Visible surface detection | Computer graphics
Hello everyone, So today we are going to discuss one of the main topic in computer graphics i.e. Visible surface detection or some people also like to call this as hidden-surface removal. It is one of the many less understood topic. So let’s dive right into the topic.
Object-space methodThis is also called
continuous domain. In this method we compare the parts of the objects in
3-Dto each other and label some parts as visible. Those parts that are labelled as visible are going to make it into the final list while the others are not going to be computed by us saving us a lot of computation time. (we use bounding boxes)
Image-space methodThis is a discrete type of method where we check on each and every pixel whether the particular point is going to be in the final display or not. This method works on the 2-D display i.e. we are going to work on the image not on the object. In this type of method number of pixels on the screen is a strong limitation. Both are good methods but Image-space method is little slower as we go pixel by pixel on the other hand
object-spacemethod is not good in terms of quality.
Coherence propertiesCoherence properties helps us to reduce the computations time even more. These are some features of the computer graphics that are standardized by some great people. As we know that there are the only one difference between 2-D and 3-D that is depth. In 3-D, we also have depth along with width and height. Some coherence properties are:
- We are not going to compare two surfaces if they are perfectly separate. (Object Coherence)
- When we are going to plot the next pixel we will not compute the depth again and again rather we will use a simple value that we keep on incrementing to earlier depth level. This will also save us a lot of computation time.(Face Coherence)
- When an object from behind of a surface becomes visible then we have to show it on the screen. (Edge coherence)
- When an object penetrates inside another object then a line is created that must be drawn on the screen. (Implied edge coherence)
- scan line coherence
- Area coherence
- Depth coherence
- Frame coherence
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