Tips & Tricks
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February 14th, 2009
One of the more powerful but often overlooked tools in Adobe Photoshop is the Render/Lighting Effects filter. I use this filter often to add some texture and dimensionality to an image by creating a bump map. A bump map is an extra layer created to provide information abut the height of an image. In a 3D program, this grey-scale image would be used to render a little bit of bump on top of an otherwise flat surface. The white areas on a bump map are interpreted as the higher areas, while the black areas are the lowest parts. While Photoshop isn't a 3D program, I find the Lighting Effects filter to be perfect for making use of a bump map and adding a lot of subtlety to an illustration.
Let's look at some examples and step though how we go about creating a bump map. Here are some sneakers that I was working on for the 'StoryTime' illustration. I've got everything together the way I want it, but I'd like to add a bit of texture to the soles of the shoes. I'm going to use a bump map to create the waffled texture that I would like on the botton of my Vans.
The first thing I'm going to do is create a new layer to work on. On this layer, I start painting in where I want the texture to be. Mostly, I'm working with black. These areas that I'm painting will be depressed... No, not sad, just indented from the rest of the sole. I didn't use very much by way of white, just a small stripe that sticks out a little bit. The white is the higher-than-average area.
So black areas - things painted with a 0% brightness - are the deepest areas created by the bump map. White areas - with 100% brightness - are the highes spots. So what color do you imagine would produce a completely average height areas? That would be something with a 50% brightness... in other words, a perfectly grey zone. So let's create yet another new layer and fill it with a 50% grey. Make sure that this new layer is below the layer you have the painted bump in. Turn off all of your layers except for these two and you end up with something like the image below. The only catch is that we need this bump layer to not be a layer but a channel. Well, that's easy to fix: With just these two layers being views, go into your Channels window and copy the Red, Green, or Blue channel (they should all be identical at this point) into a new channel. Name the new channel "bump."
It's now time for the filter. We want to give the filter a clean surface to start from so let's turn off our bump layer and have the filter operate on the plain old 50% grey layer. Now go into Filter/Lighting Effects. Let's look at some of the parameters it requires. For Light Type you can use a Spotlight, an Omni Light, or a Directional Light. The first two have falloffs to the lights, but we want a nice steady light source to create a bump map so we'll choose Directional. On the left we can maneuver the light handles to choose what direction the light is coming from. I want the light coming from the upper left and the line on the left shows the light so arranged. The properties of the material will vary based on what you're working with. My sneakers are pretty obviously rubber so I choose a very low-gloss plastic material setting. For Texture Channel, we select the 'Bump' Channel that we just created. All the rest of the settings are for tweaking a little to ensure that the image on the left looks okay. You're shooting for the main part of the image to be something approximating our neutral 50% grey. When you think that you've got it, hit 'okay.'
So now our layer should look something like what you see below: No longer just a painted image, it's not the bumped-up layer that we saw in thumbnail in the Lighting Effects window.
Set this layer to 'Overlay' mode and make sure that it's on top of the layer we want it to affect (in this case, our sneakers.) The grey areas of the bump map (i.e. most of it) will not affect the underlying layer at all. The white areas of the new map will brighten what's below it, and the black areas will darken. Put it all together (and do a little bit of trimming) and you have some decent soles on your sneaks!
"Look, going good against remotes is one thing.
Good against the living? That's something else."
Okay, then, let's see how this technique would work for a more organic subject. Here we have an image of a person to start with. On a seperate layer I paint the black (deeper) lines. Then on another layer I paint the white (higher) lines. The second image is how the picture looks with both sets of lines over the face.
I also need to create my neutral 50% grey layer that I'll use as the background for the lines. At this point my layers are looking something like this:
Putting my painted lines and the grey together gives me the bump map on the left to use as the bump channel. Once I've applied the Lighting Effects filter to the blank grey channel using the bump map for height, I get the second image.
I set that layer to 'Overlay' and here we have our person in all of his wrinkly glory. If that's still not enough, you can also make visible (at a reduced opacity) the black and white layers that you painted to add a little punch. Here in the second image I have the black layer set to Multiply 50% and the white layer set to Color Dodge 50%.
And there you go!