CN101694726B - Fusing and drawing method based on multi-source terrain data - Google Patents
Fusing and drawing method based on multi-source terrain data Download PDFInfo
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Abstract
A fusing and drawing method based on multi-source terrain data comprises steps: (1) high-effectively organizing multi-source terrain data; (2) high-effectively filling regular 'F'-shaped cavities when in drawing, namely, firstly acquiring an intersected area of high-precision terrain data and given large-sized terrain data, dividing the intersected area into a plurality of rectangular strips which are adjacent mutually and different in length according to a clipmap hierarchical structure, and finally inserting apexes corresponding to the strips among the strips according to a sequence from fine to rough and guaranteeing smoothness of height of the apexes among the strips; and (3), drawing according to multi-source terrain data. On the basis of keeping the advantage of fast speed of drawing large-scale terrains by adopting a Geometry Clipmap method, the fusing and drawing method based on multi-source terrain data executes high-effective organization on access high-precision terrain data, and particularly resolves the problem of regular 'F'-shaped cavities in real-time fusion due to update of the clipmap, and simultaneously avoids the problem of hopping of different resolutions during transition when fusing data.
Description
Technical field
The invention belongs to computer virtual reality and computer graphics techniques field, particularly relate to the drawing massive terrains method in the computer graphics acceleration drawing technology.
Background technology
Large-scale terrain is the important visual key element in the virtual environment, and it can be for the user provides visual experience true to nature, and is widely used in aspects such as battlefield emulation, flight simulation, emergency response training and 3d gaming.In the last few years, the fast development of terrain data obtaining means made data volume sharply increase, for the real-time rendering of large-scale terrain has brought new challenge.
Two types of large-scale terrain real-time drawing methods are arranged at present.One type is to use the large-scale terrain real-time drawing method based on external memory (out-of-core).This class methods graphic data on a large scale deposit into effectively tissue of row outside, thereby the scheduling strategy through the time of running reduces and is written into data volume and accomplishes real-time rendering.Usually on rule-based grid or basis, improve based on the irregular grid method.For avoiding drawing constantly the same different detail model in zone (level of detail, the LOD) saltus step of generation when level switches, and provided continuous LOD method head it off based on viewpoint.For solving the problem that frequent I/O operation causes render speed to reduce, use efficiently external memory tissue and reduce I/O method of operating completion real-time rendering through prefetch policy.For solving the stability of render speed, provided level and smooth dispatching method based on viewpoint.Pajarola has provided better summary (" Survey on Semi-Regular Multiresolution Models forInteractive Terrain Rendering ", The Visual Computer, 23 (8): 583-605,2007).The another kind of large-scale terrain real-time drawing method that is based on internal memory.These class methods at first adopt compression process to reduce data volume, make to compress the back data division or all be written into internal memory, secondly separating the synthetic True Data of press operation and accomplishing real-time rendering through the time of running.For example Geometry Clipmap (GC) method is efficiently drawn large-scale terrain, and this method is used as dem data as the texture of being made up of elevation, adopts one group of nested grid storage and draws landform; The time of running with desired data real-time decompress(ion) from internal memory, reduced data are read in internal memory from external memory time; Use " L " shape update strategy simultaneously, avoid additional space use amount in the renewal process, improved greatly and upgraded and the speed of drawing.At present the GC method has become the research focus of large-scale terrain rendering, and is used in the increasing terrain rendering system.
Deepen continuously along with what use, people hope that existing terrain data can provide more rich details to change reaching specific objective, thereby the local landform that changes is carried out correct assessment and analysis.The details that is changed concentrates on some zone of landform usually, cause the sampling precision of local detail data with on every side on a large scale the sampling precision of graphic data produced difference, this for tissue of terrain data with upgrade the new problem of having brought.If according to the regular data method for organizing based on external memory details area is carried out rule sampling and set up hierarchical structure, thereby the degree of depth that when the details area scope is big, can increase index structure increases storage space and the traversal expense of the time of running.If this high precision detail data is handled according to the GC method; Owing to when pre-service, landform has been carried out the rule sampling that resolution reduces successively; In case the sampling rate of local data changes; If still the high precision detail data is handled, can be produced the information dropout phenomenon according to the sampling rate of existing landform.In order not lose details, need large-scale terrain be resampled according to the sampling precision of partial high-precision detail data, cost is higher and have little significance.Therefore how high precision detail data and existing terrain data are better merged, and it is efficiently drawn is the subject matter that this paper solves.
Summary of the invention
The technical matters that the present invention will solve: the deficiency that overcomes prior art; A kind of fusion and method for drafting based on multi-source terrain data is provided; Keep that GC method render speed is fast, on the basis of the little advantage of committed memory; Existing graphic data on a large scale tissue and drafting have efficiently been carried out; Simultaneously merged the graphic data accurately of represent details preferably, and " F " shape cavity when efficiently solving the caused data fusion of clipmap topology update, and with the hole region of the better filling of given transitional zone structure; Avoid the problem of different resolution data smoothing transition simultaneously, formed a kind of fusion and method for drafting of effective multi-source terrain data.
The technical scheme that the present invention adopts: a kind of fusion and method for drafting based on multi-source terrain data, its characteristics are that step is following:
(1) carries out the multi-source terrain data tissue
The structure that at first existing graphic data is on a large scale carried out the clipmap structure carries out the mipmap structure organization to the graphic data accurately of representing details subsequently;
(2) efficiently fill drawing rule " F " shape cavity constantly
At first try to achieve multi-source terrain data and the existing intersecting area of graphic data on a large scale; Subsequently this intersecting area is decomposed into some rectangle bands (transitional zone) adjacent one another are and different in size, at last according in the band corresponding, inserting corresponding summit and use the method for weighted value to guarantee the level and smooth of bar interband apex height with the crossing layer of clipmap by being fine to coarse order;
(3) carry out the drafting of multi-source terrain data
Use the GC method that existing large-scale terrain is drawn, use the mipmap structure that multi-source data is drawn, and transitional zone is used the method for drafting of triangle band, and the adding that guarantees transitional zone makes the level and smooth of empty two side areas transition.
The step of multi-source terrain data tissue is following in the said step (1):
(1) be the center according to viewpoint, with formula L=2
dStep-length be the clipmap structure that unit makes up landform, wherein represent the step-length that per moment of viewpoint upgrades with L, d is the hierachy number of clipmap;
(2) poor between clipmap data and True Data used LBT to change it compressed.
Multi-source detail data in the said step (2) is following with the crossing testing procedure of existing graphic data on a large scale:
(1) upgrades the bounding box of every layer on clipmap structure;
(2) bounding box of every layer of clipmap and the bounding box of high precision landform are intersected detection;
(3) joining in the record high precision landform writes down the joining in each layer of clipmap simultaneously.
Rectangle band construction step in the said step (2) is following:
(1) try to achieve clipmap and intersect the maximum layer (the most coarse) and the intersection point on graphic data border accurately in the layer, and upper left, the upper right summit of record intersect boundary;
(2) obtain two joinings point-blank that clipmap intersects smallest tier (the meticulousst) in the layer; Straight line to being made up of upper left, upper right summit draws vertical line; Try to achieve intersection point; And form the corresponding transitional zone rectangle of clipmap smallest tier together with the borderline joining of graphic data accurately according to this intersection point, and and the limit of being made up of intersection point on the graphic data border accurately in this rectangle is designated as this transitional zone high resolving power limit, another limit of correspondence is designated as this transitional zone low resolution limit;
(3) with clipmap smallest tier low resolution limit as input, try to achieve down the transitional zone rectangle of one deck clipmap layer;
(4) repeat (3) until made up the transitional zone rectangle of the maximum layer of clipmap.
The step that fill on the summit in each layer of clipmap transitional zone in the said step (2) is following:
(1) obtains clipmap and intersect the smallest tier in the layer, copy the summit on this layer intersection edges the low resolution limit of this layer transitional zone to, in like manner the summit on the multi-source terrain data intersection edges of this layer correspondence is copied to the high resolving power limit of this layer transitional zone;
(2) obtain down the crossing layer of one deck clipmap; Summit on this layer clipmap intersection edges is copied to the low resolution limit of this layer transitional zone; Again with on the adjacent vertex on the low resolution limit and the corresponding high precision landform intersection edges carry out linear interpolation after; All points are pressed into the high resolving power limit of this layer transitional zone, again the summit in the low resolution in the smallest tier also are pressed into this floor height resolution limit;
(3) iterative process (2) intersects the maximum layer in the layer until clipmap.
The step of the drafting of multi-source terrain data is following in the said step (3):
(1) the GC method is drawn existing large-scale terrain, and uses annular to get the location method and reduce the redundant copies between data;
(2) use is drawn the graphic data accurately of expression details based on the mipmap structure of error control;
(3) use trigonometric ratio band separately to draw to every transitional zone.
The present invention's beneficial effect compared with prior art is: provided a kind of multi-source terrain data and merged and the real-time method of drawing, and have the data organization mode succinct, be beneficial to characteristics such as hardware-accelerated; And found that " F " shape that is produced by the clipmap topology update when multi-source data merges is empty, provided based on the cavity of transitional zone and repaired strategy; With data by MoM and MEI, the transitional zone structure has in the operational process characteristics of filling automatically according to the size of hole region, and the summit of being filled guaranteed the level and smooth of empty two side data transition, thereby has reached the real time fusion and the drafting of multi-source terrain data.
Description of drawings
Fig. 1 is an overall process synoptic diagram of the present invention;
Fig. 2 is the synoptic diagram of the transitional zone structure of the present invention's use;
Fig. 3 is the synoptic diagram that fill on the summit in the transitional zone of the present invention;
Fig. 4 is the synoptic diagram of transitional zone apex height value of the present invention;
Fig. 5 is a LOD selection time of running flow process of the present invention;
Fig. 6 a and Fig. 6 b use the effect comparison synoptic diagram of front and back for the present invention.
Embodiment
Below in conjunction with accompanying drawing and embodiment the present invention is described in further detail:
Implementation process of the present invention comprises three key steps: the multi-source terrain data tissue makes up transitional zone and summit and fills the multi-source terrain data real-time rendering.As shown in Figure 1.
The present invention uses the clipmap structure that existing graphic data is on a large scale organized; For the clipmap structure of high precision detail data and graphic data is on a large scale merged drawing constantly preferably; To the characteristics of high precision detail data, adopt the mipmap structure that the high precision detail data is organized for the sampling rule.
In first stage, transitional zone constitutes the stage:
This paper is divided into some parallel rectangle bands with " F " shape hole region, and each band is made up of the limit that two different sample rate summits constitute.Such band is called transitional zone (Fig. 2)." F " shape cavity is made up of many transitional zones usually, and the set that will fill the required transitional zone in " F " shape cavity is called the transitional zone crowd.Some transitional zones are connected with each other in the transitional zone crowd; The limit that each bar transitional zone high sampling rate summit constitutes is the limit that constitutes in abutting connection with band low sampling rate summit; Thereby in the transitional zone crowd, accomplished the process that data sampling rate reduces successively or raises, solved the problem of " F " shape cavity both sides different sample accuracy data transition.
In second stage, fill confirming of summit planimetric coordinates in the transitional zone:
Need in two limits of every transitional zone, to fill the different summit of sampling rate.Therefore to the order of the transitional zone among the transitional zone crowd according to sampling rate reduction or rising be arranged in order.The summit that this paper uses fill direction for from both sides, " F " shape cavity by the limit that constitutes than the low sampling rate summit to being undertaken by the limit that becomes than the high sampling rate set of vertices.As can be seen from Figure 3, because high precision detail data sampling precision is higher, so direction is filled for to carry out with the intersection edges of hole region to the mipmap structure from the intersection edges of clipmap structure and hole region in the summit;
Convenient for description, remember that graphic data is O on a large scale, use O
cC layer model in the expression clipmap structure is with s (O
c) represent the step-length on summit in this layer model; Note high precision detail data is D, uses D
dD layer model in the expression mipmap structure is with s (D
d) represent the step-length on summit in this layer model; Note transitional zone data are TS, use TS
iRepresent i bar transitional zone, use
TS i Represent the limit that this transitional zone is made up of the low resolution summit, with s (
TS i ) expression
TS i The minimum step on middle summit; Use TS
iRepresent the limit that this transitional zone is made up of the high resolving power summit, with s (TS
i) expression TS
iThe minimum step on middle summit;
Comprise three transitional zones among Fig. 3.At first produce TS when filling
1, wherein
TS 1 The summit by O in the clipmap structure
M+1Form with the summit in the hole region intersection edges.TS
1The summit by right
TS 1 In the summit carry out in behind the point interpolation the summit with
TS 1 Summit two parts form.Accomplish TS
1The summit fill the back and generate TS
2, as can beappreciated from fig. 3,
TS 2 The summit by TS
1Summit and clipmap structure in O
mForm with the summit two parts in the hole region intersection edges.The rest may be inferred generates TS
2And TS
3In Interpolation Process, transitional zone i (1≤i≤M) sampling rate on the summit of filling need satisfy following condition:
s(TS
i)≥s(D
dmin) (1)
Consider that all there are the limiting case in " F " crack in high precision detail data and four limits of clipmap structure, need the summit total quantity totalNumber that fills to satisfy following relation:
totalNumber≤(3*2
n+1-3n-6)*4*clipsize (2)
Three phases is filled confirming of apex height value in the transitional zone
By the summit that guarantees institute fillings summit and transitional zone both sides landform keeps on the height territory smoothly, used a kind of weighted-average method calculating to increase the height value (Fig. 4) on summit newly.If newly-increased summit is V, with h (V) expression apex height value, D for around the summit to the multi-stress that influences of institute's insertion apex height, wi by a certain summit to the weights that influence of insertion apex height value, with the plan range replacement, then have here:
Be illustrated in figure 4 as the new interpolation summit on the current band TS limit, v3 and v4 are in the current transitional zone
TSSummit on the limit, v1 and v2 are the summit on the corresponding with it high precision details area limit.N is for inserting summit corresponding summit quantity sum on limit that details area intersects and clipmap border.
Step 3: multi-source terrain data is drawn, and is divided into to be four-stage the existing drafting of graphic data on a large scale, the update method of high precision details landform, the LOD system of selection of high precision details landform, the drafting of transitional zone.
First stage: the existing drafting of graphic data on a large scale
Employing with each layer clipmap data storage in VBO, and the method for drawing; But drawing constantly,, drawing subsequently deleting with the equitant zone of bounding box of graphic data accurately among every layer of clipmap.
Second stage: the drafting of high precision landform
Fig. 5 provides the more new technological process of the high precision detail data time of running, when the viewpoint central area is not in the represented zone of high precision detail data, adopts the mipmap method that real-time update and drafting are carried out in this zone.But when viewpoint near high precision detail data represented when zone, cause after the renewal of each layer of mipmap data volume with distance near increasing, influence the render speed of the time of running.
For improving render speed; When the viewpoint central area is positioned at the represented zone of high precision detail data fully; This paper extracts the clipmap data from high precision detail data mipmap structure, use " L " shape update strategy of GC method to reduce data volume to guarantee the real-time rendering of high precision detail data.
Three phases: the LOD system of selection of high precision details landform
In order to reduce calculated amount, this paper is converted into problem the projection rather than the projection of accurate Calculation area of calculating line segment through calculating the method for each layer of mipmap structure in the projection of ken inner boundary line segment.If pl
iBe the projection of mipmap structure layer boundary sections on screen, nt
iBe the quantity of triangle edges that this line segment comprises, q is that certain layer of mipmap data comprise in the ken border number draws with formula (4) and is positioned at the projection P of ken mipmap data on screen:
Four-stage: the drafting of transitional zone.
For reducing the time overhead that summit trigonometric ratio process is brought in the transitional zone, utilize
TS i With TS
iBetween the characteristics of vertex position, during drafting according to
TS i This band of big young pathbreaker of middle summit step-length is divided into some zones that are connected with each other (zone of being made up of red phantom line segments among Fig. 6).And through each is distinguished the trigonometric ratio that the method for carrying out trigonometric ratio is separately accomplished whole band.
Lose problem for the triangle of avoiding interregional frontier point to cause when the trigonometric ratio, adopt the mode head it off that frontier point is stored in forward and backward two adjacent areas respectively.
Final drawing result is as shown in Figure 6, can find out and introduce the fusion and the drafting that can effectively solve multi-source terrain data after the transitional zone structure.
Claims (6)
1. fusion and method for drafting based on a multi-source terrain data is characterized in that step is following:
(1) carries out the multi-source terrain data tissue
The multi-source data source is divided into single graphic data on a large scale of resolution and the graphic data accurately of representing details; At first the existing graphic data on a large scale in the multi-source terrain data is carried out the structure of clipmap structure, the terrain data to the high precision details carries out the mipmap structure organization subsequently;
(2) fill drawing rule " F " shape cavity constantly
At first try to achieve graphic data and the existing intersecting area of graphic data on a large scale accurately; Subsequently this intersecting area is decomposed into some rectangle bands adjacent one another are and different in size, at last according to inserting corresponding summit in the corresponding band of layer and use the method for weighted value to guarantee the level and smooth of bar interband apex height toward intersecting with clipmap by being fine to coarse order;
(3) carry out the drafting of multi-source terrain data
Use the GC method that existing large-scale terrain is drawn, use the mipmap structure that graphic data is accurately drawn, and transitional zone is used the method for drafting of triangle band, and the adding that guarantees transitional zone makes the level and smooth of empty two side areas transition.
2. fusion and method for drafting based on multi-source terrain data according to claim 1 is characterized in that: it is following in the said step (1) the existing graphic data on a large scale in the multi-source terrain data to be carried out the step of structure of clipmap structure:
(1.1) be the center according to viewpoint, with formula L=2
dStep-length be the clipmap structure that unit makes up landform, wherein represent the step-length that per moment of viewpoint upgrades with L, d is the hierachy number of clipmap;
(1.2) poor between clipmap data and True Data, it compresses to use the LBT transfer pair.
3. fusion and method for drafting based on multi-source terrain data according to claim 1 is characterized in that: in the said step (2) to try to achieve graphic data accurately following with the intersecting area step of existing graphic data on a large scale:
(2.1) upgrade the bounding box of every layer on clipmap structure;
(2.2) bounding box of every layer of clipmap and the bounding box of high precision landform are intersected detection;
(2.3) joining in the record high precision landform writes down the joining in each layer of clipmap simultaneously.
4. fusion and method for drafting based on multi-source terrain data according to claim 1 is characterized in that: the rectangle band construction step in the said step (2) is following:
(2.1) try to achieve clipmap and intersect the rough layer and the intersection point on graphic data border accurately in the layer, and upper left, the upper right summit of record intersect boundary;
(2.2) obtain two joinings point-blank that clipmap intersects the detailed level in the layer; Straight line to being made up of upper left, upper right summit draws vertical line; Try to achieve intersection point; And form the corresponding transitional zone rectangle of detailed level of clipmap together with the borderline joining of graphic data accurately according to this intersection point, and and the limit of being made up of intersection point on the graphic data border accurately in this rectangle is designated as this transitional zone high resolving power limit, another limit of correspondence is designated as this transitional zone low resolution limit;
(2.3) with the detailed level low resolution limit of clipmap as input, try to achieve down the transitional zone rectangle of one deck clipmap layer;
(2.4) repeat (2.3) until made up the transitional zone rectangle of the rough layer of clipmap.
5. fusion and method for drafting based on multi-source terrain data according to claim 1 is characterized in that: the step of inserting corresponding summit in the said step (2) is following:
(2.1) obtain clipmap and intersect the detailed level in the layer, copy the summit on this layer intersection edges the low resolution limit of this layer transitional zone to, in like manner the summit on the intersection edges of graphic data accurately of this layer correspondence is copied to the high resolving power limit of this layer transitional zone;
(2.2) obtain down the crossing layer of one deck clipmap; Summit on this layer clipmap intersection edges is copied to the low resolution limit of this layer transitional zone; Again with the adjacent vertex on the low resolution limit with after linear interpolation is carried out on the summit on the corresponding high precision landform intersection edges; All points are pressed into the high resolving power limit of this layer transitional zone, and the summit in the low resolution in again will detailed level also is pressed into this floor height resolution limit;
(2.3) repetitive process (2.2) intersects the rough layer in the layer until clipmap.
6. fusion and method for drafting based on multi-source terrain data according to claim 1, its characteristics are: the step of the drafting of multi-source terrain data is following in the said step (3):
(3.1) adopt the GC method to draw existing large-scale terrain, and use annular to get the location method and reduce the redundant copies between data;
(3.2) use based on the mipmap structure of error control graphic data is accurately drawn.
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| CN102890829B (en) * | 2011-10-24 | 2015-05-27 | 克拉玛依红有软件有限责任公司 | Method for rendering terrain based on graphic processing unit (GPU) |
| CN103425801B (en) * | 2013-09-04 | 2016-08-17 | 中测新图(北京)遥感技术有限责任公司 | A kind of data fusion method towards digital earth and device |
| CN109410736B (en) * | 2018-09-14 | 2019-08-30 | 广州海洋地质调查局 | A kind of multi-source dem data seamless integration method and processing terminal |
| CN109559376B (en) * | 2018-11-21 | 2020-11-24 | 北京理工大学 | Three-dimensional terrain generation method and device |
| CN111260780B (en) * | 2020-01-13 | 2021-04-16 | 陕西心像信息科技有限公司 | Real-time terrain modification method based on elevation of altitude map |
| CN111724477B (en) * | 2020-07-06 | 2024-08-02 | 中铁二局第一工程有限公司 | Method for constructing multi-level three-dimensional terrain model by multi-source data fusion |
| CN111736751B (en) * | 2020-08-26 | 2021-03-26 | 深圳市千分一智能技术有限公司 | Stroke redrawing method, device and readable storage medium |
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