Advanced C++ Programming Tutorial 2

In this tutorial we learn how to transform our shit. Move it around, make it bigger (no pills or pumps required), flip it and reverse it. And later on we make a camera system to scroll our shit in the world. You're gonna like it.

Topics

Part 1

• Polyline drawing
• Vertices
• Trivial line clipping
• Translation
• Flipping across an axis
• Screen coordinate transformation
• Scaling

Part 2

• Camera scrolling
• Concatenating (combining) transforms
• Drawable packet design

Video Timestamp Index

Tutorial 2.1

• What are transformations? 0:26
• Storing vertices and drawing polygons/polylines 1:00

• Implementing Graphics::DrawClosedPolyline() 2:30
• Introducing a Star polygon generator class 3:40

• Clipping (trivial implementation) 4:22

• For more advanced line clipping, you can use the Cohen-Sutherland line clipping algorithm

• Translation: moving your model on the screen 6:13
• Coordinate systems: screen vs. world (/math model) coordinates 7:09

• Implementing a Coordinate Transformer class 8:25

- Essentially this is a "screen translator"; a structured way to apply transformations

- analogy of an "assembly line", this will be developed into a Pipeline system

• Implementing a persistant Entity class to hold models 13:37
• Integrating Entity control in Game::UpdateModel() (the game loop) 16:06

• Reasons for keeping a static model: avoid floating point calculation drift 16:30

• Scaling polylines 18:36

• Note: Rotations will be covered in a later tutorial
• Note: Scaling sprites requires more advanced techniques

Tutorial 2.2

• Scrolling with a Camera system 0:54

• Pipeline (Filter sequence) with camera added 2:58
• Camera implementation 3:24
• Demo time 6:29

• Camera zooming (scaling transformation) 6:50

• Mind the order of the transformations (translation first, scaling second) 8:41

• Concatenating multiple transformations 9:46
• Implementation of concatenation using a Drawable class 13:41

• Demo time 22:06

• Recap: how to chain filter operations (Pipeline concept) 22:25
• Homework assignments 23:53

Links

• GitHub Repo (advmath)

Homework

1. Create random starfield in large rectangular region with randomized positions, sizes, and shapes. Stars should not overlap.
2. Implement scrolling via mouse dragging.
3. Process vertices in-place (don't use a buffered polyline copy).
4. Only draw models that appear in the viewport.
5. Animate the scale (size) and color of stars so that they pulsate.

The Homework solution is here.

See also

• Next in series (Tutorial 3)
• Advanced C++ Programming Series
• Planet Chili Patreon