Making the Reflection Level Map
In CG we often defy the laws of physics to make things look better or look more accurate and this is a perfect example, we're actually going to use reflection mapping to make an object appear to be partially see trough and to make it appear like its changing the direction of the light that passes trough therefore making the areas you see trough the leaf look blurry, so you can say were partially faking transparency and refraction with reflection.
Why not simply use transparency or opacity? With reflections you can get control of how the things you see trough the object look and you don't get that control using transparency, with transparency all of the things that you see through the object remain the same. And opacity would make the object disappear entirely unlike transparency witch the object is see trough but its still there. If you place a real leaf in front of the television or monitor screen you will notice that you can see what is behind it but you will also notice that what you see is distorted, in other words it looks very blurry that's because
the leaf's thickness allows a rather high amount of light to pass trough it but as the light passes trough the leaf it leaves in slightly different direction causing the things you see to look blurry, you will learn how to fake this effect using reflections in a later tutorial.
What does the reflection level map do? We will make a reflection level map in order to control witch areas reflect more than others, for example we don't want the center vain to reflect as much, and a leaf is thinner on the outside than on the center therefore we will make the leaf reflect more progressively as it gets to the side edges and areas like the brown damage areas don't reflect as much as well. We will be able to achieve this using a reflection level map.
Start of by creating a new set and call it "Reflection Level", create a new layer inside it and call it reflection base. Control click on the specular level layer to select the leaf, this time shift marquee select to deselect one of the leaves. Activate the gradient fill tool, change the gradient type to "linear". Change the gradient so it fades from white to light gray and back to white again like you see here:
Now fill the leaf selection with the gradient like you see here:
This will make the outer edges of the leaf more reflective progressively from the center, do the same with the other leaf.
We're also going to duplicate details from our specular set to our reflection set, we'll start by duplicating the pattern
detail layer and moving it to the reflection set, rename it to detail reflection, adjust the hue/saturation by giving it a value of -10, now we want this to also fade progressively as it gets toward the edge, the way to do this is by first creating a mask layer with the "detail reflection" layer selected by clicking on the add layer mask button, do the same you did to
paint the fading color for the reflection base level but this time make it in the mask layer but this time make the
colors so they fade from white in the middle to dark in the edges like this:
Duplicate the leaf pattern layer from the specular set, move it to the reflection set and rename it accordingly, open the hue/saturation and change the lightness value to -50 since we don't want the pattern to reflect as much also.
For the last layer in the reflection level map we are going to paint the center vain of the leaf almost completely black because we don't want it to have any reflection at all. Make a new layer and call it center root reflection, Using a soft brush with no scattering nor textures and using the wireframe reference, paint on the inside of the center vain to make it completely black, after your finished apply a Gaussian blur of 15, make a copy of this layer and give a Gaussian blur of 50 to the new layer, now make a copy of the new layer and merge the three layers together (control+e) and that finishes the reflection level layer!. here's a screen of the finished reflection level map.
Here's a render with the reflection level map at work, you might not see if straight off but you will definitely see a difference if you compare it to the dirt leaf render. This effect should not be exaggerated, we don't actually want people to recognize what they see trough the leaf and too much of it makes the leaf look like a cheat of plastic, we want to keep it at a subtle amount, this will also make the leaf blend in just about any environment by disguising itself with some of it's color.