Stereological techniques for synthesizing solid textures from images of aggregate materials

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2005.Includes bibliographical references (leaves 121-130).When creating photorealistic digital scenes, textures are commonly used to depict complex variation in surface appearance. For materials that have spatial variation in three dimensions, such as wood or marble, solid textures offer a natural representation. Unlike 2D textures, which can be easily captured with a photograph, it can be difficult to obtain a 3D material volume. This thesis addresses the challenge of extrapolating tileable 3D solid textures from images of aggregate materials, such as concrete, asphalt, terrazzo or granite. The approach introduced here is inspired by and builds on prior work in stereology--the study of 3D properties of a material based on 2D observations. Unlike ad hoc methods for texture synthesis, this approach has rigorous mathematical foundations that allow for reliable, accurate material synthesis with well-defined assumptions. The algorithm is also driven by psychophysical constraints to insure that slices through the synthesized volume have a perceptually similar appearance to the input image. The texture synthesis algorithm uses a variety of techniques to independently solve for the shape, distribution, and color of the embedded particles, as well as the residual noise. To approximate particle shape, I consider four methods-including two algorithms of my own contribution. I compare these methods under a variety of input conditions using automated, perceptually-motivated metrics as well as a carefully controlled psychophysical experiment. In addition to assessing the relative performance of the four algorithms, I also evaluate the reliability of the automated metrics in predicting the results of the user study. To solve for the particle distribution, I apply traditional stereological methods.(cont.) I first illustrate this approach for aggregate materials of spherical particles and then extend the technique to apply to particles of arbitrary shapes. The particle shape and distribution are used in conjunction to create an explicit 3D material volume using simulated annealing. Particle colors are assigned using a stochastic method, and high-frequency noise is replicated with the assistance of existing algorithms. The data representation is suitable for high-fidelity rendering and physical simulation. I demonstrate the effectiveness of the approach with side-by-side comparisons of real materials and their synthetic counterparts derived from the application of these techniques.by Robert Carl Jagnow.Ph.D

Continuous mush disaggregation during the long-lasting Laki fissure eruption, Iceland

Plagioclase textures were investigated in the products of the voluminous AD 1783–1784 Laki eruption from the Eastern Volcanic Zone (EVZ) of Iceland to establish whether mush disaggregation occurred solely at the onset of the eight-month eruption or throughout its whole duration. Phase proportions and plagioclase size distributions were determined using standard optical and manual techniques as well as automated approaches based on Quantitative Evaluation of Minerals by SCANing electron microscopy (QEMSCAN). Based on optical microscopy and the explicit combination of textural and compositional information in QEMSCAN images, plagioclase crystals were divided into two populations: small ( 4) microcrysts with low-anorthite (0.5 mm long), low-aspect ratio(length/width = 2–3) macrocrysts with high-anorthite (An₈₄–An₉₂) cores. Small microcrysts grew from their carrier liquid during the final phase of pre-eruptive crystallization while large macrocrysts, which are out of geochemical equilibrium with their carrier liquids, were entrained from crystal mushes. Changes in phase proportions and plagioclase size distributions between eruptive episodes demonstrate that macrocryst entrainment efficiency varied substantially during the eruption; material erupted in later episodes contain proportionally more mush-derived material. Using stereologically corrected plagioclase size distributions, we estimate that the pre-eruptive residence times of microcrysts in the Laki carrier liquid were probably of the order of 2–20 days. Because microcryst crystallization was concurrent with macrocryst rim growth, these day-to-week residence times also indicate that macrocryst entrainment occurred on much shorter timescales than the eruption’s eight- month duration. In line with constraints from independent geochronometers, macrocryst entrainment and mush disaggregation thus appears to have continued throughout the eruption. Magmas were assembled on an episode by episode basis, and the volume of eruptible magma in the plumbing system at any given time was probably closer to 1–2 km³ than the final erupted volume of 15.1 km³.This work was supported by NERC grants NER/S/A/2004/12727, NE/1528277/1 and NE/I012508/1. DAN acknowledges support from the Alexander von Humboldt Foundation

Stereology of random lines through idealised composite particles of variable texture

Imperial Users onl

Modelling of liberation in Ta- and W-rich minerals

With the general trend across all commodities towards the treatment of lower grade and medium grade ores, it is becoming increasingly important to develop the proper design for comprehensive mineralogical characterization and a complete procedure based on image analysis and grade distribution is proposed for the measurement of the liberation in the particles to reach the mineral liberation modeling. This thesis aims to develop an appropriate methodology to characterize complex low-grade Ta and medium grade W ores for the purpose of developing the most appropriate physical separation strategy. As result of this investigation a methodology is proposed for the mineralogical characterization and it consists of three different levels of characterization using different analytical techniques. Level 1, the simplest (which included chemical analysis, XRD, optical microscopy, SEM, and EMPA), was applied to Penouta and Mittersill ores and successfully characterized the mineralogy. Level 2, which included mineral characterization of the processed ores, and were XRD, SEM, and EMPA were needed for ores. The ores required the added sophistication of Level 3. In addition to the techniques of Level 1 and Level 2, Level 3 included the use of chemical analysis and automated SEM to estimate the mineralogical attributes of the ores. The insights from the mineralogical characterization were then used to inform the physical separation testing that was undertaken, for example, selective or bulk concentration. These results, together with the mineralogical characterization, indicated that selective gravity separation would be an appropriate processing route for this ore. The fine-grained Ta minerals required a P80 of about 100 µm. The final flow sheet produced a rougher concentrate that contained 103 ppm of Ta, at a recovery of 52%. In the Mittersill ore, the majority of the scheelite (>99%) was contained in hornblende, which itself represented approximately 33% of the ore. A bulk separation strategy using shaking table and the introduction of grinding to generate a P80 of 150 µm, was necessary to recover scheelite minerals to achieve a rougher concentrate of 2260 ppm W at a recovery of 87%. The mineralogical characterization of Mittersill, during which an association was found between scheelite and quartz, accounting for more than 17% of quartz in this ore with most of the remainder occurring as fine-grained quartz helped to guide the mineralogical characterization. This work describes a method for determining the downstream milling energy requirements for the mill products based on a Bond mill test performance. The grade distribution of particles at a given size fraction was calculated using a predictive liberation model. The recovery of particles in size/grade classes, image analysis using mineral liberation analysis (MLA), and function calculations were implemented for the modeling of the liberation. By describing the size, grade, and recovery data of particles in size/grade classes, a technique for the measurement of distribution functions was developed that relates beta distribution, a model for the function based on the incomplete beta function, and a solution to produce liberation modeling. It was shown that the predicted results agreed well with the observed results. The model was implemented in MATLAB, a simulation model, with King’s solution to the beta distribution function model that includes the liberation distributionComo indica la tendencia general en todos los productos hacia el tratamiento de minerales de leyes baja y media, se está volviendo cada vez más importante desarrollar diseños adecuados para una caracterización mineralógica integral. En este caso se propone un procedimiento completo basado en el análisis de imágenes y la distribución de leyess para la medición de liberación en las partículas, con el objetivo de alcanzar el modelo de liberación mineral. El objetivo de esta tesis es desarrollar una metodología adecuada para caracterizar los minerales complejos de Ta de baja y mediana ley con el fin de desarrollar estrategias de separación física más adecuada. Como resultado de esta investigación, se propone una metodología para la caracterización mineralógica y consta de tres niveles diferentes utilizando diferentes técnicas analíticas. El nivel 1, el más simple (que incluye análisis químicos, DRX, microscopía óptica, SEM y EMPA), se ha aplicado a los minerales de Penouta y Mittersill y se ha caracterizado correctamente la mineralogía. El nivel 2, que incluye la caracterización mineral del material ya procesado (entre ellos XRD, SEM y EMPA). Pa un mayor detalle de los minerales existentes, se requerían un nivel mas sofisticado de caracterización. Además de las técnicas del Nivel 1 y Nivel 2, el Nivel 3 incluía el uso de análisis químicos y SEM automatizado para estimar los atributos mineralógicos. Todos los datos obtenidos por la caracterización mineralógica fueron utilizados para supervisar las pruebas de separación física que se llevaron a cabo, por ejemplo, si se trata de una concentración selectiva o una concentración total. Estos resultados, junto con la caracterización mineralógica, indicaron que la separación por gravedad selectiva sería una ruta de procesamiento apropiada para este mineral. Los minerales Ta de grano fino requirieron un P80 de aproximadamente 100 µm. El diagrama de flujo final produjo un concentrado que contenía 103 ppm de Ta, a una recuperación del 52%. En el mineral de Mittersill, la mayoría de la scheelita (> 99%) estaba contenida en hornblende, que a su vez representaba aproximadamente el 33% del mineral. Fue necesaria una estrategia de separación a granel usando la mesa de sacudidas y la introducción de la molienda para generar un P80 de 150 µm, en la recuperación de minerales de scheelita para lograr un concentrado de 2260 ppm W con una recuperación del 87%. La caracterización mineralógica de Mittersill, durante la cual se encontró una asociación entre el scheelita y el cuarzo, representando más del 17% del cuarzo en este mineral, y la mayor parte del resto se produjo cuando el cuarzo de grano fino ayudó a guiar la caracterización mineralógica. Este trabajo describe un método para determinar los requisitos de energía de molienda aguas abajo para los productos de fábrica basados ¿¿en el rendimiento de la prueba de molturabilidad de Bond. La distribución en la leyes de las partículas en una fracción de tamaño dada se calculó usando un modelo de liberación predictivo. La recuperación de partículas por clases de tamaño / ley, fue desorrollado por medio de un MLA (Mineral liberatio analysis), desarrollando una técnica adaptando los datos del la miscroscopía con las funciones estadistica de ditribución beta. Los resultados coincidían con la modelización y se han obtenido los parametros de la distribución beta para los minerales de tantalio y tungsteno

Modelling of liberation in Ta- and W-rich minerals

With the general trend across all commodities towards the treatment of lower grade and medium grade ores, it is becoming increasingly important to develop the proper design for comprehensive mineralogical characterization and a complete procedure based on image analysis and grade distribution is proposed for the measurement of the liberation in the particles to reach the mineral liberation modeling. This thesis aims to develop an appropriate methodology to characterize complex low-grade Ta and medium grade W ores for the purpose of developing the most appropriate physical separation strategy. As result of this investigation a methodology is proposed for the mineralogical characterization and it consists of three different levels of characterization using different analytical techniques. Level 1, the simplest (which included chemical analysis, XRD, optical microscopy, SEM, and EMPA), was applied to Penouta and Mittersill ores and successfully characterized the mineralogy. Level 2, which included mineral characterization of the processed ores, and were XRD, SEM, and EMPA were needed for ores. The ores required the added sophistication of Level 3. In addition to the techniques of Level 1 and Level 2, Level 3 included the use of chemical analysis and automated SEM to estimate the mineralogical attributes of the ores. The insights from the mineralogical characterization were then used to inform the physical separation testing that was undertaken, for example, selective or bulk concentration. These results, together with the mineralogical characterization, indicated that selective gravity separation would be an appropriate processing route for this ore. The fine-grained Ta minerals required a P80 of about 100 µm. The final flow sheet produced a rougher concentrate that contained 103 ppm of Ta, at a recovery of 52%. In the Mittersill ore, the majority of the scheelite (>99%) was contained in hornblende, which itself represented approximately 33% of the ore. A bulk separation strategy using shaking table and the introduction of grinding to generate a P80 of 150 µm, was necessary to recover scheelite minerals to achieve a rougher concentrate of 2260 ppm W at a recovery of 87%. The mineralogical characterization of Mittersill, during which an association was found between scheelite and quartz, accounting for more than 17% of quartz in this ore with most of the remainder occurring as fine-grained quartz helped to guide the mineralogical characterization. This work describes a method for determining the downstream milling energy requirements for the mill products based on a Bond mill test performance. The grade distribution of particles at a given size fraction was calculated using a predictive liberation model. The recovery of particles in size/grade classes, image analysis using mineral liberation analysis (MLA), and function calculations were implemented for the modeling of the liberation. By describing the size, grade, and recovery data of particles in size/grade classes, a technique for the measurement of distribution functions was developed that relates beta distribution, a model for the function based on the incomplete beta function, and a solution to produce liberation modeling. It was shown that the predicted results agreed well with the observed results. The model was implemented in MATLAB, a simulation model, with King’s solution to the beta distribution function model that includes the liberation distributionComo indica la tendencia general en todos los productos hacia el tratamiento de minerales de leyes baja y media, se está volviendo cada vez más importante desarrollar diseños adecuados para una caracterización mineralógica integral. En este caso se propone un procedimiento completo basado en el análisis de imágenes y la distribución de leyess para la medición de liberación en las partículas, con el objetivo de alcanzar el modelo de liberación mineral. El objetivo de esta tesis es desarrollar una metodología adecuada para caracterizar los minerales complejos de Ta de baja y mediana ley con el fin de desarrollar estrategias de separación física más adecuada. Como resultado de esta investigación, se propone una metodología para la caracterización mineralógica y consta de tres niveles diferentes utilizando diferentes técnicas analíticas. El nivel 1, el más simple (que incluye análisis químicos, DRX, microscopía óptica, SEM y EMPA), se ha aplicado a los minerales de Penouta y Mittersill y se ha caracterizado correctamente la mineralogía. El nivel 2, que incluye la caracterización mineral del material ya procesado (entre ellos XRD, SEM y EMPA). Pa un mayor detalle de los minerales existentes, se requerían un nivel mas sofisticado de caracterización. Además de las técnicas del Nivel 1 y Nivel 2, el Nivel 3 incluía el uso de análisis químicos y SEM automatizado para estimar los atributos mineralógicos. Todos los datos obtenidos por la caracterización mineralógica fueron utilizados para supervisar las pruebas de separación física que se llevaron a cabo, por ejemplo, si se trata de una concentración selectiva o una concentración total. Estos resultados, junto con la caracterización mineralógica, indicaron que la separación por gravedad selectiva sería una ruta de procesamiento apropiada para este mineral. Los minerales Ta de grano fino requirieron un P80 de aproximadamente 100 µm. El diagrama de flujo final produjo un concentrado que contenía 103 ppm de Ta, a una recuperación del 52%. En el mineral de Mittersill, la mayoría de la scheelita (> 99%) estaba contenida en hornblende, que a su vez representaba aproximadamente el 33% del mineral. Fue necesaria una estrategia de separación a granel usando la mesa de sacudidas y la introducción de la molienda para generar un P80 de 150 µm, en la recuperación de minerales de scheelita para lograr un concentrado de 2260 ppm W con una recuperación del 87%. La caracterización mineralógica de Mittersill, durante la cual se encontró una asociación entre el scheelita y el cuarzo, representando más del 17% del cuarzo en este mineral, y la mayor parte del resto se produjo cuando el cuarzo de grano fino ayudó a guiar la caracterización mineralógica. Este trabajo describe un método para determinar los requisitos de energía de molienda aguas abajo para los productos de fábrica basados ¿¿en el rendimiento de la prueba de molturabilidad de Bond. La distribución en la leyes de las partículas en una fracción de tamaño dada se calculó usando un modelo de liberación predictivo. La recuperación de partículas por clases de tamaño / ley, fue desorrollado por medio de un MLA (Mineral liberatio analysis), desarrollando una técnica adaptando los datos del la miscroscopía con las funciones estadistica de ditribución beta. Los resultados coincidían con la modelización y se han obtenido los parametros de la distribución beta para los minerales de tantalio y tungsteno.Postprint (published version

High quality solid texture synthesis using position and index histogram matching

International audienceThe synthesis quality is one of the most important aspects in solid texture synthesis algorithms. In recent years several methods are proposed to generate high quality solid textures. However, these existing methods often suffer from the synthesis artifacts such as blurring, missing texture structures, introducing aberrant voxel colors, and so on. In this paper, we introduce a novel algorithm for synthesizing high quality solid textures from 2D exemplars. We first analyze the relevant factors for further improvements of the synthesis quality, and then adopt an optimization framework with the k-coherence search and the discrete solver for solid texture synthesis. The texture optimization approach is integrated with two new kinds of histogram matching methods, position and index histogram matching, which effectively cause the global statistics of the synthesized solid textures to match those of the exemplars. Experimental results show that our algorithm outperforms or at least is comparable to the previous solid texture synthesis algorithms in terms of the synthesis quality