To see the glassy effect, you will need to place the glass object above a textured surface, otherwise it may not be noticeable enough. A photo is just fine for the job:
Now draw your glass object, here I used a rounded rectangle as I think it look smooth, but it can be anything: circle, ellipse, freeform. Depending on what you want to get (the type of glass) fill it with a light or dark color, with high transparency. Here I used a gradient going from transparent light gray to transparent lighter gray. A stroke (also transparent) is optional:
This is the simplest glass:
Let's make it stand out better by adding a shadow.
Add a new object with the same shape as the glass but with a slightly larger size (if your glass object is very complex, duplicate it and use outset), color it in black and move under the glass, it will work as a shadow:
Add blur to the shadow and decrease its opacity (the transparent glass must have a transparent shadow):
And have the simplest shadow:
However, I do not like this shadow, it is too dark and it change the color and transparency of my glass object so will use a Mask to get a clever shadow.
Duplicate the glass object (I made the copy red only to have it more visible for the tutorial):
Add a new shape (in my case a rectangle) with a size large enough to cover all the shadow. Color it in white (the color is very important for the mask operation) and move it below the glass copy:
Select both the glass copy and the white object and perform a Difference operation:
And get a white mask:
Temporarily move the glass object out of the way (either Cut it or lower it under the shadow), we need easy access to the blurred shape:
Select the white shape and the shadow and apply the mask:
And get this advanced (masked) shadow:
Now put the glass back (paste in place or raise, depending on how it was put out of the way) and get a much better (in my opinion) glass effect:
But we can abuse it even more, I will try now a magnification effect, our glass is not plain glass, it has optical properties :D
Duplicate the background photo, put it under both the glass object and its shadow and resize it (keep Ctrl pressed to preserve the aspect-ratio) to make it larger (do not add transparency, I made it transparent only to have the resize visible in the tutorial):
Make another duplicate of the glass object, select it and the resized photo and clip the photo:
FeedbackYou can leave comments, complaints, suggestions, praises on my blog.
Update: a Romanian translation is also available.
friends at OpenArt.ro, www.xdrive.ro and Inovatika for motivating me to write this.