Extending the collision system

[nightm4re94]

^{This post has been migrated automatically from the old LITIENGINE forum (2018 - 2022).
Posted: 2020-07-21 15:44:28
User: Sinus [] (age: 832 days 🙌; posts: 1)}
Hello everyone,
i started to create a game some days ago. It is going to be a hobby project for the next two or three month. I saw the LITIENGINE, looked into it, liked it and decided to choose it for the game.
As a first intermediate step the game should be basicially a top-down car driving simulation. I implemented the player-controlled car as a subclass of Creature with a subclass of KeyboardEntityController for controlling the steering and speed. As the car can rotate freely, and not just 0°/90°/180°/270°, i used a single image for all directions and rotated that image by overriding "getAffineTransform()" in my subclass of EntityAnimationController:
@Override public AffineTransform getAffineTransform() { AffineTransform transform = new AffineTransform(super.getAffineTransform()); transform.rotate(Math.toRadians(-this.getEntity().getAngle()), this.getEntity().getWidth() / 2, this.getEntity().getHeight() / 2); return transform; }
This works fine and i can now drive around with the car, but i realised soon, that the implementation of collision will be more tricky.
As i understand it, at the moment the LITIENGINE supports non-rotated rectangular collision boxes, because the return type of ICollisionEntity's getCollisionBox() is Rectangle2D. This is not sufficient for my application so i plan to implement any changes to the collision system i require. Because the car is nearly rectangular, the minimum requirement is the rotation of the rectangular collision box with respect to the entity's angle. I would prefere an implementation with arbitrary collision shapes, similar to the hit box of CombatEntitiy.
Is my understanding of the engine's current capabilities correct and my (planned) implementation resonable?
Is an extention of the current collision system to support rotated rectangular collision boxes or even arbitrary collision shapes of interest for the LITIENGINE? In case it is, i would try to implement that in a hopefully useful way and commit my work to the eninge. Otherwise i will probably implement it in a way it just works for me.
How would an (useful) implementation look like? I believe i would have to replace "public Rectangle2D getCollisionBox()" with something like "public Shape getCollisionShape()" in the ICollisionEntity interface and make corresponding changes in the PhysicsEngine to support arbitrary shapes. This feels like a big change for a rare use-case?
I would like to hear your ideas,
Sinus

[nightm4re94]

^{This post has been migrated automatically from the old LITIENGINE forum (2018 - 2022).
Posted: 2020-07-21 19:55:04
User: nightm4re [Admin 👑, Mod 🔧] (age: 1567 days 🔥; posts: 185)}
Lovely to hear how you've already managed to dig into some advanced features. Your understanding of the requirements is correct - basically, we would have to handle shapes instead of Rectangles. However, generic awt shapes are computationally a lot heavier than Rectangles in terms of collision and intersection detection. This would drastically affect our framerate. However, feel free to experiment!

[nightm4re94]

^{This post has been migrated automatically from the old LITIENGINE forum (2018 - 2022).
Posted: 2020-07-23 14:09:40
User: nightm4re [Admin 👑, Mod 🔧] (age: 1567 days 🔥; posts: 185)}
this thread gives a few interesting thoughts on awt shape intersection. LITIENGINE currently resolves collision similarly to what is shown below:
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[nightm4re94]

^{This post has been migrated automatically from the old LITIENGINE forum (2018 - 2022).
Posted: 2020-09-01 14:55:25
User: nightm4re [Admin 👑, Mod 🔧] (age: 1567 days 🔥; posts: 185)}
I have been thinking about this topic again and I think awt shapes would not be the right way to go. Much like dyn4j, a very active project of a dynamic java collision engine, we would have to come up with our own efficient shape implementation to make this work properly.
By the way, dyn4j has recently hit a new major version and it's miraculous! I just checked out their sandbox examples and now I'm hooked :D