The Physics behind Video Games
By Laurin Fisher
Nov
26
Slopes
Now let's actually look at the physics behind slopes with a Diagram!
As you can see there are 3 different forces acting on our object now. We have the Normal Force, which is the contact force between the object and the slope/ground. The ground is pushing up on the object which makes it not fall through the floor.
We also have the Friction force, if the object is not moving the friction is static (our picture above where friction is keeping it from sliding down the hill). If the object is moving the friction is kinetic and slowing down the object's movement.
And of course gravity-but now gravity is more of a hassle. We cannot just point gravity down because we don't want our character to move through the floor. So we have to break it up into gravity of the x and y directions (though x is what we really need).
And so using sin and cos we have that Gravity in the X direction = |Gravity|sin(theta). This is the pull of gravity down the hill on the object.
When implementing slopes in a video game, remember that the character has to move in both the x and y direction, based on the steepness of the slope. For more information on this go to http://higherorderfun.com/blog/2012/05/20/the-guide-to-implementing-2d-platformers/ .
Further reading
Nov
26
Sum up of Slopes
Looking at the forces behind the scenes is actually helpful for a place to start when implementing game play. If there was no friction the slope would be ice. Gravity is acting in the x direction with a smaller magnitude.