[Hands]

I'm tryin to do a creature with long ears and i did a like saliva effect before where it looked translucent but i can't remember how. If any1 knows of any tutorials on how to make a translucent effect or can give me sum info i'd appreciate it. =cD

[Ian Jones]

As usual in art and illustration, before a tutorial is really needed, I would suggest you simply observe something translucent that is around you. Real life has so many examples, whether it be man-made or from nature.

For example go and pick up a glass from your cupboard and observe how it looks, and how the environment through it looks. Unlike a matte surface that is opaque, transparent objects have to somehow show their form, yet also show the form of objects behind them. So how do they do that? Well as an example think about a car that has been just been painted, but is not all glossy and waxy yet. It wont have the shinyness and reflectivity of a car that has been waxed so it pretty much just looks like any other matte surface that can be rendered. Now consider the car after it has had wax applied. Rather than repainting it with a glossy paint they have just applied another surface which happens to be transparent and shiny / reflective. So you could for example paint a car as a matte object, then in a completely different layer paint the glossy wax. The wax is mostly transparent, but it conceals the matte object under it with reflections in some areas. Wherever a reflection of light is needed you can almost render it separately and treat it as a different object ( 3d programs use multipass rendering for just this reason ). It is when the two are combined that you see the whole effect come together. Go outside and observe that effect on your car (it has to be in some sort of sunlight to be visible). You should be able to see how the light effects the matte paint under the surface of the wax. You will also be able to see the areas which are mostly affected by the glossy reflections of the wax surface. Its a mix of the two.

So going back to the glass. Now you should realise that its like a mix of two things. The background rendered and then the shinyness and reflection in areas that the glass catches the light. It's a mix of transparent, semi-transparent etc... and you can do it using layers in photoshop, or the opacity settings with a Wacom tablet on one layer. Dont forget that glass also refracts or bends light. This is why when you look through the glass the background is distorted. Thats refraction and once again it can be understood by careful observation as well as science and tutorials, but thats a whole other subject and I won't get into that. Try something simpler without refractions to start with.

I hope that helps. If you want more specific advice just tell us what in particular you are trying to paint.

[Hands]

errr i meant to say i'm usin the transparency on the ears, sorta like the look of a bat wing. i'll try usin diff layers and opacity thx

[Ian Jones]

hehe sorry...

ok well I spose with the bat ears, you should consider that you wouldn't actually see through them much, even if at all. You would see that if a light shone from behind the ears they would light up in the thin areas, much like if you were to put a torch in your mouth, try this and look in the mirror it's cool!

Other things to note are the veins... you would see them when the light shines thru. Once again looking in the mirror or some sort of similar situation would be good reference.

Hope that helps.

[Utanapishti]

I would just like to say, for the record, that the difference between translucency and transparency is when something is transparent, you can see a coherrant image through the material, thus, glass and clear plastic are transparent materials. Translucent objects, however, does let through light, but the light bounces around inside and gets diffused, therefore, a sheet of paper, a cotton shirt and a human ear are all translucent objects.

Henrik Wann Jensen at Stanford has come up with a good way to approximate translucency in computer generated images, his research has been used, most notably, in the all CGI motion picture, Shrek.

Download Wan Jensen's technical paper "A Practical Model for Subsurface Light Transport".
Also, you should read this article by Neil Blevins, on the subject, it has some interesting photos of the phenomenon.

--
Hans Sjunnesson

[Tarandon]

quote:

---

Originally posted by Utanapishti:
I would just like to say, for the record, that the difference between translucency and transparency is when something is transparent, you can see a coherrant image through the material, thus, glass and clear plastic are transparent materials. Translucent objects, however, does let through light, but the light bounces around inside and gets diffused, therefore, a sheet of paper, a cotton shirt and a human ear are all translucent objects.

--
Hans Sjunnesson

---

Not entirely true. For instance, a sheet of glass, like the one in your window is transPARENT however, if that glass were to be tinted, red for example, it would be transLUCENT. Anything that does not allow 100% light through, is technically translucent (Within reason of course). A cotton shirt is not translucent, it just has holes in it. (You wouldn't call a fishing net translucent would you?) The human hear is not translucent either, it is quite opaque considering you cannot distinguish an image through it, the same goes for paper.

Hope that's a bit clearer.



[ January 20, 2002: Message edited by: Tarandon ]

[Ben Barker]

It's great how people in other countries call flashlights "torches". You post made me imagine an image of someone sticking a flaming, medieval style torch into their mouth in a dark bathroom. "It's cool!"

[Silverwolf]

Sorry to have to correct you Tarrandon, but transparent means that you can discern what is on the other side. So a red tinted window that you can see through, (no distortion of the light, just the color) is actually transparent.

Something is translucent when the light that passes through it is diffused or "bounced around" inside the object, (well said), making the image undiscernable.

So to put it simply, tranparent objects, you can make out what is behind them. Tranlucent objects you can see light comming through them only, the light has been diffused.

The words are often confused and even the Oxford dictionary concedes this with tranclucent.

Transparent: 1. Allowing light to pass through so that bodies can be distinctly seen.

Translucent: 1. Allowing light to pass through diffusely; semi-transparent. 2. transparent.

As for portraying them in art, it really depends on what your looking at.

Tranparent objects in general have increadibly smooth surfaces. If they don't then they distort the light, warping or diffusing the image. The surfaces usually reflect light to some extent. So you might get a reflection on them of the surrounds, especially the brightest pieces like the lights, (usually seen as bright spots on the transparent layer of liquid on the outside of eyes, these are just reflections of the light source in the scene). These reflections aren't total like in a mirror or a piece of chrome or polished metal, they are partial, tranparent, (there's that word again), kind of like light water colour wash over the image. There is also bending of light in most of these things, (look through a glass at home to see how this works...).

Translucent objects in general get lighter when you shine a light through them. In the instance of bats ears, they might be a grey color witha hint of brown untill you shine a light through them. Then they may turn mor of an orange colour, more reds as the white light passes through the skin which is full of blood, adding more of an orange cast to it, (increased red and white, maybe some yellow for the skin...don't know), but a lot of the time these things seem to have a light of their own, (which I suppose they do in a wierd way), almost glowing.

I just remembered I did a pic the other day with some translucency in it. The preying mantis below has a lot of tranclucency. Below the head, in the mid section and in one or two of the legs. Not sure if this is what you are looking for but hopefully it might give you some ideas, (this was done from reference mainly for the purpose of practicing portraying just this! ). I think it's a little dull but I learn't from it...:>

Sorry if I seem a bit picky but I've had problems with clients and work a couple of times because of these two often confused words!

Anyway, hope all this helps.

[Marvel]

I have to agree with Tarandon here, technically put only 100% transparent objects / spaces are _really_ transparent, eg. to that regard even air isn't transparent really - everybody knows how air eg. 'becomes' blue after a long distance, thus transparency is a mathematical absolute, like a circle, a straight line etc. It's like it isn't possible to make a full 100% reflecting mirror, it isn't possible to have space/object that would be 100% transparent (it ought to be a total vacuum in order to be that, and a total vacuum isn't possible to achieve).

And about that opacity one can see in certain places on your skin (say ears, nose, even in the 'webbing' between your fingers), it's called 'subsurface scattering' and as mentioned here before, Henrik Wann Jensen is one of the forerunners in that field of study (he had plenty of good stuff at siggraph last year, if a tad technical ).

Hope I wasn't too confusing here.

[Tarandon]

Thanks Marvel, I was about to flip out and then I read your post. At least I learned something in grade 12 physics eh?

Gotta run.

[Ian Jones]

Interesting discussion...

Some of those things mentioned I had not really thought about carefully. I think the argument is a little pointless, because you can't really separate the two terms from one another. However it is important to recognise the common associations with the words, like 'transparent = to see through' and 'translucent = to see through but diffuse'. So whenever we have to consider an object or surface that lets light pass through it we need to keep in mind both things. One thought provoking way to look at it would be this example.

Consider the difference between the view through a clear window, and a view through that same window with frost, fog, or condensation. There are two situations that require a close relationship of transparency and transluceny.

Well enough of my babbling.. hehe


btw Ben, "flashlights" is a funny one too, considering they don't flash! anyways..."flashlights" is a distinctly American thing, like "sidewalk". hehe.
But I agree, torch is a bit silly too.

[ January 21, 2002: Message edited by: Ian Jones ]