Let's learn Values!

[Christian223]

I want to get better with painting values, and I noticed that some people also need it, so why not make a thread about values that everyone can contribute?. I am not a master about values but I can teach a couple of things or two to people who need it, but if you have something to share, please do so! I need to get better! :)

So why not start with simple sphere studies, here is a good place to try:
http://www.fineart.sk/show.php?w=215

And here is a little study by me, I was trying to get as realistic values as posible, I think "a" and "d" are the best ones. Ball "a" is too bright though, the other lack something, can't put my finger on what it is though, pleace share your critiques or tips/advice, thanks a lot.

[bloodless]

Hey nice thread you started there! could use some advice on values too!

[Christian223]

Thanks, I hope we all can learn something.

Here is another try, ball d. is a blurred version of version c, so it seems the stripes are well placed and more or less "accurate", it looks good I think, could be better i guess.

This spheres don't look too good without more light in the shadow area, as you can see.

Ball a. looks great, b. not so much, I rendered b. with a very small brush ad shown in the little black dot in the upper right part, maybe it needs a better "
gradient from shadow to light, maybe that's why It doesn't look as good as a., or maybe it's that it has no speculars, and speculars make everything look more realistic?, I dunno.

In case you never saw it, check this out, it has some rendereing tips: http://www.itchstudios.com/psg/art_tut.htm

[surfandsnow]

If you want to work on value in terms of materials then using 3d shader balls as reference could help.

http://mxmgallery.maxwellrender.com/

Ive been meaning to do some material studies for a while.
I'll try to update with a few more material reference links and hopefully I can render some line art of some basic forms as a standard outline to practice materials with.

[Christian223]

Those are good ideas, I'll try getting some reference photos to study and I'll also try some of those materials.

Here are a few more of my studies. One of the important thing I learned is that in ball d. the darkes value on the corners should be very short and have a very smooth transition, otherwise the ball looks distored as if the corners where flat pointing to the viewer, if the transition is smooth and the dark values are change rapidly, (meaning that the dark value goes from 30% brigthness goes to 60%, instead of 30% to 40%) the correct effect can be achieved, the sides of the ball point to the sides instead of to the viewer. I hope that makes sense :), the thing is: flat surfaces have a constant value without change, so make sure to make smooth changes even when the jump in values is big.

[Muz]

Make your background a mid tone, and stop using such a bright highlight.

Highlights should be the cherry on the cake :).

[Christian223]

Thx for the tips Muz, I impleneted them in this study.

I was browsing through that MaxwellRender page and some of the materials have things I do not understand, I mean, textures, glow, speculars, reflections, and other weird things, all mixed together at once, since I do not understand how reflections and speculars and glows work together it makes the study imposible, I tried it and i just got very confused, so I think I'll leave it for later :)

I got a picture of a pool ball to study, here is what I learned.

1) A small change in value can still make a lot of difference, no need to go to extremes to differentiate between shadow and light.

2) Smooth gradients are extremely important, the 2 last ones shows this perfectly, compare them with the second ball, all the difference is in the smooth gradient in the lighted area, the second one is just very flat, the two last ones have a very nice gradient.

3) The "terminator" or "last light" is also very important to convery realism, you got to make it hard to notice exactly where the light and shadow beign, but at the same time the change must be abrupt, there must be a sudden change, not a continuous smooth gradient from shadow to light.

4) as you can see there can be many different kinds of gradients, but the second and fourth ball show gradients that don't seem to work, maybe they would resemble reflecting materials if i took out the highlight, maybe they would look like very polished metal, I don't know exactly why they don't look too good as the others.

[Muz]

Dont ignore the bounce light from the ground, add that in and the balls will suddenly pop.


Oh and this thread is a gold mine of info for speculars... http://www.conceptart.org/forums/showthread.php?t=156556&highlight=specular

[surfandsnow]

@Christian223: you might want to take a look at some of the simpler materials first their are some simple ones there.

as far as the properties of light go, light is either absorbed reflected or refracted. I like to think of things in terms of 3's at various combination's.

absorption simply determines local value.

reflection
Diffuse
dull or diffuse surface reflect light in many directions so the light scatters evenly which results in lower contrast.

Shiny
as the surface material becomes smoother and shiny it will be able to clearly reflect the light source as a specular highlight. because the light is reflected more cleanly instead of being scattered the specular highlight gets brighter as the rest of the form get darker, long story short, higher contrast.

Reflective
at some point the surface becomes so smooth that it reflects the environment so the values have more to do with reflections than the location of the light source, reflections are hard.

refraction
transparent
light can pass through a surface cleanly and be refracted cleanly so that you can see clearly to the other side, clear clean glass with various amount of refraction.

translucent
sometimes light can still pass through something but is scattered in the process so you cant see whats on the other side.ex frosted glass, wax paper.

semi translucent or subsurface scattering.
light can pass through a certain amount of the material but not always all the way through and is often reflected back out of the material on a layer beneath the surface, some of the materials internal color can be picked up and emitted at thin points in the material. ex skin, wax .


I am trying to work on materials right now so this was a good opportunity for me to review and clarify these ideas.
I converted some of the shader balls to line art and provided a reflection reference.

Finally I have my first material study, the material is reflective but is somewhat translucent which is what is causing the specular highlights to diffuse.

more materials

http://www.luxology.com/asset/materials/
http://www.vray-materials.de/all_materials.php

[Christian223]

This study took me quite a while, in fact im stoping it right here or else im going to keep working on it forever, I want to move to another study.

What I learned from it is a very nice "template" for spherical objects regarding reflection, it is quite a nice study to learn how reflections work. I can say that thanks to the thread linked above by Muz (thanks a lot Muz! awesome thread) and this excersize, I finally understood how reflections work.

An important thing to have in mind is that the farther the reflection is, the darker it gets, and the closer the reflection is, the brighter, clearer it gets, that's why you can see smooth gradient from light to dark, this is important to give the sence of a reflective material.

@surfandsnow: thanks for those explanations, they are informative and pretty short, to the point, I like that :)

I'm going to try some new photo studies soon and some other material too, a rather shiny one.

[Christian223]

New study, nice :D

[Christian223]

A new value study, maybe the local value of the car is too high. More critiques regarding values are appreciated, thanks.

[kikindaface]

Wow christian, your studies are looking good ! We can feel the light on both your paintings !

Well, for the car, First, try to define a light source, then think about how where the light is hitting the surface. It should give you the main light and shadow areas ! Then you can add the bounced light, and, maybe another light source.

A good exercise is to paint with only black and white color, no grey ! ( just look through Mr delicious and Miles' sketchbooks, there is plenty of stuff like that ) It'll force you to think where the light hits the surfaces, and you should be able to create volume and some reconizable stuff with only black color !

Also, it's cool to learn values ! I ( maybe too late ) understood the importance of values (and i'm sure that you're not totally aware of the power of values, but the more you'll study it, the more you'll be aware of the importance of values in a painting :D ) ! but if you really wanna improve at values, you should try to make values studies either from life, or from color refs ! I always found it harder, because sometimes the hues and saturation are bothering you when you're trying to focus on colors, and well, sometimes, 2 colors havin different values will look similar, and vice versa, so studying from color ( and especially from life ) will really improve your values knowledge !

I see that you're trying to paint different materials and textures, it's cool, keep at it ! While you're painting them, try to analyze the material, and try to create some " rules" about how to paint metal, glass, etc ! Creating rules will help you to use your knowledge on you pieces from mind !

Also, to understand how light works, and being able to use it you should know some stuff about it ! Here are some resources :

http://www.itchy-animation.co.uk/light.htm
http://www.itchstudios.com/psg/art_tut.htm
http://conceptart.org/forums/showthread.php?t=148355 ( first part )
Mike Bierek's Mystery of From looks also really interesting !

About edges !

http://conceptart.org/forums/showthread.php?t=51913&highlight=edges

Well, i hope it helped you, if i'm wrong, please correct me, i would be glad to improve my way way of thinking regarding values !

[surfandsnow]

Cool, first, walid definitely had some pretty good thoughts on value, all good stuff.

It would definitely be a good idea to try and work from colored sources to try and understand the value of color better. Very simply put a key idea about color and value is that red and blue are generally dark and that yellow and cyan are generally bright and work from there.

The whole white/black exercise is pretty much about separating light and shadow to create a solid form, you can also try to block off the shadows with as few lines as possible. One thing thats helped me a lot with this exercise is to try and see the values as 2d Shapes Formed By the 3D Planes.

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On the car first off watch the perspective lines the far hubs seam off. With the specular highlights on the form, you want to gradate them to a bright point. It is a reflection of a light source after all and light light sources are often too small to be reflected evenly across a entire form. I am assuming off course that you wanted spec highlights because I can only see a few on the head light and roof, if you want speculars make them much brighter(If you were going for a different material ignore all that)

For the earlier study on the material I actually provided the one on the left as a reflection reference of the environment so that materials from the other sites could be analyzed and painted with the lighting information provided by the reflective reference, but that would be very difficult beyond the most basic materials though.

In regards to reflections most reflection are a extension of linear perspective, so reflection in curved objects are a extension of curvilinear perspective. when trying reflections in any curved surface pay close attention to the cross contours and there density.

some info on curvilinear perspective http://handprint.com/HP/WCL/perspect5.html
Some great tutorials on curved reflections http://www.conceptart.org/forums/showthread.php?t=84904 hmmm, something familiar about that thread, cant quite put my finger on it though :)

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As far as light sources go I try to simplify thighs to 4 types(there are more)

Quality
Direct - strong light from a single direction, ex the sun, flashlight
Diffuse - weak light from all directions, ex cloudy day, ambient light

Location
Point - local light source, ex light bulb flashlight
Parallel - light from far away source with parallel rays, ex the sun



In computer graphics their is something called ambient occlusion that is very similar to diffuse light. It is a type of lighting where the object is hit with light from all sides(ambient light) and then subtracted when interrupted by another object or something blocking the light(occlusion) (technically speaking, its a subtractive process).

The two main things that cause the ambient light to be occluded are crevi and proximity of objects. When two objects get closer to each other light is blocked and shadows occur(I like to call them proximity shadows). A crevice would be two planes with a acute angle, when light goes in it bounces back and forth between the two planes getting absorbed on each bounce, and thus has little chance of escape making the crevice darker. Youll also note that the darkest point is almost always in the pit of the crevice(like the corner of a wall).

Diffuse light is present in almost all lighting situations, but the thing that makes pure or only diffuse lighting bad is that even though it defines proximity and crevi really well it defines planes very poorly. More specifically obtuse planes because there is nothing to absorb or block the light and planes pointing in distinctly different directions have the same value.

Diffuse or ambient light also causes shadows to soften the further they get away from the source that created them and sharpen and darken towards the contact point(softer with distance). One more way of looking at diffuse lighting is to think about the number of angles a point has access to light. As a final note, without the presence of strong light and shadow local value takes a higher priority in a diffuse lighting situation.

similar but slightly different
diffuse- scattered light, cloudy day, slightly directional
ambient- fill light or sky light(blue sky) equal from all angles and directions
reflected light - heavily effected by distance, more directional. sharper,
harsher and more directional at a short distance and softer and more
diffuse at a longer distance(2-point lighting fill light bounce cards).


Diffuse lighting
-proximity of objects
-crevices
-local value
-soft shadows

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light and shadow exercise followed by 3d ref dump for copy(sry for the large number of images)

and so concludes my lengthy mindless rant, I always learn a lot when I write one these things

[Christian223]

Thanks Walid, very usefull links, here is another one I got:

http://www.handprint.com/HP/WCL/color11.html

The car has a lightsource, I think I'm having difficulties on getting the planes to match with it?. Thanks for reminding me about the bounce light, that's one of the things that really make something look realistic.

Thanks again, and post some studies of yours if you have them and if you want to, so we all can learn from eachother.