CN105069841A - Sea and land combined visualization method based on OSG three-dimensional engine - Google Patents

Abstract

The present invention relates to a sea and land combined visualization method based on an OSG three-dimensional engine, belonging to the technical field of graphical visualization. The method comprises a step of using an OSG three-dimensional rendering engine to build a three-dimensional scene framework, a step of using a VPB to generate a large-scale terrain model file, a step of using a sea drawing plug-in to generate a sea node, a step of loading the sea node and the terrain model file into the scene tree of an OSG to carry out visualization, a step of setting the sea node as a dynamic node if the sea node drawn by the sea drawing plug-in does not move with the movement of a view point, and a step of setting the sea node to dynamically change with a view point height and display according to a sea height. Compared with the prior art, through adding a large-scale land node and the sea node in the same scene at the same time, the height of a sea is dynamically adjusted according to the view point height, thus when the view point is far from sea and land scenes, the deep buffer difference of the sea and land is not too small, thus the problem of land and sea strobe is avoided, and the method is simple and efficient at the same time.

Description

A kind of extra large land based on OSG d engine engages method for visualizing

Technical field:

This method relates to a kind of use OSG 3 d rendering engine, and flood and field is carried out visual solution simultaneously; Generate large-scale terrain model in particular to use VPB, and in scene, add the large scale scene of ocean, belong to graph visualization technical field.

Background technology:

Three-dimensional scenic visual is for many years computer graphics, especially the focus studied of field of virtual reality and emphasis.In recent years, the hot issue be depicted as in order to a large amount of paper and periodical of large-scale terrain, on the basis of large-scale terrain, added ocean in scene, and namely extra large land is carried out visual is simultaneously one of each three-dimensional artificial platform function of all needing emphasis to realize.

OSG 3 d rendering engine is the visual programming tools bag that a rendering efficiency is high, increase income.Utilize the API that OSG provides, the modeling of three-dimensional scenic can be completed quickly and efficiently.VirtualPlanetBuilder is called for short VPB, it is a large-scale terrain modeling plug-in unit based on OSG, by configuring the command line parameter of VPB, existing terrain elevation data and data texturing process can be generated the three-dimensional model that OSG can directly resolve, being stored as IVE form.Use OSG 3 d rendering engine as above and VPB large-scale terrain rendering plug-in unit, can rapidly large-scale terrain be carried out visual.

But it is visual that large-scale terrain is generally used for land, can show the information of hills, mountain range, surface relief well, the part of ocean is then simple pinup picture.It is visual in order to flood and field is carried out simultaneously, usual needs add separately ocean node in the large-scale terrain scene of having completed, this just brings a problem: when video camera is roamed in three-dimensional scenic, and when land, view distance sea scene is far, the drafting degree of depth of flood and field can become more and more close, to such an extent as to land was covered, sometimes sometimes lower than land in ocean, produce the effect of visualization that irrational extra large land is frequently flashed, this by this problem referred to as extra large land stroboscopic problem.

The method that problem is frequently flashed in current solution has two kinds: one avoids viewpoint height too high, and great majority application does not need viewpoint and scene to keep great distances, can avoid extra large land stroboscopic problem by restriction viewpoint height; The detection algorithm of wiring is handed in its extra large land of two uses, and namely calculate shore line in real time, this kind of method fundamentally solves extra large land stroboscopic problem, but calculation cost is very high, largely have impact on scene drawing efficiency.

Summary of the invention:

The object of this method is for above-described extra large land stroboscopic problem, proposes a kind of extra large land visual solution simultaneously of carrying out scene modeling based on OSG 3 d rendering engine, using VPB generation large-scale terrain model.The program adds extensive land node and ocean node in one scenario simultaneously, according to the height of viewpoint height dynamic conditioning ocean, when making viewpoint away from extra large land scene, the depth buffer difference of flood and field can not be too small, thus avoid the problem of extra large land stroboscopic.

What most of three-dimensional scenic needed concentrated observation is land model, does not need to overemphasize sea details.So when land model optimization Yu Haiyang model is observed, the depth buffer that sea height increases both Hai Lu suitably can be reduced.According to test, the mathematical model using following formula to adjust as sea height is comparatively reasonable.

$H=\left\{\begin{array}{cc}{H}_0-\frac{dis\tan ce}{\frac{5}{6}\×W\÷h}& dis\tan ce\≤\frac{5}{6}\×W\\ H_0-h& dis\tan ce>\frac{5}{6}\×W\end{array}\right.;---\left(1\right)$

Wherein, W is extra large land scene scale, H ₀for height is drawn in initialization ocean, distance is the height of land, view distance sea scene, and h is ocean wave height.It should be noted that, the ocean displaying scheme used in this solution is dynamic sea, and land model is static land.Namely along with viewpoint moves, land modal position can not change, but center, ocean can be moved along with viewpoint and move, and makes center, ocean be in the position of viewpoint at surface projection all the time.When viewpoint is away from earth's surface, land model can carry out convergent-divergent and become more and more less, and ocean model size can not change.Experiment test is when viewpoint height reaches 5/6 scene size, and extra large land scene details has become enough fuzzy, and ocean has not needed to show.When sea height reduces h, ocean is under local horizon, if now there is ocean pinup picture, removes ocean node, no longer draws dynamic sea; If without ocean pinup picture, sea height no longer changes.Now can not there is the problem that flood and field frequently flashes in three-dimensional scenic.

If need to concentrate and observe sea details, the depth buffer that sea height increases both Hai Lu suitably can be raised.Now the minus sign in formula is changed to and adds, that is:

$H=\left\{\begin{array}{cc}{H}_0+\frac{dis\tan ce}{\frac{5}{6}\×W\÷h}& dis\tan ce\≤\frac{5}{6}\×W\\ H_0+h& dis\tan ce>\frac{5}{6}\×W\end{array}\right.;---\left(2\right)$

The object of the invention is to be achieved through the following technical solutions:

A kind of use OSG 3 d rendering engine, carries out visualization method by flood and field simultaneously, comprises the following steps:

Step one, use OSG 3 d rendering engine carry out three-dimensional scenic framework and build.

Step 2, use terrain modeling plug-in unit, as VPB, generate large-scale terrain model file.Using existing terrain elevation data and data texturing as input, by configuration VPB command line parameter, export the ive model file of large-scale terrain.

Step 3, use ocean to draw plug-in unit, as osgocean, generate ocean node, ocean node and relief block file are loaded into simultaneously carry out in the scene tree of OSG visual.

If the ocean node that step 4 ocean drafting plug-in unit is drawn out can not be followed viewpoint and moved and move, arranging ocean node is dynamic node.Namely arranging ocean drafting scope is fixed size, and in the keyboard call back function of OSG rover, arrange ocean centre coordinate is eye coordinates.

Step 5, sea height is set with viewpoint height dynamic change, then carries out ocean scenes display according to sea height.

Step 5.1 adds rover in three-dimensional scenic, such as trackmanipulator etc.

Step 5.2 revises the convergent-divergent call back function of rover, the zoommodel function in the trackmanipulator rover that such as OSG carries, and composes the distance value in mathematical model for class members variable _ distance.Initialization is carried out to each variable of mathematical model.In call back function, sea height value is set according to above-mentioned formula (1) or (2), formula (1) is the situation for focusing on when observing land model, and formula (2) is the situation for focusing on when observing oceanic purpose.

Step 5.3, according to the sea height value calculated, is distinguished following situation and is shown:

If the pelagic division i. in the relief block drawn out of terrain modeling plug-in unit has pinup picture, then, after distance rises to 5/6W, ocean node no longer shows, only display pinup picture.

If the pelagic division ii. in the relief block drawn out of terrain modeling plug-in unit does not have pinup picture, then, after distance rises to 5/6W, ocean node continues display, highly no longer changes; Now viewpoint height is enough high, and also enough far away apart from extra large land model, do not need to observe whole three-dimensional scenic from farther place, can limit viewpoint height maximal value is 5/6W.

Just can draw out by above step the three-dimensional scenic that flood and field carries out showing simultaneously, and this scene is when viewpoint is away from scene, and the problem frequently glimmered in extra large land can not occur.

A kind of use OSG 3 d rendering engine, flood and field is carried out visible apparatus simultaneously, comprise extra large land three-dimensional scenic drafting module and sea height with viewpoint height dynamic conditioning module.Drafting module just completes when program initialization, and height control module constantly circulates until program exits when graphical interfaces is visual.

Described extra large land three-dimensional scenic drafting module produces scene for using OSG 3 d rendering engine to draw, and uses VPB to generate large-scale terrain model;

Described sea height adjusting module is used for when each viewpoint position changes, and according to aforementioned formula (1) or formula (2) adjustment sea height, and carries out ocean scenes display according to the sea height after adjustment.

May pelagic division be comprised in described large-scale terrain model, show as ocean pinup picture, or the part not comprising ocean and only have land to rise and fall.It is static land that land is loaded in scene, and namely terrestrial location and size can not change along with the change of viewpoint; It is dynamic sea that ocean is loaded in scene, no matter where viewpoint moves to, center, ocean is identical with eye coordinates all the time.

Realize in the call back function that the adjustment of described sea height changes at the viewpoint position of rover, such as zoommodel function.

Beneficial effect:

In the three-dimensional scenic that flood and field shows simultaneously, avoid in a simpler way viewpoint height too high time the flood and field problem frequently flashed, ensure that the efficiency of scene drawing simultaneously.

Accompanying drawing illustrates:

Fig. 1 is that the three-dimensional scenic that a kind of land based on OSG and VPB of the embodiment of the present invention and ocean show simultaneously draws schematic flow sheet;

Fig. 2 is the extra large land three-dimensional scenic schematic diagram under general viewpoint;

Fig. 3 is the parameters of the extra large land three-dimensional scenic under general viewpoint, draws frame per second approximately between 7 ~ 10.

Fig. 4 is extra large land three-dimensional scenic schematic diagram when viewpoint is too high when not adopting this method, and in figure, there is stroboscopic problem at square box mark place.

Fig. 5 is extra large land three-dimensional scenic parameters when viewpoint is too high when not adopting this method.

Fig. 6 is extra large land three-dimensional scenic schematic diagram when viewpoint is too high when adopting this method, and square box home position stroboscopic problem is solved.Frame number is stabilized between 7-10.

Fig. 7 is extra large land three-dimensional scenic parameters when viewpoint is too high when adopting this method.

Fig. 8 is extra large land three-dimensional scenic when viewpoint is too high when not adopting this method and parameter, and wider landform more can find out the existence of stroboscopic problem.

Fig. 9 is extra large land three-dimensional scenic when viewpoint is too high when adopting this method and parameter, and the contrast of Fig. 8 and Fig. 9 can be known and finds out that stroboscopic problem is solved.

Extra large land three-dimensional scenic when viewpoint is the highest when Figure 10 is employing this method and parameter.Viewpoint enough then only loads ocean pinup picture away from after scene, does not reload ocean and draws node.Frame number is still between 7 ~ 10.Now viewpoint height reaches 5/6W maximal value.

Embodiment:

Below in conjunction with drawings and Examples, the present invention is described in detail, also describe technical matters and the beneficial effect of technical solution of the present invention solution simultaneously, it is pointed out that described embodiment is only intended to be convenient to the understanding of the present invention, and any restriction effect is not play to it.

Embodiment 1

Be illustrated in figure 1 the invention process one and use OSG 3 d rendering engine, flood and field is carried out visual solution schematic flow sheet simultaneously, below the step in flow process is described in detail:

Step one, use OSG 3 d rendering engine carry out three-dimensional scenic framework and build.

Set up landform node and ocean node respectively, be mounted in OSG scene tree root node.Code sample is as follows:

osgViewer::Viewerviewer；

Osg::Group*root=newosg::Group; // set up root node

Root->addChild (scene->getScene ()); // add ocean node

Root->addChild (islandTransform.get ()); // add landform node

Viewer.setSceneData (root); // link what comes into a driver's device by scene tree

Step 2, use VPB generate large-scale terrain model file.Using existing terrain elevation data and data texturing as input, by configuration VPB command line parameter, export ive model file.

Download the Taiwan Precision Elevation data of 90 meters of resolution in CGIAR-CSI website, download obtain data texturing at GoogleEarth, the two all can download in frame choosing.Use GoogleMapper14 to carry out re-projection to texture maps, select unified coordinate system such as WGS84.Configure VPB command line parameter afterwards, altitude figures and data texturing tif file are inputted, run output model file.Order line example:

Osgdem--xx10--yy10-t data texturing--xx10--yy10-d altitude figures-v1-l6-otaiwan.ive

Model is loaded in the landform node of OSG scene tree after generation.

Step 3, use ocean to draw plug-in unit, as osgocean, generate ocean node, ocean node and relief block file are loaded into simultaneously carry out in the scene tree of OSG visual.

If step 4 ocean node is not mobile with the movement of viewpoint, then arranging ocean node is dynamic node.

First arranging ocean drafting scope is fixed size, when setting up ocean node, default situations Ocean is drawn scope and is fixed, namely not in the rover convergent-divergent call back function of three-dimensional scenic such as trackballmanipulator zoommodel function in dynamically change ocean and draw scope.

Then in the keyboard call back function of OSG rover, arranging ocean centre coordinate is eye coordinates.Can in the rover call back function of three-dimensional scenic such as trackballmanipulator keyboard event call-back function in ocean centre coordinate is set.Namely use setpositon function, during such that viewpoint moves horizontally each time, ocean centre coordinate all moves identical amount.

Step 5, sea height is set with viewpoint height dynamic change.

Step 5.1 adds rover in three-dimensional scenic, such as trackballmanipulator etc.Example code:

osgGA::TrackballManipulator*tb＝newTrackballManipulatorI；

viewer.setCameraManipulator(tb)；

Step 5.2 revises the convergent-divergent call back function of rover, arranges sea height value according to above-mentioned formula; .

Zoommodel function in the trackballmanipulator rover that amendment OSG carries, this function all can call when using mouse to carry out scene convergent-divergent each time.Distance value in mathematical model is composed as class members variable _ distance.Initialization is carried out to each variable of mathematical model.Add following statement:

pubscene->getOceanScene()->setOceanSurfaceHeight(-38.0-_distance/2000)；

This statement, namely when viewpoint height changes each time, is got viewpoint height value and is substituted in formula, reset sea height.Wherein pubscene is ocean node pointer.Along with viewpoint raises, sea height reduces, and makes flood and field draw degree of depth difference and becomes large, avoid the problem of the two frequent flicker.

Step 5.3, according to the sea height value calculated, is distinguished following situation and is shown:

If the pelagic division i. in the relief block drawn out of VPB has pinup picture, then, after distance rises to 5/6W, ocean node no longer shows, only display pinup picture.Now scene node is removed.

root->removeChild(scene->getScene())

If the pelagic division ii. in the relief block drawn out of VPB does not have pinup picture, then, after distance rises to 5/6W, ocean node continues display, highly no longer changes.Now viewpoint height is enough high, and also enough far away apart from extra large land model, do not need to observe whole three-dimensional scenic from farther place, can limit viewpoint height maximal value is 5/6W.

This example for when observing emphatically land model, the solution of flood and field stroboscopic.In program operation process, ocean model height constantly reduces the depth buffer increasing flood and field.Corresponding result figure is 4, shown in 5,6,7.

Embodiment 2

If for the solution of the flood and field stroboscopic of focusing on when observing oceanic purpose, then change the minus sign in formula into plus sige, that is:

$H=\left\{\begin{array}{cc}{H}_0+\frac{dis\tan ce}{\frac{5}{6}\×W\÷h}& dis\tan ce\≤\frac{5}{6}\×W\\ H_0+h& dis\tan ce>\frac{5}{6}\×W\end{array}\right.$

In program operation process, ocean model height constantly raises the depth buffer increasing flood and field, avoids the two stroboscopic.Corresponding operation result is Fig. 8, shown in 9.

Test findings

About 30000 the OSG world coordinate system units of region, Taiwan scene scale, draw frame number between 7 ~ 10 frames, reach the requirement of real-time rendering, as shown in Figure 2,3.When viewpoint height reaches OSG world coordinate system unit about 11000, there is land, ocean stroboscopic problem in the subregion in the scene of land, as shown in Figure 4,5.By using the method, same scene is when viewpoint height reaches OSG world coordinate system unit about 11000, and land stroboscopic problem is eliminated, and now draws frame number still about 10 frames, as Fig. 6, shown in 7.When viewpoint height reaches about 18000, whole scene sea part stroboscopic problem is serious, now draws between frame per second 7 ~ 10, as shown in Figure 8.By using the method, avoid the stroboscopic problem of whole scene sea part when viewpoint height reaches about 18000, frame per second is still stabilized between 7 ~ 10, and scene has good stability, as shown in Figure 9.Viewpoint height reaches 25000 units when can look down Taiwan scene overall picture, and load ocean pinup picture, no longer draw actual ocean model, now frame per second is between 9 ~ 10, as shown in Figure 10.In sum, flood and field, based on OSG 3 d rendering engine and VPB terrain rendering plug-in unit, is carried out the problem that visual solution solves extra large land stroboscopic well simultaneously, and ensure that scene drawing efficiency by this.

Above-described specific descriptions; the object of inventing, technical scheme and beneficial effect are further described; be understood that; the foregoing is only specific embodiments of the invention; the protection domain be not intended to limit the present invention; within the spirit and principles in the present invention all, any amendment made, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (4)

1. the extra large land based on OSG d engine engages a method for visualizing, it is characterized in that, comprises the following steps:

Step 1, uses OSG 3 d rendering engine to carry out three-dimensional scenic framework and builds;

Step 2, uses terrain modeling plug-in unit to generate large-scale terrain model file;

Step 3, uses ocean to draw plug-in unit and generates ocean node; And ocean node and relief block file are loaded into simultaneously carry out in the scene tree of OSG visual;

Step 4, can not follow viewpoint and move if the ocean node drawn out of plug-in unit is drawn in ocean and move, arranging ocean node is dynamic node, and namely ocean node drafting scope can not dynamic change, and should follow viewpoint and move and move;

Step 5, arrange sea height with viewpoint height dynamic change, then carry out ocean scenes display according to sea height, detailed process is as follows:

Step 5.1 adds rover in three-dimensional scenic;

Step 5.2 revises the convergent-divergent call back function of rover, in call back function, (1) or (2) arranges sea height value according to the following equation, formula (1) is the situation for focusing on when observing land model, and formula (2) is the situation for focusing on when observing oceanic purpose:

$H=\left\{\begin{array}{cc}{H}_0-\frac{dis\tan ce}{\frac{5}{6}\×W\÷h}& dis\tan ce\≤\frac{5}{6}\×W\\ H_0-h& dis\tan ce>\frac{5}{6}\×W\end{array}\right.;---\left(1\right)$

$H=\left\{\begin{array}{cc}{H}_0+\frac{dis\tan ce}{\frac{5}{6}\×W\÷h}& dis\tan ce\≤\frac{5}{6}\×W\\ H_0+h& dis\tan ce>\frac{5}{6}\×W\end{array}\right.;---\left(2\right)$

Wherein, W is extra large land scene scale, H ₀for height is drawn in initialization ocean, distance is the height of land, view distance sea scene, and h is ocean wave height;

Step 5.3, according to the sea height value calculated, is distinguished following situation and is shown:

(1) if the pelagic division in the relief block drawn out of terrain modeling plug-in unit has pinup picture, then, after distance rises to 5/6W, ocean node no longer shows, only display pinup picture;

(2), if the pelagic division in the relief block drawn out of terrain modeling plug-in unit does not have pinup picture, then after distance rises to 5/6W, ocean node continues display, highly no longer changes.

2. the extra large land based on OSG d engine engages a visualization device, it is characterized in that: extra large land three-dimensional scenic drafting module and sea height are with viewpoint height dynamic conditioning module;

Described extra large land three-dimensional scenic drafting module produces scene for using OSG 3 d rendering engine to draw, and uses VPB to generate large-scale terrain model;

Described sea height adjusting module is used for when each viewpoint position changes, and according to formula described in claim 1 (1) or formula (2) adjustment sea height, and carries out ocean scenes display according to the sea height after adjustment.

3. a kind of extra large land based on OSG d engine according to claim 2 engages visualization device, it is characterized in that, in described large-scale terrain model or comprise pelagic division, show as ocean pinup picture, or the part not comprising ocean and only have land to rise and fall; It is static land that land is loaded in scene, and namely terrestrial location and size can not change along with the change of viewpoint; It is dynamic sea that ocean is loaded in scene, no matter where viewpoint moves to, center, ocean is identical with eye coordinates all the time.

4. engage visualization device according to the arbitrary described a kind of extra large land based on OSG d engine of Claims 2 or 3, it is characterized in that, realize in the call back function that the adjustment of described sea height changes at the viewpoint position of rover.