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Depth Buffer Method

The depth buffer method is an image-space approach that determines the closest visible surface at each pixel position by comparing the depth values of surfaces. It uses two buffers: a depth buffer to store the depth value of each pixel and a frame buffer to store the color value. For each polygon, it calculates the depth value at each projected pixel position and, if closer than the current depth buffer value, updates both buffers with the surface color and new depth value. This allows efficient hidden surface removal for polygons but requires large memory and processing time.

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Sinduja Baskaran
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157 views12 pages

Depth Buffer Method

The depth buffer method is an image-space approach that determines the closest visible surface at each pixel position by comparing the depth values of surfaces. It uses two buffers: a depth buffer to store the depth value of each pixel and a frame buffer to store the color value. For each polygon, it calculates the depth value at each projected pixel position and, if closer than the current depth buffer value, updates both buffers with the surface color and new depth value. This allows efficient hidden surface removal for polygons but requires large memory and processing time.

Uploaded by

Sinduja Baskaran
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Depth Buffer Method

Depth Buffer Method


Depth Buffer Method
• It is an image-space approach. The basic idea is to test the Z-depth of each
surface to determine the closest surface.

• In this method each surface is processed separately one pixel position at a


time across the surface.

• The depth values for a pixel are compared and the closest surface
determines the color to be displayed in the frame buffer.

• It is applied very efficiently on surfaces of polygon. Surfaces can be


processed in any order.
Depth Buffer Method
• To override the closer polygons from the far ones, two buffers named
1. frame buffer &
2. depth buffer, are used.

• Depth buffer is used to store depth values for position, as surfaces are
processed
• The frame buffer is used to store the intensity value of color value at
each position
Depth Buffer Method
Algorithm:
• Step-1 − Set the buffer values −
• Depthbuffer = 0
• Framebuffer = background color

• Step-2 − Process each polygon


• For each projected pixel position of a polygon, calculate depth z.
• If Z > depthbuffer
• Compute surface color,
• set depthbuffer = z,
• framebuffer = surfacecolor
Depth Buffer Method
Advantages:
• It is easy to implement.
• It reduces the speed problem if implemented in hardware.
• It processes one object at a time.

Disadvantages:
• It requires large memory.
• It is time consuming process.
A Buffer Method
A Buffer Method
• A buffer is used in transparent objects.
• Different surface colors can be correctly composed using it.
• Each position in the buffer can reference a linked list of surfaces.
• The key data structure in the A buffer is the accumulation buffer.

Each position in the A buffer has 2 fields :


1) Depth field
2) Surface data field or Intensity field

• A depth field stores a positive or negative real number.


• A surface data field can stores surface intensity information or a
pointer to a linked list of surfaces that contribute to that pixel
position.
A Buffer Method

if the value of depth is >= 0,

• the number stored at that position is the depth of single


surface overlapping the corresponding pixel area.

• The 2nd field, i.e, the intensity field then stores the RGB components
of the surface color at that point and the percent of pixel coverage.
A Buffer Method

• Multiple-surface contributions to the pixel intensity is


indicated by depth < 0.

• The 2nd field, i.e, the intensity field then stores a pointer to a
linked list of surface data.
A Buffer Method
A Buffer Method
• In A-buffer method, each pixel is made
up of a group of sub-pixels.

• The final color of a pixel is computed


by summing up all of its sub-pixels.

• Here, the depth and opacity are used to


determine the final color of the pixel.

• Due to this accumulation taking place


at sub-pixel level, A-buffer method
gets the name accumulation buffer.

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