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.

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