Keep in mind that the purpose of scientific visualization is to visualize relationships in the data, not show every value with precision. It isn't necessary to know the exact value of a data point by looking at an image of it. It is important to be able to see how that data point relates to others. Annotation can quickly reach the point of clutter and confusion. If the application user requests additional information about the data, the application can provide interactive manipulation and picking techniques to alter the mapping and make queries about the data in the image.
A few rendering techniques follow. Many more are available.