Adding a little ambient occlusion
Video: Adding a little ambient occlusionThe last property of light we'll explore on this castle is a catch-all for all remaining darks that I call ambient occlusion. The definition of ambient occlusion is if something is surrounded by other things, it is more likely to be blocked out by a shadow cast upon it or occluded. Ambient occlusion calculates how much of some object, such as a surface, is blocked out by something else as compared to how much of that object is open to the rest of the environment.
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After you've perfected your perspective drawing, the next step in the matte painting process is to layer in tone: the master tool in the matte artist's arsenal for establishing a fully formed structure. David Mattingly, a matte artist for many groundbreaking motion pictures, takes a black-and-white drawing and shows how to use the five elements of light—dark sides, light sides, cores, cast shadows, and final darks— to paint the surfaces and create a realistically shaded environment in Adobe Photoshop.
This course is part 3 in David's Digital Matte Painting Essentials series. Go back to part 2 to recreate the castle drawing he uses in this course, or if you simply want to learn more about form, you can use the example provided in the exercise files.
- Selecting the silhouette
- Find the dark sides and light sides in the drawing
- Using mask-holding layers
- Examining the light and dark sides of rounded surfaces
- Looking at the cores
- Adding cast shadows
- Separating surfaces with final darks
- Adding ambient occlusion
Adding a little ambient occlusion
The last property of light we'll explore on this castle is a catch-all for all remaining darks that I call ambient occlusion. The definition of ambient occlusion is if something is surrounded by other things, it is more likely to be blocked out by a shadow cast upon it or occluded. Ambient occlusion calculates how much of some object, such as a surface, is blocked out by something else as compared to how much of that object is open to the rest of the environment.
Believe it or not, that's the simple language explanation from Wikipedia. So let's take a look at an example to see if we can figure out what they're talking about. Where two surfaces meet at an interior angle that will become a little darker. So wherever you see an interior corner on our castle you should go through and subtely darken it. You'll need to finesse this one. You don't want a hard line but a soft shadow of darkness. Internal angles like this will be darker for a couple of reasons.
Ambient inclusion says we'll be getting less reflective light in a corner and natural weathering will make internal angles darker because of rain runoff. And dirt and crud that will get trapped in corners. First, load in the selection from the Silhouette layer so we can't paint onto the background. Make sure you're on your Final Darks layer. Then go all over your castle and find those inside corners. You'll generally want to take a couple of passes on this, building it up slowly so that you don't get a harsh line.
You should resize your brush as you work, putting a smaller dark line right where the walls meet and a larger pass to blend that in. Why doesn't this happen on exterior angles, like this corner of the castle? Because the surrounding surfaces are not blocking the reflected light. And an exterior angle won't pick up dirt from weathering.
Next, we'll deal with areas where one structure is in front of another. By applying a little dark tone behind the bastin on the wall, we clearly show that the bastin is in front of the wall. Add this tone to separate structures on both your light and dark sides to emphasize the form of your castle. As an artist, you'll want to cheat this a bit. Case in point is the footing on the front bridge. It's the same tone as the wall behind it. You'll want to add a bit of tone to separate it from the lower wall of the castle.
So load in the under bridge mask holding layer, Invert it and intersect it with the castle silhouette. Make sure you're still on your final darks layer and paint a little tone on the wall behind the bridge to make it fall back. This may not be completely realistic but it helps to set up the forms in space. This side tower is another example where Ambient Occlusion would be helpful in setting the tower forward of the castle walls. Since the tower is in front of the wall, it would be lighter than the walls of the castle.
Here I'm going to do some fancy mask loading by first loading in the castle silhouette. Then subtracting the Dome and Side Tower Mask Holding layer, and then darkening the walls of the castle right behind the side tower. Then subtract the bridges under Bridges and Lower Walls layer, to isolate the area behind the tower and bridge.
And add some tone to make the bridge to the side tower go back. We can also darken the area around that bridge to make it clear that it's projecting out from the wall. Other features that would be slightly darker are any cut lines on the castle. Let's go through and add some tone to the arch details of this lower wall. Ambient occlusion looks for areas of complexity and darkens them up and that's why in 3D programs, ambient occlusion darkens areas that have a lot of geometry.
Cut lines would also darken because they would collect dirt from weathering. These decorative cut lines on the edges of the bastions and castle walls should all be darkened. Since they're straight you can probably do a better job toning them if you have your brush set to a Soft Round brush. And then turn off Transfer in the Brush panel. This makes the brush always lay down the tone at full opacity and not be pressure sensitive. Press 3 to set the opacity to 30% so the line won't be too dark.
And go through and trace over these cut lines. Since you have transfer turned off on the brush, you can also click, hold down the Shift key and click again to get a straight line through two points. I'm going to speed this up by 200% so you don't have to watch me doing all of these cut lines in real time. If you want to fast forward to where this section is done, just look for where the 2X Speed icon disappears.
I'm going to slow down again to work on the dome. All of these detail lines on the dome can be darkened slightly.
And darken the arches on this tower. You should go through and darken the windows on the dome, also on the side wall.
And these two windows at the front of the castle. Now go through and darken in the areas that haven't been attended to and adjust any forms that still need work. Some of the cache shadows on the front of the castle are missing, so add them where needed. I've made an effort to stay organized and do the different kinds of toning and order but as you come close to finishing this section you'll need to skip all around and balance the different areas.
And finish the areas that you've missed. The area where this dome and tower are very close together should be darkened with an ambient occlusion shadow. The dome would be darker since the tower would block its light. So load in the Dome and Side Tower Mask Holding layer. Make sure you're still on the final Darks layer. And add a little tone to the area of the stone that would be darkened by the tower. The back of the stone would probably be darker all around, so go ahead and blend that in.
This back tower would also be darker, so load in that Towers1 Mask Holding layer and darken the area where the tower meets the dome. We're almost done. In the next section, I'll show you how to restore some of the line work from your drawing.
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