# Minosoft rendering system

(I'll extend this document when I find time or motivation)

## General

Minosoft uses OpenGL 3.3+ for rendering. The whole rendering system is abstract, so a port to opengl es or vulkan should be *easily* possible.

Everything is working in shaders (written in glsl), some things even have multiple shaders.

## Integration

The whole render system is like a separate module. There are almost no references to it, only in `PlayConnection.kt`. Everything is event driven (or abstract).

## Loading

The whole render system gets loaded, as soon as you tell eros to connect to a server. Everything gets downloaded then and the render subsystem loads.

## Textures

### Static textures

Textures that don't get modified anymore (like block textures or items).
The textures are stored in 5 dimensional way (2d for x and y coordinates, 1d for the texture index (aka. what texture), 1d for the resolution (like `16x16` or `32x32`) and the last dimension for mipmaps).
Every vertex can have an additional animation id, that is done via a uniform buffer.

### Dynamic textures

Used for e.g. skins.

## (Performance) optimizations

- Chunking (like minecraft does it)

### Culling

Minosoft is using multiple culling techniques that all work together to archive the best performance.

- Face culling (`glCullFace`; gpu only)
- Neighbour culling (hide unseen faces; cpu only)
- Frustum culling (hide what is behind you/not in the camera perspective)
- View distance clipping (maximum render distance)
- Occlusion culling (hide chunks that are not visible (e.g. caves from the surface); cpu and gpu)
- ~~Greedy meshing (combining multiple blocks into a single face)~~ not really worked and even got removed

## Renderers

Even the render system is dynamic. There are a lot of so-called renderers (e.g. `WorldRenderer`, `ParticleRenderer` or `GUIRenderer`) that get registered dynamically while loading. So extending the system is pretty easy and moddable.

## Render phases

There are multiple render phases. 3D breaks when it comes to transparency, or it gets optimized when drawing in a specific order (gpu occlusion culling). For example a render phase is `OPAQUE` or `TRANSLUCENT`.
It basically lets all renderers draw their opaque objects first and then draw transparent ones.

## Transparency

100% transparent pixels get `discard`ed in the shader. That makes no problem. Translucency is getting hacked with `glDepthMask(false)`. It is not the best solution but a good workaround. Some face sorting is needed in the future.

## Lighting

All lighting data is received from the server and not reliable. A light engine is needed in the future.

The lighting on the render side is done via a lightmap, basically another uniform buffer.
