Medium Between Wire Removal And Cg Compositing English Language Essay


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Wire removal and CG compositing are techniques, which is used in compositing for different kind of shots in visual effects films. Where, as wire removal is mostly used in doing stunts as the object or person appears to be fly in the air. In CG compositing, we can place an object which is not really appeared in the original footage and match according to the background.

So in that cases we can apply both the techniques either Wire removal or CG compositing. In some cases its not.

This dissertation is to analyze the two techniques and applying it in project to show the which is the easier and better way and which gives the quality.

1. Research Questions

What is wire removal?

What is CG compositing?

In which areas the wire removal and cg compositing is used and why?

Which way is easier to do either cg compositing or wire removal?

Which way will gives the quality?

2. Aim

The aim of the project is to find out which is the effective medium the wire removal and the CG Compositing for a vfx shot.

3. Statement of the Problem

To understand about the wire removal and CG compositing. Applying both the techniques for the same shot in project, to prove the best one.

4. Objectives

To explain about wire removal.

To explain about CG compositing.

Comparison between wire removal and CG compositing.

To find which is the effective medium.

Implementation in the project.

5. Significance of Study

Many of the shots can be done by using the wire removal technique or CG composited. This dissertation helps to know that which technique is better to use to get the good quality of the work by applying it in project for one of the shot.

This study mainly helps the people who aspired to be in this field.

6. Summary of the Chapters

Research Methodology:

This chapter contains the which kind of research methodology is been used to do this dissertation.

Review of Literature:

This chapter shows the information collected from the books or websites which has written by the experts in this field.

CG Compositing:

This chapter contains how CG element is composited with a real time video footage or still background.

Wire Removal:

This chapter contains how the introduction to wire removal and how the technique is used to create the effects.

Integration of Dissertation:

This chapter contains implementation of dissertation into the project to prove the better technique for particular shot.

Analysis and Research:

This chapter contains analyzing about the wire removal and CG compositing techniques and finding which technique is better to use.

Chapter - 2: Review of Literature


1. Compositing Visual Effects : Essential For The Aspiring Artist

Written by Steve Wright in 2008

Wire Removal:

This book explains about the wire removal and the techniques like motion tracking, digital painting, morphing, compositing used in wire removal while composited with the background.

CG Compositing:

This book explains about the CG compositing with different types of rendered passes like

a) Diffuse and Specular passes

b) Occlusion and Shadow passes

c) Reflection pass

The CG element composited with the background taking alpha channel matte and the depth compositing as per the scene required.

2. The Art and Science of Digital Compositing

Written by Ron Brinkmann in 2008

CG Compositing:

This book explains about the CG element composited with the bg either live footage or image or matte painting using alpha channel, depth and multipass compositing.

Also deals with the case studies of various films, explaining how they used the CG compositing technique in their films to get the required output.


The article contains information in the above link.

3. The Art of Wire Removal written by Mike Seymour, posted on 27th Oct 2007.

Wire Removal:

The article discussed about the general techniques for the wire removal, showing with the some examples in movies used wire removal technique.

CG compositing:

In this article, author explained about the 3d set extension for the original plate in the Die hard 4 film with lighting and the camera techniques.

The article information is in the above link.

4. The importance of Invisible Effects written by Steve Wright in Creative Cow Magazine

Wire Removal:

In this article, the author discussed about the removal of wire in the frame by cloning and also about the background which need to be the same after cloning it. Author talks about scene salvage, sometimes the scratches would be there when the things go wrong on the scene.

The article information is available in the above link:

5. Prasad Group News Letter, editor S. sivaraman issued on 18th Nov 2010.

Wire Removal:

He described about the shot in a Magadheera movie for which the company worked and got awards. The scene was the helicopter flying in the sky and hero is hanging to that. There, wires were used to hang the hero over the helicopter and also to the helicopter as it has to appear to be flying.

CG Compositing:

In the same movie Magadheera, there was a huge palace which is created in 3d and composited over the background as a set extension.

The article information is available in the above link:

6. VFX Helper published on Tuesday, 16th Oct 2007

Wire Removal:

In this article, the anonymous described about the wire removal with the combination of other techniques and the problems arising at the background while removing it.


The information in this book is available at the above link:

7. The Visual Effects Arsenal by Bill Byrne in 2009

In this book, Bill explained about the CG compositing and wire removal techniques with some case studies. Also, described about the different soft wares which is used to do these techniques.

This information in this book is available in the above link:

8. The VES Hand book of Visual Effects : Industry Standard VFX Practices and Procedures by Jeffrey A. Okun and Susan Zwerman in 2010.

In this book, the author clearly explained the process of the two techniques the wire removal and the CG compositing.

Web sites:

silk set animation information is available in the above link:

9. Silk Set Animation

CG compositing:

This website explained about the 2d and 3d compositing in visual effects, related with the other vfx techniques and process of the work with different softwares.

The information is available in the above link:

10. Written by Admin on 15th Dec 2009

Wire Removal:

In this Admin discussed about the shot which has wire removal technique and the process of doing it with out errors.

Chapter - 4 : CG Compositing

4.1 Introduction:

Digital compositing has historically been considered as a "2d-displane. The term reflects the fact that all the elements that are been brought together are two dimensional images. They may be a representation of a three dimensional object or scene but they have been captured by a device that reduces them to a flat 2d image1.

4.2 Overview:

The CG compositors will creatively combine all the layers and bring the final output as a single image. Although it is 3d work, the compositors should have the knowledge of CG process and artistic skills to get the final output. The compositors receive the data from various sources like rendered data, live action footage, static background, graphics, etc2.

But much of your work as a compositor will be ensure that the images you produce feel as if they taken from a view of a three-dimensional scene. Objects in your composite will need to reflect the effects of perspective, occlusion, atmospheric depth-cues, etc3.

1Ron, B,. "The art and science of digital compositing, 2008" Morgan Kaufmann publishers, 2nd ed.

Burlington, MA 01803, USA [Accessed on 25 November, 2010] p .428

2Available at [Accessed on 25 November, 2010]

3Ron, B,. "The art and science of digital compositing, 2008" Morgan Kaufmann publishers, 2nd ed.

Burlington, MA 01803, USA [Accessed on 25 November, 2010] p .428

CG compositors have the knowledge about the 3d lighting technology and which relates to taking the multi-pass rendering. Finally, they combine all the layers into a single image4.

4.3 History:

Historically the process of creating and rendering 3D imagery has been a reasonably separate discipline from that of compositing. The 3D "color and lighting" artist would position and balance lights, change the color and properties of materials, and keep an eye on things like shadows and reflections5.

It is becoming more and more common to see facilities where the same individual will do both-3D lighting and compositing. This can bring a tremendous boost to both quality and efficiency since a single person will be in complete control over the process. They can choose whether something can be modified acceptably using compositing tools6.

4Available at

[Accessed on 25 November, 2010]

5Ron, B,. "The art and science of digital compositing, 2008" Morgan Kaufmann publishers, 2nd ed.

Burlington, MA 01803, USA [Accessed on 25 November, 2010] p .455

6Ron, B,. "The art and science of digital compositing, 2008" Morgan Kaufmann publishers, 2nd ed.

Burlington, MA 01803, USA [Accessed on 25 November, 2010] p .455

Examples of early compositing CGI:

The technique of photography is used in the movie King Kong in 1933, by taking the images of the model or character changing the position from frame to frame. When we played the sequence of images continuously like a filp book it shows a continuous animation. After the development of the footage, it was projected on a large screen projection in a full sized staged view. Then the foreground action of the character (the actress in the tree) was takes place in front of the large screen resulting to show the entire action with background and foreground composited. This particular type of compositing is known as an in-camera effect, since there was no additional postproduction work needed to complete the shot7.

Nowadays, compositing has effectively been replaced with general-purpose computer systems and some highly specialized software, but the concepts have not really changed8.

In the film James and the Giant Peach there was a particular composited scene created from a different original images9.

7Ron, B,. "The art and science of digital compositing, 2008" Morgan Kaufmann publishers, 2nd ed.

Burlington, MA 01803, USA [Accessed on 25 November, 2010] p .7

8Ron, B,. "The art and science of digital compositing, 2008" Morgan Kaufmann publishers, 2nd ed.

Burlington, MA 01803, USA [Accessed on 25 November, 2010] p .7

9Ron, B,. "The art and science of digital compositing, 2008" Morgan Kaufmann publishers, 2nd ed.

Burlington, MA 01803, USA [Accessed on 25 November, 2010] p .7

The giant peach, shown in fig. The peach is a miniature element, about a foot in diameter, and was photographed on a stage in front of a blue background, or bluescreen10.

The giant mechanical shark, shown in fig. This element is a computer-generated image, built and rendered as a three-dimensional model completely with in the computer11.

The water, shown in fig. The water is also computer generated 3D imagery12.

The sky, shown in fig. This element is a hand - painted backdrop (painted on canvas) that was photographed as a single frame13.

Many of the other elements make up this composite as well, most of them 3D elements. These include the reflections of the peach and the shark in the water, the smoke coming from the shark, shadows for the various elements, and spray and foam on the top of the water14.

10, 11Ron, B,. "The art and science of digital compositing, 2008" Morgan Kaufmann publishers, 2nd ed.

Burlington, MA 01803, USA [Accessed on 25 November, 2010] p .7

12, 13Ron, B,. "The art and science of digital compositing, 2008" Morgan Kaufmann publishers, 2nd ed.

Burlington, MA 01803, USA [Accessed on 25 November, 2010] p .8

14Ron, B,. "The art and science of digital compositing, 2008" Morgan Kaufmann publishers, 2nd ed.

Burlington, MA 01803, USA [Accessed on 25 November, 2010] p .9

Chapter - 5: Creating CG Elements

A specific work flow is needed based on the nature of the CG and how scenes must be built. It begins with the modeling process, which leads to the texturing and then animation. Lighting should follow, with rendering pulling up the rear, as it must15.

5.1 Modeling:

Modeling is the first step to create the CG elements where ever you need to place them. There are many modeling techniques used to create a model Polygon modeling, NURBS modeling and Surface modeling16.

5.2 Texturing:

Once the modeling is completed, it's a good idea to go with texturing and shading. Where comes the process of applying colors and textures to the model or object and then render it17.

5.3 Lighting:

CG is fundamentally all about light, manipulating how light is created and reflected on the object which is created. The lighting changes the mood of the scene and gives highness to the model and texture. There are various types of light that we can place and get the realistic scene.

a) Ambient Light:

Ambient lights cast an even light across the entire scene. These lights are great for creating a quick, even illumination in a scene. Used for low intensities as fill lights or backfround lights.

b) Directional Light:

This lights are perhaps second to the spot lights as the most commonly used light type. They are perfect for sunlight or general indoor lighting.

c) Point Lights:

This light can illuminate an object far away as evenly as it does up close. You can use the Decay Rate settings to illuminate nearby objects and to leave distant ones unaffected. These lights are good for effects and mood setting.

d) Spot Lights:

These lights are similar to the Directional light, and it emphasize the direction. It emits from a specific point and radiate out in a clone shape. Where as directional light emits from an infinite source from a certain direction. But spot lights can create a circular focus of light on the geometry like flash light on the wall.

Chapter - 6 : Rendering

Multi-Pass Rendering

At the very specific instance of an additional image that can be generated to aid some aspects of the compositing process. But in fact there are an unlimited number of images that might be rendered out of out 3D package. Generically, then, we will refer to this concept as multi-pass rendering and we will include any situation where the CG element is rendered as anything more than a single.

a) Diffuse and Specular Pass:

We begin with the diffuse pass shown in fig. the diffuse layer of a cGI object represents the "flat" light that is reflected from the surface as if it was made of felt. No shinny bits. Note that it has shading, which means that those parts that face towards the light are brighter than the parts that face away from the light. We have one strong light to the upper right of the camera, and a soft light to left of camera. Often the matte is also rendered as a separate pass as shown in the example.

The next pass is specular pass, shown in fig. This represents just the shinny bits of rendered surface. Note that it is a different color than the diffuse layer. Specular highlights can either take on the color of the light source, the color of the surface material, or change color base on the viewing angle, all depending on what kind of material you are modeling - plastic, metal, wood and so forth. In addition, different materials have different specular behaviors. Like I said annoyingly complex.

b) Occlusion and Shadow Pass:

One of the most common things to render separately are the shadows that an object casts onto its environment. In this case if we look at our object composite without the shadows it will immediately give away the synthetic nature of the scene.

It would be easy enough to render a hard, directional shadow of the object here but the lighting cues in the scene tell us that it would be completely in appropriate - there's nothing else in the scene to indicate a bright, directional light source. Instead we will use a softer shadow-rendering technique to produce what is known as ambient occlusion layer. This method gives us nice soft shadows under the object and the surrounding, and over the surface. The nice thing about an ambient occlusion layer is that we can use it to increase the realism of the CG element as well as to integrate it with the background plate.

c) Reflection Pass:

The last pass in CGI compositing is the reflection pass. For this pass, the CGI surface attribute was set for 100% reflectivity as if it were a mirrored surface, then the intended background image was reflected off the surface. The results shown in fig, and the background plate is shown in fig.

Chapter - 7 : Depth Compositing

Whenever a 3D database is created for the purpose of rendering a CG image, every object in the scene will have a specific color, material, and illumination assigned to it. When it comes to render a scene from the database, each pixel in the image that is generated will correspond to a certain point on one of the objects in the scene. But there is more information in this database than just color and lighting description of the scene. The spatial relationships of the objects in this scene are also very well defined. Every object in this virtual scene has a specific location in virtual space, and the 3D software is obviously able to determine these locations with great accuracy.

It makes sense, then, that we should be able to extract this information and put it into a form that is useful to the compositing artist. To accomplish this we will use a technique known as Z-depth compositing.

Z-depth compositing (or sometimes just "Z-compositing") uses a special image that is explicitly created to quantify these spatial relationships, allowing us to incorporate depth information into the compositing process. Thus, in addition to the standard color image that is rendered for a scene, the 3D software will be instructed to also render a specialized depth image. As with a matte image, this new type of image requires only a single channel to represent its data. But instead using of pixels to represent transparency information for the corresponding point in the color image, each pixel specifies the spatial depth location for each point.

Chapter - 8 : Compositing with background:

Clean Plates:

Whenever you are shooting an object that you intend to eventually extract or ignore from the background. It is often useful to shoot what is known as a 'clean plate'. When we looked at the use of clean plate to help create a difference matte for a foreground object. Theoretically, everything is identical between the two plates, with the exception of the subject and object. This sort of technique works best when there is a perfect match between the camera, lighting, and exposure on both plates. Consequently, clean plates tend to be much more common whenever the camera does not move through out the shot (or if there is a motion-controlled camera involved).

There are a number of uses for such a clean plate, but they tend to fall into two primary categories. The first use would be to help extract a matte for an object. Mostly you will find that blue screen methods can benefit dramatically from the availability of a clean plate for a given shot.

Ron, B,. "The art and science of digital compositing, 2008" Morgan Kaufmann publishers, 2nd ed.

Burlington, MA 01803, USA [Accessed on 27 November, 2010] p .353

Ron, B,. "The art and science of digital compositing, 2008" Morgan Kaufmann publishers, 2nd ed.

Burlington, MA 01803, USA [Accessed on 27 November, 2010] p .353

The second primary use of a clean plate is an a source of image information that can be used to selectively remove or replace some unwanted portion of the foreground element. Replacing a portion of a scene with a clean plate can either be accomplished by standard compositing techniques or by having a digital paint artist carefully merge pixels from the clean plate into the main plate.

Lighting and Color Matching:

Whenever we put together a composite, one of the most difficult is the proper tuning of color and lighting for all the elements so that they feel well-integrated. As we are always inserting two different images or footages in the scene, to get the final scene as it was shot in single scene. So you can't even separate the concepts of ''color'' and ''lighting''.

Ron, B,. "The art and science of digital compositing, 2008" Morgan Kaufmann publishers, 2nd ed.

Burlington, MA 01803, USA [Accessed on 27 November, 2010] p .353

Ron, B,. "The art and science of digital compositing, 2008" Morgan Kaufmann publishers, 2nd ed.

Burlington, MA 01803, USA [Accessed on 27 November, 2010] p .369

To integrate this the problems should be looked at from two different perspectives. The first considered would be from the real world point, to understand the lighting of the object that effect any other objects in the same environment. The actual numerical values of color can be measured directly because there is purely digital perspective. The second would be as you are using the knowledge of the first to manipulate the things in terms of the second. Ultimately the only objects that are truly being with are pixels, channels, and other collections of data. This data is used to represent the objects and lights, but at some level the representation is inaccurate, or at least limited.


Ron, B,. "The art and science of digital compositing, 2008" Morgan Kaufmann publishers, 2nd ed.

Burlington, MA 01803, USA [Accessed on 27 November, 2010] p .369

Chapter - 9 : Wire Removal

9.1 Introduction:

We have all seen Kung-fu masters and super-heroes leaping and flying around the screen defying the laws of gravity. This is all done by suspending the stunt actors on wires with crews off-camera pulling on them at the right movement to give the hero a boost. This type of is called a wire gag and is very common in action films of all kinds. However, after the film is shot someone has to remove the wires, and that someone is the digital compositor.

9.2 Overview:

Wire removal that is particularly well suited to a combination of painting and compositing techniques. Unlike the traditional compositing scenario in which the goal is to add objects to a scene, paint tools often prove more necessary when the need arises to remove objects from a scene.

Many times a photographed scene will inadvertently contain unwanted harnesses, ropes, or wires that were used as part of a stunt or a practical effect. It is not always possible or cost-effective to fully hide these items from the camera, and consequently digital tools may be employed to remove them from the scene. Since the process seems to be most often used to remove wires, the term "wire removal" has to a certain extent grown to be a generic term for the removal of undesirable stage elements from a scene.

Ron, B,. "The art and science of digital compositing, 2008" Morgan Kaufmann publishers, 2nd ed.

Burlington, MA 01803, USA

[Accessed on 27 November, 2010] p .456

Ron, B,. "The art and science of digital compositing, 2008" Morgan Kaufmann publishers, 2nd ed.

Burlington, MA 01803, USA

[Accessed on 27 November, 2010] p .457

9.3 Working techniques:

Using the full library of techniques described above such as motion tracking, warping, morphing, rotoscoping, compositing, and even digital painting, the wires are removed frame by frame. The process can get very complex because the background region where the wire are removed must be replace. If the wire removal is for a bluescreen shot, this is less of an issue. It gets even more complex when the wires drape over the front of the talent onto textured surfaces such as a herringbone jacket.

Some times the actors or props are supported by poles or mechanical arms called rigs, which must be removed as well.

Examples of wire removal:

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