Quadtree Lod Crack

• The Cause of Crack Quadtree LOD algorithm is a part simplification method, each terrain piece has different resolution after it being dealt with.
• A New Quadtree-based Terrain LOD Algorithm Quadtree LOD algorithm will reduce the total number The Cause of Crack Quadtree LOD algorithm is a part simplification.

91 The Improvement on Terrain LOD Algorithm Using Quadtree Jian Wu1,2, 1,2Yanyan Cao1, Zhiming Cui, and Xiaojun Wang1 1 The Institute of Intelligent.

A New Quadtree-based Terrain LOD Algorithm Jian Wu, Yan-yan Cao, Zhi-ming Cui, Crack Elimination Algorithm Quadtree LOD algorithm will reduce the total.

Looking for an example on quadtree based LOD terrain

Ages ago 10 years I wrote a quadtree based terrain renderer, that directly reads Terragen-1 files. You need to supply a prerendered surface/illumination texture. The whole thing never was meant to be something serious. The first iteration of the code started as a keep me from boredom during a lengthy train trip, within about 6 hours. Then I added to it LOD and some other goodies.

I ve put the code as it was on my harddisk on Github, enjoy:

https://github.com/datenwolf/codesamples/tree/master/samples/OpenGL/qt_terr

This thing renders the terrain using immediate mode. Turning this in a vertex array based renderer is left as an exercise to the reader.

GPU-Aware Hybrid Terrain Rendering, 2012C. Dick, J. Krüger, R. Westermann Munich, Saarbrucken, builds on

rasterization and ray-casting in every frame simultaneously

to determine eye ray intersections

shifts workloads flexibly between the triangle setup stage and the

parallel execution units, depending on the GPU capacities

As is frequently the case with modern papers, there is no algorithms

or pseudocode or shader code, just a high-level overview of the approach.

Continuous Distance-Dependent Level of Detail for Rendering Heightmaps

CDLOD, 2010by Filip Strugar, originally

journal of graphics, gpu, and game tools, 2009

GPU-based rendering, quadtree based, smooth geomorphing based on

predictable detail across LODs.

Supports dynamic loading/paging of large datasets.  No skirts.

Supports all graphics hardware with Shader Model 3.0 and above.

Demo and complete DirectX source code is available under a free

GPU Ray-Casting for Scalable Terrain Rendering, Eurographics

2009C. Dick, J. Krüger, R. Westermann Munich, Utah

The authors started with an existing terrain rendering system, which

handles very large out-of-core datasets using a quadtree, and replaced the

rendering portion with a GPU-based ray-casting algorithm.  There are

many complex multi-pass operations, e.g. to exploit occlusion.  It

performs well in certain cases with very high-resolution data with multiple

height samples per on-screen pixel, but poorly compared to normal

rasterization with higher screen resolutions and lower DEM resolutions.

No known public implementation.

Based on a terrain rendering system described in this paper:

Patches for GPU-Based Terrain Rendering,

WSCG 2007Yotam Livny, Zvi Kogan,

Jihad El-Sana Ben-Gurion University

Yet another approach using a quadtree, with the unusual approach of

handling each quad as four right triangles, each whose resolution is chosen

to match its neighbor, with a triangle strip running down the seam to stitch

Claims to balance computation load among the CPU and GPU and dramatically

reduces the communication between them, sending elevation as a vertex

texture via Fragment Buffer Object extensions FBO.

Integrates paging of elevation from disk and texture LOD as well.

Survey on Semi-Regular Multiresolution Models for Interactive Terrain

Rendering, 2007R. Pajarola, E.Gobbetti, 2007

A survey paper giving an overview of all the various semi-regular

terrain LOD approaches: models based on tiled blocks and nested regular

grids, quadtrees and triangle bin-trees triangulations, as well as

cluster-based approaches LOD error metrics and system-level data

management aspects of interactive terrain visualization, including dynamic

scene management, out-of-core data organization and compression, as well as

Rendering using Spherical Clipmaps, Eurographics 2006Malte Clasen and Hans-Christian Hege Zuse Institute Berlin

using GPU-based geometry clipmaps to handle spherical planets, using an

ambitious, novel approach which pushes a GPU to it limits

spherical coordinates centered at the viewpoint produce concentric rings

of detail of increasing size, so unlike nearly every other LOD approach,

there are no problems with gaps between adjacent areas of differing LOD

however, this requires doing plenty of math on the GPU, including trig

functions, and a vertex texture lookup which is as of 2006 only available

the bottleneck is the vertex texture lookup, which the authors feel might

be solved in future GPUs by a unified shader architecture

GPU-Friendly High-Quality Terrain Rendering Journal of WSCG

2006J. Schneider, R. Westermann Technische Universität München

divides the terrain into a flat array of 257x257 tiles, uses ribbons of

zero area polygons to fill the gaps between tiles

GPU programming is used to decode vertices as 9 bits X, 9 bits Y, 14 bits

re-use of vertices and progressive transmission of vertices and indices

for less bus traffic and better GPU cache behavior

paging is done with complex memory management, implemented as a mixture

LRU and a tightest fit TF strategy

the primitive used is indexed triangle fans

Terrain Rendering Engine TRE : Cell Broadband Engine Optimized Real-time

intriguing paper on a unconventional approach:

ray-casting simpler than ray-tracing using the Cell distributed-processing

architecture to achieve realtime framerates

the special hardware consists of a Cell Broadband

Engine CBE with one dual-threaded Power Processor Element

PPE with eight SIMD Synergistic Processor Elements SPE

interestingly, there are no triangles involved at

all in the rendering, just rays and heightfields

Streaming and Rendering of Large Terrains using Strip Masks, 2005describes a very simple paging approach using a simple grid of tiles, each

containing a simple strip mask

boundary gaps are filled using a texture shadow plane which has the

ground texture repeated just below the terrain

although crude, this works fairly well for very light devices such as PDAs

Rendering Procedural Terrain by Geometry Image Warping. Eurographics

Dachsbacher, M. Stamminger University of Erlangen-Nuremberg

describes a way to use the GPU to do most of the work with both CLOD and

one very interesting step is the calculation of an importance map which

factors distance, frustum and terrain surface characteristics

the procedural detail is a fairly straightforward noise function

no known public implementation

clipmaps: Terrain rendering using nested regular grids. Siggraph

applies the concept of texture clipmaps to regular grid elevation,

using the GPU to smooth the transitions between detail levels

simplifies purely on distance, so it doesn t fit high-contrast terrain

well, but polygon count can be pushed so high on modern hardware that it

the clipmap construction allows compression, so that they can claim a

memory usage of only 0.1 bytes per heixel, or less.

using GPU-based geometry clipmaps, 2005, A.

an extension of the previous algorithm to

perform nearly all computations on the GPU itself, thereby reducing CPU

the technique is easy to implement

although it requires an NVidia GeForce6-class card, and there is no

this paper also appears in the GPU Gems

Terrain Rendering Using Geometry Clipmaps, Nick Brettell, 2005

Nick implements the Losasso/Hoppe paper,

as well a several others, and compares their relative strengths and

weaknesses.  However, there is no public implementation.

Planet-Sized Batched Dynamic Adaptive Meshes P-BDAM, IEEE

Visualization 2003Paolo Cignoni, Fabio Ganovelli, Enrico Gobbetti, Fabio Marton, Federico

Ponchio, and Roberto Scopigno of

claims: a batched host-to-graphics communication model which outperforms

other adaptive tessellation solutions, guaranteed overall geometric

continuity, exploits programmable graphics hardware, a compressed out of

core representation and speculative prefetching for hiding disk latency

the tessellation structure is topologically like a normal RTIN, but the

vertex locations are allowed to leave the grid for more efficiency

significant pre-computation is required

BDAM - Batched Dynamic Adaptive Meshes for High Performance Terrain

The open-source project RATMAN

contains an implementation of BDAM see

C-BDAM - Compressed Batched Dynamic Adaptive Meshes for Terrain Rendering,

long list of claimed features and benefits: simplicity of

data structures, overall geometric continuity for planar and spherical

domains, support for variable resolution input data, management of multiple

vertex attributes, efficient compression and fast construction times,

ability to support maximum-error metrics, real-time decompression and shaded

rendering with configurable variable level-of-detail extraction, and runtime

Real-time Terrain Rendering using Smooth Hardware Optimized Level of Detail,

pdf B. D. Larsen, N. J. Christensen, Technical University of Denmark

based on a regular grid, quadtree of triangulated tiles, with a hardware

vertex program to do geomorphing on each vertex

there is no significant difference in the framerates with or without

morphing which indicates that the morphing feature does not cause a

performance penalty when vertex programs are implemented in hardware

each tile is loaded into a display list, created as needed based on LOD of

surrounding tiles, rather than created each frame, to further cut down on

CPU usage and improve triangle throughput

their implementation enforces the constraint that two adjacent tiles may

their test implementation uses OpenGL and the NVidia vertex API on a

Algorithm: CLOD for Height Fields, 2001

Henri Hakl, University of Stellenbosch

based on frame-coherent ROAM, with an alternative geometric structure:

claims: better for triangle strips, fewer split and merge operations

uses 4 LIFO buffers instead of priority queues

T-junctions are avoided with ad hoc splits that are not

inherent in the geometric structure

Visualization of Large Terrains Made Easy, 2001

Peter Lindstrom, Valerio Pascucci, LLNL, in Proceedings of IEEE

mentions, and draws on, virtually every CLOD paper to date, including

Lindstrom s previous work, ROAM, Hoppe s papers, and interestingly,

prominent use of Jonathan Blow s nested spheres.

the two main innovations claimed are an efficient memory indexing

scheme for better paging performance, and a new split/cull/stripping

claims that previous approaches have been overly complicated, and

offers a new way which is simple and easy to implement, yet still

Terrain Rendering at High Levels of Detail pdf, 2000

presented at GDC 2000 by Jonathan Blow

summarizes the Lindstrom-Koller and ROAM approaches, then proposes a

major improvement in how to treat the ROAM error metric, by looking at

the variance as a spherical isosurface around each vertex

best understood by looking at the illustrations in his slides for the

lecture; browse all his writings

the benefit applies only. to frame-coherent ROAM implements

Jonathan discusses his approach vs.

Real-Time Generation of Continuous

Levels of Detail for Height Fields 1998

by Stephan Röttger, W. Heidrich,

Ph. Slusallek, H.-P. Seidel University of Erlangen-Nuremberg

uses a quadtree which corresponds to the height grid

very low memory requirement height value 1 byte

recommends using triangle fans, centered around each parent vertex, as

an efficient way to render a vertex quadtree

is available which is very fast and extensible to paging of large

ROAMing Terrain: Real-time Optimally Adapting Meshes, 1997 primary paper by

Mark Duchaineau et al, from IEEE Visualization 97 Proceedings

features claimed:optimizes flexible view-dependent error metrics,

produces guaranteed error bounds,

achieves specified triangle counts directly,

uses frame-to-frame coherence to operate at high frame rates

new site now has extensive implementation notes and Unix source.

Right Triangular Irregular Networks ps, 1997

Gregg Townsend at the University of Arizona

uses 12 bytes/vertex, plus the grid of elevation values, so typically

uses a sophisticated storage approach which avoids having to allocate

includes an example program with complete, functional source codethe sample program is designed to illustrate the LOD

it isn t optimized for rendering speed, e.g.. they generate

Articles and Presentations Describing Algorithms

Large Terrain, 2010 by skytiger A completely modern approach which uses a vertex shader to transform

world-space positions into texture-space, sample the height map using VTF

Vertex Texture Fetch and displace the height of the mesh, then use

on-the-fly interpolation to smooth the result.

The result: Uses almost no CPU, no CPU-to-GPU bandwidth, and is very

GPU friendly. There is no need for quadtrees, octrees, clipmaps, roam or

There are demonstration videos but no source code.

Rendering Massive Terrains using Chunked Level of Detail Control pdf Thatcher Ulrich, presented at the at the Super-size it. Scaling up to

Massive Virtual Worlds course at SIGGRAPH 02

a quadtree of chunks, where each chunk is a rectangular, precomputed

section of optimized geometry, and skirts to fill cracks rather than force

from the paper, advantages of this approach:

Low CPU overhead and high triangle throughput.

Efficient use of triangles within aggregates.

Texture LOD integrated with geometry LOD.

Easy to integrate with out-of-core storage.

Efficient, smooth vertex morphing; no vertex pops.

Low CPU load, even when viewpoint moves rapidly.

Non-trivial preprocessing required.

Uses more triangles than a primitive-level algorithm, for the same

Some data size overhead, depending on lossiness of preprocessing.

Continuous LOD Terrain Meshing Using Adaptive Quadtrees, 2000

Gamasutra article by Soul Ride

his approach uses a single quadtree of 3x3 blocks, with the LOD

computation performed directly on each block

the tree of blocks approach allows for memory to be used sparsely,

only where needed, instead of a single monolithic vertex array

it s handling an area of 64K x 64K meters, yet allows the finest grid

data to be 1m x 1m in selected areas

memory usage is typically around 12 bytes/vertex

Real-Time Dynamic Level of Detail Terrain Rendering with ROAM, 2000

Terrain Rendering Using Geometrical MipMapping, 2000

flipcode article by Willem H. de

a quadtree LOD approach, like Röttger s but has less detail about how

LOD levels are managed to avoid cracks

introduces a very direct analogy of texture MipMapping to terrain LOD,

Visualization of Large Textured Terrains, 2005Anders Brodersen, University of Aarhus

Claims to extend Boer s GeoMipMaps with efficient paging of large

textures.  However, the texture handling is barely described one small

sub-section in section 5 of the paper.   No known public implementation

Landscapespresentation at GDC 2001 by Glenn Corpes

includes a description of a regular-grid LOD algorithm which:

makes heavy use of precomputed vertex buffers, for each possible

deals with edge conditions by storing each possible permutation

the precomputed LOD only varies by a maximum of. 5 on adjacent

cells - this condition is assured by walking through the map and

dragging the LOD of high detail cells neighbors up.

A Fast Algorithm For Large Scale Terrain Walkthrough, 2001 pdf

Zhou, Jiaoying Shi, Zhigeng Pan

contains a good overview of the other papers on the subject

briefly describes a CLOD approach which prevents cracks by allowing

Real-time Continuous LOD for PCs and Consoles . ppt, 2000

no longer online presented at GDC 2000 by Louis Castle et al. Westwood Studios

based on Röttger s paper above, extends it with:

Simplified quadtree subdivision: fewer subdivision tests and

Linked quadtree storage: rather than in a height-field-sized

what they call a optional detail map is considered a fundamental

requirement variance by other algorithms

the detail map is a rather crude workaround for the problem that

their split metric is based only on distance

Large Scale Terrain Visualization Using The Restricted Quadtree

Renato Pajarola, IEEE Visualization 98

the approach looks very similar to Lindstrom-Koller 96, cleaned up a

little and fleshed out, and made unambiguously top-down

Fast Multiresolution Surface Meshing postscript,

M. H. Gross, R. Gatti, O. Staadt, Proceedings of the IEEE

a very math-intensive paper which uses a wavelet approach

doesn t use RTINs, but rather a lookup-table of special cases to

Terrain LOD algorithm is a dynamic and local dough sheet subduction algorithm. On the basis of the research on traditional quadtree algorithm, this paper proposed a.

Official Full-Text Publication: The Improvement on Terrain LOD Algorithm Using Quadtree on ResearchGate, the professional network for scientists.