Image rendering apparatus and method

Patent metadata

Field	Value
Publication number	US-2016005218-A1
Application number	US-201414321493-A
Country	US
Kind code	A1
Filing date	Jul 1, 2014
Priority date	Jul 1, 2014
Publication date	Jan 7, 2016
Grant date	—

Abstract

An image rendering apparatus comprises an image data unit for obtaining volumetric image data representative of a three-dimensional region, a rendering unit configured to perform a rendering process on the volumetric image data that includes a sampling process that comprises, for each of a plurality of sampling paths, determining a respective color or grayscale value for a corresponding pixel based on a plurality of sampled points along the sampling path. For each sampling path, the sampling process performed by the rendering unit comprises for each of at least some of the sampled points, calculating a significance factor for the sampled point based on accumulated opacity along the sampling path for the sampled point, selecting for the sampled point one of a plurality of rendering calculation processes in dependence on the calculated significance factor, and performing the selected rendering calculation process to obtain at least one image data value for the sampled point. For each sampling path the rendering unit is configured to determine the color or grayscale value for the corresponding pixel based on the determined image data values for the plurality of sampled points for the path.

First claim

1 . An image rendering apparatus comprising:—
an image data unit for obtaining volumetric image data representative of a three-dimensional region;
a rendering unit configured to perform a rendering process on the volumetric image data that includes a sampling process that comprises, for each of a plurality of sampling paths, determining a respective color or grayscale value for a corresponding pixel based on a plurality of sampled points along the sampling path, wherein:—
for each sampling path, the sampling process performed by the rendering unit comprises for each of at least some of the sampled points:—calculating a significance factor for the sampled point based on at least accumulated opacity along the sampling path for the sampled point;
selecting for the sampled point one of a plurality of rendering calculation processes in dependence on the calculated significance factor; and
performing the selected rendering calculation process to obtain at least one image data value for the sampled point; and wherein

for each sampling path the rendering unit is configured to determine the color or grayscale value for the corresponding pixel based on the determined image data values for the plurality of sampled points for the path.

2 . An image rendering apparatus according to claim 1 , wherein for each of the sampling paths, and for said each of at least some of the sampled points, the calculating of the significance factor for the sampled point is based on accumulated opacity along the sampling path for the sampled point and opacity at the sampled point.

3 . An image rendering apparatus according to claim 1 , wherein the plurality of rendering calculation processes comprise a first rendering calculation process and a second rendering calculation process, wherein the second rendering calculation process is at least one of less complex, less time consuming, requires less processing power, or requires less memory than the first rendering calculation process.

4 . An image rendering apparatus according to claim 3 , wherein, for at least some of the sampling paths, the rendering unit is configured to select the first rendering calculation process for at least some of the sampled points and to select the second rendering calculation process for at least some other of the sampled points.

5 . An medical image rendering apparatus according to claim 3 , wherein the second rendering calculation process at least one of omits a calculation that is included in the first rendering calculation process or includes a simplified version of the calculation that is included in the first rendering calculation process.

6 . An image rendering apparatus according to claim 5 , wherein the calculation of the first rendering calculating process that is omitted or simplified in the second rendering calculation process comprises at least one of:—
a pre-integration calculation;
a lighting calculation;
a shading calculation;
a segmentation interpolation calculation;
an object-to-object blending calculation;
an irradiance calculation of a global illumination algorithm;
a shadow ray calculation;
an ambient occlusion calculation.

7 . An image rendering apparatus according to claim 5 , wherein the calculation of the first rendering calculating process that is omitted or simplified in the second rendering calculation process comprises a lighting calculation that includes calculation of a normal to a sampled point and determining light level based on the normal to the sampled point, and the second calculation process omits the calculation of the normal to the sampled point in determining light level.

8 . An image rendering apparatus according to claim 7 , wherein for the second calculation process the lighting calculation comprises determining light level for a sampled point based on at least one of ambient light level, a proportion of diffuse light, or a proportion of specular light.

9 . An image rendering apparatus according to claim 3 , wherein, for volumetric image data and a sampling path that comprises, for increasing distance from a source of the sampling path, sampled points corresponding to one of air or vacuum, followed by sampled points corresponding to anatomy of a patient or other subject, the selecting of one of the plurality of rendering calculation processes by the rendering unit comprises:—
selecting the second rendering calculation process for substantially all of the sampled points that correspond to one of air or vacuum;
selecting the first rendering calculation process for at least some of a sub-set of the sampled points corresponding to anatomy of the patient or other subject;
selecting the second rendering calculation process for substantially all of a further sub-set of the sampled points corresponding to anatomy of the patient or other subject,
wherein the further sub-set of sampled points are further from the source of the sampling path than the first sub-set of sampled points.

10 . An image rendering apparatus according to claim 1 , wherein the rendering unit is configured, for each of at least some of the sampled points, to compare the significance factor for the sampled point to a threshold and to perform the selecting of one of the plurality of the rendering calculation processes in dependence on the outcome of the comparison.

11 . An image rendering apparatus according to claim 1 , wherein the determined image data values for the plurality of sampled points comprise color or grayscale values and, for each sampling path, the color or grayscale value for the corresponding pixel is determined by the rendering unit based on the color or grayscale value for each sampled point of the sampling path, the opacity for each sampled point, and the accumulated opacity for each sampled point.

12 . An image rendering apparatus according to claim 1 , wherein the rendering process comprises a ray casting process, and the sampling paths comprise ray paths.

13 . An image rendering apparatus according to claim 1 , wherein the rendering process comprises a shear warp rendering process and the sampling paths pass through a sheared volume.

14 . An image rendering apparatus according to claim 1 , wherein for each sampling path the sampling process comprises, for each of the at least some of the sampled points, determining a respective opacity value for the sampled point and the a respective accumulated opacity value for the sampled point.

15 . An image rendering apparatus according to claim 14 , wherein determining an opacity value for the sampled point comprises determining an intensity value for the sampled point and at least one of: determining the opacity value from the intensity value in accordance with a transfer function, determining the opacity value from the intensity value in accordance with a classifier.

16 . An image rendering apparatus according to claim 14 , wherein determining an accumulated opacity value for a sampled point comprises determining the accumulated opacity value for the sampled point from the opacities of a plurality of previous sampled points on the sampling path.

17 . An image rendering apparatus according to claim 1 , wherein the volumetric image data comprises opacity values and at least one of color or grayscale values for positions in the three-dimensional region.

18 . An image rendering apparatus according to claim 2 , wherein the volumetric image data comprises intensity values, the rendering unit is configured to obtain converted volumetric image data by converting the intensity values to opacity values and at least one of co

Assignees

• Toshiba Kk
• Toshiba Medical Sys Corp

Inventors

• Day Timothy
• Myles Morvyn
• Reynolds Steven
• Hancox James

Classifications

• G06T2210/41

  Medical · CPC title

• G06T15/08 Primary

  Volume rendering · CPC title

• G06T15/06

  Ray-tracing · CPC title

• G06T2210/56

  Particle system, point based geometry or rendering · CPC title

• G06T15/503 Primary

  Blending, e.g. for anti-aliasing · CPC title