15 minutes, split into groups and share homework
introduction to boolean expressions, and how they result in a boolean variable. 5 < 10 turns into true
introduce loops first with the while loop. to prevent an infinite loop we need a boolean expression which begins as true but eventually becomes false. (we need variables. need to compare against memory and change the memory).
introduce for-loops, connect the dots: 3 parameters in the for loop relate to the 3 lines of code using the while loop.
start
while (end) {
increment
}
for (start; end; increment)
tabs are whitespace that is ignored by the compiler but extremely helpful for human eyes. be strict about good tab spacing!
challenge: pick a shape (rect, circle, ellipse) and put it in the for-loop. but how can you make it different every time. ofRandom? ofGetElapsedTimef()
the for-loop comes with a built-in counter. you need something that changes between each iteration of the loop? use the i iterator.
challenge: draw a color gradient by drawing a bunch of vertical lines next to one another the i will be used to change the x-position of the lines, as well as the color.
problem: both position and color are tied to the same variable, how can we make this gradient larger in size than 255, without breaking the colors? we need ofMap.
right now the i is too-directly mapped to the location. we can use math (* 2) to increase the size. why is our for-loop between 0 and 255 to begin with?
for-loops and the draw() function are different kinds of loops. the for-loop completely finishes all in the span of nano or micro seconds. the draw() loop waits an eternity in computer time, 1/60th of a second (in most cases).
a sketch where sine of elapsed time is mapped to position. and play with the frequency of the sine function.
ofBackground(0);
for (int i = 0; i < 20; i++){
float y = ofMap(sin(ofGetElapsedTimef()*i*0.2), -1, 1, ofGetHeight()/2-100, ofGetHeight()/2+100);
ofDrawCircle(i * 50, y, 20);
}
challenge: inside a for-loop, place 100 random tiny dots, creating the night-sky. it’s impossible because every frame, a randomly placed dot changes positions!
can you imagine writing out 100 variables? int x1; int x2; int x3…
arrays are a way of storing a list of variables. it solves the problem how can we store one variable for every iteration of the loop.
you should know
for(int i = 0; i < random(10); i++)does not do what you probably think it does.
the iterator in the for loop counts 0 to whatever is the upper limit. play with a for-loop that represents 2 things at once (or 3, or more..), the iterator needs to be mapped. Consider the ranges of the mapped iterators (0…PI, 0…ofGetWidth(), -1…1). Play with different ranges and different increments.
have fun with harmonic animation, sine of elapsed time in a loop, with the i modifying each instance.