Compositing the Scene Using After Effects
After the scene has been rendered in Cinema 4D, locate the corresponding folder containing the "city.aec" file in your Browser/Finder. This is the compositing file and it can be opened by double-clicking on it.
If you worked with Cinema 4D’s Linear Workflow, this project must be adapted accordingly in After Effects as well. To do so, open the Project Settings from the main menu and select the color profile you used in Cinema 4D. Also, enable the Linearize Working Space option so your project’s color profile matches the color values used in Cinema 4D.
Three folders are displayed in the Project window, each of which represent individual elements or passes from the scene: "Special Passes" contains various Material and Object Buffers, "Solids" contains objects and "City.c4d" the composition itself, which in turn contains the individual passes, camera animations and light sources. All passes are in the correct order and in the correct layer copy mode - in this example mostly the Add mode. Furthermore, this composition contains all objects to which an External Compositing tag was assigned, either as a Null Object with corresponding coordinate information or as a colored 3D layer - for those for which the Solid option was enabled. As in the image below you will notice two bright red surfaces in the scene located on the billboard and video wall, respectively. If you slide the Timeslider back-and-forth you will notice that these surfaces maintain their correct position and 3D perspective at all times.
Before we begin with compositing, though, we need to clean the project up a little. If, for example, the scene was rendered to include all Multi-Pass channels, this is the time to check each channel to see which ones contain information, if any at all (i.e. if something is visible on each channel). Channels that are completely black or white can be deleted because they contain no information relevant to the image. The fastest way to do this is to set the given channel to Solo mode so it can be viewed individually. Then enable the third icon from the left (a round point) in the Time Ruler.
As you can see, all lights were also carried over from Cinema 4D to After Effects. However, these lights also affect the colored planes, i.e., they are illuminated by all lights and thus appear bright red. But since we only want to work with the lights for the billboard all superfluous lights can be removed. If you are not entirely sure which lights to remove or don’t want to remove them from the scene, you can simply disable the lights in question so they no longer illuminate anything in the scene. Now only the lights for the billboard are left and we can see how the surface looks when properly illuminated. Note that these "real" lights will only affect 3D color surfaces or 3D layers in After Effects. Everything hat has already been rendered, i.e., exists as movie or image sequence, will not be affected.
Next we will import two source files that will be placed on the billboard and video wall, respectively. The easiest way to do this is to double-click on an empty surface in the project window. Select the files "no_keyframes.mov" and "MAXON_Banner.psd" from the "\tex\tutorials" folder located in your Cinema 4D installation directory.
Since each element has its own placeholder - the colored surface - all we have to do is replace this with the desired object (in this case the movie and image). To replace the billboard’s colored surface, select the "Billboard_Surface" layer in the Time Ruler. While pressing the Alt key, click and drag the PSD file from the Time Ruler onto the selected layer. All pertinent parameters such as position and rotation will be assumed from the original layer and no further adjustment is required.
Our surface is illuminated correctly by the three lights. These lights can even be subsequently modified, for example by changing their color.
As long as this layer does not have to be scaled or masked, no mask has to be defined for it. However, since this layer was assigned a Compositing tag and an Object Buffer in Cinema 4D, adding a mask would not be a problem because the file "City_object_8.mov" offers the fitting Object Buffer.
Before we add the movie for the video wall we suggest that you place this file into its own composition so we can define which part of the film should be played and let us have more control over the film, e.g., for adding effects. To do so, drag the file "no_keyframes.mov" from the project window onto the Create New Composition icon. This will create a Composition with exactly the same parameters as the file (size, length, aspect ratio). You can now adjust the Start point within the new Composition until you have found the range with which you’re happy. We can also use this opportunity to give the video wall a look as if it consists of several separate, pixelated screens. This effect is most easily created using the Grid with a correspondingly large value which will look like several video screens set up next to each other. Adding an additional grid effect can be used to create the pixelated look. Make sure the second grid effect’s Fill Method is set to Multiply. Otherwise only the grid itself would be visible.
Return to the main Composition and select the "Video_Content" layer in the Time Ruler. Replace it by Alt+click & dragging the "no_keyframes" layer onto it. The surface appears black and the movie seems not to appear on the surface. This is due to the fact that, although the plane can be illuminated by default, it is not because the only real lights in the scene are those illuminating the billboard. Since the video wall should illuminate itself and not be illuminated by other source of light we can disable the default option (Material Options/Accepts Lights). The scaling is also not correct but this is due to the fact that colored surfaces exported from Cinema 4D can have a maximum size of 1000 pixels. This surface is larger. This does not, however, pose a problem because what counts is the positioning. Simply scale the layer until it covers the video wall completely. If the movie appears reversed, this can be corrected quite simply by deleting the layer’s existing keyframes (they are not needed because the layer is not animated) and setting the Y Rotation value to +180°.
If, for example, you go to frame 90 you will see that the spaceship, which should actually be in the foreground, is covered. This is because the spaceship lies on the rendered layer and not on a 3D layer. As such, the spaceship needs to be masked out on the movie layer. Since we assigned the correct tags and the Object Buffer is available, this is will be no problem. Add the file "city_object_9.mov" from the Special Passes folder to the Time Ruler and place this file directly over the movie layer. Define the movie layer as No Track Matte and the file above it as Luma Matte - this will make the spaceship appear in the foreground because the spaceship is masked out of the movie layer. It now appears as if the spaceship lies "in front of" the video wall. This can be seen in detail in the following movie:
You can also modify the appearance of the lights that have already been rendered. If you take a closer look at the names of the individual layers you will see that they carry the same names as the objects in Cinema 4D. As soon as you disable one of these " … Light … " layers the result will be visible - it will look as if the light has actually been turned off. If you want to weaken the effect of the light simply reduce the layer’s opacity. In addition to turning lights on and off or dimming a light you can also change a light’s color. For example, select the "City_Light_Building.mov" layer and select Color in the Effects and Presets window to apply this effect to the selected layer. In the effect’s settings you can select the menu and define a different color. Right away you will see that the light has changed color, as if it had been rendered in that color in Cinema 4D. To color the second light on this building the same color simply select the effect and copy it (
Since each light exists as a separate layer their intensity can be adjusted individually. The scene contains two main lights that illuminate the scene from below: a blue light at the left and a yellow light at the right. The blue light, however, appears to be a little weak. Select the "City_Main_Light_Low.mov" layer and add a Curve effect. Increase the mid-tones slightly to increase the light’s brightness. Alternatively you can duplicate the layer you want to brighten and adjust the Opacity, if necessary.
To make the small windows in this cityscape look more realistic, select the "City_ambient.mov" layer and set it to Solo. You will see that this channel only contains information regarding these windows and their respective light points. Add a Luminance effect to the layer to make the light points look more natural and give them a slight glow. Experiment with the values and increase the intensity, if necessary, until you are satisfied with the result. In our example, the Threshold is set to 50% and the Intensity to 2.0.
You can also add and modify more lights. For example, we also have a separate channel for the lights at the tip of the antennae and on the corners of the houses. Open the Special Passes folder and add the "City_object_4.mov" file to the composition. The Layer Copy Mode should be set to Add.
Add the Luminance effect to this layer also. The red lights, however, must be modified differently. If you observe red lights at night you will notice that they always have a certain look. Since the human eye is very sensitive to red light, these are more noticeable at night. Furthermore, red light never really looks fully illuminated at its center but looks more white than red. The glow effect is what gives these lights their red color. Therefore, adjust the Luminance effect to achieve the most realistic look. Set the Color parameter to Color A and B with both colors set to red, which will generate a more intense red glow. Reduce the Threshold to about 20% and increase the Intensity to 4.0. To avoid the center of the glow from being completely white, reduce the Opacity a little to about 90%.
Since the scene also contains other object with special channels, these can be added as well. For example, the files "city_object_5.mov" and "city_object_6.mov" and "city_object_7.mov" are each individual marker lights that can be added to the scene. The file "city_object_5.mov" contains lights at the corner of the building at the center. These will also be added to the composition and be assigned an effect, as was done with the previous layers. This layer can be easily animated to make these marker/warning lights blink, which will also add more life to the scene. Simply animate the Opacity value from 0% to 100% and back to 0% over the course of a few frames. Copy and paste these keyframes in regular intervals to create a continuous blinking of the lights.
Now you will notice that the background is completely black and it looks like the (theoretically endless) cityscape ends there abruptly. However, since the scene contains the necessary transparency information we can easily add a matte painting, photo or a layer with a slight gradation to the background. This is also a benefit of the excellent connectivity between Cinema 4D and After Effects - it’s certainly easier to add a background image than to model an endless city in 3D.
And finally we can fine-tune the scene a little by doing a little color correction, adding some grading and a little depth of field. To do so, place a new composition within the main composition by dragging the composition "city_final.c4d" onto the Create New Composition icon. Now drag the "city_depth.mov" file into the new composition. This makes the necessary depth information available and you can, for example, apply the Wiggle effect to the "city_final.c4d" layer. To do so define the "city_depth.mov" layer as the Depth Map Layer and reduce the Iris Radius to about 5.0.
Of course you can fine-tune the scene some more, add lights or even use the Motion Vector Pass to add motion blur. The possibilities are endless!