COCOMO-Model
December 25, 20243D
| Question 6 |
Which of the following statements is/are True regarding the solution to the visibility problem in 3D graphics ?
S1 : The Painter’s algorithm sorts polygons by depth and then paints (scan – converts) each Polygon onto the screen starting with the most nearest polygon.
S2 : Backface Culling refers to eliminating geometry with back facing normals.
Code :
| S1 only | |
| S2 only
| |
| Both S1 and S2 | |
| Neither S1 Nor S2 |
Question 6 Explanation:
Visibility problem in 3D graphics
1. Painter’s algorithm
– A depth sorting method
– Surfaces are sorted in the order of decreasing depth
– Surfaces are drawn in the sorted order, and overwrite the pixels in the frame buffer
– Subtle difference from depth buffer approach: entire face drawn
– Two problems:
• It can be nontrivial to sort the surfaces
• There can be no solution for the sorting order
2. Back Face Culling
– Back faces: faces of opaque object which are “pointing away” from viewer
– Back face culling – remove back faces (supported by OpenGL)
How to detect back faces
– If we find backface, do not draw, save rendering resources
– There must be other forward face(s) closer to eye
– F is face of object we want to test if backface
– P is a point on F
– Form view vector, V as (eye – P)
– N is normal to face F
3. View-Frustum Culling
– Remove objects that are outside the viewing frustum
– Done by 3D clipping algorithm (e.g. Liang-Barsky)
4. Ray Tracing
– Ray tracing is another example of image space method
– Ray tracing: Cast a ray from eye through each pixel to the world
5. Z(Depth buffer algorithm)
Reference: https://web.cs.wpi.edu/~emmanuel/courses/cs543/slides/lecture08_p2.pdf
1. Painter’s algorithm
– A depth sorting method
– Surfaces are sorted in the order of decreasing depth
– Surfaces are drawn in the sorted order, and overwrite the pixels in the frame buffer
– Subtle difference from depth buffer approach: entire face drawn
– Two problems:
• It can be nontrivial to sort the surfaces
• There can be no solution for the sorting order
2. Back Face Culling
– Back faces: faces of opaque object which are “pointing away” from viewer
– Back face culling – remove back faces (supported by OpenGL)
How to detect back faces
– If we find backface, do not draw, save rendering resources
– There must be other forward face(s) closer to eye
– F is face of object we want to test if backface
– P is a point on F
– Form view vector, V as (eye – P)
– N is normal to face F
3. View-Frustum Culling
– Remove objects that are outside the viewing frustum
– Done by 3D clipping algorithm (e.g. Liang-Barsky)
4. Ray Tracing
– Ray tracing is another example of image space method
– Ray tracing: Cast a ray from eye through each pixel to the world
5. Z(Depth buffer algorithm)
Reference: https://web.cs.wpi.edu/~emmanuel/courses/cs543/slides/lecture08_p2.pdf
Correct Answer: B
Question 6 Explanation:
Visibility problem in 3D graphics
1. Painter’s algorithm
– A depth sorting method
– Surfaces are sorted in the order of decreasing depth
– Surfaces are drawn in the sorted order, and overwrite the pixels in the frame buffer
– Subtle difference from depth buffer approach: entire face drawn
– Two problems:
• It can be nontrivial to sort the surfaces
• There can be no solution for the sorting order
2. Back Face Culling
– Back faces: faces of opaque object which are “pointing away” from viewer
– Back face culling – remove back faces (supported by OpenGL)
How to detect back faces
– If we find backface, do not draw, save rendering resources
– There must be other forward face(s) closer to eye
– F is face of object we want to test if backface
– P is a point on F
– Form view vector, V as (eye – P)
– N is normal to face F
3. View-Frustum Culling
– Remove objects that are outside the viewing frustum
– Done by 3D clipping algorithm (e.g. Liang-Barsky)
4. Ray Tracing
– Ray tracing is another example of image space method
– Ray tracing: Cast a ray from eye through each pixel to the world
5. Z(Depth buffer algorithm)
Reference: https://web.cs.wpi.edu/~emmanuel/courses/cs543/slides/lecture08_p2.pdf
1. Painter’s algorithm
– A depth sorting method
– Surfaces are sorted in the order of decreasing depth
– Surfaces are drawn in the sorted order, and overwrite the pixels in the frame buffer
– Subtle difference from depth buffer approach: entire face drawn
– Two problems:
• It can be nontrivial to sort the surfaces
• There can be no solution for the sorting order
2. Back Face Culling
– Back faces: faces of opaque object which are “pointing away” from viewer
– Back face culling – remove back faces (supported by OpenGL)
How to detect back faces
– If we find backface, do not draw, save rendering resources
– There must be other forward face(s) closer to eye
– F is face of object we want to test if backface
– P is a point on F
– Form view vector, V as (eye – P)
– N is normal to face F
3. View-Frustum Culling
– Remove objects that are outside the viewing frustum
– Done by 3D clipping algorithm (e.g. Liang-Barsky)
4. Ray Tracing
– Ray tracing is another example of image space method
– Ray tracing: Cast a ray from eye through each pixel to the world
5. Z(Depth buffer algorithm)
Reference: https://web.cs.wpi.edu/~emmanuel/courses/cs543/slides/lecture08_p2.pdf
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