WO2016173067A1 - 多彩表示的三维打印方法及系统 - Google Patents

多彩表示的三维打印方法及系统 Download PDF

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WO2016173067A1
WO2016173067A1 PCT/CN2015/080191 CN2015080191W WO2016173067A1 WO 2016173067 A1 WO2016173067 A1 WO 2016173067A1 CN 2015080191 W CN2015080191 W CN 2015080191W WO 2016173067 A1 WO2016173067 A1 WO 2016173067A1
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selection
triangular
color
dimensional shape
dimensional
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PCT/CN2015/080191
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English (en)
French (fr)
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师宁远
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北京敏速自动控制设备有限公司
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Publication of WO2016173067A1 publication Critical patent/WO2016173067A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C67/00—Shaping techniques not covered by groups B29C39/00 - B29C65/00, B29C70/00 or B29C73/00

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  • the invention belongs to the field of three-dimensional printing, and in particular relates to a three-dimensional printing method and system for colorful representation.
  • the colors and/or materials used in the nozzles of the existing three-dimensional printers are relatively fixed.
  • the nozzles can only use one material to print a complete three-dimensional object in a single time, or use one type.
  • the color is colored on the entire object. Finished products with a single print/coloring are relatively monotonous and cannot form a complex combination of multiple materials and multiple colors.
  • the prior art generally uses a block printing recombination method to manufacture complex three-dimensional printed matter, and even some three-dimensional printers use multiple nozzles, but the multiple nozzles still independently complete one component and then assemble and/or Bonding.
  • the split/combination design of multiple components is difficult and difficult to implement; on the other hand, the structural strength and durability of the joints of multiple components are poor, which seriously affects the product life; The joints of the components obviously have waste such as repeated coloring, which increases the time and hardware cost of product manufacturing.
  • the object of the present invention is to provide a three-dimensional printing technology capable of multi-material mixed printing.
  • three-dimensional shapes are prepared in three-dimensional printing software, different materials are used to represent different materials, and the whole is utilized.
  • the coloring scheme of the three-dimensional body surface determines the material used to control the printhead to print a specified triangular face using different materials.
  • a three-dimensional printing method of a colorful representation comprising the steps of:
  • the three-dimensional shape is controlled by the at least one nozzle according to the number and color representation data.
  • the selecting is performed by at least one of a single selection, a multiple selection, a full selection, a frame selection, a same color selection, a water drop selection, and a segmentation selection.
  • the water droplets are selected by using the adjacent triangular surface information of the three-dimensional shape, and searching for one layer element in the search tree each time using the breadth-first algorithm, and searching layer-by-layer elements one by one until the selection is stopped.
  • the segmentation selection is to automatically analyze the three-dimensional shape, and divide the three-dimensional shape into a plurality of parts having independent semantics for the selection.
  • the analysis finds a region having the most obvious feature difference as a boundary of different portions by calculating local features and/or global features of the three-dimensional shape, thereby obtaining the plurality of portions having independent semantics.
  • the color representation data corresponds to the material used, and each material is separately supplied by the at least one showerhead.
  • the setting color representation data comprises:
  • a three-dimensional printing system of a colorful representation comprising:
  • a numbering module for determining all triangular faces in the three-dimensional shape model mesh and numbering each triangular face
  • the printing module is configured to control the three-dimensional printing of the three-dimensional body by the at least one nozzle according to the number and the color representation data.
  • the selection setting module includes:
  • the water drop selection module is configured to use the breadth-first algorithm to search for one layer element in the search tree each time by using the breadth-first information of the three-dimensional shape, and successively search for the layer-by-layer element until the selection is stopped.
  • the selection setting module includes:
  • a segmentation selection module configured to automatically analyze the three-dimensional shape, and divide the three-dimensional shape into a plurality of parts having independent semantics for performing the selection.
  • the segmentation selection module includes:
  • An analysis module is configured to find a region having the most obvious feature difference as a boundary of different portions by calculating local features and/or global features of the three-dimensional shape, thereby obtaining the plurality of portions having independent semantics.
  • the printing module includes:
  • the nozzle control module is configured to correspond the color representation data to the material used, and each material is separately supplied by the at least one nozzle.
  • the selection setting module includes:
  • the invention can quickly select a plurality of triangular faces by a plurality of selection methods and means, thereby determining a triangular face/triangle face group to be colored in a digital model of the three-dimensional shape, thereby controlling an appropriate nozzle to perform multi-material according to a specified color value.
  • the hybrid prints to print a three-dimensional shape with richer colors/materials.
  • the technical solution of the invention is fast and efficient, has high automation degree, and is free and flexible in operation, greatly enriches the color effect of three-dimensional printing, and can even change the structure of the three-dimensional body.
  • FIG. 1 is a flow chart showing a three-dimensional printing method of a colorful representation according to an embodiment of the present invention
  • FIG. 2 is a schematic structural diagram of a three-dimensional printing system module of a colorful representation according to another embodiment of the present invention.
  • Fig. 3 is a schematic view showing the effect of a colorful representation of the system before and after the selection of the triangular faces in a preferred embodiment of the present invention.
  • the digital model of a three-dimensional shape is represented by the data of a triangular mesh, that is, each three-dimensional shape is composed of a triangular mesh containing a plurality of triangular faces, wherein each triangular face has three vertices, and The connecting edges between the three vertices determine the extent; each triangular face is adjacent to at most three triangular faces, and one edge and two vertices are shared with each adjacent triangular face.
  • the process of three-dimensional printing is a process in which the nozzles respectively print the respective triangular faces and finally obtain the three-dimensional shape formed by the triangular meshes.
  • three-dimensional shapes are continuously printed by using different materials for controlling the plurality of nozzles. Body, using a colorful coloring scheme to distinguish between triangular faces using different materials, thus achieving accurate control of multiple nozzles.
  • FIG. 1 is a flow chart showing a three-dimensional printing method in a colorful representation in accordance with an embodiment of the present invention.
  • the three-dimensional printing method of the present invention includes the steps of:
  • the color representation data corresponds to the material used, and further, the various materials are respectively supplied by the plurality of nozzles, so the color representation data actually corresponds to the nozzle of the supply material.
  • the color data of the model it is possible to intuitively indicate the selection of the triangular faces, and freely specify the materials selected for each part of the model, so that multiple nozzles can be scheduled for multi-material mixed printing, enriching the three-dimensional printing effect.
  • the multi-nozzle printing can be sequentially printed layer by layer for each nozzle, or multiple nozzles can be printed in parallel within the respective responsible range.
  • the specific printing mode is selected according to the comprehensive consideration of the shape of the model, the selection result, the material strength, and the control difficulty of the nozzle.
  • a plurality of means for selecting a triangular face are employed, and in actual operation, at least one of the means may be selected as needed.
  • Commonly used selection methods include single selection, multiple selection (selecting consecutive or discontinuous multiple triangle faces) and all selection.
  • a frame selection is also provided (select all triangles in the user specified range box). Face) and the same color selection (select all triangle faces that are the same or similar to the specified triangle face color).
  • a more intelligent water droplet selection and multiple segmentation selection methods are provided to make the selection operation more reasonable, natural, fast and accurate.
  • the water droplets are selected like a water droplet that rises to the surface of the water, and the selected area will expand in a layer-by-layer manner as time passes.
  • the selection method utilizes the adjacent triangular surface information of the three-dimensional shape and is completed by using the breadth-first algorithm. The specific steps are as follows:
  • step 2 until the end of the selection (such as releasing the mouse click button), the triangle face in the selected area is the result of this drop selection.
  • the selection of the water droplets is performed by the user continuously clicking (ie, long pressing) the mouse button to expand the selection range, for example, selecting a water droplet at a certain time (for example, 0.5 seconds) when the long press is pressed;
  • a breadth-first algorithm is performed; each breadth-first algorithm searches only one layer of elements in the search tree, successively searches for layer-by-layer elements; and stops when the long press ends (ie, the user lifts the finger release button) Water droplets are selected.
  • the segmentation selection automatically analyzes the three-dimensional shape and divides it into multiple parts with independent semantics for the user to select.
  • the selection method mainly consists of calculating the local features of the three-dimensional shape (such as the similarity information of the triangular face) and the global features (such as the difference information of the triangular faces), and searching for the region with the most obvious feature difference is the boundary of the different parts. This results in several components with independent semantics.
  • the further preferred embodiment of the present invention can be automatically completed by using multiple methods/algorithms:
  • the segmentation is performed by analyzing the three-dimensional shape structure:
  • the first seed triangle face is the triangle face farthest from the center of the three-dimensional body; each subsequent seed triangle face Sn +1 needs to meet
  • D is the corresponding minimum value of d in any path passing between the seed triangle face s i to any non-seed triangle face f k
  • F is all triangle faces
  • the calculation of this embodiment does not include an iterative process, and the complexity is low, the calculation speed is fast, and the effect is better. If the seed triangle is specified in user interaction mode, the number of divisions and the approximate area can be artificially controlled.
  • the number and location of the segmentation are specified through user interaction:
  • the influence of the above local features on the relationship between the triangular faces is: the closer the distance is, the more similar the similarity is; the similarity of the normal vector variation is within a certain range; the edge with abrupt change of smoothness may be the regional boundary line; The part of symmetry may be separable; parts beyond a certain geometric size may be separable;
  • This embodiment can artificially control the number of divisions and the approximate area. Contains an iterative process with slower calculations.
  • the three-dimensional shape comparison in a set of three-dimensional physical database is divided into two:
  • each three-dimensional shape may obtain at least one segmentation combination, and each segmentation combination divides the three-dimensional shape into at least one segment;
  • score(S i ) Sum(area(s j )/area(W i )*w sj ), where the function Sum() represents the sum, W i is the i-th three-dimensional shape, s j is the j-th part obtained in the segmentation combination S i , and area(s j ) is the area of s j , area(W i ) is the total area of W i , and w sj is the segmentation quality score of s j ;
  • each of the segmentation combinations is found to maximize the sum of the two-part combination score and the two-part combination consistency score, and the two-part combination is used as the segmentation result of the two different three-dimensional shapes, that is, the use
  • the above calculation formula finds the segmentation result corresponding to Max (score(S 1 )+score(S 2 )+consistency(S 1 , S 2 )), that is, the segmentation result of the three-dimensional shapes W 1 and W 2 ;
  • the segmentation selection may also be implemented by other alternative algorithms, and thus the segmentation selection algorithm herein should not be construed as limiting the specific embodiments of the present invention.
  • clustering algorithms such as K-Means, Hierarchical Clustering, etc.
  • the shape matching of the sub-grids may be performed to divide, for example, dividing the three-dimensional mesh into multiple sub-grids.
  • each triangular surface has a color value, that is, the entire triangular surface has only one color;
  • Each vertex has a color value, that is, the color of each point in the triangular face is calculated by interpolating the color values of the three vertices, and the triangular face color is a transition color of three vertices;
  • each vertex has a texture map coordinate, that is, a triangular face The color of each point in the interior is calculated by the texture mapping coordinate interpolation of three vertices to find the corresponding texture point color.
  • the specific triangular face corresponding to the selected color can be known.
  • the present invention also includes a three-dimensional printing system 2 of a colorful representation, as shown in FIG. 2, corresponding to the steps of the above method,
  • the system 2 include:
  • a numbering module 201 configured to determine all triangular faces in the three-dimensional shape model mesh, and number each triangle face;
  • the setting module 202 is configured to select a triangular surface or a triangular surface group to be colored from all the triangular faces, and set color representation data for the selected triangular surface or triangular surface group;
  • the printing module 203 is configured to control at least one nozzle to perform three-dimensional printing on the three-dimensional shape according to the number and the color representation data.
  • the original design of the three-dimensional shape model is selected by a triangular surface, and the model is divided into a plurality of sub-portions, which are respectively represented by different colors, thereby providing mixed printing for various materials.
  • the control scheduling enables multiple nozzles to continuously perform multi-material mixed printing, which improves the mixed printing efficiency and enriches the three-dimensional printing effect.
  • the invention aims to protect a colorful three-dimensional printing method and system, and can select a plurality of triangular faces quickly by using various selection methods and means, thereby determining a triangular surface/triangular surface group to be colored in a digital model of a three-dimensional shape.
  • the appropriate nozzles are controlled to perform mixed printing according to the specified color values, so that a colorful three-dimensional shape can be printed.

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Abstract

一种多彩表示的三维打印方法及系统，该方法包括步骤：确定三维形体模型网格中的全部三角面，并为每个三角面编号（S1）；从全部三角面中选取要着色的三角面或三角面组，并为选取的三角面或三角面组设定色彩表示数据（S2）；根据编号及色彩表示数据控制至少一个喷头对三维形体进行三维打印（S3）。该方法可在三维形体中自由选取三角面，为整个三维形体的不同三角面确定着色方案，从而控制喷头使用不同的材料打印出指定的三角面。

Description

多彩表示的三维打印方法及系统 技术领域
本发明属于三维打印领域，特别涉及一种多彩表示的三维打印方法及系统。
背景技术
借助于计算机控制和快速成型材料等技术的发展，三维打印成为当前工业设计、制造行业的热门话题，通过计算机控制喷头，现有技术已可以成功地将计算机虚拟设计的三维数字模型打印成真实的物品。
但是受限于控制和材料工艺，现有的三维打印机中喷头使用的颜色和/或材料相对固定，打印时喷头一般只能使用一种材料单次打印出一个完整的三维物体、或者使用一种颜色对整个物体着色。采用单次打印/着色的成品相对单调，无法形成多材质多色彩的复杂组合形式。
为解决上述问题，现有技术一般采用分块打印再组合的方式制造复杂三维打印物，甚至有些三维打印机中还采用了多喷头，但多喷头仍然是各自独立完成一个组件再进行组装和/或粘合。采用现有技术的方式，一方面多个组件的拆分/组合设计难度较大，不易实施；另一方面多个组件的结合部结构强度和耐用性较差，严重影响产品寿命；再者多个组件的结合部明显存在重复着色等浪费，增加了产品制造的时间、硬件成本。
发明内容
本发明的目的是提供一种可多材料混合打印的三维打印技术，在三维打印软件中准备三维形体时，通过不同的色彩表示采用不同的材料，利用整个 三维形体表面的着色方案确定用料，从而控制喷头使用不同的材料打印出指定的三角面。采用本发明的技术方案可灵活自由高效地实现一个三维形体的多材料混合打印。
根据本发明的一个方面，提供了一种多彩表示的三维打印方法，包括步骤：
确定三维形体模型网格中的全部三角面，并为每个三角面编号；
从全部三角面中选取要着色的三角面或三角面组，并为选取的三角面或三角面组设定色彩表示数据；
根据编号及色彩表示数据控制至少一个喷头对三维形体进行三维打印。
优选地，所述选取采用单选、多选、全选、框选、同色选取、水滴选取和分割选取中至少一种手段进行。
优选地，所述水滴选取利用所述三维形体的邻接三角面信息，使用广度优先算法每次对搜索树中的一层元素进行搜索，逐次搜索逐层的元素直至停止所述选取。
优选地，所述分割选取是自动对所述三维形体进行分析，并将所述三维形态分割成多个具有独立语义的部分进行所述选取。
优选地，所述分析通过计算所述三维形体的局部特征和/或全局特征，寻找拥有最明显的特征差异的区域作为不同部分的分界处，从而得到所述多个具有独立语义的部分。
优选地，所述色彩表示数据与采用的材料相对应，各材料由所述至少一个喷头分别供应。
优选地，所述设定色彩表示数据包括：
直接设定三角面颜色值；或
设定各顶点颜色值，再按照三个顶点的颜色值插值计算三角面颜色值；或
设定各顶点纹理贴图坐标，再按照三个顶点的纹理贴图坐标插值计算三 角面内每个点的颜色。
根据本发明的另一个方面，还同时提供了一种多彩表示的三维打印系统，包括：
编号模块，用于确定三维形体模型网格中的全部三角面，并为每个三角面编号；
选取设定模块，用于从全部三角面中选取要着色的三角面或三角面组，并为选取的三角面或三角面组设定色彩表示数据；
打印模块，用于根据编号及色彩表示数据控制至少一个喷头对三维形体进行三维打印。
优选地，所述选取设定模块中包括：
水滴选取模块，用于利用所述三维形体的邻接三角面信息，使用广度优先算法每次对搜索树中的一层元素进行搜索，逐次搜索逐层的元素直至停止所述选取。
优选地，所述选取设定模块中包括：
分割选取模块，用于自动对所述三维形体进行分析，并将所述三维形态分割成多个具有独立语义的部分进行所述选取。
优选地，所述分割选取模块中包括：
分析模块，用于通过计算所述三维形体的局部特征和/或全局特征，寻找拥有最明显的特征差异的区域作为不同部分的分界处，从而得到所述多个具有独立语义的部分。
优选地，所述打印模块中包括：
喷头控制模块，用于将所述色彩表示数据与采用的材料相对应，各材料由所述至少一个喷头分别供应。
优选地，所述选取设定模块中包括：
色彩设定模块，用于通过下述方式设定色彩表示数据：
直接设定三角面颜色值；或
设定各顶点颜色值，再按照三个顶点的颜色值插值计算三角面颜色值； 或
设定各顶点纹理贴图坐标，再按照三个顶点的纹理贴图坐标插值计算三角面内每个点的颜色。
本发明通过多种选取方式和手段，能够快速地选取多个三角面，从而在三维形体的数字模型中确定需要着色的三角面/三角面组，进而控制适当的喷头按指定颜色值进行多材料的混合打印，从而可打印出色彩/材料更丰富的三维形体。本发明的技术方案快捷高效，自动化程度高，操作自由灵活，极大地丰富了三维打印的色彩效果，甚至可改变三维形体的结构。
附图说明
图1是本发明一个实施方式的多彩表示的三维打印方法流程示意图；
图2是本发明另一个实施方式的多彩表示的三维打印系统模块结构示意图；
图3是本发明的一个优选实施例中三角面选取前后系统采用多彩表示的效果示意图。
具体实施方式
为使本发明的目的、技术方案和优点更加清楚明了，下面结合具体实施方式并参照附图，对本发明进一步详细说明。应该理解，这些描述只是示例性的，而并非要限制本发明的范围。此外，在以下说明中，省略了对公知结构和技术的描述，以避免不必要地混淆本发明的概念。
在三维打印机中，三维形体的数字模型是以三角网格的数据形式表示的，即每个三维形体由一个包含多个三角面的三角网格构成，其中每个三角面有三个顶点，并由三个顶点间的连接边确定范围；每个三角面最多与周围的三个三角面邻接，与每个邻接三角面共享一条边和两个顶点。三维打印的过程就是喷头分别打印各个三角面最终得到三角网格所构成的三维形体的过程，在本发明的技术方案中，为了控制多个喷头采用不同材料连续打印出三维形 体，采用多彩着色方案来区分使用不同材料的三角面，从而实现了对多喷头的准确控制。
图1是根据本发明的一个实施例中多彩表示的三维打印方法流程示意图；在该实施例中，本发明的三维打印方法包括步骤：
S1，确定三维形体模型网格中的全部三角面，并为每个三角面编号；
S2，从全部三角面中选取要着色的三角面或三角面组，并为选取的三角面或三角面组设定色彩表示数据；
S3，根据编号及色彩表示数据控制至少一个喷头对三维形体进行三维打印。
其中，色彩表示数据与采用的材料对应，更进一步地，各种材料由多个喷头分别供应，故色彩表示数据实际与供应材料的喷头对应。通过设置模型的色彩数据，既可以直观地表示出三角面的选取情况，又可自由指定模型各个部位所选用的材料，从而可调度多个喷头进行多材料的混合打印，丰富了三维打印效果。优选地，多喷头打印可以各个喷头依次逐层打印，也可在各自负责范围内多个喷头并行打印，具体打印方式根据模型形状、选取结果、材料强度、喷头控制难度等综合考虑选用。
在本发明的优选实施方式中，采用了多种选取三角面的手段，实际操作中可以根据需要采用其中至少一种手段进行选取。常用的选取手段包括单选、多选(依次选取连续或不连续的多个三角面)和全选，此外，为了提高操作的便捷性，还提供框选(选取用户指定范围框内的所有三角面)和同色选取(选取与指定三角面色彩相同或相近似的所有三角面)。在更优选的实施方式中，还提供更为智能的水滴选取和多种分割选取手段，让选取操作更加合理、自然、快捷和准确。
其中，水滴选取像水滴落到水面激起的涟漪一样，选取的区域会随着时间的流逝逐层扩大范围。其选取方式利用了三维形体的邻接三角面信息，使用广度优先算法完成，具体步骤如下：
1.如果是第一次选取(比如鼠标初次点选三角面)，对当前选中区域中 的三角面寻找邻接三角面，将它们添加到队列Q中和已选区域中；
2.如果是之后的选取(比如一定时间内未释放鼠标点选按键，则表示继续选取)，弹出队列Q的第一个三角面，寻找它的邻接三角面，如果是新选取的三角面，则将它添加到队列Q中和已选区域中；
3.重复第2步操作，直到结束选取(比如释放鼠标点选按键)，此时已选区域中的三角面即为本次水滴选取结果。
在本发明的优选实施例中，水滴选取依靠用户持续点击(即长按)鼠标按键扩大选取范围，比如在长按时每隔一定时间(如0.5秒)进行一次水滴选取；除去第一次外，每次水滴选取都做一次广度优先算法；每次广度优先算法仅仅对搜索树中的一层元素进行搜索，逐次搜索逐层的元素；在长按结束(即用户抬起手指释放按键)时停止水滴选取。
而分割选取则是自动对三维形体分析并分割成多个具有独立语义的部分，供用户选取。其选取方式主要通过计算三维形体的局部特征(如三角面的相似度信息)和全局特征(如三角面的差异度信息)，寻找拥有最明显的特征差异的区域即为不同部分的分界处，从而得到数个具有独立语义的组成部分。
对于分割选取，本发明进一步的优选实施方式中可采用多种方式/算法自动完成：
实施例一，通过分析三维形体结构进行分割：
1.根据相邻三角面间的夹角，计算每个三角面各边的通过概率p；
其中，根据相交的边求出相邻三角面的通过概率，有p＝Exp(e,-d/t)，其中e为相交的边长，d为相邻两面法向量的距离，t为经验参数；三角面三边的通过概率和为1；其中，t的取值根据实际情况和经验进行设置，优选地，t取值预设为1.0；
2.自动指定至少一个种子三角面(亦可通过用户交互完成)；
其中，第一个种子三角面为离三维形体中心最远的三角面；之后的每个种子三角面Sn+1需符合
Figure PCTCN2015080191-appb-000001
其中D为从种子三角面si到任一非种子三角面fk间通过的任意路径中对应的最小的d值和， F为所有三角面；
3.应用随机游走(Random Walks)算法，计算每个非种子三角面到达每一种子三角面的概率；
4.对每个非种子三角面，找出概率最大的种子三角面与其分为一组(即按概率将各非种子面划分到种子面的分组中)，所得分组结果即为最终的分割。
本实施例的计算不含迭代过程，复杂度低，计算速度快，效果比较好。如果采用用户交互方式指定种子三角面，可以人为控制分割数量和大致区域。
实施例二，通过用户交互指定分割数量和位置：
1.对各个三角面提取局部特征，如欧几里得距离，法向量，平滑度，曲率，对称性，几何直径等；
其中，上述局部特征对三角面间关系判定的影响有：距离越近相似性越大；法向量变化在一定范围内的相似性大；平滑度突然变化的边极有可能是区域分界线；具有对称性的部分有可能是可分割的；超出一定几何尺寸的部分有可能是可分割的；
2.对邻接三角面建立三角面邻接图(Dual Graph)；
3.根据相邻的三角面的局部特征，计算邻接图中各边的权重；
4.由用户指定c个种子区域(c为最终分割出的子区域数量)，每个种子区域k被指派一个标签Lk(k＝1…c)；
5.使用流形排序(Manifold Ranking)算法传播标签，使每个三角面拥有一组概率(p1,…px,…,pc)，其中px表示拥有标签Lx的概率(x取值为1到c)，概率最大的标签即为该三角面最终的标签；
6.拥有同一标签的三角面即为三维形体中相对独立的子区域；
7.如果结果不符合预期，需要重新执行第4-6步的操作进行分割。
本实施例可以人为控制分割数量和大致区域。含有迭代过程，计算速度较慢。
实施例三，通过对一组三维形体数据库中的三维形体两两比较进行分割：
1.通过随机切割(Randomized Cuts)算法将数据库中的所有三维形体分割。其中根据分割方式的不同，每个三维形体可得到至少一个分割组合，每个分割组合将三维形体分割成至少一个分片；
2.根据每个分割组合中各分片面积及各分片的分割质量得分计算该分割组合Si的得分，计算方式如下：score(Si)＝Sum(area(sj)/area(Wi)*wsj)，其中函数Sum()表示求和，Wi为第i个三维形体，sj为分割组合Si中得到的第j个部分，area(sj)为sj的面积，area(Wi)为Wi的总面积，wsj为sj的分割质量得分；
3.对于两不同的三维形体，两两比较其各个分割组合，计算一致性得分；例如计算三维形体W1和W2的分割组合S1和S2的一致性得分为：consistency(S1,S2)＝Sum(Max(score(Mxy)))，其中Mxy为从Sx到Sy的映射，对于S1和S2此处xy取值为12和21，score(Mxy)＝a*sim(Mxy)+b*adj(Mxy)，其中a和b为经验参数，可根据实际效果自行选择，sim(Mxy)为两分割组合的相似性值，例如表示为sim(Mxy)＝Sum(area(c)/area(Wc)*wc)，adj(Mxy)为两分割组合的邻接优先关系值，例如表示为adj(Mxy)＝Sum((area(c)/area(Wc)+area(c’)/area(Wc’))*wcc’)，这里，c和c’表示两个三维形体中相互对应的分片；
4.对于两不同的三维形体，各找到一个分割组合，使两分割组合得分和两分割组合一致性得分总和最大化，将所述两分割组合作为所述两不同三维形体的分割结果，即利用上述计算式求出Max(score(S1)+score(S2)+consistency(S1,S2))所对应的分割结果，即为三维形体W1和W2的分割结果；
5.对数据库中的所有三维形体，每两个都进行一次上述步骤，获得该数据库中各三维形体的分割结果。
采用上述方式，对于每个新三维形体，将其加入数据库进行比较分割，即可学习得到理想的分割结果。本实施例需要拥有(可以人工建立，亦可自 动学习收集)一组三维形体数据库。计算复杂度高，计算时间长，效果好。
此外，优选地，分割选取还可采用其他替代算法实现，因而此处分割选取算法不应视作对本发明具体实施方式的限制。典型地，可根据提取的局部特征使用聚类算法(如K-Means，Hierarchical Clustering等)分割三角面；还可进行子网格的形状匹配进行分割，比如将三维网格分成多个子网格，使用形状匹配算法(如RANSAC等)尝试匹配子网格基础形状(包括但不限于平面、圆柱、圆球等)，如果子网格形状接近基础形状则分为一个独立的子部分，将最终未匹配的三角面合并到已经确定的分割区域中。
本发明的技术方案主要进行三维形体的多彩或混合材料打印，对于要着色的三角面，一般有这样几种色彩表示方式：每个三角面带有颜色值，即整个三角面只有一种颜色；每个顶点带有颜色值，即三角面内每个点的颜色按照三个顶点的颜色值插值计算，三角面颜色为三个顶点的过渡色；每个顶点带有纹理贴图坐标，即三角面内每个点的颜色按照三个顶点的纹理贴图坐标插值计算找到对应的贴图点颜色。在本发明的优选实施例中，为便于计算和控制，最优选采用第一种方式设定三角面的色彩数据。
对每个三角面编上编号，将各编号对应的颜色值绘制到后缓冲区；在进一步编辑和/或操作时，给定鼠标坐标，可从后缓冲区画面中得到对应点的颜色值，根据颜色值逆转换成编号，即可得知所选取的此颜色对应的具体三角面。在三维打印时，根据具体三角面(或具体坐标点)及对应的颜色值，控制适当的喷头使用不同的材料打印出指定的三角面，即可打印出色彩丰富的三维形体。
本领域普通技术人员可以理解，实现上述实施例方法中的全部或部分步骤是可以通过程序来指令相关的硬件完成，所述的程序可以存储于一计算机可读取存储介质中，该程序在执行时，包括上述实施例方法的各步骤，而所述的存储介质可以是：ROM/RAM、磁碟、光盘、存储卡等。因此，本领域相关技术人员应能理解，与本发明的方法相对应的，本发明还同时包括一种多彩表示的三维打印系统2，如图2所示，与上述方法步骤一一对应地，该系统2 包括：
编号模块201，用于确定三维形体模型网格中的全部三角面，并为每个三角面编号；
选取设定模块202，用于从全部三角面中选取要着色的三角面或三角面组，并为选取的三角面或三角面组设定色彩表示数据；
打印模块203，用于根据编号及色彩表示数据控制至少一个喷头对三维形体进行三维打印。
更具体地，本发明上述各优选实施例中的方法或其步骤均依赖特定的功能模块实现，原则上各模块的功能划分与上述方法步骤一一对应，对于重复内容在此不再赘述。
采用本发明的技术方案，如图3所示，对原始设计的三维形体模型进行三角面选取，将模型划分为多个子部分，分别采用不同的颜色进行表示，从而为多种材料的混合打印提供了便利。其中，通过设置模型的色彩数据，既可以直观地表示出不同子部分的选取情况，又可自由指定模型各个部位所选用的材料，既方便了三维打印的设计预览，又可实现多个喷头的控制调度，使得多个喷头可连续进行多材料的混合打印，提高了混合打印效率，丰富了三维打印效果。
本发明旨在保护一种多彩三维打印方法及系统，通过多种选取方式和手段，能够快速地选取多个三角面，从而在三维形体的数字模型中确定需要着色的三角面/三角面组，进而控制适当的喷头按指定颜色值进行混合打印，从而可打印出色彩丰富的三维形体。
应当理解的是，本发明的上述具体实施方式仅仅用于示例性说明或解释本发明的原理，而不构成对本发明的限制。因此，在不偏离本发明的精神和范围的情况下所做的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。此外，本发明所附权利要求旨在涵盖落入所附权利要求范围和边界、或者这种范围和边界的等同形式内的全部变化和修改例。

Claims (13)

  1. 一种多彩表示的三维打印方法，其特征在于，所述方法包括步骤：
    确定三维形体模型网格中的全部三角面，并为每个三角面编号；
    从全部三角面中选取要着色的三角面或三角面组，并为选取的三角面或三角面组设定色彩表示数据；
    根据编号及色彩表示数据控制至少一个喷头对三维形体进行三维打印。
  2. 根据权利要求1所述的方法，其特征在于，所述选取采用单选、多选、全选、框选、同色选取、水滴选取和分割选取中至少一种手段进行。
  3. 根据权利要求2所述的方法，其特征在于，所述水滴选取利用所述三维形体的邻接三角面信息，使用广度优先算法每次对搜索树中的一层元素进行搜索，逐次搜索逐层的元素直至停止所述选取。
  4. 根据权利要求2所述的方法，其特征在于，所述分割选取是自动对所述三维形体进行分析，并将所述三维形态分割成多个具有独立语义的部分进行所述选取。
  5. 根据权利要求4所述的方法，其特征在于，所述分析通过计算所述三维形体的局部特征和/或全局特征，寻找拥有最明显的特征差异的区域作为不同部分的分界处，从而得到所述多个具有独立语义的部分。
  6. 根据权利要求1所述的方法，其特征在于，所述色彩表示数据与采用的材料相对应，各材料由所述至少一个喷头分别供应。
  7. 根据权利要求1所述的方法，其特征在于，所述设定色彩表示数据包括：
    直接设定三角面颜色值；或
    设定各顶点颜色值，再按照三个顶点的颜色值插值计算三角面颜色值；或
    设定各顶点纹理贴图坐标，再按照三个顶点的纹理贴图坐标插值计算三角面内每个点的颜色。
  8. 一种多彩表示的三维打印系统，其特征在于，所述系统包括：
    编号模块，用于确定三维形体模型网格中的全部三角面，并为每个三角面编号；
    选取设定模块，用于从全部三角面中选取要着色的三角面或三角面组，并为选取的三角面或三角面组设定色彩表示数据；
    打印模块，用于根据编号及色彩表示数据控制至少一个喷头对三维形体进行三维打印。
  9. 根据权利要求8所述的系统，其特征在于，所述选取设定模块中包括：
    水滴选取模块，用于利用所述三维形体的邻接三角面信息，使用广度优先算法每次对搜索树中的一层元素进行搜索，逐次搜索逐层的元素直至停止所述选取。
  10. 根据权利要求8所述的系统，其特征在于，所述选取设定模块中包括：
    分割选取模块，用于自动对所述三维形体进行分析，并将所述三维形态分割成多个具有独立语义的部分进行所述选取。
  11. 根据权利要求10所述的系统，其特征在于，所述分割选取模块中包括：
    分析模块，用于通过计算所述三维形体的局部特征和/或全局特征，寻找拥有最明显的特征差异的区域作为不同部分的分界处，从而得到所述多个具有独立语义的部分。
  12. 根据权利要求8所述的系统，其特征在于，所述打印模块中包括：
    喷头控制模块，用于将所述色彩表示数据与采用的材料相对应，各材料由所述至少一个喷头分别供应。
  13. 根据权利要求8所述的系统，其特征在于，所述选取设定模块中包括：
    色彩设定模块，用于通过下述方式设定色彩表示数据：
    直接设定三角面颜色值；或
    设定各顶点颜色值，再按照三个顶点的颜色值插值计算三角面颜色值；或
    设定各顶点纹理贴图坐标，再按照三个顶点的纹理贴图坐标插值计算三角面内每个点的颜色。
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