• ETRI Journal
• /
• v.42 no.4
• /
• pp.608-618
• /
• 2020

We present a novel GPU-based ray-casting algorithm for volume rendering of unstructured grid data. Our volume rendering system uses a ray-casting method that guarantees accurate rendering results. We also employ the per-pixel intersection list concept in the Bunyk algorithm to guarantee an accurate result for non-convex meshes. For efficient memory access for the lists on the GPU, we represent the intersection lists for all faces as an array with our novel construction algorithm. With the intersection lists, we perform ray-casting on a GPU, and a GPU thread handles each ray. To increase ray-coherency in a thread block and improve memory access efficiency, we extend a prior image-tile-based work distribution method to fit modern GPU architectures. We also show that a prior approach using a per-thread local buffer to reduce redundant computation is not appropriate for modern GPU architectures. Instead, we take an on-demand calculation strategy that achieves better performance even though it allows duplicate computations. We applied our method to three unstructured grid datasets with different characteristics. With a GPU, our method achieved up to 36.5 times higher performance for the ray-casting process and 19.7 times higher performance for the whole volume rendering process compared with the Bunyk algorithm using a CPU core. Also, our approach showed up to 8.2 times higher performance than a GPU-based cell projection method while generating more accurate rendering results. These results demonstrate the efficiency and accuracy of our method.

• Journal of Korea Game Society
• /
• v.12 no.2
• /
• pp.53-62
• /
• 2012

Visualizing a volume dataset with ray-casting which of visualization methods provides high quality image. However it spends too much time for rendering because the size of volume data are huge. Recently, various researches have been proposed to accelerate GPU-based volume rendering to solve these problems. In this paper, we propose an efficient GPU-based empty space skipping to accelerate volume ray-casting using octree traversal. This method creates min-max octree and searches empty space using vertex splitting. It minimizes the bounding polyhedron by eliminating empty space found in the octree traveral step. The rendering results of our method are identical to those of previous GPU-based volume ray-casting, with the advantage of faster run-time because of using minimized bounding polyhedron.

• Journal of the Korea Computer Graphics Society
• /
• v.21 no.3
• /
• pp.17-26
• /
• 2015

In this paper, we explain a volume rendering system for client-server environment. A single GPU-equipped PC works as a server which is based on the ideas that only a few concurrent users use a volume rendering system in a small hospital. As the clients, we used Android mobile devices such as smart phones. User events are transformed to rendering requests by the client application. When the server receives a rendering request, it renders the volume using the GPU. The rendered image is compressed to JPEG or PNG format so that we can save network bandwidth and reduce transfer time. In addition, we perform an event pruning method while a user is dragging the touch to enhance latency. The server compensates the pruning by interpolating the touch positions. As the result, real-time volume rendering is possible for 5 concurrent users on single GPU-equipped commodity hardware.

• Journal of Korea Multimedia Society
• /
• v.10 no.3
• /
• pp.316-324
• /
• 2007

Maximum Intensity Projection (MIP) identifies patients' anatomical structures from MR or CT data sets. Recently, it becomes possible to generate MIP images with interactive speed by exploiting Graphics Processing Unit (GPU) even in large volume data sets. Generally, volume boundary plane is obliquely crossed with view-aligned texture plane in hardware-texture based volume rendering. Since the ray sampling distance is not increased at volume boundary in volume rendering, the aliasing problem occurs due to data loss. In this paper, we propose an efficient method to overcome this problem by Re-rendering volume boundary planes. Our method improves image quality to make dense distances between samples near volume boundary which is a high frequency area. Since it is only 6 clipping planes are additionally needed for Re-rendering, high quality rendering can be performed without sacrificing computational efficiency. Furthermore, our method couldbe applied to Minimum Intensity Projection (MinIP) volume rendering.

• Journal of KIISE:Computing Practices and Letters
• /
• v.16 no.12
• /
• pp.1165-1176
• /
• 2010

In order to realistically visualize such participating media as cloud, smoke, and gas, the light transport process must be physically simulated inside the media. While it is known that this process is well described physically through the volume rendering equation, it usually takes a great deal of computation time for obtaining high-precision solutions. Recently, GPU-based, fast rendering methods have been proposed for the realistic simulation of participating media, however, there still remain several problems to be resolved. In this article, we describe our rendering techniques applied to enhance the performances and features of our GPU-assisted participating media renderer, and analyze how such efforts have actually improved the renderer. The presented techniques will be effectively used in volume renderers for creating various digital contents in the special effects industries.

• Journal of Korea Multimedia Society
• /
• v.14 no.10
• /
• pp.1229-1237
• /
• 2011

The volume ray-casting method is one of the direct volume rendering methods that produces high-quality images as well as manipulates semi-transparent object. Although the volume ray-casting method produces high-quality image by sampling in the region of interest, its rendering speed is slow since the color acquisition process is complicated for repetitive memory reference and accumulation of sample values. Recently, the GPU-based acceleration techniques are introduced. However, they require pre-processing or additional memory. In this paper, we propose efficient point-primitive based method to overcome complicated computation of GPU ray-casting. It presents semi-transparent objects, however it does not require preprocessing and additional memory. Our method is fast since it generates point-primitives from volume dataset during sampling process and it projects the primitives onto the image plane. Also, our method can easily cope with OTF change because we can add or delete point-primitive in real-time.

• 한국HCI학회:학술대회논문집
• /
• 2007.02a
• /
• pp.1025-1030
• /
• 2007

여러 학계와 산업계로부터 인체영상과 같은 정적인 볼륨 데이터뿐만 아니라, 유체 흐름과 같은 동적으로 움직이는 Time-Variant 볼륨 데이터에 대한 실시간 렌더링의 요구가 계속되고 있다. 일반적으로 Time-Variant 데이터는 그 크기가 정적 볼륨 데이터의 수배에서 수백 배에 이르러, 이를 실시간으로 가시화하는 데에 많은 어려움이 있어왔다. 한편, PC 그래픽스 하드웨어의 급격한 발전에 따라 슈퍼컴퓨터나 다수의 컴퓨터들을 이용한 병렬/분산 렌더링으로나 가능했던 Time-Variant 볼륨 데이터의 실시간 볼륨 렌더링을 한대의 일반 PC에서 수행하려는 시도가 계속되고 있다. GPU의 꼭지점 및 프래그먼트 쉐이더(vertex & fragment shader)는 수치 계산에 최적화된 벡터 연산과 사용자 프로그래밍 기능으로 빠른 볼륨 렌더링을 일반 PC에서도 가능하게 했다. 본 논문에서는 GPU를 이용해서 Time-Variant 볼륨 데이터를 빠르게 가시화하고, 이렇게 개발한 GPU 볼륨 렌더링 프로그램을 사용자가 사용하기 편리하도록 사용자 친화적인 유저 인터페이스를 설계하고 구현하였다. 특히, 시간에 따라 동적으로 변화해야 하는 전이함수를 최대한 편리하게 생성할 수 있도록 전이함수 에디터에 중점을 두었다.

• Journal of Korea Game Society
• /
• v.9 no.6
• /
• pp.191-196
• /
• 2009

Volume rendering is a method which extracts meaningful information from volume data and visualizes those information. In general, since the size of volume data gets larger, it is very important to devise acceleration methods for interactive rendering speed. Min-max octree is data structure for high-speed volume rendering, however, its creation time becomes long as the data size increases. In this paper, we propose acceleration method of min-max octree generation using CUDA. Firstly, we convert one-dimensional array from volume data using space filling curve. Then we make min-max octree structures from the sequential array and apply them to acceleration of volume ray casting.

• Journal of the Korea Computer Graphics Society
• /
• v.23 no.3
• /
• pp.47-54
• /
• 2017

In this paper, we propose an improved curvature-based GPU (Graphics Processing Unit) isosurface ray-casting technique. Our method adopts the fast evaluation method proposed by Sigg et al. [1] to find the isosurface, but replaces the computation of the gradient and Hessian with the de Boor algorithm. In this way, we can reduce the number of additional texture fetches from 84 to 27 thus improving the performance by up to ${\approx}30%$, depending on the platforms.

• The Journal of Korean Institute of Next Generation Computing
• /
• v.15 no.5
• /
• pp.75-83
• /
• 2019

Direct volume rendering is a widely used method for visualizing three-dimensional volume data such as medical images. This paper proposes a method for applying depth-of-field effects to volume ray-casting to enable more realistic depth-of-filed rendering in direct volume rendering. The proposed method exploits a camera model based on the human perceptual model and can obtain realistic images with a limited number of rays using jittered lens sampling. It also enables interactive exploration of volume data by on-the-fly calculating depth-of-field in the GPU pipeline without preprocessing. In the experiment with various data including medical images, we demonstrated that depth-of-field images with better depth perception were generated 2.6 to 4 times faster than the conventional method.