Woden 2: Developing a modern 3D graphics engine in Smalltalk

Woden 2: Developing a modern 3D
graphics engine
Ronie Salgado
Universidad de Chile

Talk Outline: Foundations
● Why rewriting Woden?
– OpenGL problems
– Classic graphics API (OpenGL, Direct 3D except 12)
– “Modern” PC architecture
– Modern graphics API (Vulkan, Direct 3D 12 and Metal)
● Core abstraction layers
– AbstractGPU
– Dastrel (Data Stream Language)
– Slovim (Dastrel back-end)

Talk Outline: Woden 2 Layers
● WodenMath library
● Core
– Pipeline state cache
– Resource cache
– GPU resource management
● Basic layers
– Scene graph
– Woden athens backend
● Application layers
– Woden Roassal ported to Woden 2
– Woden 2 Game System
– Level Editor

Why rewriting Woden 2?
● OpenGL is very complex.
● OpenGL drivers are very buggy!
– NVIDIA does not follow strictly the spec.
– AMD is very strict.
– Intel, OS specific behavior.
● OpenGL uses a thread local context.
● OpenGL is old.
● GLSL compiler is in the driver.

Choose a desktop OpenGL version
OpenGL GLSL
1.2 Not available
2.0 1.10
2.1 1.20
3.0 1.30
3.1 1.40
3.2 1.50
3.3 3.30
4.0 4.00
4.1 4.10
4.2 4.30
4.4 4.40
4.5 4.50

Classic graphics API
Canvas
Shader
CPU
● Set shader, depth buffer state, ...
● Set texture.
● Set vertex buffer.
● Set index buffer.
● Draw indexed elements.
GPU/CP

“Modern” PC Architecture
CPU
RAM
IOMMU VRAM
GPU
CP

Modern Low-Level Graphics API
CPU
CPCommand List
Pipeline State Object
Vertex BufferUniform Buffer Index Buffer
GPUMMap
Texture
Descriptor Set
DMA

Core Abstraction Layers
● AbstractGPU
– https://github.com/ronsaldo/abstract-gpu
● Dastrel (Data Stream Language)
– http://smalltalkhub.com/#!/~ronsaldo/Dastrel
● Slovim (LLVM inspired typed SSA form)
– http://smalltalkhub.com/#!/~ronsaldo/Slovim

AbstractGPU
● Abstraction above Vulkan, Metal and D3D 12.
● API in C inspired by OpenCL
● Implementation in C++
● XML spec for headers and bindings
● Mostly tested with Vulkan in Linux

Dastrel (Data Stream Language)
● Intended to be a semi-visual language
● Statically typed
● Syntax inspired by C, Rust, Swift and Smalltalk
● Dumb type inference
● Compiler front-end written in Pharo
● Emits Slovim SSA form

Dastrel Sample
import environment;
import fragment;
import material;
import lighting;
code_block(fragment) main
{
let N = normalize(FragmentInput.normal);
let V = normalize(-FragmentInput.position);
color: FragmentOutput.color <== forwardLightingModel
albedo: FragmentInput.color*MaterialState.albedo
fresnel: MaterialState.fresnel smoothness: MaterialState.smoothness
normal: N viewVector: V position: FragmentInput.position;
}

Dastrel Sample
struct ObjectStateData
{
matrix: float4x4;
inverseMatrix: float4x4;
color: float4;
visible: int;
}
uniform(set=0, binding=0) ObjectState
{
objectState: ObjectStateData;
}
buffer(set=0, binding=1) InstanceObjectState
{
instanceStates: ObjectStateData[];
}
uniform(set=1, binding=0) CameraState
{
inverseViewMatrix: float4x4;
viewMatrix: float4x4;
projectionMatrix: float4x4;
currentTime: float;
}

Dastrel
function transformPositionToWorld(position: float3) -> float4
{
using ObjectState;
using InstanceObjectState;
using VertexStage;
return objectState.matrix *
(instanceStates[instanceID].matrix * float4(position, 1.0f));
}

Slovim
● LLVM style SSA form in Pharo.
● Strongly typed.
● Some very basics optimizations.
● Backends for:
– Spir-V (Done)
– GLSL (Done for Vulkan, missing OpenGL)
– C++ (For testing/experimenting)
– HLSL (To be done)
– Metal Shading Language (To be done)

WodenMath
● 3D graphics linear algebra
– Vectors (2D, 3D, 4D)
– Complex
– Quaternions
– Matrices (3x3 and 4x4)
● Same memory layout as C/GPU structures.
● Optimized using Lowcode extended bytecodes.

Woden 2 Core
● WTEngine is the main entry point
● WTPipelineStateCache loads PSO from JSON
● WTResourceCache for loading files
● WTApplication provides support for Morphic
and OSWindow
● They are wrappers above the AbstractGPU
object for supporting image session saving and
restoring

Woden 2 Core Utilities
● Custom bitmap font format
● Mesh building
● Some GPU structures matching shader
definitions
– WTObjectState
– WTCameraState
– WTLightSourceData
● 3D Model with skeletal animation loading

How do I get Woden 2
● https://github.com/ronsaldo/woden2
● newImage.sh builds dependencies and creates
a Woden 2 image
● Warning: this currently requires a modified VM
at https://github.com/ronsaldo/pharo-vm-
lowcode

Woden 2 Scene Graph
● Simpler than the scene graph in Woden 1.
● Only rendering a 3D scene (except for
WTSNodeModel)

3D Scene Rendering
● Standard forward rendering.
● WTSForwardSceneRenderer
● Command lists are reused if the scene topology
does ot change
● Shadows and a deferred shading renderer are
not yet implemented

Level Editor
● Bloc over Woden 2

Where is Woden 2?
● https://github.com/ronsaldo/woden2
● But, it requires a modified Pharo VM
● https://github.com/ronsaldo/pharo-vm-lowcode

Woden 2: Developing a modern 3D graphics engine in Smalltalk

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Woden 2: Developing a modern 3D graphics engine in Smalltalk