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Using Projection Layers to create a gobos and projector type effects

COW Library : Adobe After Effects Tutorials : Rick Gerard : Using Projection Layers to create a gobos and projector type effects
Using Projection Layers to create a gobos and projector type effects



Projectors a plenty
Rick Gerard

Rick Gerard, Roseville, California
DP, Motion Graphics, Producer/Director, Special Effects
©Rick Gerard and CreativeCOW.net. All rights reserved.



Article Focus:
Rick Gerard explains the use of the Light Transmission property added to Layer Material Options in After Effects 5.5. Basic and advanced techniques demonstrate only a few creative possibilities opened up by this exciting new feature


Download: Advanced Movie,
Download: Fake 3D Movie
Project file Download Stuffit Expander for Windows


Introduction

 Prerequisites - Stuff you should know before attempting to follow through with this tutorial.
  1. Software: After Effects 5.5 (standard version)
  2. Footage: All required footage is included in the tutorial.
  3. Knowledge: You should have a basic understanding of the 3D features in After Effects 5.5 including how to manipulate layers in 3D space, add lights and cameras, and manipulate the Layer Material Properties in the timeline. Familiarity with basic expressions and parenting is also a plus.
  4. Time to complete: The tutorial will take thirty minutes to walk through, but I should issue a warning. You can easily spend all day trying different ideas with this filter. The possibilities are endless.

When After Effects implemented 3D layers and lights in After Effects Version 5 the task of creating shadows from layers became much easier. The addition of Light Transmission adds a new dimension to the process. Let's start off with some basics.


Basic Projection

The first thing you should do is open up the Projection_tut.aep project. It contains all the footage and projects you need to complete this tutorial. The Basic Projection composition should be open.

In order for you to cast a shadow or project an image, you need three things: A light source, a surface to reflect the light, and an object between the light source and the surface to cast a shadow.


The key to creating the projector effect is found in Material Options. Setting Cast Shadows to On or Only and enabling 100% light transmission turns the shadows normally cast by the layer into a full color projection of the layers pixels.

In the Basic Projection composition there is a pale blue wall and floor (layer 5 and 6) to catch the light, a spotlight light on layer 2 called "White Projector," and a star and circle pattern created by stroked masks on a yellow solid in layer 3 called "Lens," for lack of a better name. The Wall and Floor are 3D solids arranged at right angles. The White Projector is a Spotlight pointed at the center of the Lens layer. A camera has been added so we can move around the composition and view it from any angle. A little Ambient light has been added as Layer 1 so we can see the objects in the scene that are not illuminated by the spotlight.



TIP: It is easy to accurately setup the geometry of the Wall and Floor from the Timeline window. Follow these steps. Select the Floor and Wall layers. Press the letter 'a' and then hold down the shift key and press the letter R. The anchor point and rotation properties for both layers should now be visible. Change the Y value in either layer to the height of the layer. In this case Y=240. Both layers should now have the anchor point exactly at the bottom of the layer. Now select only the Floor layer and type 90° in the Y rotation property. Now parent the Floor to the Wall. The Floor and Wall group can now be freely moved around the composition by moving only the Wall.



Position keyframes have been set in layer 3 that swing the light up and down. Scrub through the Timeline and observe how the shadow moves as the position of the spotlight changes. When the composition is first opened, the relationship between the Lens and the White Projector (Layer 3 and 4) is established by Parenting. The relationship is different from normal parenting to a footage layer because of a third variable in lights and cameras called "Point of Interest." Because "Orient Towards Point of Interest" is turned on in Layer 3, parenting forces the Lens to look at the parent light source (Layer 3). Cmnd/Ctrl + Option/Alt + "o" will bring up the Auto orientation window for the selected layer. Selecting "Off" will change the behavior of the child layer (the Lens) so that it acts like any other footage layer. Another option for controlling the relative position of the light source and the shadow-casting layer is to use a simple expression. I've included a simple expression that sets the point of interest for the White Projector light to the position of the Lens layer. Turning off parenting and enabling the expression by clicking the equal sign in the timeline, will setup a different relationship between the layers. When you are experimenting with shadows effects, parenting or expressions will simplify the task of keeping your light sources lined up with your footage. I recommend that you become familiar with these great tools.

The key to this effect is both the relative position of the layers and the Material Properties of the footage and light layers. Open up the Material Properties of the Lens layer by pressing the "a" key twice to reveal the settings. Just below Cast Shadows is the Light Transmission property new to AE 5.5.

The following table explains how each property affects the Lens layer and the shadow it casts:

Property Option Effect
Casts Shadows On
Only
Off
Casts shadow
Layer becomes invisible
Shadow off
Light Transmission 0% -
100 %
No color in shadow
All layer colors in shadow.
Accepts Shadows On
Off
Other layers cast
shadows
Accepts Lights On
Off
Lights effect layer
Lights effects shadows only
Ambient 0% -
100 %
Will not cast shadows
Diffuse 0% -
100 %
Light from directional
sources - effects shadows
Specular 0% -
100 %
Reflected from directional
sources - No effect on shadows
Shininess 0% -
100 %
Modifies Specular light
No effect on shadows
Metal 0% -
100 %
Glossiness of layer
No effect on shadow
In the Basic Projection comp, the most interesting properties are Light Transmission and Casts Shadows. Experiment with a few of these settings to see what they do. Changing Casts Shadows to only makes the Lens layer disappear. You'll be able to see the mask outlines used to create the patterns while the layer is selected, but the layer itself will be invisible when rendered and only the colored shadow will remain.

Great, so what can we do with this tool? There are two additional compositions included in the project that explore other options. The Advanced Projection project uses the projection technique to create a reflection of the Creative Cow icon in a pond, and the Fake 3D composition uses cast shadows to sell the 3D effect of the Creative Cow logo flying past a skyscraper. The Fake 3D composition is inspired by the title sequence created by Computer Café and The Picture Mill for the feature film "Panic Room."


Advanced Projection

Let's take a look at the Advanced Projection project first. There are two copies of the composition. Advanced Projection contains all footage and lights. To simplify the project all masks have been drawn, lights have been added and the composition is ready to experiment with. The Advanced Projection Final is a completed version of the comp.

I want the Creative Cow icon to rise from behind the tree line and cast a reflection in the pond. To achieve the effect hand drawn masks divide two 3D copies of the Background Plate (Layer 7) into elements that can accept lights and shadows from the Spotlight in front and the Backlight behind. The duplicate layers are called "Foreground Plate" and "Water Only." The Cow.ai layer is duplicated, renamed "Cow Projector," inverted, and blurred to provide a source for the colored shadow used as a reflection in the pond. A parallel light source is used as the backlight is used for the backlight and a spotlight is used for front light. The numbers in this Custom View correspond to the layers in the Timeline.


The first task is to arrange the elements in 3D space. Change all footage layers except the Background Plate to 3D elements. Add a spotlight called Front Light and a parallel light named Back Light to the composition. A new view is added (Shift + Option/Alt + N) and set to Left or Top as an aid in lining up the 3D elements. The visibility of the Background temporarily turned off in the Timeline Window by clicking the eyeball for that layer to make it easier to see the elements in the left or top view window. It is easiest to accurately move the Back Light is moved into position by typing position values directly into the timeline. You can also drag the backlight into position, but if you grab only the Z axis and drag the point of interest will move along with the light. In this case, we want the Point of Interest to remain at the default position for now.


Once the 3D layers are in their approximate positions the material options for the Back Light, Cow Projector, Cow.ai, and Water Only layers need to be modified. The Water Only layer (not shown in the screen shot) is set to Accept Shadows and Light Transmission is set to 100% so we can see the effects of lights behind the layer. The Cow.ai layer has casts shadows turned off so that it will not cast a shadow on the Water Only layer. A slight adjustment is made in the Specular value to improve the appearance of this layer. The Cow Projector layer's Cast Shadows property is set to Only, and Light Transmission is set to 100%. When Cast Shadows is set to Only, Light Transmission and Diffuse values are the only properties that have an effect on the composition. The intensity of the Back Light and the shadow darkness are adjusted to values that produce pleasing results.

TIP: If you choose to arrange the position in 3D space by dragging in this composition, it will be easier if you change the 3D handles to World Axis Mode. Three different axis modes are available at the bottom of the Tools Palate


The final steps are to adjust the position of the back light point of interest so the shadow just appears at the edge of the pond. The line between the Backlight and the Point of interest provides a visual guide to help line up the light and shadow layers. Keyframes are added to the Cow Projector and Cow.ai layers to complete the Cow Rise illusion. Small adjustments in the Front Light position and Material Options polish the project and you're ready to render.



Fake 3D

The third example in this tutorial is called Fake 3D. It was inspired by the title sequence from the feature film Panic Room. To sell the illusion that the flying Creative Cow logo is in front of the building we need to cast a shadow matches the perspective cast by a real shadow. It would also be nice to see distorted reflections of the logo in the windows of the building. For now we'll fake it by projecting a colored shadow on the building.

The first task is to create copies of the far left side of the building and the first right face of the building. For this example I distorted a copy of these portions of the building in Photoshop to remove the perspective. You could do the same thing in After Effects using duplicates of the footage, masks to isolate the parts of the building that need to be flattened, and corner pin (Production Bundle Effect) to square up the planes of the building and remove the perspective.


The timeline is a little more complex than the previous example. Starting at the bottom, Layer 10 is a 2D copy of the building. Layer 9 is the squared up version of the first right side panel of the building. Layer 8 is the squared up version of the left side of the building. Layer 7 and 6 are duplicates of the Cow.ai footage with different material options. The Cow Projector layer is set up like the previous composition to cast shadows only. We vary the opacity of the Cow projector to change the intensity of the shadow. The Front Cow layer has Cast Shadows set to Off. Layers 5 and 4 are also duplicates and are set up exactly the same way as layer 7 and 6. The text layers were created with paths copied from Illustrator and pasted to a solid in AE.

The first task is to change the anchor points of the Left Side SQ to the far right, and the Right Side SQ to the far left. This will make it easy to match the edges and creates a hinge on the vertical edge of the layers. The layers can now swing away from the camera to simulate the perspective in the background. The left side is set as the parent of the right side and they are moved into position. Using the top view, with the background layer turned off, a guess is made at the proper “y” rotation for these layers. 34° for the left side and -73° seems to be about right.


A camera is added and placed well below and well back. In this example, the camera position is 324, 3723, -7657 and the zoom is 7162. I ended up with these values by dragging the Y and Z position values in the timeline and then dragging the zoom value until the 3D layers closely matched the original 2D footage.

Because no camera position or lens data was available the position of the camera and the zoom setting was simply a guess. Holding down the shift key while dragging values in the Timeline, multiplies the movement by a factor of 10 and will greatly speed up roughing in the camera position. It’s only important to get close enough to sell the effect.


The next step is to add the Cow logo elements, position them in 3D space, and adjust the material properties and animate the motion path. Parenting is used to keep all of the logo elements together. Once the initial position of the logo is established in front of the building and the rotation is set, keyframes are added for the start and end position of the title. In this case, it is far easier to set the position of the logo by setting the axis view options to Local Axis Mode in the Tool Bar. With Local Axis Mode enabled you can just grab the X axis and slide the layers along parallel to the right building face.

Once the geometry is setup, the Material Options for the logo layers are adjusted. As a final touch an additional point source light is placed close to the right edge of the Creative Cow text layers to add a little fake specular reflection. The project isn’t perfect, but it should give you the basics you need to add 3D shadows to 2D footage.


Final Notes:

Here are a few things that may help you when you start experimenting with complex projects. I hope they will save you some time when you don't see what you expect. First, the color values of cast shadows will not add in the same way visible light does. Stacking multiple colored projections on top of each other darkens image when projected light would become lighter. You can work around this problem by some creative pre-composing and transfer modes between layers. You can also get some interesting effects using negative intensity values for the lights. This brings up all kind of interesting effects you can create with displacement mapping, but that’s a topic for another tutorial. Some times it would be nice to cast a white shadow on a black solid to use as a track matte. You can work around this problem by casting a black shadow on a white solid and then applying the levels effect to the layer and inverting the black and white output levels. You can also try changing the transfer mode to difference. If you look closely, you’ll see a Bonus Project folder in the Project window. There’s a composition inside that uses the transfers mode, levels and Pre-comps to create 3D shadows only. It’s a more elegant, but complicated solution to the Fake 3D composition. Dive in and take a look, but be prepared to do some head scratching and spend some time dissecting the project.

This is a great tool. It can be used for everything from stained glass windows to reflection maps. The only limit is your imagination. Adding production value to a shot without re-shooting or re-rendering 3D has never been easier. Good luck and happy rendering.

Rick is a leader in the Adobe After Effects forum at CreativeCow.net.




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