Rendering Pipeline¶

The rendering pipeline in Evoker Engine is built on top of Vulkan and provides a modern, high-performance rendering system for both 2D and 3D graphics.

Overview¶

The rendering pipeline includes:

Render Passes: Define rendering stages
Graphics Pipelines: Shader programs and rendering state
Command Buffers: Recording draw commands
Frame Synchronization: Managing frame presentation
Resource Management: Buffers, textures, and samplers

Current Implementation Status¶

✅ Implemented¶

Vulkan context and device initialization
Swapchain creation and management
Window resize handling
Cross-platform surface creation

🚧 In Development¶

Graphics pipeline creation
Render pass configuration
Command buffer recording
Shader compilation (GLSL to SPIR-V)
Vertex and index buffer management
Texture loading and binding

📋 Planned¶

Deferred rendering
Shadow mapping
Post-processing effects
Particle systems rendering
Skeletal animation
Level of Detail (LOD) system

Rendering Architecture¶

┌─────────────────────────────────────┐
│         Application Layer           │
├─────────────────────────────────────┤
│         Scene Management            │
│    (Entities, Components, Camera)   │
├─────────────────────────────────────┤
│       Rendering Interface           │
│    (Draw calls, material binding)   │
├─────────────────────────────────────┤
│      Graphics Pipeline              │
│  (Shaders, buffers, render passes)  │
├─────────────────────────────────────┤
│      Vulkan Abstraction             │
│  (Device, queues, command buffers)  │
├─────────────────────────────────────┤
│         Vulkan API                  │
└─────────────────────────────────────┘

Planned Pipeline Stages¶

1. Geometry Stage¶

// Load and manage meshes (planned)
var mesh = MeshLoader.LoadFromFile("models/character.obj");
var vertexBuffer = CreateVertexBuffer(mesh.Vertices);
var indexBuffer = CreateIndexBuffer(mesh.Indices);

2. Vertex Stage¶

// Vertex shader example
#version 450

layout(location = 0) in vec3 inPosition;
layout(location = 1) in vec3 inNormal;
layout(location = 2) in vec2 inTexCoord;

layout(location = 0) out vec3 fragPosition;
layout(location = 1) out vec3 fragNormal;
layout(location = 2) out vec2 fragTexCoord;

layout(set = 0, binding = 0) uniform UniformBufferObject {
    mat4 model;
    mat4 view;
    mat4 projection;
} ubo;

void main() {
    gl_Position = ubo.projection * ubo.view * ubo.model * vec4(inPosition, 1.0);
    fragPosition = vec3(ubo.model * vec4(inPosition, 1.0));
    fragNormal = mat3(transpose(inverse(ubo.model))) * inNormal;
    fragTexCoord = inTexCoord;
}

3. Fragment Stage¶

// Fragment shader example
#version 450

layout(location = 0) in vec3 fragPosition;
layout(location = 1) in vec3 fragNormal;
layout(location = 2) in vec2 fragTexCoord;

layout(location = 0) out vec4 outColor;

layout(set = 1, binding = 0) uniform sampler2D texSampler;

void main() {
    vec3 lightDir = normalize(vec3(1.0, 1.0, 1.0));
    float diff = max(dot(fragNormal, lightDir), 0.0);

    vec3 texColor = texture(texSampler, fragTexCoord).rgb;
    vec3 result = diff * texColor;

    outColor = vec4(result, 1.0);
}

Forward Rendering (Current)¶

The engine currently implements forward rendering:

For each object:
    1. Set pipeline state
    2. Bind resources (textures, uniforms)
    3. Draw geometry

Advantages: - Simple implementation - Good for simpler scenes - Transparent objects rendered easily

Disadvantages: - Performance degrades with many lights - Lighting calculated multiple times per pixel

Deferred Rendering (Planned)¶

Planned deferred rendering pipeline:

Pass 1 - G-Buffer:
    Render all geometry to multiple render targets:
    - Position
    - Normal
    - Albedo/Color
    - Material properties

Pass 2 - Lighting:
    For each light:
        Calculate lighting using G-Buffer data

Pass 3 - Forward Pass:
    Render transparent objects
    Apply post-processing

Advantages: - Efficient with many lights - Decouples geometry from lighting - Enables advanced effects

Render Pass Example (Planned)¶

public class GameRenderer
{
    private RenderPass _mainRenderPass;
    private Pipeline _geometryPipeline;
    private Pipeline _lightingPipeline;

    public void Initialize()
    {
        // Create render passes
        _mainRenderPass = CreateMainRenderPass();

        // Create pipelines
        _geometryPipeline = CreateGeometryPipeline();
        _lightingPipeline = CreateLightingPipeline();
    }

    public void Render(Scene scene, Camera camera)
    {
        var commandBuffer = BeginFrame();

        // Begin render pass
        commandBuffer.BeginRenderPass(_mainRenderPass);

        // Render opaque geometry
        RenderOpaqueGeometry(commandBuffer, scene, camera);

        // Render transparent geometry
        RenderTransparentGeometry(commandBuffer, scene, camera);

        // End render pass
        commandBuffer.EndRenderPass();

        // Present frame
        EndFrame(commandBuffer);
    }

    private void RenderOpaqueGeometry(CommandBuffer cmd, Scene scene, Camera camera)
    {
        cmd.BindPipeline(_geometryPipeline);

        // Update camera uniform
        UpdateCameraUniform(camera);

        // Render all opaque meshes
        var renderers = scene.Registry.GetAllComponents<MeshRendererComponent>();
        foreach (var renderer in renderers)
        {
            var transform = scene.Registry.GetComponent<TransformComponent>(renderer.Entity);
            if (transform != null)
            {
                // Update model matrix
                UpdateModelUniform(transform);

                // Draw mesh
                DrawMesh(cmd, renderer.MeshId);
            }
        }
    }

    private void RenderTransparentGeometry(CommandBuffer cmd, Scene scene, Camera camera)
    {
        // Sort transparent objects back-to-front
        // Render with alpha blending
    }
}

Resource Management¶

Vertex Buffers (Planned)¶

// Create vertex buffer
var vertices = new Vertex[]
{
    new Vertex { Position = new Vector3(-0.5f, -0.5f, 0), Color = new Vector3(1, 0, 0) },
    new Vertex { Position = new Vector3(0.5f, -0.5f, 0), Color = new Vector3(0, 1, 0) },
    new Vertex { Position = new Vector3(0, 0.5f, 0), Color = new Vector3(0, 0, 1) }
};

var vertexBuffer = CreateVertexBuffer(vertices);

Uniform Buffers (Planned)¶

// Camera uniform
struct CameraUniform
{
    public Matrix4x4 View;
    public Matrix4x4 Projection;
    public Vector3 Position;
}

var cameraBuffer = CreateUniformBuffer<CameraUniform>();
UpdateUniformBuffer(cameraBuffer, cameraData);

Textures (Planned)¶

// Load texture
var texture = TextureLoader.LoadFromFile("textures/albedo.png");
var sampler = CreateTextureSampler(FilterMode.Linear, WrapMode.Repeat);

Performance Considerations¶

Batching¶

// Batch similar draw calls (planned)
public class DrawBatch
{
    public Material Material { get; set; }
    public List<MeshInstance> Instances { get; set; }
}

// Draw all instances with same material in one call
foreach (var batch in batches)
{
    BindMaterial(batch.Material);
    DrawInstanced(batch.Instances);
}

Frustum Culling¶

// Cull objects outside camera view (planned)
public bool IsInFrustum(BoundingBox bounds, Camera camera)
{
    var frustum = camera.GetFrustum();
    return frustum.Intersects(bounds);
}

// Only render visible objects
foreach (var renderer in renderers)
{
    if (IsInFrustum(renderer.Bounds, camera))
    {
        RenderObject(renderer);
    }
}

Level of Detail (LOD)¶

// Use different mesh detail based on distance (planned)
public class LODGroup
{
    public Mesh HighDetail { get; set; }  // < 10 units
    public Mesh MediumDetail { get; set; }  // 10-50 units
    public Mesh LowDetail { get; set; }  // > 50 units
}

var distance = Vector3.Distance(objectPos, cameraPos);
var mesh = distance < 10 ? lod.HighDetail :
           distance < 50 ? lod.MediumDetail :
           lod.LowDetail;

Best Practices¶

✅ Do's¶

Batch draw calls with the same material
Use frustum culling for large scenes
Implement LOD for distant objects
Sort transparent objects back-to-front
Use texture atlases to reduce draw calls
Pool and reuse command buffers

❌ Don'ts¶

Don't rebind resources unnecessarily
Don't render objects outside the view frustum
Don't use unique materials for every object
Don't allocate resources every frame
Don't perform CPU-side calculations that could be done in shaders

Future Features¶

Planned Additions¶

Compute Shaders: GPU-accelerated computations
Ray Tracing: Real-time ray traced reflections and shadows (RTX)
Mesh Shaders: Advanced geometry processing
Variable Rate Shading: Performance optimization
HDR Rendering: High dynamic range output
Temporal Anti-Aliasing: Advanced anti-aliasing