Taking a detour to play around with some things

Yes, I decided that I want to build a game. Yes, I also decided to build some small games first before embarking on the main idea I have. And yes, I also also will take some detours just for fun and/or experimentation along the way!

The first such detour was playing around with moving the camera around and some quaternion math.

The Detour

Wheeeeeeee.

The above clip is only the camera rotating (and the “player” staying in the same position with no rotations applied).

Another approach I tried was fixing the camear over the player’s shoulder and rotating the player instead. The code for this option feels like there should be a better way to implement it, but this is the first thing I got to have the behaviour I wanted: rotate the player (with its camera) by 1rad per tick, and move forward/backward along that rotated angle by 0.1units per tick.

if let Some(player) = context.scene.graph[self.player].cast_mut::<Pivot>() {
    let mut angle = 0.0f32;
    if self.move_left {
        angle = 1.0f32.to_radians();
    } else if self.move_right {
        angle = -1.0f32.to_radians();
    }
    let rotation = UnitQuaternion::from_axis_angle(&Vector3::y_axis(), angle);
    let trans = player.local_transform_mut();
    trans.set_rotation(trans.rotation().deref() * rotation);

    let mut pos_update = Vector3::zero();
    if self.move_up {
        pos_update.z = 0.10f32;
    } else if self.move_down {
        pos_update.z = -0.10f32;
    }
    pos_update = trans.rotation().deref() * pos_update;
    Log::info(format!("Moving player by {:?}", pos_update));
    trans.set_position(trans.position().deref() + pos_update);
}

… I also added a camera bobbing based on the elapsed time (code not shown, but it’s just height+sin(t)).

The Real Game

I’ve also been spending some time fleshing out my main ideas. I’m used to doing design docs in my profession life as a software engineer, so I don’t know why I was surprised to learn that game devs write a Game Design Doc (GDD) before diving into a project (which are basically the same thing). It make so much sense! I was already making copious notes, so this is just a sort of formalisation.

For some fun reading, here are two GDDs from old games:

• GTA 1 (aka Race’n’Chase)
• Diablo 1