Showing papers on "Gouraud shading published in 2003"

Synthetic vision systems: human performance assessment of the influence of terrain density and texture

Abstract: The implementation of Synthetic Vision Systems (SVS) has posed a number of design questions. One of these questions is centered on the minimum required resolution of the Digital Elevation Model (DEM) database. Although a very detailed database may be desirable from a product appeal point of view or for improved representation of the elevation information., there simply may not be enough processing power available to render the high number of polygons with a texture at a high frame rate. Also, there may be a marginal rate of return of increasing DEM resolution when it comes to pilot performance, workload and situational awareness (SA). Another important issue is the choice of texture used on the synthetic terrain images. In the past, researchers and designers have debated about the relative merits of different textures (e.g., photo-realistic, elevation coloring, checkerboard). A third issue concerns the shading model, which may influence performance or SA through the potential for depth perception cues. The Operator Performance Laboratory (OPL) at the University of Iowa conducted a series of three experiments to assess human performance as a function of DEM resolution, terrain texture and shading methods. The DEM resolutions that were studied ranged from 3 arc seconds (best resolution) to 30 arc seconds (worst resolution). Textures included wire-frame (green on black), checkerboard, elevation coloring, contour lines, photo-realistic, and a non-textured plain brown color. Shading models included no shading, Gouraud shading, and flat shading. Part I involved an image identification task, in which the ability of non-pilot participants to recognize terrain features for static (Experiment 1) and dynamic terrain images (Experiment 2) was measured. Part II (Experiment 3) measured pilot performance by cross track error when na

Hardware-accelerated anti-aliased graphics

Abstract: In order to render a primitive, the primitive is subdivided into trapezoids and triangles. The subdivision occurs using scanline-aligned lines. These simple scanline-aligned regions are further subdivided so that the primitive is divided into simple scanline-boundaried trapezoids and other complex scan shapes. The simple scanline-boundaried trapezoids are rasterized. One rasterization method uses a texture map containing slope-based coverage information to edge areas. Gouraud shading may be used to provide the anti-aliasing effects on the scanline-boundaried trapezoids. The simple scanline-boundaried trapezoids may also be rasterized using a software rasterizer. Complex scans are rasterized using a software rasterizer. As data is already rasterized, it is thereby efficiently transferred to the GPU.

Shading computer-generated objects using generalized shading regions

Abstract: Computer-generated objects (201) are tessellated into generalized shading regions (203) having any number of vertices (120) The shading regions (201) are passed to a shader (102) via a generalized parametric scheme that accommodates shapes having different number of vertices (120) The shader (102) determines and assigns color values (107) to the exact area defined by each shading region (201), without requiring the use of approximations such as bounding boxes or ellipsoids The use of generalized shading regions (201) facilitates greater flexibility and accuracy in shading regions (201)

Shot Shading Method and Apparatus

Abstract: A method for shading objects in a first image and a second image includes receiving a geometric description of a first object, performing once for both the first image and the second image, a first set of shading operations for the first object, performing a second set of shading operations for the first object in the first image, performing a third set of shading operations for the first object in the second image, combining results of the first set of shading operations for the first object and results of the second set of shading operations for the first object to determine shading values of the first object in the first image, and combining results of the first set of shading operations for the first object and results of the third set of shading operations for the first object to determine shading values of the first object in the second image.

Hardware accelerated anti-aliased primitives using alpha gradients

Abstract: Systems and methods are provided for providing anti-aliasing by introducing a falloff area around a graphics object to be rendered. The falloff area is shaded, using Gouraud shading or texture mapping to reduce the aliasing effects of the graphics object. The outside edge of the falloff area is set to be fully transparent, and the inside edge to an opacity matching the outer edge of the graphics object being rendered. To counteract bloating effects, the graphics object is shrunk by half the width of the falloff area. While the width of the falloff area may vary, generally, the width of the falloff area stays constant. In one embodiment, this width corresponds to the edge or diagonal of the square area mapped to each pixel.

Fast specular highlights by modifying the Phong-Blinn model

Abstract: Shading is a technique that is used in computer graphics to make faceted objects appear smooth and more realistic. In the research presented in this thesis we have investigated how shading can be generated as efficiently as possible without sacrificing quality.In the classical approach to high quality shading proposed by Phong, the illumination equation is computed per pixel using an interpolated normal. The normals at the vertices are bi-linearly interpolated over the polygon to obtain a normal per pixel. Correct shading requires normalization of these normals, which is computationally demanding involving a square root. In our research we have shown how this normalization can be eliminated through the use of spherical interpolation and the Chebyshev recurrence formula, reducing the calculation to a few single arithmetic operations per pixel.Still a substantial setup operation is needed for each scanline. We have studied how also this can be made more efficient, with some limited progress so far. An alternative approach is to do the most of the setup on polygon level and incrementally compute the setup needed per scanline. In particular, we have studied quadratic shading approaches, i.e. fitting second degree surfaces to the polygons. The most successful approach has been through what we have called X-shading, where the setup is calculated by using an efficient approximation for the mid-edge normals. This setup is about four times faster than previously known methods.In the process of studying shading methods we have also made some contributions to improving bump-mapping and simulation of different kinds of light sources.The developed methods will be of interest in future generations of computer graphics software and hardware systems, ranging from high end systems to generate realistic movies and 3D games, to handheld devices such as mobile phones with graphics displays.

Voxel-based Surface Shading of Three-dimensional Medical Objects

Abstract: In many medical imaging modalities, such as CT , MRI or PET, a 3D anatomy is usually represented by a set of planar images. For its 3D visualization, a voxel model with a ray casting algorithm was introduced. Unlike the triangle method, this algorithm does not require a detection of the boundary of the 3D object beforehand, but derives the surface image directly from the object. The algorithm includes the capability of performing ray castings for different screen pixels concurrently. The concurrent capability facilitates hardware implementation to speed up the surface rendering. The function was given to rotate and to zoom the 3D object in object coordinates and show the result in screen coordinates. Some examples of the depth shading, Gouraud shading, the combination of the depth shading and Gouraud shading, 2D image map to 3D image were shown by using simple threshold segmentation.

Efficient handling of shading discontinuities for progressive meshes

Abstract: For visual perception of 3D models, shading plays one of the major roles. The shading quality of level-of-detail models is limited generally because existing LOD algorithms assume a conceptually smooth surface. A complex mesh, however, is likely to have conceptually smooth and angular parts. We introduce an extension to the progressive mesh LOD approach that efficiently handles triangle meshes with large numbers of shading discontinuities. For this, the algorithm distinguishes three principal shading situations for mesh vertices: completely continuous shading, completely discontinuous shading, and mixed continuous/discontinuous shading. Remarkably, the algorithm does not introduce any overhead for completely smooth surfaces. As one field of application, we briefly outline its application for LOD representations of 3D city models.

Method for producing shading effects

Abstract: An image processing method which can produce shading effects similar to those of ray tracing without cosine calculations comprises a first step of calculating a distance component which is distance between a screen and model surface; and a second step of adding a shading value obtained based on the distance component and a brightness value inpre-shading color data (color data before shading) to obtain a brightness value in post-shading color data (color data after shading) .