- The first - and perhaps easiest - part of implementing any rigid body physics system is getting the entities in your scene to move in response to linear forces. - With this implementation alone, you can achieve an interesting level of realism in your 2D (and even 3D) scene. -
-- Let's begin by recalling the relationships between acceleration, velocity, and position. -
-- Knowing all this, you should be able to understand the following source code fairly easily; -
-
- function update(dtSeconds) {
- // Add up the forces acting on the circle
- const GRAVITY = 9.8;
- const lGravityForce = vec2(0, -1.0 * (lCircle.mass * GRAVITY));
- lCircle.force = addVec2(lCircle.force, lGravityForce);
-
- // Figure out acceleration (a = F / m)
- const lCurrentAcceleration = scaleVec2(lCircle.force, 1.0 / lCircle.mass);
-
- // Calculate the new velocity: v = v0 + a * t
- lCircle.velocity = addVec2(lCircle.velocity, scaleVec2(lCurrentAcceleration, dtSeconds));
-
- // Update the position based on velocity: x = x0 + v * t
- lCircle.position = addVec2(lCircle.position, scaleVec2(lCircle.velocity, dtSeconds));
-
- // Update the model matrix accordingly
- lCircle.model = translateMatrix(mat4(), lCircle.position.x, lCircle.position.y, 0);
-
- // Reset the force vector for the next update
- lCircle.force = vec2()
- }
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