Making the Translucency Map

What is translucency? Translucency is when a light doesn't simply bounce off the surface but when a certain amount of light rays make it trough the surface and travel inside that given object until those rays get absorbed or leave in another direction therefore making other areas look illuminated. A leaf contains thin translucency, therefore a rather high amount of light will pass trough the leaf other than being reflected of absorbed, therefore making the opposite side of the leaf more illuminated as well as the front side or side with direct illumination. Right now standard max does not contain a very accurate model for making translucency, its translucency attribute works better with very thin objects but only to a certain degree, there could be more accurate models for making translucency with max using an extension but with this tutorial I want to make everything using the base app, therefore were going to be using max's translucency attribute in combination with self-illumination and luminosity to make it look like thin translucency is taking place. This will only work to a certain degree, this effect will look better on the side witch light hits it directly it will indeed look as if some amount of light was spread throughout the object's surface and made it trough the opposite side instead of just bouncing off, its disadvantage being that not much light will make it trough the opposite side but our leaf will the ability to be backlit but just to a certain degree. Take note that there are different ways to fake translucency an some ways look better for certain types of objects than others, therefore if you try to apply this thin translucency method to other thicker objects chances are that it will not end up looking correctly but this method should leave the doors open for experimentation for faking other kinds of translucency for other objects.

How will this translucency map work? This map will be used in combination with max's translucency attribute and the self illumination channel (called extra lighting in a raytrace map type). The translucency map will be connected to those two attributes using shadow/light falloff maps therefore making their influence stronger in the areas that light hits directly and falloff in influence toward areas that otherwise would be in shadow, unlike most of the other maps that we've been working on lately this map will use color information because both translucency and self illumination use color information too determine the color tone of the areas that are influenced by them, a real leaf would tend to have a greenish/yellowish tone in areas that are illuminated the most. Note that were going to recreate the way a leaf would look like under bright/sunny lighting conditions.

Making the Translucency map is going to be rather simple, it's basically going to be a copy of our reflection level set with a few modifications.

Right click on the reflection level set and duplicate it, rename it to "translucency map", the change we want to apply to this map is first of all to change the colors of the base color layer, we still want to use a gradient to fill it but this time w want it to go from darker on the sides and lighter in the center like the we painted for the mask in the pattern detail reflection layer. Therefore you could simply control click on the base layer to make a selection of the leaf than copy the image in the mask layer using this selection, paste and use as our base layer, delete the old base layer.

As we already know a translucency/self illumination map in this case does indeed need to use color information to get a better effect, therefore activate the pattern detail reflection layer and add a hue/saturation adjustment layer to it, that way the adjustment layer will only affect the base and pattern detail layers since we don't want translucency to add much color to details such as our brown damage and red damage, check colorize and give the adjustment layer a hue value of 58, saturation value of 65 and lightness value of -10, this should give you a yellowish green color tone.

For our last adjustment were going to change the color of our center root reflection layer, so open the hue/saturation for it, check colorize and give it a hue of 60, saturation of 50, and lightness of 13, adding a bit of translucency to the center vain will also make It appear to be a bit of a translucent material as it is. Here's a screen of the finished translucency map.

Here's a render with the translucency map in action, this makes a tremendous difference, it gives our leaf a whole new level in realism by changing the way the leaf interacts with virtual lights, its now starting to look as if some light scattered inside of it and passed trough the object.