给游戏物体加力（跳跃后的滑动效果）——deltatime相乘导致的抖动问题

Question

//inside update method which is called 60/120 times per second
long currentFrameTime = System.nanoTime();
float deltaTime = (currentFrameTime - lastFrameTime) / 1_000_000_000.0f;
lastFrameTime = currentFrameTime;

float nextForceSlide = forceSlide - forceSlideDecreaseRate * deltaTime;
if (nextForceSlide < 0) {
   forceSlide = 0;
} else forceSlide = nextForceSlide;

updatePosition(this, game.joyStick.angle, forceSlide * deltaTime);


//method
public void updatePosition(Entity entity, double angle, float length) {
   entity.position.x = entity.position.x + length * (float) Math.cos(Math.toRadians(angle));
   entity.position.y = entity.position.y + length * (float) Math.sin(Math.toRadians(angle));
}

这就是我尝试向玩家当前所看方向添加一点力的方法。由于我想支持 30 60 120 fps，因此每个施加的力的结果应该相同。但现在当玩家滑动时，感觉很紧张，不顺畅。为什么？

当我的玩家在跳跃动作后滑动时，我尝试给它添加一点力。目前感觉非常紧张。我以为会很顺利。

Answer 1

发生抖动是因为您在更新位置时应用了

deltaTime

两次。

更新方法

// inside update method which is called 60/120 times per second
long currentFrameTime = System.nanoTime();
float deltaTime = (currentFrameTime - lastFrameTime) / 1_000_000_000.0f;
lastFrameTime = currentFrameTime;

float nextForceSlide = forceSlide - forceSlideDecreaseRate * deltaTime;
if (nextForceSlide < 0) {
    forceSlide = 0;
} else {
    forceSlide = nextForceSlide;
}

// Update the position with forceSlide (not multiplied by deltaTime here)
updatePosition(this, game.joyStick.angle, forceSlide);

更新位置方法

public void updatePosition(Entity entity, double angle, float length) {
    // Multiply by deltaTime here to apply the force over the frame time
    entity.position.x = entity.position.x + length * (float) Math.cos(Math.toRadians(angle)) * deltaTime;
    entity.position.y = entity.position.y + length * (float) Math.sin(Math.toRadians(angle)) * deltaTime;
}

基本上，在

updatePosition

中，应用位置更改时只需乘以

deltaTime

。这样，力就会随着时间的推移而适当缩放，从而避免抖动。现在在不同的帧速率下应该是平滑的。