Mjolnir Engine

Mjolnir is a minimalistic game engine to help people enjoy game programming

Get Started

To use Mjolnir in your odin code, run make shader to compile shaders to SPIR-V and then copy mjolnir directory to your project and start using mjolnir API. See examples for common use cases.

Notable features

• Physically-Based Rendering
• Camera, Light, Shadow
• Skinning, Animation
• GLTF
• Post-processing
• Billboard, Sprite
• Tween, Spline
• Particles Simulation
• Render to texture
• Physics
• Recast/Detour
• Inverse Kinematics
• HUD, text

And more in development

• Procedural Animation (Tail, Spider Leg)
• Animation Layering

Build Commands

# Build and run in release mode
make run
# Build and run in debug mode and vulkan validation
make debug
# Build only (release mode)
make build
# Build only (debug mode)
make build-debug
# Build all shaders
make shader
# Run all tests
odin test . --all-packages
# run a single test called "test_name" inside "module_name"
odin test . --all-packages -define:ODIN_TEST_NAMES=module_name.test_name

Architecture Overview

Core Engine Structure

The engine is organized 3 layers with clear responsibility boundaries. Systems on the same level must not depends on each other directly or indirectly. For example Render module and World module must be able to independently developed by 2 different teams without much communication.

Lower Level Systems:

• GPU: mjolnir/gpu/ - Vulkan context, memory/texture/mesh management, swapchain, pipeline helpers
• Containers: mjolnir/containers/ - Generic data structures (handle pools, slab allocators)
• Geometry: mjolnir/geometry/ - Camera, transforms, primitives, BVH, octree, AABB, frustum
• Animation: mjolnir/animation/ - Skeletal animation support

Higher Level Systems:

• Render: mjolnir/render/ - Frame graph-driven render pipeline
  • Geometry Renderer (PBR, opaque)
  • Lighting: Ambient + per-type Direct Light (point/spot/directional)
  • Shadow Renderer (spot/directional/sphere cubemap)
  • GPU Occlusion Culling + Depth Pyramid
  • Transparency Renderer
  • Particle Renderer (GPU compute)
  • Post-process Renderer
  • UI Renderer
  • render/graph/ — declarative frame graph (resource aliasing, barrier inference, pass scheduling)
• World: mjolnir/world/ - Scene graph, GLTF/OBJ loading
• Physics: mjolnir/physics/ - Rigid body dynamics, collision detection
• Navigation: mjolnir/navigation/ - Recast + Detour

Engine System:

• Engine: mjolnir/engine.odin - Final integration point, user-facing API

For more information, see usage (WIP)

Development Notes

GPU Resource Management

• Uses custom slab allocators to sub-allocate vertices/indices/bone matrices
• Bindless: All GPU resources managed in array-based system. Draw commands send resource IDs to index into GPU arrays instead of raw data

Shader Development

• Shaders are in mjolnir/shader/ organized by render pass
• Use make shader to rebuild all shaders. It’s fast and incremental, you need not to build individual shader
• Compute shaders include:
  • Particle system: compute.comp, compact.comp, emitter.comp
  • Culling systems: culling.comp for visibility

Debugging Tips

• To debug visual issues, build with FRAME_LIMIT set to something like 10, then check the log
• Collect screenshot with make capture
• To slow down the engine to examine render logs, build with RENDER_FPS set to low value like 4 or 2

Build Flags

• REQUIRE_GEOMETRY_SHADER: Compile with geometry shader support (required for spherical shadow mapping)
• USE_PARALLEL_UPDATE: Enable dedicated update thread for parallel scene updates
• FRAME_LIMIT: limit renderer to only render a few frames
• RENDER_FPS: limit renderer FPS
• UPDATE_FPS: limit logic update FPS