Scan-line method, Computer Graphics

In contrast to depth-buffer method, here we identify one surface at one time, scan-line method deals along with multiple surfaces. Since it processes each scan-line at one time, all polygons intersected from that scan-line are examined to find out that surfaces are visible. The visibility test includes the comparison of depths of all overlapping surfaces, to find out that one i.e. closer to the view plane. It is declared like a visible surface and the intensity values at the positions beside the scan- line are entered in the refresh-buffer, if it is determined.

Assumptions:

a)      Plane of projection is Z=0 plane.

b)      Orthographic parallel projection.

c)      Direction of projection as: d = (0,0, -1)

d)      Objects made up of polygon faces.                     

 Scan-line algorithm resolves the hidden-surface issue, one scan-line at one time, generally processing scan lines starting the bottom to the top of the display.

 The scan-line algorithm is a one-dimensional version of the Z-Buffer. We need two arrays, intensity [x] and depth [x] to hold values for a particular scan-line.

 

                                          1519_Scan-line method.png

This time at Q1and Q2 both polygons are active that called sharing

Compare the z-values at Q1 for both the planes (P1 and P2). Let z1(1),z1(2) be the z-value at Q1 ,consequent to P1and P2 polygon correspondingly.

As the same z2(1), z2(2) be the z-value at Q2, consequent to P1and P2 polygon correspondingly.

Case1: z1(1)< z1(2)                         

             z2(1) < z2(2)  

In this case Q1, Q2 is filled along with the color of P2.

Case2: z1(2) < z1(1)

             z2(2) < z2(1)  

In this case Q1, Q2 is filled along with the color of P2.

Case3: Intersection is taking place.

In this condition we have to return to pixel by pixel and find out which plane is closer. After that choose the color of pixel

 

 

Posted Date: 3/22/2013 8:44:18 AM | Location : United States







Related Discussions:- Scan-line method, Assignment Help, Ask Question on Scan-line method, Get Answer, Expert's Help, Scan-line method Discussions

Write discussion on Scan-line method
Your posts are moderated
Related Questions
Question 1 Discuss the overview of multimedia networks Question 2 Discuss the types of synchronization in multimedia system >> Basic synchronization issues Content R

Distinguish between convex and concave polygons? If the line joining any two points in the polygon lies totally inside the polygon then, they are called as convex polygons. If

Question 1: (a) Explain what are Final Gathering and Global Illumination and state why you would use those features when you render in MAYA. (b) List clearly the steps in

Representational Animation - Computer Animation This method permits an object to change its shape throughout the animation. There are three sub-types to this. The initial is th

What Is Computer Graphics? The term Graphics mean is Graphical Tricks. All image or picture is actually a graph and when various mathematical tricks are utilized to manipulate

Spline curve - Modeling and Rendering Spline curve is created by using Control points that control the shape of the curve Spline curve is a composite curve formed along with s

What is cubic spline?  Cubic splines are a straight forward extension of the methods underlying parabolic spline. The total curve in this case is a sequence of arcs of cubic ra

Projections - Viewing Transformation Specified 3-D object in a space, Projection can be explained as a mapping of 3-D object into 2-D viewing screen. Now, 2-D screen is termed

Types of Light Resources - illumination Model Let us discuss about the types of light resources. The light sources can not merely be natural like light from Sun or Moon or Sta

Explain the working of Animators Animators want to create a human image that moves and interacts with its background in such a way that viewers can't tell if a specific scene i