Method updatePhysics

src/engineObject.js:155–365

Update the object physics, called automatically by engine once each frame. Can be overridden to stop or change how physics works for an object.

()

    /** Update the object physics, called automatically by engine once each frame. Can be overridden to stop or change how physics works for an object. */
    updatePhysics()
    {
        // child objects do not have physics
        ASSERT(!this.parent);

        // bail if a collision callback destroyed us mid-frame
        if (this.destroyed) return;

        if (this.clampSpeed)
        {
            // limit max speed to prevent missing collisions
            this.velocity.x = clamp(this.velocity.x, -objectMaxSpeed, objectMaxSpeed);
            this.velocity.y = clamp(this.velocity.y, -objectMaxSpeed, objectMaxSpeed);
        }

        // apply physics
        const oldPos = this.pos.copy();
        this.velocity.x *= this.damping;
        this.velocity.y *= this.damping;
        if (this.mass)
        {
            // apply gravity only if it has mass
            this.velocity.x += gravity.x * this.gravityScale;
            this.velocity.y += gravity.y * this.gravityScale;
        }
        this.pos.x += this.velocity.x;
        this.pos.y += this.velocity.y;
        this.angle += this.angleVelocity *= this.angleDamping;

        // physics sanity checks
        ASSERT(this.angleDamping >= 0 && this.angleDamping <= 1);
        ASSERT(this.damping >= 0 && this.damping <= 1);

        // don't do collision for static objects or if solver disabled
        if (!enablePhysicsSolver || !this.mass) return;

        const wasFalling = this.velocity.y < 0 && gravity.y < 0 || this.velocity.y > 0 && gravity.y > 0;
        if (this.groundObject)
        {
            // apply friction in local space of ground object
            const friction = max(this.friction, this.groundObject.friction);
            const groundSpeed = this.groundObject.velocity.x;
            this.velocity.x = groundSpeed + (this.velocity.x - groundSpeed) * friction;
            this.groundObject = undefined;
        }

        if (this.collideSolidObjects)
        {
            // check collisions against solid objects
            const epsilon = .001; // necessary to push slightly outside of the collision
            for (const o of engineObjectsCollide)
            {
                // skip destroyed, child objects, or self collision
                if (o.destroyed || o.parent || o === this) continue;

                // non solid objects don't collide with each other
                if (!this.isSolid && !o.isSolid) continue;