Any way to get milk-glass or transluminance?


(Tiberius) #1

Are there any tutorials to get such effects?

I would like to make a tree where the leaves are luminated on their backside by sun. The leaves themselves should then emit some of this light on the opposite side - and maybe structures which are inside the leave should appear also.

I dont know the correct name for this effect (google was’nt that good with “transluminace”) but I would appreciate any hints from the experts here :stuck_out_tongue:

Thanks,
t


(osxrules) #2

I think the experts are all busy so you’ll have to make do with me ;).

I reckon the effect you want is translucency. There is a slider in the Blender materials for it just below the specular section.


(sundialsvc4) #3

One way that you could do it would be to coat the leaves with a material that emits light.

Always remember as a rule of thumb that, in the CG world, you do not have to actually mimic reality; you only need to do something that convincingly appears to do so. The viewer is, of course, thoroughly familiar with the real world and will interpret what he sees in terms of the real world, as long as you do not present him with any obvious inconsistency.

Consider, for example, how they create the illusion in the theatre that a scene is in sunlit woods. The quality of the light … provided by a simple gobo on the lens of a spot … carries the effect. Actual trees are not required. It can be very informative to assist a professional studio photographer when s/he’s setting up a catalog or food shot. If you knew what that “tasty food” actually was, you would not eat it! “Models cry glycerin tears.”

You do not have to simulate the total effect perfectly. You only have to do it well-enough to be convincing, for this shot. There might be several light-qualities (or whatever) that might be present in the “real” scene, but only one or two of them are most noticeable. Do only those.

Every shot is different. For instance, any shot where translucency of leaves is very apparent is probably an extreme close-up. Okay, what is the quality of this shot that is going to make your eye say, “oh, looky, there’s sunlight shining through the leaves!” Now, try to list at least six different ways that you could “cheat” to get that.

When you “CUT TO” the next shot in the same picture, maybe a medium shot covering some bit of action, then you do not actually have to carry the effect consistently throughout. Having seen the effect the first time, the viewer remembers it and “sees” it even if it is not actually there. (Case in point: Star Wars Episode I actually shipped to theatres with a crowd-shot in the Pod Race sequence where the crowd actually consisted of painted Q-tips. No one noticed until a subsequent “Making Of” documentary purposefully exposed the trick.) As long as the play of light along the ground (gobos again…) is consistent with what the trees have been shown doing, you can safely cheapen the rendering.

Remember that in CG you can also do things in “layers,” shooting more than one strip of film and superimposing it seamlessly. Maybe you could do a general “bright wash of color,” maybe (literally) in Gimp or Photoshop, make that wash very translucent (low Alpha value), then sandwich that layer on top of everything else using Blender’s Sequence-Editor tool or a third-party tool like After Effects, Premier, or even iMovie.

There is no rule that says that a finished image must pop-out of the initial rendering pass, just as there is no rule that says you must simulate physics. Be creative in your cheating. It’s not cheating, after all.


(purple) #4

Subsurface scattering is often used for the ‘milk-glass’ type effects - leaves, skin, fluid, etc. translucency.

have a look at this - http://www.elysiun.com/forum/viewtopic.php?t=30101

If you do a google search on ‘subsurface scattering leaves’ it returns a lot of papers on the subject.

It’s a heavy technique to use for what you want. I think a material with reasonable ‘translucency’ and a textured light (like effect used to get stained glass) is enough to get good results.


(Tiberius) #5

Many thanks for this great information. It helped me a lot. Let’s see what the result is … :o

Cheers,
t


(Marty_D) #6

Hey Tiberius. Just wanted to make sure you’re aware of the very fast faked SSS python script from the Make Human project. Can be found here.
Simple Subsurface Sampling
SSS on leaves with real thickness and sundialsvc4’s trick of adding a glow (and all that other expert advice(I should be taking notes or something)) would render a nice effect. (hmm, very nice (makes a quick mental note)).


(Tiberius) #7

It was a very interesting reading about SSS. I think for my problem this is maybe “too real”. I tried out Translucency and made a little test render (see below). It looks pretty much like the effect I was looking for my exercise.

Is there anything SSS would make better for this kind of application? … Still learning :slight_smile:

OK. this is my test-render:

http://img447.imageshack.us/img447/9726/leaves6rz.jpg

Objects are pretty cheap just to get an imagination… I also followed the recommendation to set some Emit on the leaves Material with the result that the leaves which are directly hit by sun rays really glow a bit and those which are located in shadows appear more dark.

Regards,
t


(indigomonkey) #8

I believe enabling TraShad on the ground (or whatever the shadow of the leaves is falling on) will make the shadows green (or whatever colour the leaves are). This may help to add to the reality.