CN100454341C - Process type ground fast drawing method based on fractal hierarchical tree - Google Patents

Abstract

Process-type fast landform draw method based on tree of elementary arrangements. It establishes the elementary arrangement tree structure of landform, gets afBm sub-tree according referenced threshold, estimates making progression of node according error precision, carries five alignments optimal scheduling of draw node, making and drawing elementary piece through GPU. It constructs the elementary arrangement tree structure afBm-tree by the elementary information of recorded landform. It is a kind of approach to original landform and gets different making precision and compressibility by adjusting making referenced threshold. The afBm-tree creates landform grid depended for viewpoint during the draw process and leaps over the enormous making process with landform arrangement detail model data. Compared with tradition arithmetic, the afBm-tree with same data size can overlay more area with lower multilevel scheduling cost and owns more advantage on computer with single CPU. It can be used in those fields, such as geography information simulation, dummy scene ramble and game engine.

Description

A kind of process type landform fast drawing method based on fractal hierarchical tree

Technical field

The present invention relates to general terrain data and handle or produce, relate in particular to a kind of process type landform fast drawing method based on fractal hierarchical tree.

Technical background

Fractally propose by French mathematician Mandelbrot the earliest, can be with reference to [Mandelbrot1975], Mandelbrot, B.B.On the Geometry of Homogeneous Turbulence, with Stress on theFractal Dimension of Iso-Surfaces of Scalars.Journal of Fluid Mechanics.1975,72 (2): 401-416.This is a geometry that is research object with non-regular geometric form, has the characteristics of unlimited and statistical self-similarity, and it can generate complicated scenery with simple rule with recursive algorithm.Because the irregular phenomenon of occurring in nature ubiquity self similarity, so fractally provide a mathematical model of describing spontaneous phenomenon well for the researcher.(fractional Brownian motion fBm) as a kind of fractal noise, can represent effectively that landform, cloud, snowflake etc. have the natural scene of self-similarity at random to divide the dimension Brownian movement.

FBm function calculation complexity is very high, therefore need simplify fBm, reduces calculated amount.As far back as nineteen eighty-two, people such as Fournier have proposed an iteration subdivision algorithm and have been similar to fBm, be called mid point method of replacing (Midpoint Displacement), can generate landform with self-similarity, can be with reference to [Fournier1982], Alain Fournier, Don Fussell and Loren Carpenter.Computer Rendering ofStochastic Models.Communications of the ACM.1982,25 (6): 371-384.They have at first constructed the one dimension fBm model based on line segment, are generalized to the landform of two dimension then, thereby generate the fractal details on mountain range.This method is reduced to linearity to the computation complexity of fBm from O (nlog (n)), calculates simple.But the mid point displacement is not the fBm algorithm of a strictness, and statistical property is not a stable state, can reduce the sense of reality that generates landform.

People such as Musgrave analyze from the frequency domain angle of fBm, have proposed band-limited noise accumulation algorithm (Summing Band-Limited Noises), utilize the Perlin noise to generate terrain mesh as basis function.The statistical property that this method generates landform is a stable state, and it is better than mid point replacement algorithm therefore to generate quality, but computation complexity is O (nlog (n)), and is bigger than mid point replacement algorithm, more consuming time.Can be with reference to [Musgrave1989] F.Kenton Musgrave, Craig E.Kolb and Robert S.Mace.The Synthesis and Renderingof Eroded Fractal Terrains.Computer Graphics.Jul.1989,23 (3): 41-50.

For simulating nature circle landform more accurately, people such as Kaplan have proposed self-similarity (the extended self-similar of expansion, ESS) notion, can be with reference to [Kaplan1995] Lance M.Kaplan andC.-C.Jay Kuo.Texture Roughness Analysis and Synthesis via Extended Selt-Similar (ESS) Model.IEEE Transactions on Pattern Analysis and Machine Intelligence.Nov.1995,17 (11): 1043-1056.And based on this, provide a general fBm model, be called the Brownian movement of gradual branch dimension (asymptotic fBm, afBm), the permissible roughness factor changes and changes along with sampling interval, thereby the fluctuating quantity that generates landform also can change thereupon.

More than the method for Jie Shaoing all is to study how off-line type generates landform, does not consider the terrain rendering problem.The terrain rendering method of process type is that landform generation and drafting are combined, and generates the terrain mesh that viewpoint relies at drawing process, realizes the generation as required and the drafting of landform.Losasso and Hoppe regard landform as texture how much, Geometry Clipmap technology has been proposed, the rectangular node that landform is divided into hollow is drawn, can be with reference to [Losasso2004] Frank Losasso and Hugues Hoppe.Geometry Clipmaps:TerrainRendering Using Nested Regular Grids.Proceedings of Siggraph 2004.2004,769-776..They also generate the detailed information of landform by fractal noise, but whole landform is only used a component shape parameter, and therefore the landform that generates is difficult to satisfactory.

Summary of the invention

At the deficiencies in the prior art, the object of the present invention is to provide a kind of process type landform fast drawing method based on fractal hierarchical tree, approach the initial landform model effectively, can draw large-scale landform scene fast, and data volume is less.

For realizing above-mentioned purpose, the technical solution used in the present invention is as follows:

1) set up the fractal hierarchical tree structure of landform: a given relief block, landform is carried out four fork subdivisions, set up quad-tree structure, the corresponding plot shape of each node zone, writing down fractal information, comprising afBm information and basic height value information, this fractal hierarchical tree structure is called afBm-tree;

2) obtain the afBm subtree according to threshold value: before drafting, according to user's preset threshold, extract the afBm subtree from afBm-tree, threshold value is represented initial landform and is generated the difference that allows between the landform.

3) estimate the generating series of node according to error precision: the random chance value of setting according to the user at first, determine minimum, the maximum height value of fractal box; Calculate the projection error of height value on screen that add up then; Then, determine the generating series of node according to this projection error;

4) to drawing the Optimization Dispatching that node carries out five formations: initialization five formation Q at first _r, Q _p, Q _g, Q _dAnd Q _mAt each frame of drawing, adjust all nodes in five formations then; Then respectively to formation Q _gWith formation Q _mIn the node processing that hockets, up to formation Q _rIn node reach needed rendering request;

5) by GPU generation and fractal of drafting: at first the pixel shader by GPU generates fractal, passes through the vertex shader tectonic landform grid of GPU then.

The method of the drafting node being carried out the Optimization Dispatching of five formations can be: at first the root node of afBm-tree is sent into formation Q _r, and empty remaining formation; At each frame of drawing, adjust nodes all in five formations then; Then take out formation Q _gThe node of middle limit priority, and be moved into formation Q _rOr formation Q _pIn, its child node is according to handling with quadrat method; Take out formation Q subsequently _mThe node of middle lowest priority, and be moved into formation Q _rOr formation Q _pIn; To formation Q _gWith formation Q _mIn the node processing that hockets, up to formation Q _rIn node reach needed rendering request.

By GPU generation and the method for drawing fractal can be: at first the pixel shader by GPU generates fractal, and uses three textures, is respectively other fractal texture of upper level, mask table and Gaussian noise figure texture; By the vertex shader tectonic landform grid of GPU, from fractal, take out the height value on summit then, and from connect template, determine the two-dimensional position on summit, be combined into actual three dimensions point, construct at last and draw terrain mesh and carry out the drafting of landform.

The present invention compares the beneficial effect that has with background technology:

The present invention constructs fractal hierarchical tree structure by the fractal information of record initial landform, is called afBm-tree.AfBm-tree approaches expression to landform a kind of, generates threshold value by adjusting it, can obtain different generation precision and compressibility.By afBm-tree, can when drawing, generate the terrain mesh that viewpoint relies on, thereby skip the constructive process of huge landform level detail model data.Compare with traditional terrain rendering algorithm, it is wider that the afBm-tree of same size of data covers, and can effectively reduce the cost of multi-stage scheduling, more has superiority on the machine of single CPU.In addition, the afBm-tree application is wider, allows the user to edit, and just can be directly used in drafting.The present invention can be applicable in the fields such as geography information emulation, dummy scene roaming, game engine.

Description of drawings

The invention will be further described below in conjunction with drawings and Examples.

Fig. 1 is the process flow diagram of the inventive method;

Fig. 2 is the construction process of fractal hierarchical tree afBm-tree;

Fig. 3 is a generating series of estimating node according to error precision;

Fig. 4 is the process flow diagram of fractal generation and drafting.

Embodiment

A kind of process type landform fast drawing method that the present invention proposes based on fractal hierarchical tree, comprise the fractal hierarchical tree structure of setting up landform, according to threshold value obtain the afBm subtree, according to error precision estimate node generating series, carry out the Optimization Dispatching of five formations and generate and draw fractal five steps drawing node by GPU.Flow process is as shown in Figure 1: at first according to original landform altitude value, set up the fractal hierarchical tree structure afBm-tree of landform; Obtain the afBm subtree according to threshold value then; Estimate the generating series of node according to viewpoint and error precision, and select suitable afBm node; Then to drawing the Optimization Dispatching that node carries out five formations; Generate and fractal of drafting by GPU at last.

Now specifically introduce five steps of this method:

1) sets up the fractal hierarchical tree structure of landform

In order to represent the different undulating states of landform diverse location, whole landform is set up the afBm-tree structure, each node is writing down the fractal information in plot shape zone.If the size of initial landform is (2 ^M+ 1) * (2 ^M+ 1), landform is carried out the recurrence subdivision, set up quad-tree structure.The level index is 0 the corresponding whole landform altitude of root node, and the level index is that the landform area size of the node correspondence of i is (2 ^M-i+ 1) * (2 ^M-i+ 1), Zui Xiao landform area size is designated as (2 ^m+ 1) * (2 ^m+ 1), 1≤m＜M wherein.Needing the computation layer secondary index is the quaternary tree node of i, i span i=0, and 1 ..., M-m.

The Brownian movement (afBm) of gradual branch dimension, the permissible roughness factor changes and changes along with sampling interval, thus the fluctuating quantity that generates landform also can change thereupon.If function Var (x) is the statistical variance of one group of random number x, σ ²It is a constant.(x y) can regard (x, the Terrain Elevation value of y) locating in the position as to F.With two-dimentional fBm model class seemingly, the variance of afBm model can be write as

Var[F(x+d _x，y+d _y)-F(x，y)]＝σ ²f(d _t) (1)

Function f (t) is called structure function, when f (t)=| d _t| ^2HThe time, formula (1) is the formula of variance of fBm model.The structure function of afBm is expressed as

$f\left(t\right)=(1-A)\frac{{\mathrm{\ρ}}^{\left|t\right|}-1}{\mathrm{\ρ}-1}+A{\left|t\right|}^{2H}---\left(2\right)$

Here 0≤ρ＜1, constant A is a smoothing factor.

The basic height value of each afBm node is used to control the contour shape that generates landform, comprises four angle point height values 1 on the corresponding landform zone boundary, shown in the real circle 3 among Fig. 2, needs to calculate four parameter values 2 of afBm, is respectively H, σ ², ρ and A at first use statistical method to obtain H and σ ²Use E (t) expression mathematical expectation function, the fractal statistical attribute according to afBm can obtain

logE(|F(x+d _x，y+d _y)-F(x，y)| ²)＝logσ ²+(2log|d _t|)H (3)

Can obtain thus a little to log | d _t|, log E ([F (x+d _x, y+d _y)-F (x, y)] ²), H and σ ²Can obtain by linear regression algorithm, the pairing tropic is shown among Fig. 24.After obtaining these two parameters, can be according to document [Kaplan1995] Lance M.Kaplan and C.-C.Jay Kuo.Texture RoughnessAnalysis and Synthesis via Extended Self-Similar (ESS) Model.IEEE Transactionson Pattern Analysis and Machine Intelligence.Nov.1995,17 (11): the method for 1043-1056 calculates coefficient ρ and A.

After according to the intact all landform zones of top-down sequential processes, just constructed afBm-tree, as 5 among Fig. 2.

σ ²Represented to generate the statistical discrepancy between landform and the initial landform, σ ²Big more, the difference between them is big more, therefore can use σ ²Control the approximation accuracy that generates landform.For the correct afBm node of selecting, further σ ²Be adjusted into saturation mode.

${\mathrm{\&sigma;}}_{T_i}^2=\left\{\begin{array}{cc}{\mathrm{\&sigma;}}_{T_i}^2,& i=M-m\\ \max ({\mathrm{\&sigma;}}_{T_i}^2,{\mathrm{\&sigma;}}_{T_{i+1}}^2),T_{i+1}\&Subset;T_i,& 0\&le;i<M-m\end{array}\right.---\left(4\right)$

Here $T_{i+1}\&Subset;T_i$ Expression T _I+1Be T _iChild node.

2) obtain the afBm subtree according to threshold value

Before drafting, at first, from afBm-tree, extract the afBm subtree according to user's preset threshold Ω, threshold value Ω represents initial landform and generates the difference that allows between the landform.

AfBm-tree is traveled through from the top down, to each node T, if its statistical variance ${\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="C20061005360500122.png"\; state="\{\{state\}\}">T</figure-callout>}}^2\&le;\mathrm{\&Omega;},$ Then T satisfy to generate the requirement of precision, otherwise its child node is carried out the recurrence visit.After finishing all traversal visits, just construct the afBm subtree.Below, will in drafting, use the afBm subtree to create the terrain mesh that viewpoint relies on.

3) estimate the generating series of node according to error precision

As shown in Figure 3,,, be called fractal box (being 1), require the height value on all summits all to drop in this box box of node T definition in order to control the scope that generates the terrain block height.The two-dimensional projection of fractal box equals the pairing landform area size of T.Fractal box is very similar to traditional bounding box, and different is, bounding box is to weigh the space of object across scope, and size remains unchanged, and fractal box is the scope that generates height in order to limit, and its size can be subjected to user's control break.If the basic height value of T is F (x _i, y _j), (i, j=0,1), a certain summit of T is designated as (x _p, y _q), 0≤p, q≤1, then according to the notion of afBm, the height value of this position is

$F(x_p,y_q)=\stackrel{-}{F}(x_p,y_q)+\underset{k=0}{\overset{k_{\max }}{\mathrm{\&Sigma;}}}{\mathrm{\&Delta;}}_k\&CenterDot;N_{\mathrm{gauss}}$

Here F (x _p, y _q) be the bilinear interpolation of basic height value, if use the afBm model, then, can obtain Δ from formula (1) _kFor:

${\mathrm{\&Delta;}}_k={\mathrm{\&sigma;}}^2[f\left(2^{-k}\right)-\frac{1}{4}f\left(2^{-k+1}\right)]---\left(6\right)$

N _GaussBe that average is 0, variance is 1 Gaussian random variable.Because Gaussian number mainly is distributed in certain zone, so can preestablish a certain probable value a, determine the distribution range of Gaussian number, thereby estimate generate height value across scope.As shown in Figure 3, be a (2 among Fig. 3 (b)) if most of Gaussian number drops on the probable value of shadow region, then can obtain its distribution range [G by following formula ₀, G ₀], see the scope that 3 and 4 among Fig. 3 (b) determines.

P{|x|＜G ₀}＝a→P{x＜G ₀}＝(a+1)/2 (7)

P represents the probable value of one group of random number, and x is a Gaussian random variable.For example, if a equals 95%, then most of random number all can drop on the zone in the scope of [2,2].Obtain G ₀After, just can control the scope that generates height, minimum, the maximum height value of establishing fractal box are Here F _TIt is the average of the base height of T.Set by this, the height value of all generations can guarantee to drop in the fractal box.

Next, the fractal progression that needs definite node T to generate.Fractal height value is to create in the mode of incremental, fractal of every increase one-level, and the new height value of creating increases Δ _kN _GaussWhen given probable value a, added value is in fact less than Δ _kG ₀, as 5 among Fig. 3 (a), therefore, this value is projected on the screen, and with predefined screen error E _ScrCompare, thereby determine fractal progression k.For viewpoint v _p, as 6 among Fig. 3 (a), establishing w and h is the width 7 and the height 8 of ken screen, fov is the video camera wide-angle that is used to draw, d _vBe the landform zone mid point of T and the distance 9 of current view point.Projection error Prj _TCan calculate by following formula

${\mathrm{Prj}}_T=\frac{\max (w,h)}{2\tan (\mathrm{fov}/2)}\&CenterDot;\frac{{\mathrm{\&Delta;}}_k{G}_0}{d_v}<E_{\mathrm{scr}}---\left(8\right)$

If current view point is positioned at fractal box inside, then will generate fractal of maximum level, i.e. k _MaxIf externally, then use fractal of formula (8) detection k level whether to meet the demands, if can not meet formula (8), so similarly detect again (k+1), if k+1＞k _Max, the child node that then needs to visit T.

4) to drawing the Optimization Dispatching that node carries out five formations

In render phase, when viewpoint moves with less spacing, there is the continuity between frame and the frame, that is to say that the drafting grid practice change of two frames is little.Therefore, when selecting the afBm node that is used to draw, needn't all top-down traversal of every frame afBm subtree.The initial value of the result of former frame, adjust the drafting node that obtains present frame, thereby quickened the scheduling operation of node as this frame.

Adopt the dispatching algorithm of five formations to manage the afBm node and generate fractal, these five formations are called Q _r, Q _p, Q _g, Q _dAnd Q _mQ _rThe afBm node that record is used to draw, Q _pPreserve Q _rMiddle all father nodes of drawing node.Q _gIn will generating series k higher fractal of node, Q _dIn node will abandon current fractal, then use more coarse fractal.The less fractal block cache of progression k in the afBm node, is not therefore needed to carry out once more generating run.Q _mRecord can merge the father node of four child nodes.Q _gAnd Q _mNeed sort according to priority, other three formations then do not need ordering.

At the initial phase of drawing, the root node of afBm-tree is sent into Q _r, and empty remaining formation.Each frame drawing at first utilizes the estimation of error formula of introducing previously (8), handles all nodes in five formations, and adjusts in the suitable formation.Take out Q then _gThe node T of middle limit priority, through type (8) decision will generate fractal progression k.If k≤k _Max, T is moved into formation Q _rIn; Otherwise, T is split into four child nodes, simultaneously T is moved into formation Q _pIts child node is according to handling with quadrat method.Then, take out Q _mThe node T of middle lowest priority, and whether all child nodes of detection T are all at formation Q _rPerhaps Q _dIn.If, then carry out the operation of merging child node, process is to remove all child nodes of T, and T is moved on to formation Q _rIf not, so at formation Q _dIn child node, reduce their current fractal progression that is using, and transfer to formation Q _r, then T is moved on to formation Q _pIn.To Q _gAnd Q _mIn the node processing that hockets, up to Q _rIn node reach needed rendering request.

5) generate and fractal of drafting by GPU

In order to utilize the continuity of frame and frame, draw the generation rank of node according to each, incremental ground generates fractal that needs, and quickens this process by GPU.Generating before new fractal, need be kept at afBm parameter and previous stage fractal in the video memory and use for GPU.But if read back into main memory again after fractal generation from video memory, then transmission cost can be very high, even be higher than the generation cost, can reduce whole performance on the contrary.In up-to-date graphic process unit, (Vertex Shader VS) visits texture to the vertex shader of permission in GPU, therefore can be kept at fractal that generates in the video memory in the texture mode, sense data is operated in vertex shader then, has avoided being sent to the cost of internal memory.

As shown in Figure 4, use two-step approach to generate and use fractal of landform: (Pixel Shader PS) 1 generates fractal to the pixel shader by GPU; By vertex shader 2 tectonic landform grids and drafting.Specifically describe as follows:

Generating fractal stage, needing three textures to generate progression altogether, be used to calculate fractal height flat average of (k+1) level for fractal 3, the first textures of (k+1) are fractal 4 of k level.Can pass through the bilinear interpolation computation of mean values,, only need be arranged to GL_LINEAR to the texture amplifying parameters of OpenGL and get final product in order to allow graphic process unit finish automatically.Because only need generate height value in new summit in fractal to (k+1) level, the height value on existing summit can obtain from fractal of k level, so second texture is a mask table 5.If certain pixel value is 1 on the mask table, then the corresponding position need generate new height value on fractal of target; If be 0, then do not need to generate new height value, only need take out analog value and get final product from fractal of k level.The 3rd texture is a pretreated Gaussian noise Fig. 6, is used to calculate fractal noise.Before drafting, according to predefined probable value a, calculate a gaussian random value array, and be stored as the form of 2 d texture.When generating fractal, use the coordinate figure on terrain mesh summit in Gaussian noise figure, to search random value.

Generation method based on afBm can be selected in following two kinds of methods: the mid point replacement algorithm (MidpointDisplacement, MD) and band-limited noise accumulation algorithm (Summing Band-Limited Noises, SBLN).The MD algorithm is more faster than SBLN, but the quality that generates is not as SBLN.In the MD algorithm, use the F+ Δ _kN _GaussCalculating new height value, is the mean value of the adjacent height value of F here, Δ _kConsistent with formula (6) definition.It is synthetic that the SBLN algorithm is actually a kind of frequency spectrum, and one group of noise function addition is got, and the frequency of these noise functions increases successively, and amplitude reduces successively.The summit of computed altitude value is v if desired _{X, y}, can pass through F+ σ so ²∑ _I=0 ^Octavew ^-iHN (w ⁱv _{X, y}) calculate, w is a constant here, is taken as 2 usually.Octave also is a constant, is controlling the number of the noise function of addition.N (t) is the noise basis function, uses the Perlin function based on Gaussian noise here.

After the fractal generation, will pass through vertex shader tectonic landform grid together with the corresponding template 7 that is connected, and draw 8.In vertex shader, from fractal, take out the height value on summit, and from connect template, determine the two-dimensional position on summit, be combined into actual three dimensions point, construct the drafting terrain mesh at last.

In order to improve rendering quality, can adopt two kinds of texture technology, a kind of is pretreated texture quaternary tree technology, another kind is a process type texture technology.The basic ideas of texture quaternary tree technology are that a given very big texture at pretreatment stage, is set up a texture quad-tree structure, a zone of the corresponding original texture of each node, the texture block of the equal resolution of all quaternary tree nodes uses.The texture quaternary tree is organized into the form of Out-of-Core, in render phase, will selects suitable texture node, and data are called in main memory from hard disk, send into video memory again and be used for texture mapping.The more details of texture quaternary tree technology can be referring to [Cline 1998] David Cline and Parris K.Egbert.Interactive Display of Very LargeTextures.Proceedings of IEEE Visualization 1998.1998,343-350.

Another scheme of texture is that process type obtains texture information when drawing, and this technology has been widely used in the virtually drawing engine.At first, the material type map in a landform of pretreatment stage establishment comprises types such as meadow, sandstone, snowfield.When drawing landform, type map and various material texture by many texture mode, are transferred to GPU, topographical surface color when calculating drafting.Also can calculate the illumination and the echo of landform in advance, send into GPU, carry out the light and shade of landform and handle as texture.

Claims (3)

1. process type landform fast drawing method based on fractal hierarchical tree is characterized in that comprising following five steps:

1) set up the fractal hierarchical tree structure of landform: a given relief block, landform is carried out four fork subdivisions, set up quad-tree structure, the corresponding plot shape of each node zone, writing down fractal information, comprising afBm information and basic height value information, this fractal hierarchical tree structure is called afBm-tree;

2) obtain the afBm subtree according to threshold value: before drafting, according to user's preset threshold, extract the afBm subtree from afBm-tree, threshold value is represented initial landform and is generated the difference that allows between the landform;

3) estimate the generating series of node according to error precision: the random chance value of setting according to the user at first, determine minimum, the maximum height value of fractal box; Calculate the projection error of height value on screen that add up then; Then, determine the generating series of node according to this projection error;

4) to drawing the Optimization Dispatching that node carries out five formations: initialization five formation Q at first _r, Q _p, Q _g, Q _dAnd Q _mAt each frame of drawing, adjust all nodes in five formations then; Then respectively to formation Q _gWith formation Q _mIn the node processing that hockets, up to formation Q _rIn node reach needed rendering request;

5) by GPU generation and fractal of drafting: at first the pixel shader by GPU generates fractal, passes through the vertex shader tectonic landform grid of GPU then.

2. a kind of process type landform fast drawing method based on fractal hierarchical tree according to claim 1 is characterized in that: described is at first the root node of afBm-tree to be sent into formation Q to drawing the method that node carries out the Optimization Dispatching of five formations _r, and empty remaining formation; At each frame of drawing, adjust nodes all in five formations then; Then take out formation Q _gThe node of middle limit priority, and be moved into formation Q _rOr formation Q _pIn, its child node is according to handling with quadrat method; Take out formation Q subsequently _mThe node of middle lowest priority, and be moved into formation Q _rOr formation Q _pIn; To formation Q _gWith formation Q _mIn the node processing that hockets, up to formation Q _rIn node reach needed rendering request.

3. a kind of process type landform fast drawing method according to claim 1 based on fractal hierarchical tree, it is characterized in that: the described generation with the method for drawing fractal by GPU is, at first the pixel shader by GPU generates fractal, and use three textures, be respectively other fractal texture of upper level, mask table and Gaussian noise figure texture; By the vertex shader tectonic landform grid of GPU, from fractal, take out the height value on summit then, and from connect template, determine the two-dimensional position on summit, be combined into actual three dimensions point, construct at last and draw terrain mesh and carry out the drafting of landform.

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