VISIBLE SURFACE DETECTION (DEPTH BUFFER METHOD (ADVANTAGE (1.It is easy to…
VISIBLE SURFACE DETECTION
DEPTH BUFFER METHOD
2.It is an image-space approach.
3.Depth buffer is used to store depth values for (x, y) position.
1.This method is developed by Cutmull.
4.The frame buffer is used to store the intensity value of color value at each position (x, y).
1.It is easy to implement.
2.It reduces the speed problem if implemented in hardware.
1.It requires large memory.
2.It is time consuming process.
DEPTH SORTING METHOD
3.This method for solving the hidden-surface problem is often referred to as the painter's algorithm.
2.The scan conversion of the polygon surfaces is performed in image space.
1.epth sorting method uses both image space and object-space operations. The depth-sorting method performs two basic functions −
Second, the surfaces are scan-converted in order, starting with the surface of greatest depth.
First, the surfaces are sorted in order of decreasing depth.
BINARY SPACE PARTITION
2.To build the BSP trees, one should start with polygons and label all the edges.
3.Dealing with only one edge at a time, extend each edge so that it splits the plane in two.
1.Binary space partitioning is used to calculate visibility.
2.We can simplify this test by considering the normal vector N to a polygon surface, which has Cartesian components (A, B, C).
1.A fast and simple object-space method for identifying the back faces of a polyhedron is based on the "inside-outside" tests.
3.In general, if V is a vector in the viewing direction from the eye (or "camera") position, then this polygon is a back face if
V.N > 0
1.Four types of relationship :
1.Surrounding surface − One that completely encloses the area.
2.Overlapping surface − One that is partly inside and partly outside the area.
3.Inside surface − One that is completely inside the area.
4.Outside surface − One that is completely outside the area.
2.The area-subdivision method takes advantage by locating those view areas that represent part of a single surface.
SCAN LINE METHOD
1.It is an image-space method to identify visible surface.
2.Types of SCAN LINE
THE EDGE TABLE
It contains coordinate endpoints of each line in the scene, the inverse slope of each line, and pointers into the polygon table to connect edges to surfaces.
THE POLYGON TABLE
It contains the plane coefficients, surface material properties, other surface data, and may be pointers to the edge table.
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