1. Week 2 - Friday
CS 113

2. Last time
What did we talk about last time?
3D graphics

3. Project 1

4. Questions?

5. Video Games

6. Real-time rendering 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
The quality is much worse than offline rendering
But it's still pretty good

7. Real-time rendering should be impossible
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)
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

8. Texturing 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

9. Big names in the field
3Dfx Interactive was a huge developer in the field until they went bankrupt in 2002
Bought by Nvidia
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

10. Uncanny valley
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

11. Money 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
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

12. More Scratch

13. Keyboard input
One way to get user input is to use a when key pressed block
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

14. Multiple sprites 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

15. Messages 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
You can create as many different named messages as you want
A sprite needs a when I receive block to act on a message

16. Example
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

17. Lab 2

18. Upcoming

19. Next time… We will talk about bits and bytes
Read Chapter 1 of Blown to Bits

20. Reminders
Keep working on Project 1
Read Chapter 1 of Blown to Bits