Programming – Hello Neo

What is a Console?

The concept of a console is important when writing games for modern game engines. In this article we will examine the concept in light of solving the blocking input problem in modern game engines and langauges like JavaScript. In JavaScript, for example, your code is placed on the UI thread. This means that whenever a […]

November 13, 2023

Collision of Spheres in Javascript

function check_collisions() {

	// For every sprite,
	for (t = 0; t < sprites.length; t++) {
		var s1 = sprites[t];		// 1st sprite

		// Check every other sprite,
		for (k = 0; k < sprites.length; k++) {
			var s2 = sprites[k];	// 2nd sprite

			// only compare against sprites “above”
			// see diagram on whiteboard to explain why
			if (s1.id < s2.id) {
				// If both are “alive”,
				if (s1.alive == true && s2.alive == true) {
					// check collision physics.
					collision_physics(s1,s2);
				} // if alive
			} // if touching (collision)
		} // for all sprites
	} // for all sprites
}

function collision_physics(s1,s2) {
	// Step 1. Get the distance between objects.
	var dx = s2.x - s1.x; //distance between x
	var dy = s2.y - s1.y; // distance between y
	var distance = Math.sqrt(dx * dx + dy * dy);

	// Step 2. Define the minimum distance
	// (see whiteboard for diagram
	var minDistance = s1.r + s2.r;

	// Step 3. if the distance is touching (i.e. collision),
	if (distance < minDistance) {

		// Step 4. Calculate the angle of collision.
		var angle = Math.atan2(dy, dx);
		var spread = minDistance - distance;
		var ax = spread * Math.cos(angle);
		var ay = spread * Math.sin(angle);
    
		// Step 5. Solve collision (separation) angles
		s1.x -= ax/2;
		s1.y -= ay/2;
		s2.x += ax/2;
		s2.y += ay/2;

		// Step 6. Give each ball it’s share of the rebound angle;
		// change the ball’s dx and dy so they fly apart logically.
		s1.dx -= Math.cos(angle)*FPS;
		s1.dy -= Math.sin(angle)*FPS;
		s2.dx += Math.cos(angle)*FPS;
		s2.dy += Math.sin(angle)*FPS;
	}
}

function check_collisions() {

// For every sprite,

for (t = 0; t < sprites.length; t++) {

var s1 = sprites[t]; // 1st sprite

// Check every other sprite,

for (k = 0; k < sprites.length; k++) {

var s2 = sprites[k]; // 2nd sprite

// only compare against sprites “above”

// see diagram on whiteboard to explain why

if (s1.id < s2.id) {

// If both are “alive”,

if (s1.alive == true && s2.alive == true) {

// check collision physics.

collision_physics(s1,s2);

} // if alive

} // if touching (collision)

} // for all sprites

}

function collision_physics(s1,s2) {

// Step 1. Get the distance between objects.

var dx = s2.x - s1.x; //distance between x

var dy = s2.y - s1.y; // distance between y

var distance = Math.sqrt(dx * dx + dy * dy);

// Step 2. Define the minimum distance

// (see whiteboard for diagram

var minDistance = s1.r + s2.r;

// Step 3. if the distance is touching (i.e. collision),

if (distance < minDistance) {

// Step 4. Calculate the angle of collision.

var angle = Math.atan2(dy, dx);

var spread = minDistance - distance;

var ax = spread * Math.cos(angle);

var ay = spread * Math.sin(angle);

// Step 5. Solve collision (separation) angles

s1.x -= ax/2;

s1.y -= ay/2;

s2.x += ax/2;

s2.y += ay/2;

// Step 6. Give each ball it’s share of the rebound angle;

// change the ball’s dx and dy so they fly apart logically.

s1.dx -= Math.cos(angle)*FPS;

s1.dy -= Math.sin(angle)*FPS;

s2.dx += Math.cos(angle)*FPS;

s2.dy += Math.sin(angle)*FPS;

}

May 5, 2023

CALL and RET considered harmful.

The title of this post is a fun little jab at famous articles like “GOTO considered harmful“. A few years later Knuth’s “Structured Programming with go to Statements” provided a credible counterpoint. Knuth is famously quoted as saying we each develop “strong feelings” over these things because we are witnessing a revolution. So the takeaway […]

April 30, 2023