Visualisation of 3D ultrasonic NDT data

摘要

Ray-tracing and surface rendering have been found to be extremely useful techniques for interactive assessment. Surface rendering can be used to understand 3D features in an image, and estimate their positions and sizes using the locations of excavation planes. However, it cannot render the entire 3D volume in one view. For this purpose, ray-casting is an excellent tool, with the addition of symbolic depth enhancing the information content of the image. The two techniques can be effectively used in tandem, with ray-casting providing a quick aggregate view of the volume, and surface rendering providing quantitative positional information on image features. The value of any rendered NDT data can be greatly increased if a representation of specimen geometry can be superimposed. Both back-to-front voxel rendering and isosurface creation were found to be too slow for interactive use with the large data sets that ultrasonic NDT produces. The PHIGS implementation has resulted in a system which is flexible, and yet simple for an NDT data interpreter to use. The system offers a high degree of user interaction, with customised features for assessment of suspected flaws, and has been integrated with other NDT data processing tools. The effective 3D visualisation techniques should provide significant benefits in NDT data interpretation.