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Point based graphics learning notes (三)

2007-10-27 17:41:18

The field of 3D acquisition has emerged as an important source of both challenges and applications for point-based techniques. The high detail and ease of acquisition of 3D models of real-world objects have driven their acceptance in computer graphics productions, but the size and density of these datasets have required the development of efficient representations and processing algorithms.

The relations between 3D scanners and points are:
1) Size: 3D scans can be large and detailed, with models in the range of 106 to 109 samples becoming commonplace.
2) Noise: All scans have noise, and depending on the particular scanner design this noise can be on the order of the sample spacing.
3) Sparseness: Some 3D acquisition techniques, especially passive methods, can only return reliable geometry at a few locations on the surface.

A basic 3D model acquisition pipeline may include the following stages:
1) 3D scanning
2) Registration
3) Merging
4) View planning
5) Po..

类别：计算机图形学 | 阅读全文(77) | 回复(0)

Point based graphics learning notes (二)

2007-10-24 18:53:07

A common set of challenges:
1) how to edit the scene by manipulating its samples
2) how to store and compress these samples
3) how to transform and shade them
4) how to render them with correct sampling, visibility, and filtering

Image-order algorithm vs. object-order algorithm
Visibility is tantamount to sorting. The gather strategy leads to an image-order algorithm. By contrast, the scatter strategy leads to an object-order algorithm.

Procedural modeling: the generation of scene geometry using a computer algorithm (rather than interactively or by sensing).

To render a procedurally defined object using favored image-order algorithms, one must be able to compute for a given pixel which part of the object (if any) lands there. If the procedure is expensive to invert in this sense, or even uninvertible, then an object-order algorithm rendering must be used.

The curious case of displacement mapping.

The notion of using p..

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Point-based graphics learning notes (-)

2007-10-22 12:26:02

Now point-based computer graphics is a vigorous research area. There are a lot of works have been devoted to the efficient representation, modeling, processing, and rendering of point-sampled geometry. Why?
1) Its simplicity
2) The 3D digital photography and 3D scanning systems use huge point samples.

The Pointshop3D open-source software
http://graphics.ethz.ch/pointshop3d/

Point-based graphics have a huge potential for future research and development and might influence the way we will do computer graphics in the future.

The workflow of point-based graphics:

Points: they generalize pixels and voxels toward irregular samples of geometry and appearance. They carry all attributes needed for processing and rendering. There is no distinction between vertex and fragment anymore.
Lucky or unlucky?
Lucky: design leaner graphics pipelines(simpler computation)
Unlucky: need fill hole and need denser sampling
In some sense, bandwidth h..

类别：计算机图形学 | 阅读全文(72) | 回复(1)