WO1997017677A1 - Procede de generation dynamique d'images synthetiques a niveau de detail automatique, et dispositif de mise en oeuvre - Google Patents
Procede de generation dynamique d'images synthetiques a niveau de detail automatique, et dispositif de mise en oeuvre Download PDFInfo
- Publication number
- WO1997017677A1 WO1997017677A1 PCT/FR1996/001716 FR9601716W WO9717677A1 WO 1997017677 A1 WO1997017677 A1 WO 1997017677A1 FR 9601716 W FR9601716 W FR 9601716W WO 9717677 A1 WO9717677 A1 WO 9717677A1
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- WO
- WIPO (PCT)
- Prior art keywords
- detail
- observer
- terrain
- points
- level
- Prior art date
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Classifications
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T17/00—Three dimensional [3D] modelling, e.g. data description of 3D objects
- G06T17/20—Finite element generation, e.g. wire-frame surface description, tesselation
Definitions
- the present invention relates to a method for dynamic generation of synthetic images with automatic level of detail, as well as to a device for implementing this method.
- the real-time image synthesis machines used in flight simulators are capable of generating images of a quality close to reality thanks in particular to the massive use of photographic textures. But the maximum number of polygons that can be displayed in each image cycle remains their main limitation.
- the terrain model (algorithms and data structures) which manages this altimetric data must take into account the following three requirements which are essential, in particular for aircraft flight simulators: - Fidelity:
- the characteristic aspects of the relief are very important visual landmarks for pilots and influence the quality of their training and their decisions during a mission.
- the respect crest lines is therefore an essential condition for any cartographic model.
- the number of polygons representing a given terrain directly influences the response times of the real-time simulator (rendering, collision, rolling, intervisibility ).
- the roughness of a ground not being regular, the mesh must adapt to the relief, loose in the areas of constant slope, fine in the uneven parts.
- a first approach consists in precalculating different levels of detail for each region and switching in real time from one level to another. Unfortunately this method has many drawbacks:
- the memory footprint limits the number of levels of detail per region and penalizes the dynamic loading of the database. In addition, this number varies according to the relief of each region.
- the subject of the present invention is a process for dynamic generation of synthetic images making it possible to generate synthetic images in real time with the maximum possible fidelity and the best possible rendering, without requiring significant calculation means, taking into account the relevance. points of the various levels of detail as a function of the position of the observer, this process also allowing modifications to the configuration of the terrain in real time.
- the present invention also relates to a dynamic generator of synthetic images comprising means which are the cheapest possible, preferably means such as calculators and means for storing databases which are simple and commonly available.
- the method in accordance with the invention consists in constituting a database starting from a file containing the topographic data relating to the land to be viewed, eliminating the least significant data, then calculating in real time the points to be displayed as a function the level of detail required, which itself depends on the position of the observer, the maximum altitude of the terrain to be viewed, the visibility distance and the level of detail required, by selecting a subset of the points in the database defining a portion of terrain whose level of detail has changed, by making an irregular mesh of the selected portion of terrain, preferably a Delaunay type mesh, and applying a texture to the polygons resulting from the mesh.
- the accuracy of the representation of the terrain is locally adjusted by adding or removing points in the mesh, the selection of these points being made according to the relief, the position of the observer and the type of vehicle on which the observer is located.
- - Figure 2 is a diagram showing the evolution of the triangulation error of a surface as a function of the number of points chosen to represent it
- - Figure 3 is an explanatory diagram showing the effect of the insertion of a significant point on the triangulation error
- FIG. 4 is a simplified diagram of the software architecture of a graphics processor implementing the method of the invention
- FIG. 5 is a simplified explanatory perspective view defining the angular error criterion used by the present invention.
- FIG. 6 is a simplified example explaining the switch from a level of detail N to a level of detail N + 1, in accordance with the invention.
- the present invention to produce a terrain model, implements a mesh technique based on the Delaunay triangulation, and more precisely the constrained Delaunay triangulation, schematically illustrated in FIG. 1.
- the points P defining the nodes of the mesh can be arbitrarily distributed in the plan of region 1 treated.
- This region 1 is one of the areas of the terrain. In the example in Figure 1, this area is simply a rectangle.
- This mesh technique has many advantages. First, the simplicity of the objects processed (triangles) allows them to be processed in real time. This is due in particular to the fact that the majority of algorithms for visualization and geometric manipulation are simplified and accelerated thanks to the exclusive use of triangles.
- Delaunay triangulation is unique, which allows these points to be treated in any order.
- the remarkable property of Delaunay triangulation is that it generates triangles that are as equilateral as possible. This property is very advantageous in image synthesis for which it reduces the problems of aliasing and digital precision.
- Delaunay triangulation makes it possible to add or remove a point from an already triangulated set without having to recalculate all the points, due to the only local influence of such a point.
- Such interactive manipulation also promotes the modification in real time of a visualized terrain.
- the constrained Delaunay triangulation guarantees the existence of certain edges in the mesh, which makes it possible to respect the geometry of the objects integrated into the terrain (roads, railway lines, constructions, ).
- the present invention implements the filtering of the displayed terrain surfaces. This filtering eliminates the least significant points of this surface, which simplifies the processing of the geographic area to be displayed. The triangulation then carried out on the remaining points of this surface corresponds to the finest level of detail of the database which provides these points.
- Filtering consists in refining the triangulation of the terrain by an iterative process. For each point P, one calculates the distance between this point and the point Q which is the projection of P on the current triangulation. This distance corresponds locally to the error existing between the surface of the approximate terrain (resulting from the current triangulation) and the surface of the actual terrain. After having calculated the errors relating to the different points, we select the point of maximum error, and insert it into the current triangulation. This step is repeated until the maximum point error of the area considered is less than a threshold which is is fixed according to the desired realism of the display and taking into account the computing power necessary to cross this threshold for various types of terrain.
- the curve of Figure 2 shows the evolution of the error (corresponding to the distance PQ as defined above) as a function of the number of points defining a given area.
- the terrain is not, in general, a convex surface, the insertion of a point in the current triangulation can have the effect of increasing the error instead of decreasing it.
- this insertion step is repeated until the maximum error becomes less than a threshold that is set.
- a threshold that is set.
- the temporary peaks due to the insertion of points (such as P4) corresponding to reliefs having a curvature opposite to the current curvature have been eliminated.
- there is an almost exponential decrease in the maximum error as soon as the number of points defining a given area (with dimensions of the order of 100 km 2 ) exceeds one thousand. It is therefore easy, for a given type of relief (slightly uneven, moderately mountainous, very mountainous ...) to carry out tests to obtain a curve such as that of FIG.
- the invention consists in modifying the database in real time so as not to send to the graphics engine. than the characteristic polygons from the point of view of the observer.
- the precision of the terrain is adjusted locally by adding and removing points in the current mesh.
- the selection of points to insert and delete takes into account the relief (in particular to respect the ridge lines, which are an important element of the landscape for a helicopter or airplane pilot), the position of the observer and the type of mobile (tank, plane, helicopter ).
- the diagram of FIG. 4 represents in a simplified way the two main software layers 2, 3 of the graphics engine implementing the method of the invention.
- Layer 2 is the one responsible for Delaunay triangulation, performed in asynchronous mode. It performs, among other things, the processor load regulation (optimization of the processing of data packets passing in asynchronous mode), the calculation of the level of detail and the regeneration of the database (after local modification of the description of the terrain) in host processor format.
- Layer 3 is the graphic task proper, which refreshes the screen at a rate of, for example, 30 Hz. This task essentially performs the pre-setting of the regions (so as to have to display only the regions visible to the user) , display, and transition between two levels of detail.
- the cooperation between the two software layers 2 and 3 takes place in the following manner. It is assumed that the graphic system displays scenes that an observer in a mobile vehicle simulator must see at a given time. Graphic task 3 sends at regular time intervals (for example at the rate of 30 Hz, as specified above), the Delaunay mesh polygons to be displayed (depending on the movement of said vehicle). These polygons correspond to the current level of detail that is displayed. Asynchronously, the Delaunay 2 task recalculates the appropriate level of detail, in order to take into account the change in position of the observer relative to the displayed region.
- the graphics processor recalculates the relevance of the points from the database.
- all the terrain regions in the local database are processed. Otherwise (civil aircraft pilot, etc.), only the regions relating to the heading of the vehicle are recalculated. It is thus possible to reduce the number of regions to be treated.
- the selection of points to insert or delete in a mesh is done by respecting the following three criteria:
- the calculation of the relevance of a point Pn of a mesh (that is to say the determination of the need to keep this point or to delete it during a change in level of detail) is done in the following way.
- the distance Dn between Pn and Qn is not calculated by projecting Pn on the current triangulation not containing Pn. In fact, this distance becomes constant and is precalculated as explained above with reference to FIGS. 3A to 3C. During the visual simulation, this elevation error is transformed into an angular error with respect to the observer. If the angular error thus calculated is greater than a threshold value Eseuil, the point Pn is inserted, otherwise it is deleted.
- Graphic task 3 controls the switching of the level of detail, that is to say the switching between a scene prior to an operation of inserting / deleting points due to a change in position of the observer, and a correct scene after this operation.
- FIG. 6 which is a top view, the process of switching from a level of detail N to a level N + 1.
- the intermediate morphing triangulation is displayed during the entire duration of the morphing operation (to avoid having a sudden jump between the starting and finishing levels of detail).
- This intermediate triangulation is calculated by preserving the points of the triangulations of the two levels of detail, by adding to it the possible points of intersection.
- FIG. 6 there are shown on the left three adjacent non-coplanar triangles forming part of the level of detail N, together forming a left surface with a pentagonal outline a, b, c, d, e, whose common edges each with two triangles are be and bd.
- the level of detail N + 1 we have represented the level of detail N + 1 (we can all as well to speak of level N-1), whose left surface has the same pentagonal contour a, b, c, d, e as in level of detail N, but comprising a vertex f which, when viewed from above is located substantially in the center of the pentagonal outline. This vertex f is connected by five edges to the respective five vertices of the pentagon.
- the intermediate triangulation There is shown in the middle of Figure 6 the intermediate triangulation.
- the elevation speed of a point depends on several factors, in particular at least one of the following factors: - its visibility by the observer. Thus, a point which is not in the instantaneous field of vision of the observer is raised immediately.
- the other advantages of the process of the invention are: - a reduction in the volume of the database without loss of image quality.
- the visualization system is capable of calculating a rendering image equal to that obtained by the methods of the prior art with much less polygons: on average, we can eliminate 2/3 of the facets without degrading the image.
Abstract
Description
Claims
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP96937376A EP0801775B1 (fr) | 1995-11-03 | 1996-10-31 | Procede de generation dynamique d'images synthetiques a niveau de detail automatique, et dispositif de mise en oeuvre |
CA002209275A CA2209275C (fr) | 1995-11-03 | 1996-10-31 | Procede de generation dynamique d'images synthetiques a niveau de detail automatique, et dispositif de mise en oeuvre |
US08/849,733 US5986666A (en) | 1995-11-03 | 1996-10-31 | Method for dynamic generation of synthetic images with automatic detail level, and implementation device |
DE69632717T DE69632717T2 (de) | 1995-11-03 | 1996-10-31 | Verfahren zur dynamischen synthetischen bilderzeugung mit automatischem detailniveau und vorrichtung zur durchführung dieses verfahrens |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR9513001A FR2740888B1 (fr) | 1995-11-03 | 1995-11-03 | Procede de generation dynamique d'images synthetiques a niveau de detail automatique, et dispositif de mise en oeuvre |
FR95/13001 | 1995-11-03 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1997017677A1 true WO1997017677A1 (fr) | 1997-05-15 |
Family
ID=9484208
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/FR1996/001716 WO1997017677A1 (fr) | 1995-11-03 | 1996-10-31 | Procede de generation dynamique d'images synthetiques a niveau de detail automatique, et dispositif de mise en oeuvre |
Country Status (5)
Country | Link |
---|---|
US (1) | US5986666A (fr) |
EP (1) | EP0801775B1 (fr) |
DE (1) | DE69632717T2 (fr) |
FR (1) | FR2740888B1 (fr) |
WO (1) | WO1997017677A1 (fr) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1100048A1 (fr) * | 1999-11-12 | 2001-05-16 | Société N3DI S.A.R.L. | Procédé de création automatique de maquette numérique à partir de couples d'images stéréoscopiques |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
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US6693646B1 (en) * | 1999-04-28 | 2004-02-17 | Microsoft Corporation | Method and system for iterative morphing |
US6700573B2 (en) * | 2001-11-07 | 2004-03-02 | Novalogic, Inc. | Method for rendering realistic terrain simulation |
US20040158476A1 (en) * | 2003-02-06 | 2004-08-12 | I-Sim, Llc | Systems and methods for motor vehicle learning management |
US8214484B2 (en) * | 2007-11-29 | 2012-07-03 | International Business Machines Corporation | Method to predict edges in a non-cumulative graph |
US8463895B2 (en) * | 2007-11-29 | 2013-06-11 | International Business Machines Corporation | System and computer program product to predict edges in a non-cumulative graph |
US11380054B2 (en) | 2018-03-30 | 2022-07-05 | Cae Inc. | Dynamically affecting tailored visual rendering of a visual element |
US10964106B2 (en) | 2018-03-30 | 2021-03-30 | Cae Inc. | Dynamically modifying visual rendering of a visual element comprising pre-defined characteristics |
Citations (2)
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US4616217A (en) * | 1981-05-22 | 1986-10-07 | The Marconi Company Limited | Visual simulators, computer generated imagery, and display systems |
US5367615A (en) * | 1989-07-10 | 1994-11-22 | General Electric Company | Spatial augmentation of vertices and continuous level of detail transition for smoothly varying terrain polygon density |
Family Cites Families (8)
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US5793371A (en) * | 1995-08-04 | 1998-08-11 | Sun Microsystems, Inc. | Method and apparatus for geometric compression of three-dimensional graphics data |
US5850222A (en) * | 1995-09-13 | 1998-12-15 | Pixel Dust, Inc. | Method and system for displaying a graphic image of a person modeling a garment |
US5760783A (en) * | 1995-11-06 | 1998-06-02 | Silicon Graphics, Inc. | Method and system for providing texture using a selected portion of a texture map |
DE19541500A1 (de) * | 1995-11-07 | 1997-05-15 | Siemens Ag | Verfahren zur Bilderzeugung bei einem medizintechnischen bildgebenden System |
US5841441A (en) * | 1996-01-19 | 1998-11-24 | Virtus Corporation | High-speed three-dimensional texture mapping systems and methods |
US5831624A (en) * | 1996-04-30 | 1998-11-03 | 3Dfx Interactive Inc | Level of detail texture filtering with dithering and mipmaps |
US5838973A (en) * | 1996-05-03 | 1998-11-17 | Andersen Consulting Llp | System and method for interactively transforming a system or process into a visual representation |
US5844567A (en) * | 1996-08-12 | 1998-12-01 | Silicon Graphics, Inc. | Computer graphics system and method for texture mapping using triangular interpolation |
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1995
- 1995-11-03 FR FR9513001A patent/FR2740888B1/fr not_active Expired - Fee Related
-
1996
- 1996-10-31 DE DE69632717T patent/DE69632717T2/de not_active Expired - Fee Related
- 1996-10-31 WO PCT/FR1996/001716 patent/WO1997017677A1/fr active IP Right Grant
- 1996-10-31 EP EP96937376A patent/EP0801775B1/fr not_active Expired - Lifetime
- 1996-10-31 US US08/849,733 patent/US5986666A/en not_active Expired - Fee Related
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US4616217A (en) * | 1981-05-22 | 1986-10-07 | The Marconi Company Limited | Visual simulators, computer generated imagery, and display systems |
US5367615A (en) * | 1989-07-10 | 1994-11-22 | General Electric Company | Spatial augmentation of vertices and continuous level of detail transition for smoothly varying terrain polygon density |
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1100048A1 (fr) * | 1999-11-12 | 2001-05-16 | Société N3DI S.A.R.L. | Procédé de création automatique de maquette numérique à partir de couples d'images stéréoscopiques |
FR2801123A1 (fr) * | 1999-11-12 | 2001-05-18 | Bertrand Aube | Procede de creation automatique de maquette numerique a partir de couples d'images stereoscopiques |
Also Published As
Publication number | Publication date |
---|---|
FR2740888B1 (fr) | 1997-11-28 |
FR2740888A1 (fr) | 1997-05-09 |
EP0801775A1 (fr) | 1997-10-22 |
EP0801775B1 (fr) | 2004-06-16 |
DE69632717D1 (de) | 2004-07-22 |
DE69632717T2 (de) | 2005-07-07 |
US5986666A (en) | 1999-11-16 |
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