## Semi-Automatic Generation of Transfer Functions for Direct Volume Rendering (1998)

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Venue: | In IEEE Symposium on Volume Visualization |

Citations: | 249 - 7 self |

### BibTeX

@INPROCEEDINGS{Kindlmann98semi-automaticgeneration,

author = {Gordon Kindlmann and James W. Durkin},

title = {Semi-Automatic Generation of Transfer Functions for Direct Volume Rendering},

booktitle = {In IEEE Symposium on Volume Visualization},

year = {1998},

pages = {79--86}

}

### Years of Citing Articles

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### Abstract

Although direct volume rendering is a powerful tool for visualizing complex structures within volume data, the size and complexity of the parameter space controlling the rendering process makes generating an informative rendering challenging. In particular, the specification of the transfer function --- the mapping from data values to renderable optical properties --- is frequently a time-consuming and unintuitive task. Ideally, the data being visualized should itself suggest an appropriate transfer function that brings out the features of interest without obscuring them with elements of little importance. We demonstrate that this is possible for a large class of scalar volume data, namely that where the regions of interest are the boundaries between different materials. A transfer function which makes boundaries readily visible can be generated from the relationship between three quantities: the data value and its first and second directional derivatives along the gradient direction. ...

### Citations

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Citation Context ...but an exact location for the boundary can be defined with either the maximum in f 0 , or the zero-crossing in f 00 . Indeed, two edge detectors common in computer vision, Canny [4] and Marr-Hildreth =-=[14]-=-, use the f 0 and f 00 criteria, respectively, to find edges. PSfrag replacements x f(x) f 0 (x) f 00 (x) Figure 4: Measuring f , f 0 , and f 00 across boundary. 3.3 Relationship Between f , f 0 , and... |

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Citation Context ...of the National Institute for Physiological Sciences, Okazaki, Japan. 2 Related Work Two methods have been proposed for assisting the user in the exploration of possible transfer functions. He et al. =-=[7]-=- use genetic algorithms to breed a good transfer function for a given dataset. Judging from small thumbnail renderings, the user picks desirable transfer functions from an automatically generated popu... |

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28 |
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Citation Context ...subset of transfer functions. Once the opacity function has been applied to the volume, the surfaces of the opaque regions are then shaded according to a simple shading model, such as the Phong model =-=[Pho75]-=-. Although this thesis explores opacity functions only, its results would be helpful in creating more general types of transfer functions as well. In order to gain some intuition about the role opacit... |

27 |
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Citation Context ...or rendering at interactive rates on machines with 3-D texture memory [GK96]. Examples of existing techniques applied to a new domain are the extension of splatting [Wes90] to non-rectilinear volumes =-=[Mao96]-=-, and using ray casting for vector field visualization [Fru96]. Often, direct volume rendering is not the tool of choice for visualization of scalar fields, and isosurface rendering is used instead, a... |

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Citation Context ...endering, central differences are often used to calculated the gradient magnitude as part of the shading calculations [LCN98]. There are more sophisticated derivative measurement techniques available =-=[MMMY96]-=-, but a thorough exploration of them is tangential to the goal of this thesis.s124 There is another simple and common mask for our second derivative measurement, [1 − 2 1], sometimes called the “secon... |

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Citation Context ...the usual problem of derivative measurement in volume rendering, where a primary concern is continuity of the derivative between sample points to allow for correct shading of interpolated data values =-=[2, 16]-=-. The general algorithm for creating the histogram is straightforward: 1. Initialize the histogram volume to all zeroes. 2. Make one pass through the volume looking for the highest values of f 0 and f... |

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19 |
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Citation Context ...ost transfer functions used in volume rendering are still set according to the methods presented by these two authors. Examples of recent work employing Levoy-style transfer functions is described in =-=[Mur95]-=- and [YESK95]. An example of transfer functions based on data value alone is described in [PMea96]. Direct volume rendering research today tends to focus either on making the rendering algorithms fast... |

15 |
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Citation Context ... memory [GK96]. Examples of existing techniques applied to a new domain are the extension of splatting [Wes90] to non-rectilinear volumes [Mao96], and using ray casting for vector field visualization =-=[Fru96]-=-. Often, direct volume rendering is not the tool of choice for visualization of scalar fields, and isosurface rendering is used instead, as in geology [PBL96] or computational medicine [SJM95]. The ge... |

15 | Volume thinning for automatic isosurface propagation - Itoh, Yamaguchi, et al. - 1996 |

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Citation Context ...ally useful when noise or measurement artifacts upset the correlation between data value and material type. As a quick illustration of this, consider a dataset generated from limited angle tomography =-=[6]-=-, where there are often streaks and blurriness in the data caused by the unavailability of projections at some range of angles. This type of data is studied in the Collaboratory for Microscopic Digita... |

9 |
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Citation Context ...here are often streaks and blurriness in the data caused by the unavailability of projections at some range of angles. This type of data is studied in the Collaboratory for Microscopic Digital Anatomy=-=[19]-=-, an ongoing project aimed at providing remote, networked access to sophisticated microscopy resources. Fig. 1 shows two renderings of a mammalian neuron dataset, using the same viewing angle, shading... |

8 |
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Citation Context ...ization [Fru96]. Often, direct volume rendering is not the tool of choice for visualization of scalar fields, and isosurface rendering is used instead, as in geology [PBL96] or computational medicine =-=[SJM95]-=-. The generation of polygonal isosurfaces is still an area of active research [IYK96, SHLJ96]. To date there has been little research into the generation of transfer functions for direct volume render... |

4 |
Vector Calculus, chapter 2.6
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Citation Context .... The most significant implementation issue is the method of measuring the first and second directional derivatives. The first derivative is actually just the gradient magnitude. From vector calculus =-=[15]-=- we have: Dvf = rf \Delta v; (1) thus Dd rf f = rf \Delta c rf = rf \Delta rf krfk = krfk: (2) Unfortunately there is no similarly compact formula for D 2 d rf f , the second directional derivative al... |

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Citation Context ... functions used in volume rendering are still set according to the methods presented by these two authors. Examples of recent work employing Levoy-style transfer functions is described in [Mur95] and =-=[YESK95]-=-. An example of transfer functions based on data value alone is described in [PMea96]. Direct volume rendering research today tends to focus either on making the rendering algorithms faster, or extend... |

3 |
Introduction to Volume Rendering, chapter 4
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Citation Context ... dataset visible by assigning renderable optical properties to the numerical values which comprise the dataset. The most general transfer functions are those that assign opacity, color, and emittance =-=[12]-=-. Useful renderings can often be obtained, however, from transfer functions which assign just opacity, with the color and brightness derived from simulated lights which illuminate the volume according... |

2 |
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Citation Context ...ccessfully capturing information about the materials and their boundaries. It should be noted that a related technique has been used in computer vision for feature identification. Panda and Rosenfeld =-=[18]-=- use two-dimensional scatterplots of data value and gradient magnitude to perform image thresholding for night vision applications. They, however, do not assume a boundary model, instead limiting thei... |

2 | Towards Accurate and Efficient Volume Rendering
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Citation Context ...ne could simply use a classification function for the opacity function. Indeed, some authors used these terms synonymously[Lev88]. However, the speed of many rendering algorithms (such as ray tracing =-=[Nov94]-=- or the run-length encoding used by Lacroute [LL94]) varies with the number of voxels which contain opacity. In this situation it may be better for the opacity function to keep interiors13 voxels tran... |

1 |
et al. Implementing a Collaboratory for
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Citation Context ...ion to the slice, and an image rendered using the shown opacity function. vs4 Collaboratory for Microscopic Digital Anatomy (CMDA), in which the Program of Computer Graphics is a research participant =-=[EGLea96]-=-. The neuron data was tomographically generated from a sequence of transmission electron microscopy (EM) images 2 . Note that in each of these cases, the primary purpose of the opacity functions is to... |

1 |
Clinically Oriented Anatomy, page 882
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1 |
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Citation Context ...by these two authors. Examples of recent work employing Levoy-style transfer functions is described in [Mur95] and [YESK95]. An example of transfer functions based on data value alone is described in =-=[PMea96]-=-. Direct volume rendering research today tends to focus either on making the rendering algorithms faster, or extending existing rendering methods to work with a wider variety of data sets. Exciting de... |