Due - Sunday, July 21, 2024
This is a group assignment. Group members can be found in Assignment3Groups.docx.
You work for a company that produces three-dimensional printers. 3D printing, or additive manufacturing, is the construction of a three-dimensional object from a CAD model or a digital 3D model. The term "3D printing" can refer to a variety of processes in which material is deposited, joined or solidified under computer control to create a three-dimensional object, with material being added together (such as plastics, liquids or powder grains being fused together), typically layer by layer.
You have often wondered about the application of such technology (for 3D printing) towards three dimensional video. Three-dimensional imaging currently is used extensively in the medical field, where a technique is employed that combines many scans (from computed tomography, MRI or ultrasonography) computationally. Such images can then be manipulated by the radiographer or physician to aid diagnosis and surgical planning.
Is it possible that three-dimensional videos could be created in the same way 3D printers create a three-dimensional object from a digital model? How could such technology be applied to the massive world-wide consumer market? This assignment attempts to answer such questions.
There are several technologies that are used with 3D printing. There are several applications as well. These are all shown below.
Fused Deposition Modeling. Fused deposition printers use a thermoplastic filament, which is heated to its melting point and then extruded, layer by layer, to create a three dimensional object. Objects created with an FDM printer start out as computer-aided design (CAD) files. Before an object can be printed, its CAD file must be converted to a format that a 3D printer can understand - usually .STL format. FDM printers use two kinds of materials, a modeling material, which constitutes the finished object, and a support material, which acts as a scaffolding to support the object as it's being printed. (see the video Fused Deposition Modeling (FDM) Technology )
SLA - Stereolithography. Stereolithography (SLA) is an industrial 3D printing process used to create concept models, cosmetic prototypes, and complex parts with intricate geometries in as fast as 1 day. A wide selection of materials, extremely high feature resolutions, and quality surface finishes are possible with SLA. The SLA machine begins drawing the layers of the support structures, followed by the part itself, with an ultraviolet laser aimed onto the surface of a liquid thermoset resin. After a layer is imaged on the resin surface, the build platform shifts down and a recoating bar moves across the platform to apply the next layer of resin. The process is repeated layer by layer until the build is complete. (see the video Introduction to Stereolithography)
SLS - Selective laser sintering. Selective laser sintering is an additive manufacturing (AM) technology that uses a high power laser to sinter small particles of polymer powder into a solid structure based on a 3D model. The powder is dispersed in a thin layer on top of a platform inside of the build chamber. The printer preheats the powder to a temperature somewhat below the melting point of the raw material, which makes it easier for the laser to raise the temperature of specific regions of the powder bed as it traces the model to solidify a part. The laser scans a cross-section of the 3D model, heating the powder to just below or right at the melting point of the material. This fuses the particles together mechanically to create one solid part. The unfused powder supports the part during printing and eliminates the need for dedicated support structures. The platform then lowers by one layer into the build chamber, typically between 50 to 200 microns, and the process repeats for each layer until parts are complete. (see the video Selective Laser Sintering (SLS) Technology)
Question: which of the above 3D printing technologies could be conceptually suitable to 3D video?
Applications - Biomedical Engineering. 3D bioprinting is a process that employs 3D printing for biological processes such as combining cells or biomaterial to thereby create an item that features tissue properties. Similar to non-biomedical 3D printing, it's a process wherein material, in this case, biological rather than filament or resin, is deposited layer by layer comprising biolinks. These tissue-esque formations may then be used for various applications within the biomedical field. Often, a biopsy is required as a preliminary procedure. Typically a tomographic reconstruction is performed to prepare for a layer-by-layer printing process. Since biological material is being used rather than resin or filament, it's necessary to multiply as well as isolate specific cells that are then mixed up with substances such as oxygen and nutrients. This basically allows biomaterials to be printed.
Applications - Aerospace and Automobile Manufacturing. The Aerospace and Defense (A&D) industry is a great example of utilization Additive Manufacturing (AM) (commonly referred to as 3D Printing) with a clear value proposition and the ability to create parts that are stronger and lighter than parts made using traditional manufacturing. Making manufacturing tools using traditional means is rather costly and time consuming, and limitations on geometry translate into both less efficient manufacturing processes and more constraints on the geometry of end-use parts. Manufacturing tools that are 3D printed are lighter and more ergonomic, making it easier and safer for factory workers to perform their duties. That saves time and money on the factory floor. 3D printing is also applied for fast prototyping, through to a more and more widespread production of final car parts, and ending with 3D manufacturing of nearly the whole cars.
Applications - Construction and Architecture. 3D Printing in the construction industry means greatly reduced production time, due to the fact that machines themselves are very fast, some of them are capable of manufacturing 600 to 800-square-foot (55 to 75-square-meter) home in just 24 hours. Architects and other AEC (architecture, engineering and construction) professionals are increasingly using 3D printers to produce beautiful, physical, and highly-detailed architectural models. The experts can now showcase their ideas and impress their clients with tangible models that take into account precise building or construction site information.
Applications - Product Prototyping. Rapid prototyping is one of the most common applications for 3D printing, which offers a great deal of flexibility in terms of speed and material selection. 3D printing allows the manufacturing of low-to-medium performance objects at a low cost, but it's not suitable for mass production. 3D printing is considered an additive manufacturing method, meaning material is added until a specific shape is formed.
Question: Looking at how 3D printing has been applied, which application is closest to 3D video?
Volumetric Imaging. Volumetric imaging refers to the production of images with height, depth, and length, in contrast to the majority of images produced artificially as two dimensional representations. Viewers of volumetric images are able to view them from all angles and may even be able to interact with the image, depending on its characteristics. Typically, volumetric data is described by a group of 2D image slices, stacked together to form a volume.
Volumetric Imaging - Ultrasound. While ultrasound imaging of a part of anatomy in 2-dimensional (D) mode, volumetric 3D ultrasound imaging provides multiplanar images in several orthogonal (perpendicular) planes and may provide additional anatomical information. The rendered 3D volume allows an in-depth view of the anatomy from all sides (i.e., top, bottom, front, back, left, and right).
Volumetric Imaging - Computed Tomography (CT). Volumetric medical images, such as computed tomography (CT) scans, consist of a series of stacked two-dimensional (2D) images, allowing for more accurate representation of the three-dimensional (3D) nature of the body's anatomical structures. In recent years, there has been a steady increase in the number of volumetric medical images interpreted in diagnostic radiology. Although volumetric images are typically associated with better performance, missed or incorrect diagnoses remain prevalent in radiology.
Volumetric Imaging - Magnetic Resonance Imaging (MRI). Volumetric imaging is a 3D technique where all the MRI signals are collected from the entire tissue sample and imaged as a whole entity, therefore providing a high signal to noise ratio. The acquisition of isotropic voxels or thin slices with high spatial resolution allows to create multiplanar reconstructions in all planes; a compensation for the usually longer scan time. One of the greatest benefits of volumetric imaging is the elimination of subjectivity. Estimates of volume have always been incorporated into standard MRI reports. Referring physicians must be able to read these MRI reports and in doing so be able to visualize the anatomy of their patients.
Volumetric Imaging - Laminography. Whilst x-ray micro-computed tomography (CT) machines have developed into a popular laboratory tool for non-destructive 3D imaging of materials, they are not well-suited for scanning flat objects, for which there is an increasing demand. Computed laminography (CL) techniques have been developed for imaging planar samples such as fossils, paintings, printed circuit boards and composite panels. Laminography systems are capable of imaging specimens with large lateral dimensions or large aspect ratios, neither of which are well suited to conventional scanning procedures.
Topographic Imaging. topography is an imaging technique based on Bragg diffraction. Diffraction topographic images record the intensity profile of a beam of X-rays diffracted by a crystal. A topography thus represents a two-dimensional spatial intensity mapping of reflected X-rays, i.e. the spatial fine structure of a Laue reflection. This intensity mapping reflects the distribution of scattering power inside the crystal; topographs therefore reveal the irregularities in a non-ideal crystal lattice. X-ray diffraction topography is one variant of X-ray imaging, making use of diffraction contrast rather than absorption contrast which is usually used in radiography and computed tomography (CT). XRT is used for monitoring crystal quality and visualizing defects in many different crystalline materials. It has proved helpful e.g. when developing new crystal growth methods, for monitoring growth and the crystal quality achieved, and for iteratively optimizing growth conditions. In many cases, topography can be applied without preparing or otherwise damaging the sample; it is therefore one variant of non-destructive testing.
Triangulation. triangulation refers to the process of determining a point in 3D space given its projections onto two, or more, images. In order to solve this problem it is necessary to know the parameters of the camera projection function from 3D to 2D for the cameras involved, in the simplest case represented by the camera matrices. Triangulation is sometimes also referred to as reconstruction or intersection. The triangulation problem is in principle trivial. Since each point in an image corresponds to a line in 3D space, all points on the line in 3D are projected to the point in the image. If a pair of corresponding points in two, or more images, can be found it must be the case that they are the projection of a common 3D point x. The set of lines generated by the image points must intersect at x (3D point) and the algebraic formulation of the coordinates of x (3D point) can be computed in a variety of ways. In practice, however, the coordinates of image points cannot be measured with arbitrary accuracy. Instead, various types of noise, such as geometric noise from lens distortion or interest point detection error, lead to inaccuracies in the measured image coordinates. As a consequence, the lines generated by the corresponding image points do not always intersect in 3D space. The problem, then, is to find a 3D point which optimally fits the measured image points. In the literature there are multiple proposals for how to define optimality and how to find the optimal 3D point. Since they are based on different optimality criteria, the various methods produce different estimates of the 3D point x when noise is involved.
Time-Of-Flight. 3D time of flight (ToF) is a type of scanner-less LIDAR (light detection and ranging) that uses high power optical pulses in durations of nanoseconds to capture depth information (typically over short distances) from a scene of interest. A ToF camera measures distance by actively illuminating an object with a modulated light source such as a laser and a sensor that is sensitive to the laser's wavelength for capturing reflected light. The sensor measures the time delay between when the light is emitted and when the reflected light is received by the camera. The time delay is proportional to twice the distance between the camera and the object (round-trip), therefore the distance can be estimated as depth = c*delta_time/2 where c is the speed of light.
For a general video on 3-d imaging, see 3 d imaging.
Question: How would you convert from 3D imaging to 3D video? Which of these technologies would you use?
Holography. holography, means of creating a unique photographic image without the use of a lens. The photographic recording of the image is called a hologram, which appears to be an unrecognizable pattern of stripes and whorls but which - when illuminated by coherent light, as by a laser beam - organizes the light into a three-dimensional representation of the original object.
Holography - Continuous-wave laser holography. In a darkened room, a beam of coherent laser light is directed onto object O from source B. The beam is reflected, scattered, and diffracted by the physical features of the object and arrives on a photographic plate at P. Simultaneously, part of the laser beam is split off as an incident, or reference, beam A and is reflected by mirror M also onto plate P. The two beams interfere with each other; that is, their respective amplitudes of waves combine, creating on the photographic plate a complex pattern of stripes and whorls called interference fringes. These fringes consist of alternate light and dark areas. The light areas result when the two beams striking the plate are in step - when crest meets crest and trough meets trough in the waves from the two beams; the beams are then in phase, and so reinforce each other. When the two waves are of equal amplitude but opposite phase - trough meeting crest and crest meeting trough - they cancel each other and a dark area results.
Holography - Pulsed-laser holography. A moving object can be made to appear to be at rest when a hologram is produced with the extremely rapid and high-intensity flash of a pulsed ruby laser. The duration of such a pulse can be less than 1/10,000,000 of a second; and, as long as the object does not move more than 1/10 of a wavelength of light during this short time interval, a usable hologram can be obtained. With the rapidly flashing light source provided by the pulsed laser, exceedingly fast-moving objects can be examined. Chemical reactions often change optical properties of solutions; by means of holography, such reactions can be studied.
Holography - Nonphotographic holography. Holographic images are also recorded on materials other than photographic plates. Most of these nonphotographic materials, however, are still in the experimental stage, and the photographic production of holograms remains the only widely used process.
Question: Take a look at the holographic technologies. Which do you think is most suitable for 3D video?
Holography - Applications. Some current applications that use holographic technology are:
For a general video on holograms, see How 3D holograms work.
Question: Which of the above applications is most suitable for 3D video?
Vergence Accommodation Conflict. Vergence-accommodation conflict, also known as VAC, or Accommodation-vergence conflict, occurs when your brain receives mismatching cues between the distance of a virtual 3D object (vergence), and the focusing distance (accommodation) required for the eyes to focus on that object. This occurs while looking at stereoscopic imagery, such as watching 3D TV/cinema, as well as in all current, traditional head-mounted displays (HMDs). It can contribute to focusing problems, visual fatigue, and eyestrain, while looking at stereoscopic imagery, and vision effects that linger even after ceasing looking at the imagery. In traditional stereoscopic technologies, the virtual image is focused at a fixed depth away from the eyes, while the depth of the virtual objects, and the amount of eye convergence, varies depending upon the content (see HMD optical design).
Real Interference-based Holograms. A digital hologram is created by the interference between a coherent object and reference beam, which is digitally recorded by a CCD camera and processed by computational methods to obtain the holographic images. The digital hologram contains not only amplitude information of the object, but also phase. Moreover, the ability of the CCD camera to quantify the recorded light gives rise to a number of post-processing methods that can for instance be used to calculate optical thickness or refractive index variations of an object provided knowledge of one or the other is available.
2.5D. The 2.5D, or three-quarter, or preudo-3D, animation is a distinct type of animation that involves the combination of 2D objects in the 3D space for the creation of a 3D space impression. This animation technique is traditionally applied in the video game industry to create 2D graphical projections and other objects to simulate 3D. In a nutshell, 2.5D animation is thus the 2D animation in the 3D space. Other spheres of its application include title sequences, icon and GUI design, and music video production. 2.5D animation can be created by means of moving 2D objects in 3D space (both physically or with the help of computer program) or through a wise application of perspective and shadows to change the way 2D objects look. Shading is a popular technique of adding 3D volume to an object; this can be done by casting a shadow from the object onto its background, or by creating twin objects and greying them out. With proper arrangement of objects in the 3D space, the 2D objects will obtain the required depth for the 3D illusion creation. Other methods for creating the 2.5D animation include the axonometric and oblique projection, billboarding, the use of skyboxes and skydomes, parallax scrolling, and scaling along the Z axis.
Question: Can any of the above technologies practical for consumer use of 3D video?
Looking at the existing technology for 3D video, as well as the technologies for 3D printing, 3D images, and 3D holograms, can these be used to produce a better product for 3D video that could perhaps be mass produced? What concepts could be borrowed from each to produce 3D video?
Decide whether it is feasible to create a product that can be mass produced to provide 3D video. If the technology does not exist today, will it exist in the next five years?
All weekly problems are to be done in class unless otherwise specified.
Assignment 3 is worth 15% of your final grade and as such is marked out of 15 as follows:
| Does not meet expectations | Satisfactory | Good | Exceeds Expectations | |
|---|---|---|---|---|
| 3D Printing (2 marks) | Does not meet requirements | Meets the most important requirements | Meets all requirements with minor errors | Meets all requirements with no errors |
| 3D Imaging (2 marks) | Does not meet requirements | Meets the most important requirements | Meets all requirements with minor errors | Meets all requirements with no errors |
| 3D Imaging - Holograms (2 marks) | Does not meet requirements | Meets the most important requirements | Meets all requirements with minor errors | Meets all requirements with no errors |
| 3D Video (3 marks) | Does not meet requirements | Meets the most important requirements | Meets all requirements with minor errors | Meets all requirements with no errors |
| The Conclusion (3 marks) | Does not meet requirements | Meets the most important requirements | Meets all requirements with minor errors | Meets all requirements with no errors |
| Weekly Questions (3 marks) | Answers no question correctly | Answers some questions correctly | Answers most questions correctly | Answers all Questions correctly |
Please email any source code and documentation to: ali.sanaee@senecapolytechnic.ca
You will be docked 10% if your assignment is submitted 1-2 days late.
You will be docked 20% if your assignment is submitted 3-4 days late.
You will be docked 30% if your assignment is submitted 5-6 days late.
You will be docked 40% if your assignment is submitted 7 days late.
You will be docked 50% if your assignment is submitted over 7 days late.