CN101840584B - Two-dimensional digital character operating method based on interactive display - Google Patents

Abstract

The invention discloses a two-dimensional digital character operating method based on an interactive display. The traditional shape deformation technology and application are not suitable for common users and are hard to promote to the general portable mobile equipment. The method comprises the following steps: firstly establishing a two-dimensional character skeleton, calculating the characteristic points of each curve, connecting the characteristic points of each curve, connecting the characteristic points with the shortest distance between detach curves; and secondly, using one finger of a user or a stylus to appoint and move a plurality of constrained points on a character through the interactive display to operate the character to perform the corresponding deformation. During the operating process, the minimum deformation energy function is used to obtain the deformation position of the skeleton and generate a natural character posture satisfying the user restraint. The method of the invention is based on the shape deformation technology based on geometry deformation energy and establishes and optimizes the corresponding character shape deformation energy function to generate the natural character posture with visual reality.

Description

Two-dimensional digital character operating method based on interactive display

Technical field

The invention belongs to two-dimensional character cartoon technique field, particularly relate to a kind of two-dimensional digital character operating method based on interactive display.

Background technology

Along with the development of human-computer interaction technology, interactive display screen is popularized on portable mobile apparatus such as mobile phone gradually.It allows the user through the content in finger or the pointer intuitive and convenient ground operation mobile device.Therefore,, design and develop relevant application, can more service be provided for the user of specific mobile device to this novel interactive mode.

Warpage is an important technology in the computer animation field, and it creates the abundant motion and the variation effect of object through the shape that changes object, and then can produce corresponding animation sequence.Traditional warpage technology mainly comprises: Free Transform method (Free form deformation) and skeleton driving method.They are in the commercial animation software of the computing machine of main flow, and for example the Flash of Macromedia company etc. is very popular.But, this two kinds of methods or need dispose skeleton for object, or need edit object to surround the summit of control mesh, and these operations all need the user to possess certain professional animation knowledge, and need the user to drop into more time and efforts; In addition, portable mobile apparatus like mobile phone, lacks interactive meanses such as keyboard and mouse, is difficult to let the user conveniently accomplish aforesaid operations.Therefore, traditional warpage technology and application thereof are not suitable for domestic consumer, and are difficult to be generalized to general portable mobile apparatus.

Shape direct control method allows the user only need on object shapes, specify and moves several obligatory points, promptly can be object and implements corresponding warpage.Combine with interactive display screen; This method can like smart mobile phone, provide a novel entertainment applications: through the interactive display on the mobile phone for specific portable mobile apparatus; The user can use finger or pointer to change the shape of digital object, and produces simple animation.But existing shape direct control method is only applicable to the simple shape of a polygon or a curve representation, and in practical application; Some complex objects; Like two-dimensional character (as shown in Figure 1), its each characteristic member is like head, eyes, hand etc.; Need describe separately, and each characteristic member all need use one or more curve to represent its profile (as shown in Figure 2).Therefore, if can carry out direct control, abundant more application then can be provided for the relevant mobile device that has interactive display, select thereby bring the more digital entertainment of user to two-dimensional character.

Summary of the invention

The present invention is directed to the deficiency of prior art, a kind of two-dimensional digital character operating method based on interactive display is provided.

The inventive method is at first set up two-dimensional character skeleton, through energy-optimised method two-dimensional character is out of shape then.

Step (1) is set up two-dimensional character skeleton, and concrete grammar is:

At first computing curvature extreme point, cusp and flex point on each bar curve of expression role profile; The curvature extreme point, cusp and the flex point that calculate are designated as unique point; The method of computing curvature extreme point, cusp and flex point is a mature technology;

Then the unique point on every curve is moved towards straight line connection successively and formed a polygon or a tape according to curve; This changeable shape or tape are called the basic framework skeleton; The unique point of closed curve is connected to form polygon, and the unique point of open curve is connected to form tape;

Connect at last and separate the shortest unique point of distance between curve, as a whole until connecting into the basic framework skeleton on each bar curve, promptly obtain role's framework skeleton of forming by a plurality of basic framework skeletons and the line between them.

In role's framework skeleton, unique point is the skeleton node of role's framework skeleton, and the line between the skeleton node is the skeleton segment of role's framework skeleton.

Every curve of expression role profile has been divided into some strip curves by unique point, and every strip curve must be associated with a skeleton segment in role's framework skeleton.Therefore, when the user operates two-dimensional character, can drive the role through the framework skeleton and deform.

Step (2) is implemented distortion through energy-optimised method to two-dimensional character, and concrete grammar is:

Through interactive display, the user uses finger or pointer to specify and move several obligatory points in shape the role, with operation-roles and make it to take place corresponding deformation.In operating process, through the minimization deformation energy function, obtain the deformation position of framework skeleton, and then produce the natural character pose that satisfies user's constraint.This strain energy of distortion function comprises following three sub-energy functions:

A, rigidity energy function, the constraint skeleton segment time carries out rigid motion in distortion, avoiding and the corresponding sub-curve of this skeleton segment bird caging takes place when the distortion, thereby keeps role's local feature.The rigidity energy function defines as follows:

${\mathrm{\Σ}}_{j=1}^M{\∫}_0^1{\left|\right|{\hat{v}}_j\left(t\right)-{\hat{v}}_j^c-[v_j\left(t\right)-v_j^c]R_j\left|\right|}^2\mathrm{dt}---\left(1\right)$

Wherein, M is the total number of skeleton segment in the framework skeleton; For j bar skeleton segment, v _j(t) and Be respectively position, the R of each point after the initial sum distortion on the skeleton segment _jThe rotational transform matrix, the v that the time carry out rigid motion in distortion for skeleton segment _j ^c(t) and

Be respectively the position after the initial sum distortion of skeleton segment rotation center when carrying out rigid motion.Described rotation center is the mid point of skeleton segment.

B, coordination energy function retrain adjacent skeleton segment and when distortion, do as a whole moving, and with the relative position relation between the sub-curve that in deformation process, keeps correspondence, thereby keep the relative position relation between role's adjacent feature.The coordination energy function is defined as follows:

${\mathrm{\Σ}}_{j\∈N_k}{\∫}_0^1{\left|\right|{\hat{v}}_j\left(t\right)-{\hat{v}}_k^c-[v_j\left(t\right)-v_k^c]R_k\left|\right|}^2\mathrm{dt}---\left(2\right)$

Wherein, N _kFor with the framework skeleton in the skeleton segment set that links to each other of k skeleton node; R _kBe set N _kIn all skeleton segments the time make the as a whole rotational transform matrix that carries out rigid motion in distortion, and v _k ^c(t) and

Be respectively the position, initial sum distortion back of this integral body rotation center when carrying out rigid motion, described rotation center is k skeleton node.

C, position constraint energy function guarantee that user's constraint is satisfied in the position after role's distortion.The position constraint energy function defines as follows:

${\mathrm{\Σ}}_j{\left|\right|{\hat{c}}_j-c_j\left|\right|}^2---\left(3\right)$

Wherein, for j user's obligatory point, c _jBe the position after user's operation;

This user's obligatory point position of representing for the position of using after the distortion of skeleton node.

The present invention compared with prior art; The beneficial effect that has is: than with traditional warpage method; For example Free Transform method and skeleton driving method; The present invention need not the user and carries out loaded down with trivial details skeleton configuration or control the vertex edit of bounding box, and only needs the user to specify and move several obligatory points in shape simply the role.Therefore, this method can be applied to have interactive display but the portable mobile apparatus of interactive meanses such as shortage keyboard and mouse, like smart mobile phone.In addition; Compare with existing shape direct control method; This method not only can be used to operate the simple shape of a polygon or a curve description, also can be used to operate the complicated role of many curve descriptions, thereby further strengthen such technological practicality.

Description of drawings

Fig. 1 is a two-dimentional girl role;

Fig. 2 is for describing each characteristic of two-dimentional girl role member's curve;

Fig. 3 is the posture after two-dimentional girl role's distortion.

Embodiment

When carrying out the two-dimensional character skeleton extraction; At first each bar curve of describing the role is dispersed,, detect the unique point on the curve through the discrete formula of geometric attribute; Comprise curvature extreme point, cusp and flex point, and then connect these unique points to obtain role's framework skeleton.Then, each the bar curve for describing the role is divided into many strips curve to it based on characteristic point, and corresponding together with corresponding skeleton segment every strip curve.At last; For every skeleton segment; With an one of which end points is initial point, and with respectively with two end points between two parallel with vertical vector of unit length of line be coordinate axis, set up a local orthogonal coordinate system; And corresponding with it sub-curve representation in this local coordinate system, and then the framework skeleton through the role drives the role and deforms.

In operation two-dimensional character process, the user uses finger or pointer to specify and move several obligatory points in shape the role through interactive display.When the user moves obligatory point each time,, calculate the deformation position of framework skeleton at first through the rigidity energy that minimizes definition in formula (1), (2) and (3), the summation of coordinating energy and position constraint energy.Then for every framework skeleton segment; According to its deformation position,, calculate the deformation position of corresponding with it sub-curve through of the mapping of simple local coordinate to world coordinates; Finally obtaining describing the deformation position of all curves of role, also is role's current deformation position.According to role's deformation position, draw the role and output to display screen at last.So; On interactive display; The role can follow user's finger or pointer deforms, and produces to satisfy user's constraint, nature and have the character pose of visual realism, thereby lets the user feel as operating two-dimensional character of a real-world object general operation; As shown in Figure 3, the circle point among the figure is user's obligatory point.

Because the rotational transform matrix R in formula (1), (2) _jAnd R _kWith the deformation position of framework skeleton be a kind of nonlinear relationship, therefore minimizing the energy summation that formula (1), (2) and (3) define is a non-linear minimization problem.To this non-linear minimization problem, can restrain through the method for iteration and find the solution.From an initial value, for example, the current location of framework skeleton, in each iterative process, problem is found the solution by following two steps:

1) the current location of framework skeleton as its deformation position, minimize formula (1) and (2) respectively through the linear least square method, calculate the current iteration R in step _jAnd R _kTheoretical according to simple infinitesimal analysis knowledge and corresponding linear least square, can obtain R _jAnd R _kThe separating of analytical form.

2) according to the current iteration R in step _jAnd R _k, can minimize the energy summation of formula (1), (2) and (3) definition through the linear least square method, calculate the deformation position of framework skeleton.At this moment, nonlinear optimal problem has become a linear problem of finding the solution system of linear equations, can find the solution it through numerical methods such as gaussian elimination or LU decomposition.

In each iterative process, because R _jAnd R _kHave separating of analytical form, thereby main computing cost is On Solving System of Linear Equations.Because the variable number that this system of linear equations contains equals the node number in the framework skeleton; And the node in the framework skeleton corresponding the unique point that on the curve of describing the role, detects; Its number is far smaller than the number of vertices of these curves; Therefore the scale of this system of linear equations is less, thereby only needs the less calculated amount of finding the solution.Finally, the travelling speed of this method can satisfy user's true-time operation requirement, and is applicable to the portable mobile equipment with characteristics such as computing power are weak, battery life is short.

Claims (1)

1. based on the two-dimensional digital character operating method of interactive display, it is characterized in that this method comprises to set up two-dimensional character skeleton and two-dimensional character is out of shape two big steps through energy-optimised method, be specially:

Step (1) is set up two-dimensional character skeleton, and concrete grammar is:

At first computing curvature extreme point, cusp and flex point on each bar curve of expression role profile; The curvature extreme point, cusp and the flex point that calculate are designated as unique point;

Then the unique point on every curve is moved towards straight line connection successively according to curve, form a polygon or a tape; This polygon or tape are called the basic framework skeleton;

Connect at last and separate the shortest unique point of distance between the curve, as a whole until connecting into the basic framework skeleton on each bar curve, promptly obtain role's framework skeleton of forming by the line between a plurality of basic framework skeletons and the basic framework skeleton; In role's framework skeleton, unique point is the skeleton node of role's framework skeleton, and the line between the skeleton node is the skeleton segment of role's framework skeleton;

Step (2) is out of shape two-dimensional character through energy-optimised method, and concrete grammar is:

Through interactive display, the user uses finger or pointer to specify and move several obligatory points in shape the role, with operation-roles and make it to take place corresponding deformation; In operating process, through the minimization deformation energy function, obtain the deformation position of role's framework skeleton, and then produce the natural character pose that satisfies user's constraint; This strain energy of distortion function is the summation of following three sub-energy functions:

A, rigidity energy function, the constraint skeleton segment time carries out rigid motion in distortion, avoiding and the corresponding sub-curve of this skeleton segment bird caging takes place when the distortion, thereby keeps role's local feature; The rigidity energy function defines as follows:

Wherein, M is the total number of skeleton segment in role's framework skeleton, v _j(t) be each some initial position of j bar skeleton segment,

Be position after each point deformation of j bar skeleton segment, R _jThe rotational transform matrix that the time carries out rigid motion in distortion for skeleton segment,

The initial position of first rotation center when carrying out rigid motion for skeleton segment,

Position after the distortion of first rotation center when carrying out rigid motion for skeleton segment; Described first rotation center is the mid point of skeleton segment;

B, coordination energy function retrain adjacent skeleton segment and when distortion, do as a whole moving, and with the relative position relation between the sub-curve that in deformation process, keeps correspondence, thereby keep the relative position relation between role's adjacent feature; The coordination energy function is defined as follows:

Wherein, N _kFor with role's framework skeleton in the skeleton segment set that links to each other of k skeleton node; R _kBe set N _kIn all skeleton segments the time make the as a whole rotational transform matrix that carries out rigid motion in distortion,

The initial position of second rotation center when carrying out rigid motion for this integral body,

Position after the distortion of second rotation center when carrying out rigid motion for this integral body, described second rotation center is a k skeleton node;

C, position constraint energy function guarantee that user's constraint is satisfied in the position after role's distortion; The position constraint energy function defines as follows:

Wherein, for j user's obligatory point, c _jBe the position after user's operation,

This user's obligatory point position of representing for the position of using after the distortion of skeleton node.

Images