I want to render two sheets of paper (one on top of another).
See e.g. the following images:
http://3.bp.blogspot.com/-Z_xcZG_0OpM/T6QQOa_85RI/AAAAAAAAY2Y/SfjXLhylBc8/s1600/IMG_5882.JPG
https://t2.ftcdn.net/jpg/00/67/30/75/240_F_67307554_13kmP5SBUF36d3HrbcR6O0swgZcv3Hhu.jpg

I want to get this tiny shadow which is formed by the topmost sheet on the
bottom one.
Since the distance between the sheets is VERY small, I cannot just place two
meshes with different z-coordinates.

I thought of using some multilayered texture:
1. bottom sheet
2. some shadow layer (???)
3. top sheet

Post a reply to this message

On 21-3-2016 7:18, bocovp wrote:
> I want to render two sheets of paper (one on top of another).
> See e.g. the following images:
>
http://3.bp.blogspot.com/-Z_xcZG_0OpM/T6QQOa_85RI/AAAAAAAAY2Y/SfjXLhylBc8/s1600/IMG_5882.JPG
>
https://t2.ftcdn.net/jpg/00/67/30/75/240_F_67307554_13kmP5SBUF36d3HrbcR6O0swgZcv3Hhu.jpg
>
> I want to get this tiny shadow which is formed by the topmost sheet on the
> bottom one.
> Since the distance between the sheets is VERY small, I cannot just place two
> meshes with different z-coordinates.
>
> I thought of using some multilayered texture:
> 1. bottom sheet
> 2. some shadow layer (???)
> 3. top sheet
>


>
>
>

It seems to me that placing two meshes, slightly offset vertically, is 
the best method and not difficult to build. A challenge would be if the 
sheets were wrinkled but I guess that is not your intention. The layered 
texture approach does not seem to me a very good solution. Personally, I 
always used the first approach in the past.

-- 
Thomas

Post a reply to this message

"bocovp" <nomail@nomail> wrote:

> I want to get this tiny shadow which is formed by the topmost sheet on the
> bottom one.
> Since the distance between the sheets is VERY small, I cannot just place two
> meshes with different z-coordinates.

"Can't" ??
I would guess that given what POV-Ray is capable of, that you just need enough
separation and the proper camera angle to be able to see the shadow.




You could add a fake "shadow layer" which is just another "piece of paper" lying
directly on top of the lower sheet.
texture {pigment {rgbt <0, 0, 0, 0.4>}}

Maybe there's something you can do with bicubic_patches and texture /
interior_texture.

I think you can define "negative light sources" and negative pigment values -
maybe you could investigate that.

I'd probably just start googling "POV-Ray paper" or some such variant, because
there's GOT to be plenty of pieces of paper modeled in the past.  Look in the
old IRTC archives for scene files.   Scroll through the scene files sections of
this forum and see what's in there.

Post a reply to this message

Thomas de Groot <tho### [at] degrootorg> wrote:
> On 21-3-2016 7:18, bocovp wrote:
> > I want to render two sheets of paper (one on top of another).
> > See e.g. the following images:
> >
http://3.bp.blogspot.com/-Z_xcZG_0OpM/T6QQOa_85RI/AAAAAAAAY2Y/SfjXLhylBc8/s1600/IMG_5882.JPG
> >
https://t2.ftcdn.net/jpg/00/67/30/75/240_F_67307554_13kmP5SBUF36d3HrbcR6O0swgZcv3Hhu.jpg
> >
> > I want to get this tiny shadow which is formed by the topmost sheet on the
> > bottom one.
> > Since the distance between the sheets is VERY small, I cannot just place two
> > meshes with different z-coordinates.
> >
> > I thought of using some multilayered texture:
> > 1. bottom sheet
> > 2. some shadow layer (???)
> > 3. top sheet
> >


> >
> >
> >
>
> It seems to me that placing two meshes, slightly offset vertically, is
> the best method and not difficult to build. A challenge would be if the
> sheets were wrinkled but I guess that is not your intention. The layered
> texture approach does not seem to me a very good solution. Personally, I
> always used the first approach in the past.
>
> --
> Thomas

I will need to render dozens of such papers stacked on top of each other.
Besides, I am going to render a video file where the scene is rotating.
So, I believe, even small offset being multiplied by, say, 20 will look no so
good at some particular camera positions.

Post a reply to this message

On 21-3-2016 13:44, bocovp wrote:
> Thomas de Groot <tho### [at] degrootorg> wrote:
>> On 21-3-2016 7:18, bocovp wrote:
>>> I want to render two sheets of paper (one on top of another).
>>> See e.g. the following images:
>>>
http://3.bp.blogspot.com/-Z_xcZG_0OpM/T6QQOa_85RI/AAAAAAAAY2Y/SfjXLhylBc8/s1600/IMG_5882.JPG
>>>
https://t2.ftcdn.net/jpg/00/67/30/75/240_F_67307554_13kmP5SBUF36d3HrbcR6O0swgZcv3Hhu.jpg
>>>
>>> I want to get this tiny shadow which is formed by the topmost sheet on the
>>> bottom one.
>>> Since the distance between the sheets is VERY small, I cannot just place two
>>> meshes with different z-coordinates.
>>>
>>> I thought of using some multilayered texture:
>>> 1. bottom sheet
>>> 2. some shadow layer (???)
>>> 3. top sheet
>>>


>>>
>>>
>>>
>>
>> It seems to me that placing two meshes, slightly offset vertically, is
>> the best method and not difficult to build. A challenge would be if the
>> sheets were wrinkled but I guess that is not your intention. The layered
>> texture approach does not seem to me a very good solution. Personally, I
>> always used the first approach in the past.
>>
>> --
>> Thomas
>
> I will need to render dozens of such papers stacked on top of each other.
> Besides, I am going to render a video file where the scene is rotating.
> So, I believe, even small offset being multiplied by, say, 20 will look no so
> good at some particular camera positions.
>
>

Assuming you use flat meshes, stacking is trivial using a #while or a 
#for loop with a very small vertical increment and a slight random 
rotation around the vertical axis. Very basic, and I guess that, 
whatever camera position, the scene will look good video or not.


-- 
Thomas

Post a reply to this message

On 3/21/2016 12:44 PM, bocovp wrote:
> I will need to render dozens of such papers stacked on top of each other.
> Besides, I am going to render a video file where the scene is rotating.
> So, I believe, even small offset being multiplied by, say, 20 will look no so
> good at some particular camera positions.


Thomas is right. I posted an image in p.b.i with 10 bicubic patches 
stacked on top of each other. (It was easier for me to use patches 
instead of meshes.)


-- 

Regards
     Stephen

Post a reply to this message

On 21.03.2016 13:44, bocovp wrote:

> I will need to render dozens of such papers stacked on top of each other.
> Besides, I am going to render a video file where the scene is rotating.
> So, I believe, even small offset being multiplied by, say, 20 will look no so
> good at some particular camera positions.

I would say it is the other way around: if you model the geometry
based on reality then chances are better that you still get good results
after changing camera or lighting compared to just faking the effect.

But of course, there may be other reasons to prefer a different
approach. Since you are doing animation performance may be a factor.
In that case using a simple box with marble pattern, black / white
color_map and slight turbulence might work.

Post a reply to this message

On 21.03.2016 20:42, Christian Froeschlin wrote:
> On 21.03.2016 13:44, bocovp wrote:
>
>> I will need to render dozens of such papers stacked on top of each other.
>> Besides, I am going to render a video file where the scene is rotating.
>> So, I believe, even small offset being multiplied by, say, 20 will
>> look no so
>> good at some particular camera positions.
>
> I would say it is the other way around: if you model the geometry
> based on reality then chances are better that you still get good results
> after changing camera or lighting compared to just faking the effect.
>
> But of course, there may be other reasons to prefer a different
> approach. Since you are doing animation performance may be a factor.
> In that case using a simple box with marble pattern, black / white
> color_map and slight turbulence might work.

Something like

     pigment
     {
       marble scale <0.01,1,1> turbulence 0.2 color_map
       {
         [0.15 rgb 0]
         [0.2 rgb 1]
       }
     }

although it needs high antialiasing so performance may not be great
after all. I needed at least +a0.0001 for closeup render.

Post a reply to this message

> "bocovp" <nomail@nomail> wrote:
>
>> I want to get this tiny shadow which is formed by the topmost sheet on the
>> bottom one.
>> Since the distance between the sheets is VERY small, I cannot just place two
>> meshes with different z-coordinates.

Just add a very small Y offset to the top sheets.
Something like 0.001*y is probably enough.

>
> "Can't" ??
> I would guess that given what POV-Ray is capable of, that you just need enough
> separation and the proper camera angle to be able to see the shadow.
>


>
> You could add a fake "shadow layer" which is just another "piece of paper" lying
> directly on top of the lower sheet.
> texture {pigment {rgbt <0, 0, 0, 0.4>}}
>
> Maybe there's something you can do with bicubic_patches and texture /
> interior_texture.

Can also be done with mesh provided that you add an inside_vector whitch 
can point straight up in this case.

>
> I think you can define "negative light sources" and negative pigment values -
> maybe you could investigate that.

Both lights, pigments, diffuse, ambient, emission, phong, specular and 
reflection can have negative values.

>
> I'd probably just start googling "POV-Ray paper" or some such variant, because
> there's GOT to be plenty of pieces of paper modeled in the past.  Look in the
> old IRTC archives for scene files.   Scroll through the scene files sections of
> this forum and see what's in there.
>
>
>

Post a reply to this message