Part I：Previs/ Postvis/ Techvis
Using Previs, Postvis and Techvis at the beginning of the shoot helps the director explore various ideas and techniques to shoot the film quickly. Both the camera effects and art departments benefit from the preview’s unique agility and the technical data it provides. Previews can quickly provide simple effects during the editing process, saving time for post-production changes and adjustments. Movements are modeled and 3D animated digitally by artists so that directors can quickly view and test concepts, determine how best to tell the story and make the most of their time.
Previs：
Previsualization, or previs, is the process in pre-Previsualization. Modern previs uses digital technology and enables the director to explore, devise, develop and express his vision for his film’s sequences. The advantage of previsualization is that it allows the director, filmmaker or VFX Supervisor to experiment with a variety of staging and art direction options—such as lighting, camera placement and movement, stage direction and editing—without having to incur the cost of actual production.
The production Previs helps develop the action and tell the story, including visualizing the action, shots, and other settings. The production team begins to list and map out the technical knowledge and components needed for the shots and what will be involved in the live-action shots from the previs. The workflow in previs also includes developing more specific character-related work to look at the environment, including the range of movement, fighting style and props used.
Postvis：
Postvis is a way of compositing footage set in Previs into a rough 3D environment or filmed real footage before the final effects are created. Postvis allows for a quick preview of the composite visuals. This avoids the time and money spent on repeated and extensive changes during the visual effects production process. Postvis often uses complex 3D tracking programs to simulate the movement of a live camera. Once the perspective is matched in the scene, Postvis enables a preview of the real scene’s impact on the imported digital character simulation. Digital scene extensions and placeholder effects can also added at the Postvis stage. All material added at this stage can be manipulated and adjusted quickly, saving a great deal of time and resources for the subsequent production process.
Techvis：
Techvis mainly provides technical solutions to preview work, such as track positions, camera angles, green screen build distances and other issues. When the plot requires the filming of complex movements of special characters, the Techvis staff are called upon to give specific solutions and solutions. Techvis also has a role in modeling scenes and predicting the best position of light and shadows during the shooting time and works in coordination with the VFX and camera departments to achieve the best possible results.
Part II：Film Animation / VFX Animation / Game Animation
Film Animation：
The characters and scenes in film animation are mainly used to serve the plot. Whether it is 2D Film Animation or 3D Film Animation, the screen’s final visual effect must be smooth enough. A character animation that is not smooth enough will create an uncomfortable viewing experience for the audience. This is why an animator’s most important and fundamental skill is to create a character animation that conforms to the laws of motion. In Film Animation, the characters’ movements are exaggerated to ensure that they conform to the laws of motion. In addition to the characters’ characterization, the animator needs to refine the details of the character animation. Film Animation is like a film in that the audience wants to enjoy an interesting and vividly acted story. Unlike Film, Film Animation is more malleable in terms of characters and scenes.
VFX Animation：
VFX Animation is the equivalent of combining virtual things with real filmed objects to give a realistic feel to the special effects animation on the screen. Often VFX is used to create real-life, more unusual situations such as explosions, tsunamis, volcanic eruptions and other disaster phenomena. VFX is mainly used to model and post-compose material shot in a green screen environment, using realistic, detailed models instead of character movements. In order to ensure that the audience is treated to VFX Animation that matches the real-life scenes on screen, the colour of the footage is repeatedly adjusted in post-production. This allows the virtual elements added in the post to be better integrated into the real scenes being filmed. Artists still explore VFX Animation in the film and television industry, and it helps to create the mood of the scene and bring the audience into the plot.
Game Animation：
The animation is a significant part of a game, helping the game world create a sense of realism in the player’s experience. Animators simulate human movement and expression characteristics onto in-game characters in Game Animations, which serve to bring out the character’s personality. The in-game character models, embellished with animation, provide a platform for emotional and plot interaction between the player and the game character. Game animations help link the game to the integrity of the plot while also enhancing the game’s artistry and aesthetics. Some game creators also apply animation capture and facial expressions to game animation to enhance the game’s artistry and playability. Most of the characters’ movements in Game Animation are cyclical, such as jumping, walking, running, etc. Some of the movements may not conform to normal laws of movement or physics (e.g., a character can reach two stories when jumping). Still, these special character animation settings do not affect the player’s experience of the game. The fact that some of the special features are different from the real world adds to the appeal of the game.
Part III：Motion Capture with Matchmove and Rotomation
Matchmove：
Matchmove matches computer-generated (CG) scenes with footage from live footage to simulate the reconstruction of cameras, people and backgrounds in a virtual scene. Matchmove producers also visit the set to measure environmental values and set tracking marks. In subsequent Matchmove productions, the tracking markers can track the movement of the camera and calculate the relevant coordinates in the 3D scene. matchmove can use the tracking markers to reproduce the movement of characters, vehicles or other objects in the virtual scene, thus performing human and object tracking. The created motion files (camera, object or body track) are then passed through the VFX pipeline to other departments so that the compositor can seamlessly combine them. The concept of Matchmove revolves around shooting a scene with two different cameras at precise angles. The first is a virtual camera to capture an actor’s movements and expressions who a 3D object will replace. This footage is known as live-action footage. The second is shot with a 3D camera. The 3D camera replicates the real action’s perception or the virtual camera to fit the real scene’s 3D object world.
Rotomation：
The rotomation technique traces live-action footage of actors frame by frame to replicate an actor’s motion in animation 2D or 3D. Rotomation or RotoAnim is a combination of rotoscoping and animation, hand-tracking of matched 3d elements, tracked from the background of real footage. Rotation is responsible for manifesting the act of the actor on the 3D model. The model then acquires and exhibits every nuance of the behavior of the actor. The final footage consists of a 3D object in motion or action that has been fed to it by matching the movements of the actor acting on it. Rotation enables the 3D model to inherit the actor’s ability to create a 3D object using the relevant software and technical devices of VFX artists in a shorter period and at cheaper rates.
Motion Capture：
A motion capture system is a high technology device used to measure moving objects in three dimensions accurately. It is based on the principles of computer graphics. It uses several video capture devices arranged in space to record the motion of a moving object (tracker) in the form of an image.
Motion capture is a technique for recording information about human movement for analysis and playback. The data captured can be as simple as recording the spatial position of body parts or as complex as recording the face and muscle groups’ subtle movements. Motion capture as applied to computer characters, on the other hand, involves converting the movements of a real person into those of a digital actor. This conversion mapping can be direct, as when a live actor’s arm movements are used to control the arm movements of a digital actor. It can also be indirect, such as using the real actor’s arm and finger movements to control the digital actor’s skin colour and mood. In a performance motion system, the performer is responsible for making various movements and expressions according to the plot, captured and recorded by the motion capture system. The captured movements and expressions are then used to drive the character model through the animation software. The character is able to make the same movements and expressions as the performer and generate the final animation sequence.
The difference between Matchmove and Rotomation
There are two main types of Matchmove tracking, CameraTrack and ObjectTrack.
CameraTrack is required to convert camera information from live footage to digital information for post-production software. Matching live-action with CG elements, camera positions and movement. In film production, for example, the green liner in the studio is replaced in the post with a special effect or scene.
ObjectTrack is a relatively simple object with distance and perspective changes, without much of its deformation. For example, a photograph in a scene, a license plate of a moving vehicle, etc. However, if you want to replace a specific object with a more complex deformation, such as a character’s face, you need to use the Rotomation technique.
Rotomation, which mainly does the digital replacement of characters, includes erasure (elements such as wire, original character) and character performance tracking. In addition to replacing actors, Rotomation is often used in digital make-up.