49 research outputs found
Synchronized-tracing of implicit surfaces
Implicit surfaces are known for their ability to represent smooth objects of
arbitrary topology thanks to hierarchical combinations of primitives using a
structure called a blobtree. We present a new tile-based rendering pipeline
well suited for modeling scenarios, i.e., no preprocessing is required when
primitive parameters are updated. When using approximate signed distance
fields, we rely on compact, smooth CSG operators - extended from standard
bounded operators - to compute a tight volume of interest for all primitives of
the blobtree. The pipeline relies on a low-resolution A-buffer storing the
primitives of interest of a given screen tile. The A-buffer is then used during
ray processing to synchronize threads within a subfrustum. This allows coherent
field evaluation within workgroups. We use a sparse bottom-up tree traversal to
prune the blobtree on-the-fly which allows us to decorrelate field evaluation
complexity from the full blobtree size. The ray processing itself is done using
the sphere-tracing algorithm. The pipeline scales well to surfaces consisting
of thousands of primitives
Interactive Rendering Framework for Distance Function Representations
Sphere tracing, introduced by Hart in [5], is an efficient method to find ray-
surface intersections, provided the surface is represented by a signed distance
function (SDF) or a lower estimate of it.
This paper presents an interactive rendering framework for visualising exact
and estimate SDF representations. We demonstrate the performance of
the system by visualising 3D fractals and its modularity by rendering algebraic
and meta surfaces. In addition, we discuss SDF estimation of algebraic
surfaces
Interactive ray tracing of arbitrary implicits with SIMD interval arithmetic
Journal ArticleWe present a practical and efficient algorithm for interactively ray tracing arbitrary implicit surfaces. We use interval arithmetic (IA) both for robust root computation and guaranteed detection of topological features. In conjunction with ray tracing, this allows for rendering literally any programmable implicit function simply from its definition. Our method requires neither special hardware, nor preprocessing or storage of any data structure. Efficiency is achieved through SIMD optimization of both the interval arithmetic computation and coherent ray traversal algorithm, delivering interactive results even for complex implicit functions
Transparent rendering and slicing of integral surfaces using per-primitive interval arithmetic
International audienceWe present a method for efficient incorporation of integral surfaces within existing robust processing methods such as interval arithmetic and segment-tracing. We based our approach on high-level knowledge of the field function of the primitives. We show application to slicing and transparent rendering of integral surfaces based on interval arithmetic
Isosurface modelling of soft objects in computer graphics.
There are many different modelling techniques used in computer graphics to describe a wide range of objects and phenomena. In this thesis, details of research into the isosurface modelling technique are presented. The
isosurface technique is used in conjunction with more traditional modelling techniques to describe the objects needed in the different scenes of an animation. The isosurface modelling technique allows the description
and animation of objects that would be extremely difficult, or impossible to describe using other methods. The objects suitable for description using isosurface modelling are soft objects. Soft objects merge elegantly with each
other, pull apart, bubble, ripple and exhibit a variety of other effects. The representation was studied in three phases of a computer animation project: modelling of the objects; animation of the objects; and the production of the images. The research clarifies and presents many
algorithms needed to implement the isosurface representation in an animation system. The creation of a hierarchical computer graphics animation system
implementing the isosurface representation is described. The scalar fields defining the isosurfaces are represented using a scalar field description language, created as part of this research, which is automatically generated from the hierarchical description of the scene. This language has many techniques for combining and building the scalar field from a variety of components. Surface attributes of the objects are specified within the graphics system. Techniques are described which allow the handling of
these attributes along with the scalar field calculation. Many animation techniques specific to the isosurface representation are presented. By the conclusion of the research, a graphics system was created which elegantly handles the isosurface representation in a wide variety of
animation situations. This thesis establishes that isosurface modelling of soft objects is a powerful and useful technique which has wide application in the computer graphics community
Tool path generation and 3D tolerance analysis for free-form surfaces
This dissertation focuses on developing algorithms
that generate tool paths for free-form surfaces based on accuracy of desired manufactured part. A manufacturing part is represented by mathematical curves and surfaces. Using the mathematical representation of the manufacturing part, we generate reliable and near optimal tool paths as well as cutter location (CL) data file for postprocessing. This algorithm includes two components. First is the forward-step function which determines maximum distance called forward- step between two cutter contact (CC) points with
given tolerance. This function is independent of the surface type and is applicable to all continuous parametric surfaces that are twice differentiable. The second component is the side-step function which determines maximum distance called side-step between two adjacent tool paths with a given scallop height. This algorithm reduces manufacturing and computing time as well as the CC points while keeping the given tolerance and scallop height in the tool paths. Several parts, for which the CC points are generated using the proposed algorithm, are machined using a three axes milling machine. As part of the validation process, the tool
paths generated during machining are analyzed to compare the machined part and the desired part