1 A first OpenGL program Brian Farrimond Robina Hetherington.

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A first OpenGL program

Brian Farrimond

Robina Hetherington

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Ex01

• Build and run Ex01

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Program structure

Three function program

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main

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main

•Always present•Uses RGB colours (Red, Green, Blue)

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main

Sets up the scene window

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Window exercises

• Double the size of the window height and width• Make the window start at the top left corner of

the screen• Change the window title to “2D OpenGL”

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main

Set up the graphical characteristics of the new window

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initSet the background colour:•red•green•blue•alpha (transparency)

Min value: 0.0Max value: 1.0

Exercise:

Set the background colour to red

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init

Set projection to be orthographic

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Projections

• Orthographic projection shows no perspective

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Orthographic projection

• glOrtho(left, right, bottom, top, near, far)

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main

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main

Name of the function that will draw the scene

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display

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display

Clear the window using the

background colour

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display

glColor3f(red, green, blue)

Min value: 0.0Max value: 1.0

Exercise: Make the rectangle yellow

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display

Draw the rectangle (polygon with four vertices)

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glVertex(x, y, z)

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glVertex(x, y, z)

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glVertex(x, y, z)

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glVertex(x, y, z)

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glVertex(x, y, z)

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glVertex(x, y, z) Vertices are in anticlockwise order

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glOrtho(left, right, bottom, top, near, far);glOrtho(0.0 , 1.0, 0.0, 1.0, -1.0, 1.0);

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glOrtho(left, right, bottom, top, near, far);glOrtho(-0.5, 1.0, 0.0, 1.5, -1.0, 1.0);

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The new projection

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main

How we manage animation and interaction

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OpenGL drawing primitives

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OpenGL drawing primitives

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OpenGL drawing primitives

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OpenGL drawing primitives

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OpenGL drawing primitives

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OpenGL drawing primitives