1 a first opengl program brian farrimond robina hetherington
TRANSCRIPT
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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