Graphics, Animation, and Randomization continued
| Some additional techniques for programming graphics and animation, along with some new programming language concepts. This material is optional – you don’t need it to complete Project 2, or for the exams. |
| Techniques for : | ||
| Drawing geometric figures | ||
| Objects that follow the mouse | ||
| Animation | ||
| Small ideas: | ||
| Using trigonometry in programming graphical layout | ||
| Named constants | ||
| for loops (another construct for iteration) | ||
| Mouse move events & dragging | ||
| Double buffering | ||
| Big idea: | ||
| Object-oriented programming | ||
| You can download the sample code for today from the “Example Code” link on the CSE/IMT 100 web page. All the code is in a zip file; ProjectSquiral is also available separately. | ||
| Sample files: | ||
| ProjectSquiral – interactive squirals | ||
| ProjectBlackSquiral – nicer colors, full screen | ||
| ProjectDrag – dragging an object | ||
| ProjectAnimate – very simple animation | ||
| ProjectAnimatedSquiral | ||
| ProjectBufferedSqural – illustrates double buffering | ||
| In programming we often need to use various constants, e.g. RGB combinations, the number of steps to take in a squiral, etc. | ||
| It is good programming practice to give names to these, rather than embedding the constants in your code. | ||
| Advantages: | ||
| Putting them at the beginning of your code makes it easier to find and change them. | ||
| If you use the constant in several places and want to change it, there’s just one place to change. | ||
| VB has various constants already built in. Examples: | ||
| vbRed, vbBlack, vbBlue, etc: colors | ||
| vbLeftButton: code for left mouse button pushed (an integer) | ||
| Declaring your own: | ||
| Recall that VB, like most other modern environments for building graphical user interfaces, uses an event model. | |
| For example, we generate an event (and call an appropriate procedure) whenever the user clicks on a button. | |
| Whenever the mouse moves, VB generates a “mouse move event” | |
| You can do simple animations using the timer control. On each call to the Timer procedure, erase the form and draw the new figure. |
| If you are doing a complex animation, it will take VB a bit of time to do the drawing. | ||
| Problem: flicker | ||
| Solution: double buffering | ||
| Draw the figure in a different picture that is not visible | ||
| Copy the result into the visible picture | ||