OpenGL CS 148: Summer 2016 Introduction of Graphics and Imaging - - PowerPoint PPT Presentation

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OpenGL CS 148: Summer 2016 Introduction of Graphics and Imaging - - PowerPoint PPT Presentation

May 21, 2023 318 likes •1.07k views

OpenGL CS 148: Summer 2016 Introduction of Graphics and Imaging Zahid Hossain http://www.pling.org.uk/cs/cgv.html So Far: Theory of Rasterization 2 CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) Zahid Hossain

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CS 148: Summer 2016 Introduction of Graphics and Imaging Zahid Hossain

OpenGL

http://www.pling.org.uk/cs/cgv.html

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So Far: Theory of Rasterization

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 2

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Observation

  • Apply transformation
  • Barycentric Interpolation
  • Rasterize
  • Compute Light and Shading (More on it later)
  • Lookup Textures (More on it later)
  • And lot more ….

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 3

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Observation

  • Apply transformation
  • Barycentric Interpolation
  • Rasterize
  • Compute Light and Shading (More on it later)
  • Lookup Textures (More on it later)
  • And lot more ….

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 4

To Millions of Triangles and Billions of Fragments

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Observation

  • Apply transformation
  • Barycentric Interpolation
  • Rasterize
  • Compute Light and Shading (More on it later)
  • Lookup Textures (More on it later)
  • And lot more ….

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 5

To Millions of Triangles and Billions of Fragments

SIMD (Single Instruction Multiple Data)

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Graphics Hardware

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 6

2560 cores! (upto 1733 MHz, 8GB Mem)

http://www.geforce.com/hardware/10series/geforce-gtx-1080

GTX 1080

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Advice

Leave implementation of low-level features to the experts.

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 7

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Advice

Leave implementation of low-level features to the experts. Why ?

  • Abstract away hardware differences
  • Rasterization should be fast

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 8

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Introducing …

Industry Standard API for Computer Graphics (Cross Platform, since 1992)

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 9

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Not the Only One

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Related APIs in the OpenGL Family

Google Maps Angry Birds by Rovio

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Related APIs in the OpenGL Family

Google Maps Angry Birds by Rovio

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OpenGL 1.x

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 13

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OpenGL 1.x: Why ?

  • Easy to learn!
  • Little code
  • Instructional

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Simple First Program

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What OpenGL Is Not

OpenGL is not a windowing system

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Introducing GLUT (GL Utility Toolkit)

  • Simple cross-platform windowing API
  • glutInitDisplay(),

glutInitWindowSize(..)

  • Bindings: C, C++, Fortran, Ada, …
  • Features:
  • Multiple windows, menus
  • Keyboard/mouse/other input
  • Assorted callbacks: idle, timers
  • Basic font support‘
  • glutSolidTeapot,

glutSolidSphere, glutSolidCube, …

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 17

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Introducing GLUT (GL Utility Toolkit)

  • Simple cross-platform windowing API
  • glutInitDisplay(),

glutInitWindowSize(..)

  • Bindings: C, C++, Fortran, Ada, …
  • Features:
  • Multiple windows, menus
  • Keyboard/mouse/other input
  • Assorted callbacks: idle, timers
  • Basic font support‘
  • glutSolidTeapot,

glutSolidSphere, glutSolidCube, …

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 18

Other options: glfw, SDL

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Introducing GLU (GL Utility)

  • High-level graphics commands
  • Not included in OpenGL ES
  • Some interesting features:
  • Mapping between world and screen coordinates
  • Texturing support
  • Tessellation and other geometric utilities
  • OpenGL error code lookup
  • More primitives: spheres, cylinders, disks, …
  • Camera support: gluLookAt,

gluOrtho2D, …

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 19

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Simple First Program

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 20

Projection Matrix ! (GL_PROJECTION)

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Simple First Program

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 21

Camera and Model Matrices Combined ! (GL_MODELVIEW)

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gluLookAt(eye, at, up)

defines the camera/viewing matrix! where is the viewpoint? where is it pointed? which way is up?

eye at up

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 22

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gluPerspective(fovy, aspect, near, far)

The Redbook, fig. 3-14 (p. 155)

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Transformation Recall

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Transformation Recall

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 25

NDC à Viewport Transformation à Final Image

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glViewport(x, y, width, height)

(x, y) at lower left height width

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 26

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Primitive [prim-i-tiv]:

A small piece of geometry that can be rendered in OpenGL; e.g. triangles, lines, points etc.

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OpenGL Primitive Types

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 28

http://www.opengl2go.net/wp-content/uploads/2015/10/gl-primitives-with-background.png

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OpenGL Primitives (Triangles)

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 29

1 2 3 4 5 6

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OpenGL Primitives (Triangle Strip)

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1 2 3 4 5

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OpenGL Primitives (Triangle Strip)

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1 2 3 4 5

Immediate Mode (Deprecated)

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Color: glColor3f(red,green,blue)

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 32

v1 v2 v3

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GL, GLU, and GLUT notations

gl... e.g., glColor3f(...) core OpenGL function glu... e.g., gluLookAt(...) OpenGL utility function, makes common tasks easier (defined in terms of gl... functions) glut... e.g., glutSolidTeapot(...) GLUT functions

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 33

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GL, GLU, and GLUT notations

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 34

glVertex3f(...)

...3f takes 3 floats ...3d takes 3 doubles ...3i takes 3 integers ...2f takes 2 floats ...4f takes 4 floats (etc)

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Composing Transformations

glLoadMatrixf(A); glMultMatrixf(B); glMultMatrixf(C);

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Convenience Functions

  • glTranslatef(tx, ty, tz)
  • glRotatef(degrees, x, y, z)
  • glScalef(sx, sy, sz)

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Hierarchical Modeling

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 37 translate(0,4) drawTorso() pushMatrix() translate(1.5,0) rotateX(leftHipRotate) drawThigh() pushMatrix() translate(0,-2) rotateX(leftKneeRotate) drawLeg() ... popMatrix() popMatrix() pushMatrix() translate(-1.5,0) rotateX(rightHipRotate) // Draw the right side ... ...

x y

CurrentMatrix = translate(0,4) translate(1.5,0) rotateX(leftHipRotate) translate(0,-2) rotate(leftKneeRotate) Matrix Stack

translate(0,4) translate(0,4) translate(1.5,0) rotateX(leftHipRotate)

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OpenGL Matrix Stack

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 38

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OpenGL 1.x Pipeline (Simplified)

http://upload.wikimedia.org/wikipedia/commons/b/bb/Pipeline_OpenGL_%28en%29.png

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 39

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OpenGL 1.x Pipeline (Unsimplified)

http://www.opengl.org/documentation/specs/version1.1/state.pdf

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 40

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OpenGL 1.x Pipeline (Unsimplified)

http://www.opengl.org/documentation/specs/version1.1/state.pdf

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 41

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Pieces of the Pipeline

Stores “subroutines”

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 42

GLuint boxList; boxList = glGenLists(1); glNewList(boxList, GL_COMPILE); // draw box glEndList(boxList); … glCallList(boxList);

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Pieces of the Pipeline

Stores “subroutines”

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Pieces of the Pipeline

Construct geometric objects

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Pieces of the Pipeline

Change geometry Store primitive shapes

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Pieces of the Pipeline

Change geometry Store primitive shapes

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 46

Includes Clipping

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Pieces of the Pipeline

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 47

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Fragment [frag-muhnt]:

The data necessary to generate a single pixel’s worth

  • f a primitive.

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Pieces of the Pipeline

Modify and combine per-pixel information

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Pieces of the Pipeline

Prepare image to be displayed

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OpenGL State Machine

Change State Draw Draw Change State Draw Change State Change State Draw

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 51

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OpenGL State Machine

glColor3f(…) glEnable(…) glLineStipple(…) glGetFloatv(…) glIsEnabled(…) glGetLineStipple(…)

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 52

Set State Get State

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OpenGL State Machine

glColor3f(…) glEnable(…) glLineStipple(…) glGetFloatv(…) glIsEnabled(…) glGetLineStipple(…)

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Efficiently managing state changes is a major implementation challenge

Set State Get State

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OUT OF DATE.

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OUT OF DATE.

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Vertex Lighting

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Normal

A vector perpendicular to a surface; constant over a plane

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 57

https://en.wikipedia.org/wiki/Normal_(geometry)

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Specifying Normals

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 58

1 2 3 1 2 3

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Vertex Lighting

  • Diffuse Term

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Vertex Lighting

  • Specular Term

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Camera

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Vertex Lighting

  • Specular Term

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Camera

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Vertex Lighting

  • Specular Term

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 62

Camera Ambient Light

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Vertex Lighting

  • Specular Term

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 63

Camera Ambient Light

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Vertex Lighting

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Enable a Light Setup material

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Vertex Lighting

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 65

Enable a Light Setup material

Note: w=0 is directional light glutSolidTeapot specifies the normal in this case

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Vertex Lighting: Types

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 66

http://www.computing.northampton.ac.uk/~gary/csy3019/images3d/lightSources.gif

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Vertex & Index Buffers

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Vertex/Index Buffer

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8 vertices only

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Vertex/Index Buffer

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Drawing with triangles: 36 vertices!

8 vertices only

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Vertex/Index Buffer

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8 vertices only

Vertices = { v0,v1,.. V7 } Indices = { 0,1,2, 0,2,3, 1,5,6, 1,6,2 …... } v0 v1 v2 v3 v5 v6 v7

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Vertex/Index Buffer

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Next Generation APIs

  • Vulkan (Nextgen OpenGL)
  • DirectX 12 (Microsoft)
  • Metal (Apple)

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 72

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Next Generation APIs

  • Vulkan (Nextgen OpenGL)
  • DirectX 12 (Microsoft)
  • Metal (Apple)

CS 148: Introduction to Computer Graphics and Imaging (Summer 2016) – Zahid Hossain 73

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CS 148: Summer 2016 Introduction of Graphics and Imaging Zahid Hossain

OpenGL

http://www.pling.org.uk/cs/cgv.html