METHOD FOR SCULPTING
The present invention is directed to a method for preparing a three- dimensional replica of a subject or object, in particular a method for producing three dimensional sculptures.
Traditionally, three dimensional sculptures of objects, such as human heads and animals have been prepared by hand, making the process of obtaining such a sculpture very time consuming and, as with many hand made items, extremely expensive. The traditional techniques involve preparing a replica of the object being sculpted, for example from clay or the like. The replica is typically hand made, requiring a high degree of skill and a significant length of time. Once completed, the replica may be finished, for example in the case of clay by firing, to prepare the completed work. Alternatively, the replica is used to prepare a mould, from which a final work is cast.
A very well known technique for preparing the final work is by means of the lost wax casting process. In this procedure, a wax replica is prepared and then encased in a mould. The mould is heated to remove all traces of the wax and leave a cavity. Molten metal is poured into the mould to fill the cavity left by the wax. The mould is then removed to reveal the finished article in a rough cast form. The article is then finished using suitable techniques.
Accordingly, there is a need for a quicker, cheaper method of producing such sculptures, suited towards a more general market. It would also be an advantage if the method could provide accurate sculptures without the need for the high level of skill and experience required to employ the traditional techniques.
GB 2 377 506 discloses an apparatus for reproducing a human head in three- dimensional form. The replica is prepared by removing material from an oversize blank of thermoplastic material using a data set of coordinates of the surface of the subject's head.
US 5,736,201 is concerned with a process for making a replica of the head of a subject in the form of a doll's head. The process comprises scanning the head of the subject with both a laser scanner and a video camera, to produce data signals containing contour information and colour information. The countour signals are used to prepare a three-dimensional replica of the subject, after which the colour signals are used to colour the replica.
CN 1105035 C discloses a method for manufacturing three-dimensional metal statues. The method comprises scanning the subject to obtain data on the shape and configuration of the subject. The data thus obtained are input into a computer, which is then used to prepare an epoxy resin model. A silicone elastomer mould is prepared from the resin model, which is in turn used to prepared a wax model. The wax model is used in a lost wax casting process to prepare the final cast metal replica.
KR920008779B discloses a method of sculpting using a laser and an apparatus for the same. The method comprises taking an image of the subject and storing the image data in a memory. A portion, but not all, of the image data are scanned and used to generate a carved object.
FR 2855959 is concerned with a method for creating an item of so-called personal equipment, in particular a prosthesis for use by a person. The method comprises scanning the limb or portion of the person to be fitted with the prosthesis. The image data are modified, in particular to take into account the surfaces of the limb or portion of the person that are to provide support. The prosthesis is then formed using the modified data set. It will be
appreciated that the method of FR 2855959 necessarily provides a finished object that is, at least in part, has opposing surfaces to the scanned limb or body portion. Thus, the method cannot generate a replica of a scanned object.
WO 2004/077185 describes a method for producing an article, in which an object is scanned to provide a set of image data, and converting the scanned data into surface data representing surface characteristics of the model, from which instruction data for a computer-controlled machine tool are generated. Thereafter, execution of the instruction data is simulated to generate a representation of the reproduction of the article as will be produced. The results of the simulation may be used to improve the quality of the reproduction.
Finally, US 5,184,306 is concerned with a method of reproducing three dimensional objects, in particular for use in dental applications. The method comprises acquiring a set of image data of the subject and constructing a three-dimensional computer-based model of the subject. This model is superimposed on ideal geometry data which are stored on the computer. The ideal geometry data are then modified in light of the three-dimensional image , data and then used to prepare the final object.
While the aforementioned methods and procedures may assist in reducing the need for a skilled artist or sculptor to create a replica of a subject, the prior art methods do not allow for the fast and accurate replication of a subject using modern imaging and three-dimensional modelling techniques. In particular, it would be most useful if a method could be found to enable modern rapid- prototyping systems to be employed to produce either the final replica or the replica used in a casting process, such as the traditional lost wax casting techniques. A particular problem arises in that modern imaging techniques can provide an image data set that is extremely detailed. The processing of
such image data by an automated system for the production of an article, for example in the rapid-prototyping of the article, is made very difficult, if not impossible, by the high detail in the image data. This problem prevents such techniques from being used to prepare sculpted objects, such as cameos, busts and other artistic reproductions.
According to the present invention, there is provided in a first aspect a method for the preparation of sculpted objects, the method comprising the steps:
(a) scanning at least a portion of the object to be sculpted to prepare an image data set;
(b) modifying the image data set; and
(c) preparing a completed sculpture using the modified image data set
The method of the present invention employs scanning technology to provide an image data set of the object to be reproduced. This ensures that the reproduction is accurate. In addition, the data set is modified as required, as described hereinafter, in order to produce the completed sculpture. As will be described, the method may be used to prepare a range of reproductions or sculptured objects, in particular statues of people and/or animals, busts and cameos.
The method may employ any suitable scanning technique in order to obtain an image data set of the object being reproduced. The image data set will contain data of the object in three dimensions, in turn allowing a three- dimensional reproduction to be produced. Accordingly, the scanning technique employed must be one that provides a three-dimensional data set. Suitable scanning techniques are known in the art and suitable scanning systems are commercially available. Preferred scanning systems include 3D non-contact laser scanners/digitisers, for example the Konica Minolta Vi910, commercially available from Konica Minolta Sensing Europe B.V.
The scanning step is conducted to obtain an image data set of at least a portion of the object being sculpted and, in some embodiments, a complete image data set. To enable the mapping of a complete three dimensional image, the object is preferably scanned a plurality of times, in particular at least three times, more preferably at least six times and the image data set compiled from the data obtained from each scan. Each scan will typically last from 1 to 5 seconds, more particularly about 2.5 seconds.
The scanning step of the method may be carried out to generate an image data set for the entire object. In this respect, the reference to the image data set being for the entire object is to be taken to mean all the image data necessary to prepare the desired sculpture. In some cases, for example in the case of a sculpture of a person's head or bust or a complete person or animal, the image data will be of the entire object. However, in other cases, for example in the preparation of a cameo, it is necessary only to obtain image data of a part of the object or subject. Alternatively, the data set may be obtained for just a portion of the object required in order to prepare the desired sculpture. The reasons for this are as follows.
It has been found that current three dimensional scanners used in the art are of such high resolution and quality that the image data set produced contains too much detail of the image for the efficient and successful completion of the further steps of the process. In particular, it has been found that subjects with hair and fur, such as heads of people and animals, are imaged with such accuracy by current scanning systems that a very large number of bits of data are required in order to represent the object at such high resolution. The resultant large number of data renders the image data set difficult and slow to manipulate. In addition, it has been found the procedures for preparing the completed sculpture using the image data set cannot operate sufficiently with such a high image resolution.
CN 1105035 C discussed hereinbefore discloses that the sensitivity of the scanning system may be adjustable. While this is one approach to overcoming the aforementioned problem, it has been found difficult to adjust the resolution of the imaging system to compliment precisely the systems used in the later steps in the method, while at the same time maintaining the overall accuracy of the reproduction. In addition, and perhaps more importantly, it has been found most advantageous to be able to scan the object at the highest resolution possible and to amend or modify the resulting image data set. In this way, the image data set obtained from the scanning step is of the highest quality. The resolution of the entire image data set or just significant portions may be adjusted according to the nature of the subsequent sculpting procedures. Further, manual or automatic manipulation of the image data set is improved when working with the high resolution data and produces improved results.
If the object is to only have a portion of its surface scanned, it is preferable to assess the object before the scanning stage, in order to determine the nature of the features of the object and the detail thereof. The portions of the object having a level of detail above a predetermined threshold, such as the hair and fur of subjects, may be omitted from the scan. The remaining portions of the object, having surface details that do not exceed the threshold, are then scanned to produce the image data set.
Thus, for example, in the case of a completed sculpture being prepared from an image data set using rapid prototyping (RP) techniques, as in one particularly preferred embodiment of the present invention, the threshold value of the level of detail to be tolerated is set by the RP system, in particular the resolution to which the system can operate, the materials being used and the length of time to be taken in preparing a reproduction from the image data set. In general, the higher the resolution of the image data set, that is the higher the level of detail, the longer the RP system will take in translating the image
data into an object. In one case, therefore, the detail threshold will be set by the length of time to allocated to the RP system for preparing the replica.
Thus, the present invention in this embodiment, elects to have the scanning system operate at its highest resolution and omit those features that have too much detail for subsequent sculpting using the image data set. Portions of the object surface have a sufficiently low amount of detail, for example a face, clothing or the like, are imaged at the high resolution to provide a partial image data set of the object. It will thus be appreciated that the present invention defines the portions of the object to be scanned by the nature of the surface features, rather than by adjusting the sensitivity or resolution of the scanner, as is relied upon in the prior art.
In embodiments of the method in which just a portion of the object is scanned, the resulting partial image data set is modified to include image data for the omitted portions of the object. Software available to manipulate and modify an image data set in this manner is well known and commercially available in the art and. includes various computer aided design (CAD) packages and reverse engineering software packages, which allow a user to add features to an image. Examples of suitable commercially available software packages include Geomagic™, commercially available from Interplex Ltd., and Magics
RP™, commercially available from Materialise N.V. In this way, the omitted portions of the image data set may be added by hand or automatically, in order to create a modified image data set of the entire object to be reproduced.
In an alternative embodiment of this aspect of the present invention, the entire surface of the object to be sculpted is scanned and an image date set of the complete object obtained. Again, this will be carried out using the scanner at a high level of resolution, that is to capture a high level of detail. The image data set is then modified to identify those portions of the image data set that
exceed a threshold detail level determined by the subsequent processes to be undertaken. The image data set is then modified to bring the detail level of the entire image to below the threshold value. Software available to manipulate and modify an image data set in this manner is well known and commercially available in the art and includes various CAD packages and reverse engineering software packages, as aforementioned, which allow a user to modify features in an image. In this way, the level of detail of the image data set may be altered by hand or automatically, in order to create a modified image data set of the entire object to be reproduced.
Again, the image data set is adjusted according to a threshold for detail that is determined by the subsequent processing techniques to be employed, such as RP, as described hereinbefore.
Further operations or manipulations of the data in the image data set may be carried out in the preparation of the image data set. For example, the image data may be altered to remove unwanted features or alter features according to the sculptor's or subject's wishes. For example, blemishes and marks on a person's skin may be removed, as desired. In addition, the scale of the image data may be adjusted, in particular to increase or decrease the scale of the object to be prepared from the image data set. In many cases, for example in the case of the sculpting of an animal or person, in particular a full figure or a bust, the finished sculpture will be required to be considerably smaller than life-size. This will reduce both the size and weight of the completed sculpture, for example, a replica at half scale having only one eighth the volume and material of the full-size object.
The image data set may be modified to change the ratio of the sizes of the image in each dimension. In one embodiment, the image data set is modified to reduce the scale of the image in one dimension. Thus, in the case of an image having axes x, y and z, the image data set may be modified to reduce
the image along the z axis, while retaining the size of the image in both the x and y axes. In this way, a modified image data set may be prepared that can be used to prepare a replica in the form of a medal, medallion, plaque or cameo. Surprisingly, it has been found that the image data file may be modified in this way without introducing major distortions to the overall image and the final appearance of the replica. By way of example, the image data set may be modified to adjust the scale of the image in one dimension or along one axis by a factor of from 0.1 to 0.5, for example 0.25, without the final replica being distorted.
The modified image data set is used in the subsequent processing, which creates a replica and finished sculpture according to the modified data set. This may be achieved in a variety of ways.
In one embodiment, the modified image data set is used in the direct preparation of the final sculptured object. For example, the modified image data set may used as the input to a computer controlled milling machine, lathe or the like. In one particularly preferred embodiment, the modified image data set is input into a rapid prototyping (RP) system. Rapid prototyping is a modern technique, by which objects are constructed using the successive deposition of material in a solid freeform fabrication (often referred to as three- dimensional printing) according to a set of computer generated instructions. The RP system deposits liquid or powdered material in successive layers in accordance with a set of profiles or contours communicated to it, in order to construct the completed article. Suitable RP systems are known in the art and are commercially available. Examples of RP systems and techniques include stereolithography apparatus (SLA), selective laser sintering (SLS), fused deposition modeling (FDM), laminated object manufacturing (LOM), inkjet systems and three dimensional printing (3DP)
The RP systems may be used to prepare or construct a reproduction using any suitable material, most specifically plastics, ceramics and metals. Suitable plastics include acrylonitrile butadiene styrenes (ABS), polycarbonates and polyphenyl sulphones. The RP system may be employed to deposit a single material to construct the reproduction. Alternatively, two or more materials may be used. In one embodiment, a two-component system is used, in which one component has a low melting point or is soluble in a suitable solvent and such component may be removed by suitable heating or dissolving in a solvent. In this way, a reproduction may be prepared that is hollow, for example to reduce overall weight of the sculpture.
Suitable conversion of the modified image data file to a format readable by the RP system may be required. For example, many CAD and reverse engineering software systems are operable to output data files in STL format, which acts as an interface between a CAD system and an RP system. Other suitable conversions and interfaces will be known to the person skilled in the art.
A particularly preferred embodiment in which the image data set is used directly in the preparation of the finished sculpture is in the preparation of a cameo. In this embodiment, the image data set is used directly in a process, such as milling or rapid prototyping to prepare a cameo. It has been found that cameos of a very high quality comparable to those prepared using conventional and traditional techniques may be prepared quickly and cheaply, by persons with little or no skill in the art of cameo making.
As noted, the image data set may be employed directly in the preparation of the completed sculpture, for example using the various RP techniques discussed hereinbefore. In an alternative embodiment, the image data set is used to prepare a replica of the object being sculpted. Such a replica may be prepared using the aforementioned techniques, in particular RP. The replica
is then used in a further process to prepare the completed sculpture. Suitable processes include vacuum forming and casting. Casting is a particularly preferred technique for preparing the completed sculpture.
In one embodiment, the replica, for example prepared using RP, is employed in a conventional lost wax casting process, in which the replica is used to prepare a wax replica, which is used in turn in the lost wax casting in known manner. Alternatively, the replica prepared directly from the image data, in particular using RP techniques, is employed directly in an analogous process, in which the replica is prepared from a low-melting point plastic, such as ABS, and replaces the wax replica in the lost wax process. Such a process is referred to herein as a 'lost material casting process'.
As an alternative, the replica prepared directly from the image data set may be used as the form in a vacuum moulding process, in which the completed sculpture is prepared by vacuum forming a suitable material over the replica. Suitable vacuum forming techniques will be known to the person skilled in the art.
Alternatively, other techniques for forming the final object may be employed. Examples include computer controlled milling operations and computer numerical control (CNC) machining.
In still a further embodiment, the replica prepared from the image data set is used to prepare a die for the preparation of a medal or medallion or the like by striking. In the striking process, a die is prepared from a suitable material to have a negative impression of the final desired form. A blank medal, medallion or the like is then struck using the die, to leave the final form. The replica produced in the present invention may be used, in turn to prepare a die. Alternatively, the replica may be prepared having a negative form and used directly as a die itself. Suitable systems and techniques for forming a
die for striking a medal or medallion are known in the art and commercially available. One suitable technique to prepare the die is computer aided milling.
In a further aspect, the present invention provides a method for the preparation of sculpted objects, the method comprising the following steps:
(a) inspecting an object to be sculpted and identifying portions of the object with a level of detail greater than a predetermined threshold;
(b) scanning the object with the exception of the portions identified in step (a) to have detail above the predetermined threshold to provide an image data set;
(c) modifying the image data set to include data for the omitted portions, to provide a complete image data set for the object; and
(d) preparing a completed sculpture using the modified data set.
A still further aspect of the present invention provides a method for the preparation of sculpted objects, the method comprising the following steps:
(a) scanning an object to provide an image data set;
(b) assessing the image data set to identify portions of the image data having a level of detail above a predetermined threshold value;
(c) modifying the image data set to reduce the level of detail to below the predetermined threshold value; and
(d) preparing a completed sculpture using the modified data set.
The features and techniques of the steps in the methods of the aforementioned two aspects of the invention are as hereinbefore described.
In a further aspect, the present invention provides an image data set prepared as hereinbefore described, which is intended for use in the preparation of a completed sculpture, again as hereinbefore described. Accordingly, there is
provided in this aspect, a method for preparing an image data set for use in the preparation of a sculpture of an object, the method comprising the steps of (a) scanning at least a portion of the object to be sculpted to prepare an image data set; and (b) modifying the image data set to provide a modified image data set in a form suitable for use in the preparation of a sculpture of the object.
The scanning of the object and modification of the resulting image data set are as set out and described above.
In the methods of the various aspects of the invention set out above, the problem of the image data set have a level of detail or resolution exceeding that which is practicable or feasible to employ in the subsequent steps to prepare the replica and/or completed sculpture is overcome either by scanning only a portion of the object and completing the image data set by some other means or by scanning the entire object and modifying the image data set accordingly. As an alternative to these embodiments, it has been found that the problem may be overcome by preparing only a partial image data set of the object, using the partial image data set to prepare a particular partial sculpture of the object and completing the sculpture using another sculpting technique. Accordingly, in a further aspect of the present invention, there is provided a method for the preparation of a sculpted object, the method comprising the following steps:
(a) scanning a portion of an object to provide an image data set; (b) preparing a partial sculpture of the scanned portion of the object using the image data set using a first technique; and (c) preparing a full sculpted object using a second technique.
In the method of this aspect of the present invention, the object is scanned. Suitable scanning systems and techniques are as set out above. The object to be sculpted is scanned only in those portions that have a level of detail that
is below a predetermined threshold and allows the image data thus generated to be utilised in subsequent first sculpting processes. Preferably, the method comprising the step of assessing the object prior to being scanned, in order to identify the level of detail of the different portions of the object. The portion scanned is then the portion selected to have a level of detail within the working range of resolution of the subsequent first sculpting technique.
The image data set may be modified prior to being used in the preparation of the partial sculpture, for example to correct or alter features of the image, or to adjust the scale of the image, as described hereinbefore. Suitable software packages for the manipulation of the image data, such as CAD packages and reverse engineering software packages, are well known in the art, as mentioned hereinbefore.
The image data set, whether generated directly by the scanning step or modified, is used by a first sculpting technique to prepare a partial replica of the object. Suitable first sculpting techniques include milling and the various rapid prototyping systems described hereinbefore. The operation of such techniques are dependent upon the detail level in the image data.
Once the available image data have been used to prepare the partial replica, the remainder of the replica is prepared using a second sculpting technique. The second sculpting technique may be one of the aforementioned processes or systems, such as milling or RP, but operating from a different data set, such as a standard or independently programmed data set. Other second sculpting techniques include finishing the sculpting by hand. This is particularly desirable in the preparation of cameos, which have traditionally been prepared by hand.
The full sculpted object may be the completed sculpture, prepared for example by a combination of RP and hand finishing. Alternatively, the full
sculpted object may be used in further processing, such as casting, in order to prepare the completed sculpture. Suitable casting processes are as hereinbefore described. A particularly preferred casting process is the lost material casting process, using the replica prepared using RP.
The methods of the present invention may be applied to prepare a single finished article, in particular a sculpted article or replica. Alternatively, the present invention may be used to prepare two or more final articles which are subsequently combined to create a larger, finished object or sculpture.
Embodiments of the present invention are described in relation to the production of three dimensional sculptures and cameos of human heads and animals. However, it is to be understood that the invention applies to the production of three dimensional sculptures and cameos of any number of objects.
Embodiments of the present invention will now be described, by way of example only, having reference to the accompanying drawings, in which:
Figure 1 is a schematic representation of an imaging and sculpting system according to one embodiment of the present invention; and
Figure 2 is a schematic representation of methods according to embodiments of the present invention.
Referring to Figure 1 , there is shown an object 2 to be sculpted, in this case the head of a person. The object 2 comprises a portion 4 that has a level of detail below a threshold value, in particular the face of the subject. In addition, the object 2 has a portion 6 that contains many small features having a level of detail exceeding the threshold value, in particular the hair of the person.
An imaging system 8 is used to obtain several images of the object 2 and to provide an image data set. The portions of the object 2 that are scanned and imaged by the imaging system 8 are as described below with reference to Figure 2.
The image data set is supplied to a computer 10 programmed with suitable CAD software or a reverse engineering software package to modify the image data set. Again, modification of the image data set will be described below with reference to Figure 2.
The modified image data set produced by the computer 10 is fed to a rapid prototyping (RP) system 12, by way of a suitable software interface, such as STL. The RP system 12 may be used to produce a completed sculpture 14 directly from the image data set. Alternatively, the RP system 12 may be used to prepare a replica from the image data set that is in turn used in a lost material casting process 16 to prepare the completed sculpture 18.
Methods for the preparation of a completed sculpture are represented schematically in Figure 2. Thus, in a first object assessment step 100, the object to be sculpted is analysed to determine the level of detail in the features of the object. This analysis may be carried out automatically using a suitable image analysing system. Alternatively, or in addition thereto, the assessment of the object may be by eye.
Once the object assessment has been completed, the object is scanned in one of two alternative scanning steps 102 and 104. In the first alternative scanning step 102, the portion of the object having a level of detail below a predetermined threshold value is scanned. Thus, in the embodiment shown in Figure 1 , the hair 6 of the subject 2 is not scanned, as the level of detail of the hair exceeds that which is workable using the RP system 12.
The partial scan 102 generates a partial image data set. In one embodiment, the partial image data set is used directly in a RP step 106 to prepare a partial sculpted object or replica, which is then finished by a hand sculpting step 108 to add the missing portions of the sculpture and provide a full replica 110. As an alternative to this, the partial image data set is first modified in a data modification step 112, before being provided to the RP step 106.
In a second embodiment, the partial image data set is subjected to a data modification step 112, in which the image data from the scan are supplemented with image data input by hand and/or automatically generated to provide a modified, full image data set. The data modification step 112 may also include other manipulations of the image data, in particular adjustment of the scale of the replica. The modified, full image data set is fed to a RP step 114, via a suitable interface, in which a full replica 116 of the object is prepared.
In the case that the object to be sculpted is subject to a full scan 104, the image data set produced is a full image data set. This data set is subjected to a data modification step 118, in which the detail level of the image data is reduced to below the threshold level. Other modifications or manipulations of the image data as hereinbefore described, may also be made in the step 118. The modified image data set thus produced is provided, via a suitable interface, to a RP step 120, in which a full replica 122 of the object is prepared.
The full replicas 110, 116 and 122 produced in the three alternative method embodiments shown in Figure 2 may be the final, completed sculpture. Alternatively, they may be employed in a casting process, in particular a lost material casting procedure, to prepare a cast completed sculpture, or in a moulding process to produce a final moulded article. In this way, a single
product or multiple products may be prepared from the full replicas 110, 116 and 122, as indicated in Figure 2.
The hand sculpting step 108, indicated in Figure 2, may include one or more hand finishing techniques applied to the article, in order to provide the desired surface finish and patina.
Applications for the process include, but are not limited to, the sculpting of human heads to provide three dimensional portraits, and providing replicas of animals, such as dogs, cats and horses.