >
> > > > I guess it would be helpful to see the (generated) scene code.
> > > >
> > > >
> > > > regards, jr.
> > >
> > > Sure, here you go:
> > > ...
> >
> > not sure of the cause, but changing the light_source makes for a smooth shadow
> > line, ie I did:
> > ...
>
> Thanks, it worked!. But, it seems to have flipped the direction of the light.

yes.  I left out the transform.

> It's either upside-down,backwards, or both. I chose a simple sphere with one
> light just to test. But for a more complex scene it might help to know what
> exactly did you change to make it so that there wouldn't be any triangles. What
> did you do?

nothing else.

as Mr and B Pokorny have mentioned, perhaps use a "real" sphere, or, if there's
a need for the mesh2, try using 'smooth triangles' (see documentation on 'mesh2'
object).

sorry to be of little help, I do not use Blender.

> Also I found this article:
> http://wiki.povray.org/content/Knowledgebase:The_Shadow_Line_Artifact
>
> What do you think of it and the solutions?

depending on the scene you're working on, I think playing with 'shadowless' in
the lights, and or with 'no_shadow' object modifier, is definitely worth trying.


regards, jr.

Post a reply to this message

Le 2019-11-17 à 15:56, tmelram a écrit :
> Hi, I am using Blender to model and wanted to use POV ray to render my scenes.
> But, I'm getting serious shadow issues. There seem to be triangles near wherever
> there are shadows!
> 
> A picture of the problem:
> https://i.imgur.com/z6Ftxv6.png
> 
> How can I remedy this??
> 
> 
> 

This is a mesh sphere. The triangle are places where the triangles 
composing the sphere are actually pointing away from the light but their 
normals would demand that they be illuminated.

The usual solutions are :
Subdivide the mesh. (make the triangles smaller)
Use an area_light with the area_illumination feature. (make the 
terminator more fuzzy)
Rotate the object or change the location of the light. (shift the 
problem area out of view or shift the light so that it no longe cause 
the problem)

None of those are perfect. All often still show those triangles, but 
make them less visible or smaller. The last option listed can, in some 
cases, hide the problem area, but probably won't work in this case.

Post a reply to this message

Le 2019-11-19 à 07:27, jr a écrit :
> hi,
> 
> "tmelram" <taj### [at] yahoocom> wrote:
>> "jr" <cre### [at] gmailcom> wrote:
>>> "tmelram" <taj### [at] yahoocom> wrote:
>>>> "jr" <cre### [at] gmailcom> wrote:
>>>>> "tmelram" <taj### [at] yahoocom> wrote:
>>>>>> Hi, I am using Blender to model and wanted to use POV ray to render my scenes.
>>>>>> But, I'm getting serious shadow issues. There seem to be triangles near
wherever
>>>>>> there are shadows!
>>>>>>
>>>>>> A picture of the problem:
>>>>>> https://i.imgur.com/z6Ftxv6.png
>>>>>>
>>>>>> How can I remedy this??
>>>>>
>>>>> I guess it would be helpful to see the (generated) scene code.
>>>>>
>>>>>
>>>>> regards, jr.
>>>>
>>>> Sure, here you go:
>>>> ...
>>>
>>> not sure of the cause, but changing the light_source makes for a smooth shadow
>>> line, ie I did:
>>> ...
>>
>> Thanks, it worked!. But, it seems to have flipped the direction of the light.
> 
> yes.  I left out the transform.
> 
>> It's either upside-down,backwards, or both. I chose a simple sphere with one
>> light just to test. But for a more complex scene it might help to know what
>> exactly did you change to make it so that there wouldn't be any triangles. What
>> did you do?
> 
> nothing else.
> 
> as Mr and B Pokorny have mentioned, perhaps use a "real" sphere, or, if there's
> a need for the mesh2, try using 'smooth triangles' (see documentation on 'mesh2'
> object).
> 
> sorry to be of little help, I do not use Blender.
> 
>> Also I found this article:
>> http://wiki.povray.org/content/Knowledgebase:The_Shadow_Line_Artifact
>>
>> What do you think of it and the solutions?
> 
> depending on the scene you're working on, I think playing with 'shadowless' in
> the lights, and or with 'no_shadow' object modifier, is definitely worth trying.
> 
> 
> regards, jr.
> 
> 
The model already use smooth_triangle.

Using shadowless will kill any highlight from that light. It will also 
render the use of photons impossible as shadowless light NEVER shoot any 
photon.

Using no_shadow may hide those artefacts by suppressing self shadowing, 
but the object will no longer cast any shadow in the scene.

Post a reply to this message

Le 2019-11-17 à 18:03, Bald Eagle a écrit :
> 
> 
>>> Hi, I am using Blender to model and wanted to use POV ray to render my scenes.
>>> But, I'm getting serious shadow issues. There seem to be triangles near wherever
>>> there are shadows!
> 
> Well - those appear to be actual triangles.  Can you export from Blender with
> the msh2 object format, rather than mesh?
> Then you could use the smooth_triangles to get a better geometric surface.
> 
>
http://wiki.povray.org/content/Documentation:Tutorial_Section_3.1#Polygon_Based_Shapes
> 
> 
IIRC, Blender already export it's meshes with smooth triangles UNLESS 
instructed not to.

Solution : Subdivide the mesh. Wuill make the object use more memory.

Using an area_light with area_illumination can help make those less visible.

Post a reply to this message

"jr" <cre### [at] gmailcom> wrote:
> hi,
>
> "tmelram" <taj### [at] yahoocom> wrote:
> > "jr" <cre### [at] gmailcom> wrote:
> > > "tmelram" <taj### [at] yahoocom> wrote:
> > > > "jr" <cre### [at] gmailcom> wrote:
> > > > > "tmelram" <taj### [at] yahoocom> wrote:
> > > > > > Hi, I am using Blender to model and wanted to use POV ray to render my
scenes.
> > > > > > But, I'm getting serious shadow issues. There seem to be triangles near
wherever
> > > > > > there are shadows!
> > > > > >
> > > > > > A picture of the problem:
> > > > > > https://i.imgur.com/z6Ftxv6.png
> > > > > >
> > > > > > How can I remedy this??
> > > > >
> > > > > I guess it would be helpful to see the (generated) scene code.
> > > > >
> > > > >
> > > > > regards, jr.
> > > >
> > > > Sure, here you go:
> > > > ...
> > >
> > > not sure of the cause, but changing the light_source makes for a smooth shadow
> > > line, ie I did:
> > > ...
> >
> > Thanks, it worked!. But, it seems to have flipped the direction of the light.
>
> yes.  I left out the transform.
>
> > It's either upside-down,backwards, or both. I chose a simple sphere with one
> > light just to test. But for a more complex scene it might help to know what
> > exactly did you change to make it so that there wouldn't be any triangles. What
> > did you do?
>
> nothing else.
>
> as Mr and B Pokorny have mentioned, perhaps use a "real" sphere, or, if there's
> a need for the mesh2, try using 'smooth triangles' (see documentation on 'mesh2'
> object).
>
> sorry to be of little help, I do not use Blender.
>
> > Also I found this article:
> > http://wiki.povray.org/content/Knowledgebase:The_Shadow_Line_Artifact
> >
> > What do you think of it and the solutions?
>
> depending on the scene you're working on, I think playing with 'shadowless' in
> the lights, and or with 'no_shadow' object modifier, is definitely worth trying.
>
>
> regards, jr.

You left out the transform? Do you mind posting the code for that?

Post a reply to this message

hi,

"tmelram" <taj### [at] yahoocom> wrote:
> "jr" <cre### [at] gmailcom> wrote:
> > > Thanks, it worked!. But, it seems to have flipped the direction of the light.
> > yes.  I left out the transform.
> > ...
> You left out the transform? Do you mind posting the code for that?

yes, no "transformation matrix" (same code as shown before):

#if (0)
light_source {
    < 0,0,0 >
    color rgb<2, 2, 2>
    spotlight
    falloff 22.50
    radius 19.125000
    tightness 0
    point_at  <0, 0, -1>
    fade_distance 12.500000
    fade_power 2
    matrix <0.901870, 0.180445, -0.392519,  -0.417916, 0.594587, -0.686886,
0.109441, 0.783522, 0.611650,  0.000000, 18.516430, 14.742990>
}
#declare lampTarget1= vrotate(<-0,14.74,-18.52>,<0.6492,-0.1814,0.4105>);
#else
light_source {0 colour srgb 1 parallel}
#end


regards, jr.

Post a reply to this message

Op 19/11/2019 om 18:50 schreef Alain Martel:
> This is a mesh sphere. The triangle are places where the triangles 
> composing the sphere are actually pointing away from the light but their 
> normals would demand that they be illuminated.
> 
> The usual solutions are :
> Subdivide the mesh. (make the triangles smaller)
> Use an area_light with the area_illumination feature. (make the 
> terminator more fuzzy)
> Rotate the object or change the location of the light. (shift the 
> problem area out of view or shift the light so that it no longe cause 
> the problem)
> 
> None of those are perfect. All often still show those triangles, but 
> make them less visible or smaller. The last option listed can, in some 
> cases, hide the problem area, but probably won't work in this case.

I agree. In my personal experience with mesh2 objects, subdivision is 
the best way to go. It means heavy subdivision is some cases, especially 
when dealing with smooth objects. Additionally, this can be alleviated 
to some extend by applying a (micro) normal to the object, as this also 
helps to hide the triangles.

-- 
Thomas

Post a reply to this message

On 11/17/19 3:56 PM, tmelram wrote:
> Hi, I am using Blender to model and wanted to use POV ray to render my scenes.
> But, I'm getting serious shadow issues. There seem to be triangles near wherever
> there are shadows!
> 
> A picture of the problem:
> https://i.imgur.com/z6Ftxv6.png
> 
> How can I remedy this??
> 

I don't use meshes often myself, but played with your scene a bit today 
using the shipped shapes.inc HF_Sphere macro to learn. I had to 
sub-divide to around 2500 points before the artifacts mostly gone and 
10000 points before really clean. Renders without AA. Your original mesh 
had 482 points.

FYI. The problem here is a general one and called variously out and 
about as the "terminator shadow artifact" / "terminator artifact" / 
"terminator issue" / "shadow artifacts" and so on. A few tools have 
claimed fixes - which involve on the fly fudging of one sort or other 
where I've peaked at them. Christoph (clipka) was working on / had in 
mind some 'fix' for POV-Ray, but not sure where it stands implementation 
wise.

The workarounds others have suggested are the ones I'm aware of for 
POV-Ray.

Bill P.

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Le 2019-11-20 à 02:25, Thomas de Groot a écrit :
> Op 19/11/2019 om 18:50 schreef Alain Martel:
>> This is a mesh sphere. The triangle are places where the triangles 
>> composing the sphere are actually pointing away from the light but 
>> their normals would demand that they be illuminated.
>>
>> The usual solutions are :
>> Subdivide the mesh. (make the triangles smaller)
>> Use an area_light with the area_illumination feature. (make the 
>> terminator more fuzzy)
>> Rotate the object or change the location of the light. (shift the 
>> problem area out of view or shift the light so that it no longe cause 
>> the problem)
>>
>> None of those are perfect. All often still show those triangles, but 
>> make them less visible or smaller. The last option listed can, in some 
>> cases, hide the problem area, but probably won't work in this case.
> 
> I agree. In my personal experience with mesh2 objects, subdivision is 
> the best way to go. It means heavy subdivision is some cases, especially 
> when dealing with smooth objects. Additionally, this can be alleviated 
> to some extend by applying a (micro) normal to the object, as this also 
> helps to hide the triangles.
> 

Or use a noisy texture that can also help hide those triangles.

Post a reply to this message