JP3087525B2 - Fillet surface generation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for generating a fillet surface in a three-dimensional shape modeling system provided in a computer-aided design (CAD) device, and more particularly to a method for generating a fillet surface which can improve tangential continuity. It relates to a generation method.

[0002]

2. Description of the Related Art In a three-dimensional shape modeling system provided in a CAD apparatus, when a fillet surface to be embedded in a previously created shape to be rounded at a corner is generated, conventionally, the modeling system first uses A plurality of tangent arcs having a desired fillet radius that are in contact with both of the two surfaces forming the corner portion in which the fillet surface in the previously created shape is to be embedded are obtained along the corner portion, and then these tangent arcs are separated from each other. Fillet surfaces were generated by connecting them smoothly.

[0003]

However, the fillet surface generated by such a conventional method for generating a fillet surface has almost no problem when used as it is, however, the gap between the fillet surface and the previously created shape is small. Since the tangent plane continuity (the plane perpendicular vector to each plane at the connecting part of the planes coincides) is not sufficiently ensured, if the processing of offsetting the plane is performed, the shape created earlier May be separated or overlapped with the surface.

That is, for example, as shown in a cross section in FIG. 3, two surfaces F ₂ , F ₃ in the previously created shape in which the generated fillet surface F ₁ is embedded, and those surfaces F ₂ , F
When to ridge line (shown in cross-section due point) E _1, E ₂ a via connected fillet surface F ₁ and offset outwardly (equidistant moved the orthogonal direction) to _3, in the fillet surface F ₁ and previously in the position of the surface F ₂ of the shape in which the created ridge E _1, and they happen to be connected broken inwardly without being connected to the tangent plane continuous edge line E ₁ ridgeline E ₃ position it is broken that ,
It would leave to E _4. On the other hand, when offsetting inward, the fillet surface and the surface in the previously created shape overlap.

In such a case, once separation or overlap occurs, the planes cannot be easily connected even if they are extended or shortened. Therefore, the current processing is interrupted to return to the fillet plane generation processing. However, there is a problem that the fillet surface needs to be regenerated, and the efficiency and flow of the modeling process deteriorate.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for generating a fillet surface which advantageously solves the above-mentioned problems of the conventional method. When the three-dimensional shape modeling system generates a fillet surface to be embedded in a corner in the previously created shape, first, the fillet surface in the previously created shape is embedded by the tangent arc search means in the modeling system. A plurality of tangent arcs having a desired fillet radius in contact with both surfaces forming the power corner are determined along the corner, and then the tangent arcs are smoothed by the fillet surface generating means in the modeling system. To generate a fillet surface, and then the tangent plane continuity checking means in the modeling system is used to check the plurality of tangent arcs. For each space, the tangent plane continuity between the fillet surface located between the adjacent tangent arcs and the two surfaces forming the corners is inspected, and as a result of the inspection, the tangent plane continuity is not found. When there is a space between adjacent tangent arcs, a tangent arc is added between tangent arcs that are not continuous with the tangent plane by a tangent arc adding means in the modeling system, and then the tangent arc between adjacent tangent arcs to which the tangent arc is added is added. And a range including a tangent arc in the vicinity thereof is repeated from the process of generating a fillet surface by the fillet surface generation means. For a range other than the range where the process is repeated, the previously generated fillet surface is used as it is. It is characterized by the following.

[0007]

According to this method, the fillet surface generated by the fillet surface generation means from the plurality of tangent arcs obtained by the tangent arc search means is generated before embedding it in the corner of the previously created shape. The tangent continuity between the fillet surface and the two surfaces forming the corners is inspected between the tangent arcs by the tangent continuity inspection means. Since the tangent arc is added by the tangent arc adding means and the fillet surface is generated again by the fillet surface generating means, the continuity of the tangent plane of the fillet surface with respect to the corner in the previously created shape can be improved. Even when performing the process of offsetting the embedded surface, it is possible to prevent separation and overlap between the fillet surface and the surface of the previously created shape. The Deringu processing can be prevented from being hampered by the need for regeneration of the fillet surface efficiency and flow of the modeling process deteriorates.

Further, according to this method, of the generated fillet surface, only the portion that is not tangent to the tangent plane as a result of the inspection and its vicinity are regenerated, and the other portions are the previously generated fillet surface. Since the surface is used, the time for regeneration can be reduced, especially when the fillet surface is buried along a relatively long corner.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a flowchart showing a procedure of an embodiment of a method for generating a fillet surface according to the present invention. In the method of this embodiment, the present inventor first used the three-dimensional shape modeling system of a CAD apparatus in 1990. Using a surface solid coexistence modeler with topological data representing the mutual connection between surfaces, proposed in a paper `` Problems of Solid Modeler and Development of Surface Solid Coexistence Modeler '' published in the Journal of Precision Engineering in November, , shown in FIG. 2 (a), to produce a fillet surface embedded in the corners and the sides F ₄ and the upper surface F ₅ in substantially rectangular parallelepiped shape S created earlier forms.

In performing the fillet surface generation processing, here, first, in step 1 in FIG. 1, as shown in FIG. 2A, two surfaces F each forming a corner in the shape S are formed.
_4, F plurality of contact arcs both in contact with the desired fillet radius of _5, for example, five in the illustrated example against the arc A ₁ to A
_5, created respectively in a plurality of planes respectively perpendicular to the edge line E ₆ together arranged along the edge E ₆ of the corner portion,
Then in step 2, as shown in FIG. 2 (b), between a plurality of tangent arcs A ₁ to A ₅ was its creation as smoothly connecting interpolated curved surface, to produce a fillet surface F _6. Therefore, the modeling system that executes step 1 corresponds to a tangent arc search unit, and the modeling system that executes step 2 corresponds to a fillet surface generation unit.

Subsequently, here, in step 3 in FIG.
Between each of the plurality of tangent arcs, for example, between the tangent arcs A ₁ and A _2, between A ₂ and A ₃ , A ₃ and A _{4 in the} illustrated example.
In each of the two ridge lines E ₇ and E ₈ , which are tangents between the generated fillet surface F ₆ and the two surfaces F ₄ and F ₅ forming the corners, between A ₄ and A ₅ . Above, for example, one point P ₁ -P ₄ , Q ₁ -Q at the center between their tangent arcs
_4, examines the tangent plane continuity between the two surfaces F _4, F ₅ for forming the fillet surface F ₆ and the corner portion. This tangent plane continuity test is performed, for example, as shown in FIG.
The surface F ₄ or F ₅ forming the corner at the point to be inspected
For the surface perpendicular direction vector V _1, can be performed by examining the angle θ between the orthogonal direction vector V ₂ for fillet surface F _6, the corner θ is the case within a predetermined tolerance range very close to zero Can be determined to be substantially tangent plane continuous. Therefore, the modeling system that executes the step 3 corresponds to a tangent plane continuity inspection unit.

As a result of the inspection in the above step 3, the ridge lines E ₇ , E ₈
If at least one of the upper central points P and Q is not continuous with the tangent plane, the process proceeds from step 4 to step 5, where one tangent arc is added between the tangent arcs that are not continuous with the tangent plane. Returning to step 2 above, between the tangent arcs where the tangent arc is added and the fillet surface is affected by the addition of the tangent arc, for example, on both outer sides of the tangent arcs on both sides between the tangent arcs where the tangent arc is added The process is repeated from the process of generating the fillet surface up to the tangent arc.
Therefore, the modeling system that executes the step 5 corresponds to a tangent arc adding unit.

That is, for example, in the illustrated example, the tangent arc A ₃ ,
For one of the points P ₃ of the center point P _3, Q ₃ between A _4, when the surface F ₄ at its periphery is not a tangent plane continuous or dented slightly, the contact arc A _3, A ₄ after adding one contact arc a ₆ in the middle between, the process returns to step 2, also using their contact arc a _6, tangent arc a _3, further both outer contact of a ₄ arc a ₂ to a ₅ Is repeated from the process of generating a fillet surface within the range of. If a portion that is not continuous with the tangent plane still remains even in the regenerated fillet surface, an additional tangent arc is added between the tangent arcs where the tangent surface is not continuous to regenerate the fillet surface. .

[0014] the other hand, the range outside the range repeating the process to produce a fillet surface returns to Step 2 as described above, i.e., for example, for the indirect arc A _1, A ₂ the illustrated example, first in step 2 the fillet surface F ₆ which is generated is used as it is. Further, the test at step 3, if was tangent plane continuous between all contact arc, is used as it is over the fillet surface F ₆ which was generated earlier in their entirety.

According to the method of this embodiment described above, it is possible to improve the tangential continuity of the fillet surface F ₆ with respect to the two surfaces F ₄ and F ₅ forming the corners in the previously formed shape S. Therefore, even when performing a process of offsetting the surface in which the fillet surface is embedded thereafter, separation or overlap between the fillet surface and the surface of the previously created shape can be prevented, and therefore, It is possible to prevent the current modeling process from being hindered by the need to regenerate the fillet surface, thereby reducing the efficiency and flow of the modeling process.

Further, according to the method of this embodiment, of the generated fillet surface, a portion that is not continuous with the tangent plane as a result of the inspection and its vicinity, for example, the tangent arc A in the illustrated example.
To regenerate only between ₂ to A _5, since other portions are used fillet surface is generated earlier, especially when relatively long corners that embed fillet surface along, the regeneration time Can be shortened.

Although the present invention has been described with reference to the illustrated examples, the present invention is not limited to the above-described examples. For example, the positions where the tangent plane continuity is inspected are two surfaces forming a corner and a fillet surface. Two or more positions between the tangent arcs on the ridge line that is a tangent to the tangent arc may be used. It may be added to only those positions that did not exist, or may be added to two or more positions including positions that were not continuous with the tangent plane. The present invention can also be implemented using other types of three-dimensional shape modeling systems other than those described above, and can achieve the above-described effects.

[0018]

As described above, according to the method for generating a fillet surface of the present invention, it is possible to improve the continuity of the tangent plane of the fillet surface with respect to the corner in the previously created shape, and thereafter, the surface having the fillet surface embedded therein. Even when performing the process of offsetting, the separation and overlap between the fillet surface and the surface of the previously created shape can be prevented, and therefore, the current modeling process can be performed by reproducing the fillet surface. It is possible to prevent the efficiency and the flow of the modeling process from being impaired due to the necessity of formation.

Further, according to this method, of the generated fillet surface, only the portion that is not tangent to the tangent plane as a result of the inspection and its vicinity are regenerated, and the other portion is the previously generated fillet surface. Since the surface is used, the time for regeneration can be reduced, especially when the fillet surface is buried along a relatively long corner.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a procedure of one embodiment of a method for generating a fillet surface according to the present invention.

FIGS. 2 (a) to 2 (d) are explanatory diagrams showing shapes created at each stage of the method of the embodiment.

FIG. 3 is an explanatory diagram showing a state in which a shape including a fillet surface created by a conventional method is subjected to offset processing.

[Explanation of symbols]

S Shape created earlier E Ridges along the _six corners F ₄ , Two faces forming the F ₅ corner F ₆ Fillet face A ₁ -A ₅ Tangent arc A ₆ Additional tangent arc P ₁ -P ₄ , Q ₁ 〜Q ₄ Points to check tangent plane continuity

Continuing from the front page (72) Inventor Seiji Eguchi 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Nissan Motor Co., Ltd. (72) Inventor Takatsugu Ishii 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd. ( 58) Fields surveyed (Int.Cl. ⁷ , DB name) G06F 17/50

Claims (1)

(57) [Claims] When a three-dimensional shape modeling system generates a fillet surface to be embedded in a corner in a previously created shape, first, a tangent arc search means in the modeling system uses
Ri, more determined along the contact arc of the desired fillet radius in contact with both of the two surfaces forming the corner portion to embed fillet surface shape in which created the destination to the corner, then in the modeling system Fillet plane generation
Means for smoothly connecting the tangent arcs to each other to generate a fillet surface, and then checking the tangent continuity in the modeling system.
By means, between each of the plurality of tangent arcs,
Said fillet surface located between its adjacent tangent arcs,
The tangent plane continuity between the two surfaces forming the corners is inspected. If there is an adjacent tangent arc that is not tangent plane continuous as a result of the inspection , the tangent arc tracking in the modeling system is performed.
The pressurizing means for its after adding the contact arc between the tangent plane not continuous contact arc, the range including the contact arc in the vicinity of the contact arc between and adjacent to add the contact arc, the full
A method for generating a fillet surface, wherein the process is repeated from the process of generating a fillet surface by the fillet surface generating means, and the fillet surface generated earlier is used as it is for a range other than the range in which the process is repeated.