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Fix 3D movement example code not resetting vertical velocity #10953

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Fix 3D movement example code not resetting vertical velocity #10953

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26 changes: 19 additions & 7 deletions getting_started/first_3d_game/03.player_movement_code.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -188,7 +188,9 @@ fall speed separately. Be sure to go back one tab so the lines are inside the
target_velocity.z = direction.z * speed

# Vertical Velocity
if not is_on_floor(): # If in the air, fall towards the floor. Literally gravity
if is_on_floor(): # Stop falling
target_velocity.y = 0
else: # If in the air, fall towards the floor. Literally gravity
target_velocity.y = target_velocity.y - (fall_acceleration * delta)

# Moving the Character
Expand All @@ -210,7 +212,11 @@ fall speed separately. Be sure to go back one tab so the lines are inside the
_targetVelocity.Z = direction.Z * Speed;

// Vertical velocity
if (!IsOnFloor()) // If in the air, fall towards the floor. Literally gravity
if (IsOnFloor()) // Stop falling
{
_targetVelocity.Y = 0.0f;
}
else // If in the air, fall towards the floor. Literally gravity
{
_targetVelocity.Y -= FallAcceleration * (float)delta;
}
Expand All @@ -221,11 +227,11 @@ fall speed separately. Be sure to go back one tab so the lines are inside the
}

The ``CharacterBody3D.is_on_floor()`` function returns ``true`` if the body collided with the floor in this frame. That's why
we apply gravity to the ``Player`` only while it is in the air.
we apply gravity to the ``Player`` only while it is in the air and reset the vertical velocity otherwise.

For the vertical velocity, we subtract the fall acceleration multiplied by the
delta time every frame.
We subtract the fall acceleration multiplied by the delta time every frame.
This line of code will cause our character to fall in every frame, as long as it is not on or colliding with the floor.
If we are colliding with the floor, we instead reset the vertical component of the velocity.

The physics engine can only detect interactions with walls, the floor, or other
bodies during a given frame if movement and collisions happen. We will use this
Expand Down Expand Up @@ -282,7 +288,9 @@ Here is the complete ``player.gd`` code for reference.
target_velocity.z = direction.z * speed

# Vertical Velocity
if not is_on_floor(): # If in the air, fall towards the floor. Literally gravity
if is_on_floor(): # Stop falling
target_velocity.y = 0
else: # If in the air, fall towards the floor. Literally gravity
target_velocity.y = target_velocity.y - (fall_acceleration * delta)

# Moving the Character
Expand Down Expand Up @@ -337,7 +345,11 @@ Here is the complete ``player.gd`` code for reference.
_targetVelocity.Z = direction.Z * Speed;

// Vertical velocity
if (!IsOnFloor()) // If in the air, fall towards the floor. Literally gravity
if (IsOnFloor()) // Stop falling
{
_targetVelocity.Y = 0.0f;
}
else // If in the air, fall towards the floor. Literally gravity
{
_targetVelocity.Y -= FallAcceleration * (float)delta;
}
Expand Down