The Issue with Friction using Delta Time

Oct 13, 2025 by wbrum.org 132 views

Introduction

In game development and physics simulations, delta time is a crucial concept that helps maintain a consistent game speed across different hardware configurations. However, when implementing friction using delta time, developers often encounter inconsistent results. In this article, we will delve into the issue of friction using delta time and explore a better approach to achieve smooth and consistent character movement.

What is Delta Time?

Delta time, also known as delta frame time, is the time elapsed between two consecutive frames in a game or simulation. It is calculated by subtracting the previous frame's timestamp from the current frame's timestamp. Delta time is essential in maintaining a consistent game speed, as it allows the game to adjust the movement and physics calculations based on the actual time elapsed.

The Issue with Friction using Delta Time

The given formula for slowing down a character using delta time is:

this.y += this.yVel * delta;
this.yVel *= Math.pow(0.99, delta);

This formula appears to be a simple and elegant way to implement friction. However, the issue lies in the fact that the friction value (0.99) is being multiplied by the delta time. This results in a non-linear friction effect, where the character's speed decreases more rapidly at higher frame rates.

Why is this a Problem?

The problem with this approach is that it leads to inconsistent results. At higher frame rates, the character's speed decreases more rapidly, while at lower frame rates, the speed decrease is less pronounced. This inconsistency can be jarring and affect the overall gaming experience.

A Better Approach: Using a Fixed Friction Value

To achieve smooth and consistent character movement, we can use a fixed friction value instead of multiplying it by the delta time. This approach ensures that the friction effect is consistent across different frame rates.

const friction = 0.99;
this.y += this.yVel * delta;
this.yVel *= friction;

In this revised formula, the friction value is a constant (0.99) that is multiplied by the character's velocity. This approach ensures that the friction effect is consistent and predictable, regardless of the frame rate.

Why is this a Better Approach?

Using a fixed friction value has several advantages over multiplying it by the delta time:

Consistency: The friction effect is consistent across different frame rates, ensuring a smooth and predictable gaming experience.
Predictability: The character's speed decrease is predictable and consistent, making it easier to design and balance game mechanics.
Easier to Implement: The revised formula is simpler and easier to implement, reducing the risk of errors and inconsistencies.

Additional Tips and Considerations

When implementing friction using a fixed value, keep the following tips and considerations in mind:

Adjust the friction value: Experiment with different friction values to find the optimal value for your game.
Consider the character's mass: The character's mass can affect the friction effect. Consider using a mass-based friction value to achieve more realistic results.
Combine with other physics effects: Friction is just one aspect of physics simulations. Combine it with other effects, such as gravity and drag, to create a more realistic and immersive gaming experience.

Conclusion

Introduction

In our previous article, we discussed the issue of friction using delta time and explored a better approach to achieve smooth and consistent character movement. In this Q&A article, we will address some common questions and concerns related to friction using delta time.

Q: Why is friction using delta time a problem?

A: Friction using delta time is a problem because it leads to non-linear friction effects, where the character's speed decreases more rapidly at higher frame rates. This inconsistency can be jarring and affect the overall gaming experience.

Q: What is the main difference between friction using delta time and a fixed friction value?

A: The main difference is that friction using delta time multiplies the friction value by the delta time, resulting in a non-linear friction effect. In contrast, a fixed friction value is a constant value that is multiplied by the character's velocity, resulting in a consistent and predictable friction effect.

Q: How do I choose the right friction value?

A: Choosing the right friction value depends on the game's design and the desired gameplay experience. Experiment with different friction values to find the optimal value for your game. Consider factors such as the character's mass, the game's physics engine, and the desired level of realism.

Q: Can I use a variable friction value based on the character's speed or mass?

A: Yes, you can use a variable friction value based on the character's speed or mass. This approach can create more realistic and immersive gameplay experiences. For example, you can use a higher friction value for characters with higher masses or speeds.

Q: How do I implement friction using a fixed value in my game?

A: To implement friction using a fixed value, you can use the following formula:

const friction = 0.99;
this.y += this.yVel * delta;
this.yVel *= friction;

In this formula, the friction value is a constant (0.99) that is multiplied by the character's velocity.

Q: Can I use friction using delta time in certain situations?

A: Yes, you can use friction using delta time in certain situations, such as:

High-speed gameplay: In high-speed gameplay, friction using delta time can create a more realistic and immersive experience.
Special effects: Friction using delta time can be used to create special effects, such as a character's speed decreasing rapidly when they hit a wall.

Q: What are some common mistakes to avoid when implementing friction?

A: Some common mistakes to avoid when implementing friction include:

Using a non-linear friction value: Avoid using non-linear friction values, as they can lead to inconsistent and unpredictable gameplay experiences.
Not considering the character's mass: Failing to consider the character's mass can result in unrealistic and unimmersive gameplay experiences.
Not adjusting the friction value: Failing to adjust the friction value can result in gameplay experiences that are too slow or too fast.

Conclusion

In conclusion, friction using delta time can lead to inconsistent results, while a fixed friction value can create smooth and consistent character movement. By understanding the differences between these two approaches and avoiding common mistakes, you can create more realistic and immersive gameplay experiences.