I am a mathematician and I have been using povray for making pictures of 3D
surfaces which are fairly complicated. The results are much more beautiful than
what I can make using matlab or similar software but I feel like I am still
missing a great deal of potential.

I typically choose things like lighting, camera angles, colors, refraction, etc
etc almost arbitrarily. I lack the artistic training to have a good
understanding of the choices involved and I typically just change these choices
almost randomly to try and improve the picture. The resulting pictures are nice,
but still lacking quality and I want to learn how to get better.

As a typical example, I uploaded a rendered picture here:
https://imgur.com/KWl6oEy

In this sample, the background sky, lighting, and essentially every choice other
than camera placement is pretty much arbitrary. I don't have a great
understanding of how to use transmittance, reflection, lighting, etc to make
shadows and produce a nice texture. I can change these things and I get
different pictures, but I don't know how to make "intentional" changes to create
specific effects.

The images themselves represent objects with some mathematical relevance (called
manifolds for those interested). The green/red surfaces are generated as unions
of triangles (about 500,000 in this picture). The blue curves are generated as
unions of cylinders. There is probably a better way to use povray to generate
both types of object but this is likely the least of my issues.


Just a couple examples of things I would like to learn how to improve:

1. There is a great deal of fine detail here. Both the red and green surfaces
actually fold over themselves very sharply (like folding a piece of paper in
half) many times. However, I can't see this detail because the surfaces lack
texture or proper shadows.

2. In several places the reflection seems to make a the picture completely
white. Sometimes it looks cool but in other places it just looks washed out and
"hazy". I think this is because I don't know how to properly choose and place
lighting objects.

If anyone has any advice or resources for me to read I would be very
appreciative. I have read through much of the povray tutorials which covers the
kinds of functionality included in povray, but obviously its up to me to decide
how to use it and that is what I'm having trouble with. Thanks so much.

Post a reply to this message

"Shane" <shnkeply(at)gmail.com> wrote:
> I am a mathematician and I have been using povray for making pictures of 3D
> surfaces which are fairly complicated. The results are much more beautiful than
> what I can make using matlab or similar software but I feel like I am still
> missing a great deal of potential.

Welcome!  :)
I'm glad you're here - I dabble in your field as often as I'm able.
Planetary orbital mechanics, 1 and 2D Fourier transforms, parametrics,
isosurfaces, polynomials .....

> I typically choose things like lighting, camera angles, colors, refraction, etc
> etc almost arbitrarily. I lack the artistic training to have a good
> understanding of the choices involved and I typically just change these choices
> almost randomly to try and improve the picture. The resulting pictures are nice,
> but still lacking quality and I want to learn how to get better.

I'd start off with 3-point lighting
https://en.wikipedia.org/wiki/Three-point_lighting
http://warp.povusers.org/povtips/

Use a texture, even if it's a small and simple bumps or granite or agate.  I try
to keep my mathematical manifolds fairly matte, but I often use a finish
{specular 0.4} to give a slightly shiny plastic look.

> In this sample, the background sky, lighting, and essentially every choice other
> than camera placement is pretty much arbitrary. I don't have a great
> understanding of how to use transmittance, reflection, lighting, etc to make
> shadows and produce a nice texture. I can change these things and I get
> different pictures, but I don't know how to make "intentional" changes to create
> specific effects.

Check out
http://www.f-lohmueller.de/pov_tut/pov__eng.htm
it's an invaluable resource.
He's got great tutorials on realistic skies, water, media, etc.

Also - there are plenty of demo scenes in the subdirectories, and very useful
basic scene snippets in the drop-down Insert menu.

> The images themselves represent objects with some mathematical relevance (called
> manifolds for those interested). The green/red surfaces are generated as unions
> of triangles (about 500,000 in this picture). The blue curves are generated as
> unions of cylinders. There is probably a better way to use povray to generate
> both types of object but this is likely the least of my issues.

You absolutely have to check out Paul Nylander's page(s)
https://nylander.wordpress.com/2008/08/25/cross-section-of-the-quintic-calabi-yau-manifold/

He'll have lots of things you're interested in, and if you download the code
there, you'll see an excellent method of automating the triangular "mesh", which
vastly speeds up isosurface rendering.

And Mike Williams' isosurface tutorial.

Make sure you use an appropriate max_gradient, accuracy, and precompute.

> Just a couple examples of things I would like to learn how to improve:
>
> 1. There is a great deal of fine detail here. Both the red and green surfaces
> actually fold over themselves very sharply (like folding a piece of paper in
> half) many times. However, I can't see this detail because the surfaces lack
> texture or proper shadows.

I often draw a "line" - a showdowless cylinder from the light source to my
object or the origin, to see where it's shining from.

Put a thin box behind your object to give you some more visual cue from the
shadow it casts.

> 2. In several places the reflection seems to make a the picture completely
> white. Sometimes it looks cool but in other places it just looks washed out and
> "hazy". I think this is because I don't know how to properly choose and place
> lighting objects.
>
> If anyone has any advice or resources for me to read I would be very
> appreciative. I have read through much of the povray tutorials which covers the
> kinds of functionality included in povray, but obviously its up to me to decide
> how to use it and that is what I'm having trouble with. Thanks so much.

More to come - at work, and have to get back to it.   :|

Use the SEARCH at the top of the page, scroll through the image digest, and take
a tour back through the scene file section(s)  there are LOTS of great ideas
people have come up with --- too many to keep track of.

Post a reply to this message

Le 18-04-30 à 12:23, Shane a écrit :
> I am a mathematician and I have been using povray for making pictures of 3D
> surfaces which are fairly complicated. The results are much more beautiful than
> what I can make using matlab or similar software but I feel like I am still
> missing a great deal of potential.
> 
> I typically choose things like lighting, camera angles, colors, refraction, etc
> etc almost arbitrarily. I lack the artistic training to have a good
> understanding of the choices involved and I typically just change these choices
> almost randomly to try and improve the picture. The resulting pictures are nice,
> but still lacking quality and I want to learn how to get better.
> 

Make sure that you use at least version 3.7. Version 3.8 is currently in 
it's alpha stage.

Don't forget that all colour, transparency, transmittance, 
reflection,... are in the 0..1 range. They are not limited to that 
range, but 1 stand for 100%. A colour picker can return something like 
<150, 255, 75> (in the sRGB colour space) that need to be scaled to the 
0..1 range. It can be dome like this :
srgb<150, 255, 75>/255

Use srgb for colours from a colour picker, and rgb for those that you 
create yourself.

Always use global_settings{assumed_gamma 1}. This ensure that any 
reflection, highlights and areas illuminated by more that a single light 
are computed correctly.

Start with the default camera : up = +y, right = +x, forward = +z
Don't change the angle or length of the axis just yet, use the default 
values. Only play with location and look_at. Place the look_at point 
close to the centre of your object, or some area of interest. Later, 
when you get a better feel of it, you can change some of those parameters.

All colours values are in the 0..1 range. You can have larger values, 
but they'll get clipped in the resulting image.
For your light, start with a brightness of 1.

A good start point is to have some «ground» plane :
plane{y, -10 pigment{checker rgb 1 rgb 0.3}}
It will show you where the shadows fall, and will give you a sense of scale.

When you change anything, only change a single thing at a time. That 
way, you can tell what it does.

Using coloured lights can help bring out the shapes.

If reflection make your object washed out, it may be because the 
reflection is set to high, or there is only white to reflect. Reduce the 
reflection amount to less than 1 and change the environment to something 
less white.
A surface with a reflection value off 1 it perfectly reflective, higher 
values break physics. It may help to use variable reflection like this :
reflection{LowReflection, HighReflection}
If you have set an IOR, then, you can use fresnel reflection model :
reflection{MaxReflection fresnel}

If you use transparency and reflection, it's good to add conserve_energy 
in your finish. It's important when you have variable reflection.

Keep the sum of the diffuse and reflection to less than 1. Default 
diffuse is 0.6, default reflection is 0.

Using specular or phong is a great way to get accents on your surfaces. 
Normally, you want to keep those in the <1 range.

The "refraction" key word is obsolete. Use some transparent colour and 
add an interior block where you set an IOR. This will automatically 
enable refraction. The IOR work the same way as in real life but without 
dispersion unless you add "dispersion Value" in the interior block.
You can set an IOR for any object, not only the transparent ones. In 
this case, it can affect the reflection when using the fresnel model.

When you have many triangles, using "mesh" instead of "union" make 
rendering more efficient without changing the visual aspect.

If you use some union of many cylinders to make a curved path, then a 
sphere_sweep will give you smoother results.

I very rarely use no_shadow for the objects, and almost never any 
shadowless lights.

Post a reply to this message

On 30-4-2018 18:23, Shane wrote:
> I am a mathematician and I have been using povray for making pictures of 3D
> surfaces which are fairly complicated. The results are much more beautiful than
> what I can make using matlab or similar software but I feel like I am still
> missing a great deal of potential.
> 

I think the attached pdf will be of help to you. It was written by Warp, 
a seasoned POV-Ray user, more than a decade ago but the advice is 
certainly still valid.

-- 
Thomas

Post a reply to this message

Attachments:
Download '4 tips to improve a simple pov.pdf' (304 KB)

On 01/05/2018 07:57, Thomas de Groot wrote:
> On 30-4-2018 18:23, Shane wrote:
>> I am a mathematician and I have been using povray for making pictures 
>> of 3D
>> surfaces which are fairly complicated. The results are much more 
>> beautiful than
>> what I can make using matlab or similar software but I feel like I am 
>> still
>> missing a great deal of potential.
>>
> 
> I think the attached pdf will be of help to you. It was written by Warp, 
> a seasoned POV-Ray user, more than a decade ago but the advice is 
> certainly still valid.
> 

Definitely worth reading.

-- 

Regards
     Stephen

Post a reply to this message

These replies are fantastic! This is a ton of resources outside of the povray
documentation that I hadn't seen before and was exactly what I was hoping for.
Thanks so much everyone.

Post a reply to this message

Le 30/04/2018 à 18:23, Shane a écrit :
> I am a mathematician and I have been using povray for making pictures of 3D
> surfaces which are fairly complicated. The results are much more beautiful than
> what I can make using matlab or similar software but I feel like I am still
> missing a great deal of potential.
> 
> 
> 

You can make a look at <http://louisbel.free.fr/scenes/scene000.shtml>



-- 
Kurtz le pirate
Compagnie de la Banquise

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On 05/05/2018 06:17 AM, kurtz le pirate wrote:
> Le 30/04/2018 à 18:23, Shane a écrit :
> 
> You can make a look at <http://louisbel.free.fr/scenes/scene000.shtml>
> 

That is super sweet. Thanks!


I love that you included the source codes. I am working on a cartoonish 
animation that has currently moved into space, and I am stuck thinking 
up ideas. -- I find this inspiring.

(I hope those two sentences translate ok to French.)

-- 
dik
Rendered 328976 of 330000 (99%)

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