Procedural modeling of plant ecosystems maximizing vegetation cover

Vegetation plays a major role in the realistic display of outdoor scenes. However, manual plant placement can be tedious. For this reason this paper presents a new proposal in the field of procedural modeling of natural scenes. This method creates plant ecosystems that maximizes the covered space by optimizing an objective function subject to a series of constraints defined by a system of inequalities. This system includes the constraints of the environment taking into account characteristics of the terrain and the plant species involved. Once the inequality system has been defined, a solution will be obtained that tries to maximize the radius of the projected area of the trees and therefore the extension of the vegetation cover on the ground. The technique eliminates the trees that do not achieve a minimum growth radius, simulating the typical competitive process of nature. Results show the good performance and the high visual quality of the ecosystems obtained by the proposed technique. The use of this kind of optimization techniques could be used to solve other procedural modeling problems in other fields of application.Funding for open access charge: CRUE-Universitat Jaume

Efficient modeling of entangled details for natural scenes

Proceedings of Pacific Graphics 2016 (Okinawa)International audienceDigital landscape realism often comes from the multitude of details that are hard to model such as fallen leaves, rock piles orentangled fallen branches. In this article, we present a method for augmenting natural scenes with a huge amount of details suchas grass tufts, stones, leaves or twigs. Our approach takes advantage of the observation that those details can be approximatedby replications of a few similar objects and therefore relies on mass-instancing. We propose an original structure, the GhostTile, that stores a huge number of overlapping candidate objects in a tile, along with a pre-computed collision graph. Detailsare created by traversing the scene with the Ghost Tile and generating instances according to user-defined density fields thatallow to sculpt layers and piles of entangled objects while providing control over their density and distribution

Procedural Generation and Rendering of Realistic, Navigable Forest Environments: An Open-Source Tool

Simulation of forest environments has applications from entertainment and art creation to commercial and scientific modelling. Due to the unique features and lighting in forests, a forest-specific simulator is desirable, however many current forest simulators are proprietary or highly tailored to a particular application. Here we review several areas of procedural generation and rendering specific to forest generation, and utilise this to create a generalised, open-source tool for generating and rendering interactive, realistic forest scenes. The system uses specialised L-systems to generate trees which are distributed using an ecosystem simulation algorithm. The resulting scene is rendered using a deferred rendering pipeline, a Blinn-Phong lighting model with real-time leaf transparency and post-processing lighting effects. The result is a system that achieves a balance between high natural realism and visual appeal, suitable for tasks including training computer vision algorithms for autonomous robots and visual media generation.Comment: 14 pages, 11 figures. Submitted to Computer Graphics Forum (CGF). The application and supporting configuration files can be found at https://github.com/callumnewlands/ForestGenerato

On the growth performance of two competing species in an Andean pasture of southern Ecuador - monitoring and simulations

The megadiverse tropical mountain forests in the southeastern Andes of Ecuador, including their biodiversity and ecosystem services, are severely threatened due to climate warming and the clearing of forests to produce pasture land. The common local practice of recurrent burning for pasture rejuvenation has proven to be non-sustainable, since it enables bracken fern to invade pastures, causing farmers to abandon heavily infested pastures and instead clear new tracts of natural forest. No quantitative information on the growth potential of pasture grass and bracken fern under current and future environmental conditions has yet been available for the Andes of Ecuador. The scientific basis required to understand bracken invasion has yet to be established. This scientific basis would enable the development of sustainable pasture management strategies. Such strategies would, in turn, help protect the remnants of natural forest. Consequently, the present work aims at investigating the growth potential of two competing species under current and future climate conditions. Outcomes provide new knowledge and methodological developments concerning pasture invasion by bracken fern in southern Ecuador. The method entails the development of a new model, the Southern Bracken Competition Model (SoBraCoMo), realistically parameterized and validated. The model code is based on existing Soil Vegetation Atmosphere Transfer (SVAT) and vegetation dynamic models to calculate the potential growth of two main competitors, the southern bracken fern (Pteridium arachnoideum) and the pasture grass (Setaria sphacelata). Extensive field measurements and proper meteorological forcing delivered new site and species-specific parameters for realistic productivity simulations of both species. An experimental site was established to observe pasture and bracken fern development under the practice of recurrent burning, and to provide atmospheric data for a realistic forcing of the developed model. A novel balloon-borne monitoring system was developed to detect species cover and provided new insights into post-fire canopy recovery. The main results demonstrate that, under current environmental conditions, Setaria has a slightly higher competitive growth potential under undisturbed conditions (no grazing, trampling, or light competition). Furthermore, this growth advantage of Setaria should most likely increase due to global warming. Because field observations show bracken infestation, however, other factors than those investigated should be responsible for the bracken fern’s current success. The most likely cause of bracken success to be investigated in the future is cattle browsing; although browsing continuously removes aboveground biomass, this disruption of the upper soil does not affect deep roots and rhizomes of bracken plants. The newly developed SoBraCoMo can now provide an excellent basis to implement new mechanisms like browsing for future simulations

Realistic reconstruction and rendering of detailed 3D scenarios from multiple data sources

During the last years, we have witnessed significant improvements in digital terrain modeling, mainly through photogrammetric techniques based on satellite and aerial photography, as well as laser scanning. These techniques allow the creation of Digital Elevation Models (DEM) and Digital Surface Models (DSM) that can be streamed over the network and explored through virtual globe applications like Google Earth or NASA WorldWind. The resolution of these 3D scenes has improved noticeably in the last years, reaching in some urban areas resolutions up to 1m or less for DEM and buildings, and less than 10 cm per pixel in the associated aerial imagery. However, in rural, forest or mountainous areas, the typical resolution for elevation datasets ranges between 5 and 30 meters, and typical resolution of corresponding aerial photographs ranges between 25 cm to 1 m. This current level of detail is only sufficient for aerial points of view, but as the viewpoint approaches the surface the terrain loses its realistic appearance. One approach to augment the detail on top of currently available datasets is adding synthetic details in a plausible manner, i.e. including elements that match the features perceived in the aerial view. By combining the real dataset with the instancing of models on the terrain and other procedural detail techniques, the effective resolution can potentially become arbitrary. There are several applications that do not need an exact reproduction of the real elements but would greatly benefit from plausibly enhanced terrain models: videogames and entertainment applications, visual impact assessment (e.g. how a new ski resort would look), virtual tourism, simulations, etc. In this thesis we propose new methods and tools to help the reconstruction and synthesis of high-resolution terrain scenes from currently available data sources, in order to achieve realistically looking ground-level views. In particular, we decided to focus on rural scenarios, mountains and forest areas. Our main goal is the combination of plausible synthetic elements and procedural detail with publicly available real data to create detailed 3D scenes from existing locations. Our research has focused on the following contributions: - An efficient pipeline for aerial imagery segmentation - Plausible terrain enhancement from high-resolution examples - Super-resolution of DEM by transferring details from the aerial photograph - Synthesis of arbitrary tree picture variations from a reduced set of photographs - Reconstruction of 3D tree models from a single image - A compact and efficient tree representation for real-time rendering of forest landscapesDurant els darrers anys, hem presenciat avenços significatius en el modelat digital de terrenys, principalment gràcies a tècniques fotogramètriques, basades en fotografia aèria o satèl·lit, i a escàners làser. Aquestes tècniques permeten crear Models Digitals d'Elevacions (DEM) i Models Digitals de Superfícies (DSM) que es poden retransmetre per la xarxa i ser explorats mitjançant aplicacions de globus virtuals com ara Google Earth o NASA WorldWind. La resolució d'aquestes escenes 3D ha millorat considerablement durant els darrers anys, arribant a algunes àrees urbanes a resolucions d'un metre o menys per al DEM i edificis, i fins a menys de 10 cm per píxel a les fotografies aèries associades. No obstant, en entorns rurals, boscos i zones muntanyoses, la resolució típica per a dades d'elevació es troba entre 5 i 30 metres, i per a les corresponents fotografies aèries varia entre 25 cm i 1m. Aquest nivell de detall només és suficient per a punts de vista aeris, però a mesura que ens apropem a la superfície el terreny perd tot el realisme. Una manera d'augmentar el detall dels conjunts de dades actuals és afegint a l'escena detalls sintètics de manera plausible, és a dir, incloure elements que encaixin amb les característiques que es perceben a la vista aèria. Així, combinant les dades reals amb instàncies de models sobre el terreny i altres tècniques de detall procedural, la resolució efectiva del model pot arribar a ser arbitrària. Hi ha diverses aplicacions per a les quals no cal una reproducció exacta dels elements reals, però que es beneficiarien de models de terreny augmentats de manera plausible: videojocs i aplicacions d'entreteniment, avaluació de l'impacte visual (per exemple, com es veuria una nova estació d'esquí), turisme virtual, simulacions, etc. En aquesta tesi, proposem nous mètodes i eines per ajudar a la reconstrucció i síntesi de terrenys en alta resolució partint de conjunts de dades disponibles públicament, per tal d'aconseguir vistes a nivell de terra realistes. En particular, hem decidit centrar-nos en escenes rurals, muntanyes i àrees boscoses. El nostre principal objectiu és la combinació d'elements sintètics plausibles i detall procedural amb dades reals disponibles públicament per tal de generar escenes 3D d'ubicacions existents. La nostra recerca s'ha centrat en les següents contribucions: - Un pipeline eficient per a segmentació d'imatges aèries - Millora plausible de models de terreny a partir d'exemples d’alta resolució - Super-resolució de models d'elevacions transferint-hi detalls de la fotografia aèria - Síntesis d'un nombre arbitrari de variacions d’imatges d’arbres a partir d'un conjunt reduït de fotografies - Reconstrucció de models 3D d'arbres a partir d'una única fotografia - Una representació compacta i eficient d'arbres per a navegació en temps real d'escenesPostprint (published version

Where do seedlings go? A spatio-temporal analysis of seedling mortality in a semi-arid gypsophyte

Studies of seedling population dynamics often focus on survival because it provides an integrated measure of seedling performance. However, this approach involves a substantial loss of information because survival is the net result of a wide range of mechanisms. The present study overcomes these shortcomings by investigating spatial and temporal patterns in the causes of plant mortality in a population of Helianthemum squamatum seedlings. We use new point pattern analyses based on K functions combined with a new null model (‘‘independent labeling’’). A total of 871 seedlings of H. squamatum were mapped and regularly monitored over an 18-month period. More than 60% of seedlings died during this period. Causes of mortality were spatially structured, and these structures shifted through time. Small differences in either the time of emergence or the environment surrounding H. squamatum seedlings had profound influences on their fate. Seedlings emerging late in the season under the canopy of adult plants died from drought more often than expected, whereas those emerging earlier in the same microsite survived more than expected. The identity of neighbors also affected the spatio-temporal dynamics of mortality causes. Our results show that seedling-adult interactions cannot be easily predicted from simple models, and that the time of seedling emergence, its age and the identity of its neighbors determine the sign and the spatial scale of these interactions. The new methods introduced in this article open an avenue for the detailed analyses of the spatio-temporal dynamics of plant mortality and can help to disentangle the complexity of biotic interactions along environmental severity gradients

PlantGL : a Python-based geometric library for 3D plant modelling at different scales

In this paper, we present PlantGL, an open-source graphic toolkit for the creation, simulation and analysis of 3D virtual plants. This C++ geometric library is embedded in the Python language which makes it a powerful user-interactive platform for plant modelling in various biological application domains. PlantGL makes it possible to build and manipulate geometric models of plants or plant parts, ranging from tissues and organs to plant populations. Based on a scene graph augmented with primitives dedicated to plant representation, several methods are provided to create plant architectures from either field measurements or procedural algorithms. Because they reveal particularly useful in plant design and analysis, special attention has been paid to the definition and use of branching system envelopes. Several examples from different modelling applications illustrate how PlantGL can be used to construct, analyse or manipulate geometric models at different scales

Supply curves of electricity-based gaseous fuels in the MENA region

The utilization of electricity-based fuels (e-fuels) is a potential strategy component for achieving greenhouse gas neutrality in the European Union (EU). As renewable electricity production sites in the EU itself might be scarce and relatively expensive, importing e-fuels from the Middle East and North Africa (MENA) could be a complementary and cost-efficient option. Using the energy system model Enertile, supply curves for hydrogen and synthetic methane in the MENA region are determined for the years 2030 and 2050 to evaluate this import option techno-economically. The model optimizes investments in renewable electricity production, e-fuel production chains, and local electricity transport infrastructures. Analyses of renewable electricity generation potentials show that the MENA region in particular has large low-cost solar power potentials. Optimization results in Enertile show for a weighted average cost of capital of 7% that substantial hydrogen production starts above 100 €/MWhH2 in 2030 and above 70 €/MWhH2 in 2050. Substantial synthetic methane production in the model results starts above 170 €/MWhCH4 in 2030 and above 120 €/MWhCH4 in 2050. The most important cost component in both fuel production routes is electricity. Taking into account transport cost surcharges, in Europe synthetic methane from MENA is available above 180 €/MWhCH4 in 2030 and above 130 €/MWhCH4 in 2050. Hydrogen exports from MENA to Europe cost above 120 €/MWhH2 in 2030 and above 90 €/MWhH2 in 2050. If exported to Europe, both e-fuels are more expensive to produce and transport in liquefied form than in gaseous form. A comparison of European hydrogen supply curves with hydrogen imports from MENA for 2050 reveals that imports can only be economically efficient if the two following conditions are met: Firstly, similar interest rates prevail in the EU and MENA; secondly, hydrogen transport costs converge at the cheap end of the range in the current literature. Apart from this, a shortage of land for renewable electricity generation in Europe may lead to hydrogen imports from MENA. This analysis is intended to assist in guiding European industrial and energy policy, planning import infrastructure needs, and providing an analytical framework for project developers in the MENA region