Lecture 3

Question 1

Why use a pipeline?

Answer 1

Provides efficiency and allows programmer to perform number of operations on input data

Question 2

What states are there in the pipeline?

Answer 2

1) Input Assembler
2) Vertex Shader
3) Tesselation Stage (Hull Shader, Tesselator, Domain Shader)
4) Geometry Shader
5) [Stream Output]
6) Rasterizer Stage
7) Pixel Shader
8) Output Merger

Question 3

What happens at Input Assembler?

Answer 3

Reads data from buffers into primitive format for use by other stages (mainly triangle lists)

Question 4

What does graphics card render objects as?

Answer 4

Triangles

Question 5

What happens at Vertex Shader?

Answer 5

Performs operations on individual vertices (received from input assembler), including transformations and per-vertex lighting

Question 6

What view parameters does camera have?

Answer 6

EYE - where it’s located
AT - what it points at
UP - upward orientation

Question 7

What view parameters is camera’s view frustrum specified by?

Answer 7

1) fovy - rotation
2) aspect - width/height
3) zNear
4) zFar

Question 8

What happens at tesselation stages?

Answer 8

Group of optional stages (Hull Shader, Tesselator, Domain Shader)
Allow generation of multiple vertices for added detail

Question 9

What happens at Geometry Shader?

Answer 9

Operates on entire primitive (eg. triangle) and can perform number of operations, like dynamically calculating normals, particle systems, shadow volume generation

Question 10

What happens at Stream Output Stage?

Answer 10

Feed output of Geometry Shader stage to create new vertices to go back into start of pipeline for processing by another set of shaders (eg. useful for particle systems)

Question 11

What happens at Rasterizer Stage?

Answer 11

Take that 3D vertex information and converts it down into pixels, interpolating data (eg. color) between vertices to produce per-pixel data.
Clips primitives into view frustrum - everything outside screen discarded. Culling performed here.

Question 12

What is culling?

Answer 12

Triangles facing away from screen not rendered

Left hand rule - triangles with vertices in counter-clockwise order not rendered

Question 13

What happens at Pixel (fragment) Shader?

Answer 13

Produces colour values for interpolated pixels
Per-pixel lighting to be performed
Depth values can be produced for depth-buffering

Question 14

What happens at Output Merger?

Answer 14

Combines pixel shader outputs to produce final image. May include depth buffering. Put one with smallest depth value in front.

Question 15

How does water work?

Answer 15

Combines colors of both water and whatever is beneath it

Question 16

What is double buffering?

Answer 16

Don’t want to draw objects directly to screen (may no longer be visible when finished rendering) so we render next frame to a buffer. Swap buffers when completely rendered.