Hello dear graphics enjoyers! In this blogpost, my friend Murat and I will show you how to build & run the project, what user controls we implemented and some implementation details. Hope you have good time playing Blade Master!<\/p>\n\n\n\n
How to run:<\/h2>\n\n\n\n
Create a project directory and unzip blade-master.zip<\/code> there.<\/p>\n\n\n\n
On inek machines, execute the following commands in the project directory:<\/p>\n\n\n\n
On other ubuntu machines, replace the contents of Makefile<\/code> with the contents of makefile_for_other_ubuntu_machines.txt<\/code> and then run the following commands:<\/p>\n\n\n\n
The difference is that we’ve provided binaries for inek machines but they may not necessarily work on other ubuntu machines.<\/p>\n\n\n\n
All controls:<\/h2>\n\n\n\n
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Enter<\/strong> – start the game<\/li>\n\n\n\n
Space<\/strong> – stop the physics<\/li>\n\n\n\n
M<\/strong> – switch between modes<\/li>\n\n\n\n
A\/D<\/strong> – control the horizontal position of the sword<\/li>\n\n\n\n
Mouse X\/Y<\/strong> – control the sword’s roll and vertical position, respectively<\/li>\n<\/ul>\n\n\n\n
More on Blade Control and Animation<\/h2>\n\n\n\n
A slice is only as satisfying as its animation. We implemented an animation system to give the sword a sense of weight and motion.<\/p>\n\n\n\n
Player Control:<\/strong> The control scheme is simple and direct. The player’s camera is fixed, looking straight ahead.<\/p>\n\n\n\n
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A\/D Keys:<\/strong> Control the horizontal position of the sword.<\/li>\n\n\n\n
Mouse X\/Y:<\/strong> Control the sword’s roll and vertical position, respectively.<\/li>\n<\/ul>\n\n\n\n
The Slice Animation:<\/strong> When the left mouse button is clicked, we trigger a pre-scripted animation that takes over the sword’s transform for a fraction of a second. We found that a simple linear thrust felt robotic. To make it look natural, we combined three motions, all driven by a smooth sine wave for easing:<\/p>\n\n\n\n\n
Forward Thrust:<\/strong> The sword lunges forward into the scene.<\/li>\n\n\n\n
Downward Dip:<\/strong> It follows a slight arc, dipping down as it thrusts, simulating the motion of a real arm.<\/li>\n\n\n\n
Pivoted Pitch:<\/strong> This was the most crucial detail. Instead of the whole sword rotating, we made the blade “lean forward” by rotating it around a pivot point located at the handle. This was achieved by finding the pivot’s coordinate in the model’s local space and applying a Translate -> Rotate -> Inverse Translate<\/code> transformation sequence. This gives the impression that the handle stays stable while the blade does the cutting work.<\/li>\n<\/ol>\n\n\n\n
The actual slice logic is triggered at the very peak of this animation, ensuring the cut happens at the moment of maximum extension.<\/p>\n\n\n\n
Adding the juice<\/h2>\n\n\n\n
CPU Logic:<\/strong> The CPU is responsible for the particle physics. Each frame, it loops through active particles, applies gravity to their velocity, updates their position, and decreases their lifetime.<\/p>\n\n\n\n
GPU Rendering:<\/strong> We upload the position, color, and size of every active particle to a buffer in a single batch. Then we call instanced rendering (glDrawArraysInstanced<\/code>) to draw all active particles efficiently in one call, with each instance using its own position, color, and size.<\/p>\n\n\n\n
The number of particles at each moment is not higher than 15000. Therefore, we decided to not use compute shaders and stick to a simpler solution.<\/p>\n\n\n\n
Basic Physics<\/h2>\n\n\n\n
Once an object is sliced into two new pieces, they shouldn’t just hang in the air. We needed a physics system to make them react realistically. We built a simple but effective system from the ground up.<\/p>\n\n\n\n
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RigidBody Component:<\/strong> We created a RigidBody<\/code> class that can be attached to any GameObject<\/code>. It stores physical properties like mass, velocity (linear and angular), and accumulators for force and torque.<\/li>\n\n\n\n
PhysicsEngine:<\/strong> This central system manages a list of all active rigid bodies. In its update(deltaTime)<\/code> loop, it performs two key steps:\n\n
It applies a constant downward gravitational force to every object.<\/li>\n\n\n\n
It updates each object’s position based on its velocity, and its rotation based on its angular velocity.<\/li>\n<\/ol>\n<\/li>\n\n\n\n
Applying Slice Forces:<\/strong> The most important part was making the cut feel impactful. When the SliceManager<\/code> successfully creates two new pieces, it immediately applies two types of forces to their new RigidBody<\/code> components:\n\n
Separation Force:<\/strong> A force is applied along the plane’s normal, pushing the two halves directly away from each other.<\/li>\n\n\n\n
Follow-Through Force:<\/strong> A larger force is applied in the direction of the sword’s slice (the blade’s forward-facing “blue axis”). This gives the pieces momentum and makes it look like the sword’s energy was transferred to them.<\/li>\n\n\n\n
Torque:<\/strong> A small, random torque is also applied to each piece to give them a natural-looking tumble as they fly apart.<\/li>\n<\/ol>\n<\/li>\n<\/ul>\n\n\n\n
Gameplay Structure – Game Modes and Spawning<\/h2>\n\n\n\n
An enum<\/code> was introduced to manage the current state (FRUIT_MODE<\/code> or DUMMY_MODE<\/code>). Pressing the ‘M’ key now switches between these modes, cleans up old objects and prepares the new environment.<\/p>\n\n\n\n
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Fruit Mode:<\/strong> every 5 seconds, a fruit (randomly chosen between watermelon, apple and banana) is thrown into the scene.<\/li>\n\n\n\n
Dummy Mode:<\/strong> a static humanoid model in the centre of the scene.<\/li>\n<\/ul>\n\n\n\n
Also, independent from the game mode, you can stop the physics of the objects (so that they stay static) and try to slice a fruit\/dummy in several directions at once.<\/p>\n\n\n\n
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