Strange boost to velocity when applying upwards velocity to character controller while it is colliding on a "ramp"-like shape

[Mahmoud1205]

Here is a video of this problem to make the title clear https://github.com/user-attachments/assets/a8e26d5c-e9b5-4f59-a91a-db04342f117d
And for context

• Upwards velocity (for jumping) was applied to the character controller when the strange velocity boost happened, but the velocity should have only increased by 4.
• The shape for the character controller is a capsule, but the same problem happens when it is a box.
• The whole physics body for the city scene in the video is perfectly matching with the actual 3D model, and below is the code used to add it into the physics system

JPH::StaticCompoundShapeSettings meshSceneShapeSettings;
for (Mesh& mesh : model->meshes) {
    JPH::TriangleList joltTriangles;

    for (size_t i = 0; i + 2 < mesh.vertices.size(); i += 3) {
        joltTriangles.emplace_back(
            types::GlmToJph(mesh.vertices[i].Position),
            types::GlmToJph(mesh.vertices[i + 1].Position),
            types::GlmToJph(mesh.vertices[i + 2].Position)
        );
    }

    meshSceneShapeSettings.AddShape(JPH::Vec3::sZero(), JPH::Quat::sIdentity(), new JPH::MeshShapeSettings(joltTriangles));
}

return JPH::BodyCreationSettings(
    meshSceneShapeSettings.Create().Get(),
    types::GlmToJph(position), JPH::Quat::sIdentity(),
    JPH::EMotionType::Static, Layers::NON_MOVING
); // this return value is used by the application to add the body into the physics world

For more context, below is the code used, 99% of it is from the character controller sample and the below code snippet is ran every frame before the physics system and character update calls.

Character::EGroundState ground_state = pCharacter->GetGroundState();
if (ground_state == Character::EGroundState::OnSteepGround
    || ground_state == Character::EGroundState::NotSupported) {
    Vec3 normal = pCharacter->GetGroundNormal();
    normal.SetY(0.0f);
    f32 dot = normal.Dot(movementDirection);
    if (dot < 0.0f)
        movementDirection -= (dot * normal) / normal.LengthSq();
}

if (pCharacter->IsSupported()) {
    if (glfwGetKey(window, GLFW_KEY_LEFT_CONTROL) == GLFW_PRESS) {
        crouchingShape.AddRef();
        pCharacter->SetShape(&crouchingShape, FLT_MAX);
        standingShape.Release();

    }
    if (glfwGetKey(window, GLFW_KEY_LEFT_CONTROL) == GLFW_RELEASE) {
        standingShape.AddRef();
        pCharacter->SetShape(&standingShape, FLT_MAX);
        crouchingShape.Release();
    }

    Vec3 current_velocity = pCharacter->GetLinearVelocity();
    Vec3 desired_velocity = 6.0f * movementDirection;
    if (!desired_velocity.IsNearZero() || current_velocity.GetY() < 0.0f || !pCharacter->IsSupported())
        desired_velocity.SetY(current_velocity.GetY());
    Vec3 new_velocity = 0.75f * current_velocity + 0.25f * desired_velocity;

    if (glfwGetKey(window, GLFW_KEY_SPACE) == GLFW_PRESS && ground_state == Character::EGroundState::OnGround)
        new_velocity += Vec3(0, 4.0f, 0);

    new_velocity *= speedMultiplier;

    pCharacter->SetLinearVelocity(new_velocity);
}

Below is the code that sets up the character controller:

CharacterSettings character_settings;
character_settings.mMaxSlopeAngle = DegreesToRadians(45.0f);
character_settings.mLayer = Layers::MOVING;
character_settings.mShape = &standingShape;
character_settings.mFriction = 0.5f;
character_settings.mSupportingVolume = Plane(Vec3::sAxisY(), 1.0f);
Character character(&character_settings, types::GlmToJph(camera.pos), Quat::sIdentity(), 0, pPhysicsSystem);
character.AddToPhysicsSystem(EActivation::Activate);
pCharacter = &character;

[jrouwe]

I would strongly suggest to use the CharacterVirtual class instead of the Character class for player character movement.

[Mahmoud1205]

Oh so the issue is with the class I used? I will try CharacterVirtual and see if that works. 👌