Download CS 177 - My E-town

Week 2 - Friday
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What did we talk about last time?
3D graphics
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Most modern 3D video games use
real-time rendering
3D scenes are (somewhat)
realistically rendered on the fly as
characters move throughout the
world
 Scenes usually contain tens of
thousands of triangles
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The quality is much worse than
offline rendering
But it's still pretty good
Transforming, texturing, and lighting tens of
thousands of triangles is too much work for your CPU
 Most computers have special purpose graphics cards
with a powerful processor called a Graphics
Processing Unit (GPU)
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 Really great at the kind of math needed for graphics
Because GPUs are so common, Windows Vista, 7, 8
and Mac OS use GPUs to make regular desktop
animations smoother and faster
 Some computer scientists use GPUs to solve other
problems like simulations and DNA sequencing
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Texturing is gluing a (usually) 2D image onto a polygon
This is fully supported by GPUs
Large numbers of realistic textures are the reason that
graphics cards need so much memory
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3Dfx Interactive was a huge developer in the
field until they went bankrupt in 2002
 Bought by Nvidia
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Nvidia is a current manufacturer, famous for
its GeForce gaming line
AMD bought ATI in 2006 and manufactures
the Radeon line of gaming processors
Intel is also a major player in GPUs but
focuses on a budget models
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One issue, in both offline and
real-time rendering, is the
uncanny valley:
 We can relate to abstract
representations of human
beings
 We can relate to realistic
depictions of human beings
 But somewhere in the middle,
it's not real enough to be
convincing, but it is real enough
to freak us out
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Video games generate more revenue
than Hollywood movies
 In 2015, video games brought in $71 billion
compared to the $38 billion of box office
revenues
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101.6 million Wiis
13.4 million Wii Us
80 million Xbox 360s
19 million Xbox Ones
80 million PS3s
53.4 million PS4s
PC games are a small part of the pie
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One way to get user input is to use a when
key pressed block
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You'll notice that this is a starting block (it
doesn't go after other blocks)
You can add different when key pressed
blocks to respond to different keys
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Each sprite has its own set of behaviors
But you can create as many sprites as you
want
If you want several sprites to behave in a
similar way, first make one that does what
you want
Then right-click on the sprite and choose the
duplicate option
Duplicating the sprite will make a copy of the
sprites appearance and scripts
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Sprites can't control each other
If you want a sprite to interact with another sprite,
you have to broadcast a message
A message tells anyone who is listening that some
event has happened
 Messages have no contents, they just have names
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 You can create as many different named messages as you
want
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A sprite needs a when I receive block to act on a
message
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Make it so that the user can move the Scratch
Cat to the right side of the screen step by
step using the right arrow key
Send a message when the Scratch Cat
reaches the right side of the screen
Make a new sprite that cheers when it gets
the message
Duplicate the sprite so that lots of sprites
cheer when the Cat reaches the right
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We will talk about bits and bytes
Read Chapter 1 of Blown to Bits
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Keep working on Project 1
Read Chapter 1 of Blown to Bits