Processing缓动动画跨帧率速度不一致问题：帧时间的正确使用方式及代码示例求助

Absolutely—frame time is exactly the right direction to fix this inconsistency!

Your current code updates the position based on a fixed percentage per frame, which means faster devices (with higher FPS) will run through more frames per second, resulting in much quicker movement. Slower devices with lower FPS will do the opposite. To make the animation speed consistent across all devices, you need to tie your easing calculation to real time elapsed between frames instead of relying on frame count.

Why This Works #

Easing is fundamentally an exponential smoothing calculation. When frame rates vary, the time between each update (deltaTime) changes. By incorporating deltaTime into your easing formula, you ensure the animation progresses at the same rate relative to real time, regardless of how many frames are rendered each second.

Updated Code Snippet #

Here’s how to adjust your core logic to use frame time:

First, declare global variables to track time and position:

float x = 0;
float targetX;
// Adjust this coefficient to control easing speed (higher = faster)
float easingSpeed = 5; 
float lastFrameTime;

Initialize the time tracker in setup():

void setup() {
  size(600, 400);
  lastFrameTime = millis();
}

Modify your draw() loop to calculate time difference and apply time-based easing:

void draw() {
  background(255);
  
  // Calculate time elapsed since last frame (converted to seconds)
  float currentTime = millis();
  float deltaTime = (currentTime - lastFrameTime) / 1000.0;
  lastFrameTime = currentTime;
  
  targetX = mouseX;
  float dx = targetX - x;
  
  // Time-based exponential easing: ensures consistent speed across FPS
  // This formula means the remaining gap halves every ~0.2 seconds (1/easingSpeed)
  float timeBasedEasing = 1 - pow(0.5, deltaTime * easingSpeed);
  x += dx * timeBasedEasing;
  
  // Draw your object (example ellipse)
  ellipse(x, height/2, 50, 50);
}

Key Details #

• deltaTime: The time (in seconds) between the current frame and the last one. This normalizes our calculation to real time.
• easingSpeed: Adjust this value to control how quickly the object moves toward the target. A value of 5 means the remaining distance to the target will be cut in half every 0.2 seconds—this rate stays consistent no matter the FPS.
• If you prefer a simpler linear time-based easing (instead of exponential), you can replace the timeBasedEasing line with:

  float speedPerSecond = 0.3; // Moves 30% of the remaining gap per second
  float timeBasedEasing = speedPerSecond * deltaTime;
  

  Note that this will feel slightly different from the original exponential easing, but it’s still frame-rate independent.

With this adjustment, your animation will run at the same speed on a 100FPS desktop and a 30FPS mobile device.

内容的提问来源于stack exchange，提问作者Michael