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CS420 Midterm Review
Terms in this set (24)
Eye-Oriented. Otherwise known as ray-tracing
Goes from eye to light source
Light-Oriented. Very inefficient
(OpenGL style)Forward rendering. Scene is composed of geometric structures with the buiding block of a
triangle. Each triangle is projected, colored, and painted on the screen
Handled by GPU.
Where is OpenGl used?
Video games, simulations, VR, CAD,
Open GL Computer Graphics
1. Vertices - Primitives and Material Properities
2. Transformer - Transform, Rotate, Scale
3. Clipper - visibility
4. Projector - 2D to 3D
5. Rasterizer - Convert to pixels
6. Pixels - shown on screen
Immediate Mode Rendering. Application generates a stream of geo primitives.
System draws each one into FRAME BUFFER.
Entire scene is REDRAWN each time.
Different from offline rendering since it must be real time.
1. must be simple
2. must be convex
Triangles are most efficient
Flat vs Smooth Shading
Flat shading: normal vectors are the same at all vertices of the triangle.
Smooth Shading: shared vertices between multiple polygons compute normals based on the average of the two.
Flat vs Smooth shading Triangle Example from slides
flat shading produces a solid color triangle.
Smooth shading produces a gradient affect of color throughout the triangle since the values are calculated differently.
Shape Quality makes a big or small difference in OpenGL rendering?
RGB why do we use it?
Eye can only see variations of the three basic colors.
CPU is client
GPU is server.
Cache drawing commands on GPU to make more efficient.
LIsts with commands cached on the GPU.
Can't be changed.
Vertex Buffer Objects are more modern.
Immediate mode: slowest/flexible
VBO - Vertex Buffer Object
Best of between Display List and Vertex Array: Fast / flexible
GLUT Main Loop Callbacks
(Loop begins here)
5. Keyboard()->End() is possible
back to idle
Render next frame while displaying the current one to avoid flickering.
Hidden Surface Removal
Object Space: depth sort PAINTER'S ALG
Image Space:z-buffer alg
Render from back to front
Bad for complex geo
Sorting can be expensive
OpenGL does not support it.
Depth Sorting (For Painter's Algorithm)
1. sort by furthest distance z from viewer
2. minimum depth of A is greater than maximum depth of B, A can be drawn before B
3.if both x & y extents do not overlap, A and B can be drawn independently
Image Space For Visibility of Objects
* Raycasting: intersect ray with polygons
* The z-Buffer Algorithm: check if pixel is closer than current pixel drawn if so update pixel
Creates a normal vector to the two vectors used.
Normal vector is
if Adot(B) = 0 then A&B are orthogonal
||A||=(ATA)^.5 = (Adot(A))^.5 = length of A
Projects one vector onto another.
Shadow Projection Strategy
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