Renderer

Renderer interface for drawing a scene with a given camera.

The renderer owns GPU state and draw logic for rendering a Scene with a specified Camera. It is typically constructed and driven by the Application runtime but can also be used directly in manual setups.

This class defines the rendering interface only. The actual rendering implementation is provided by a backend, and multiple backends (for example, OpenGL or Vulkan) may exist behind this interface.

vglx::Renderer renderer({
  .framebuffer_width = window.FramebufferWidth(),
  .framebuffer_height = window.FramebufferHeight(),
  .clear_color = 0x444444
});

auto ok = renderer.Initialize();
if (!ok) {
  HandleError(ok.error());
}

The renderer assumes a valid graphics context is current on the calling thread. When the window is resized, call SetViewport to adjust the render area (or recreate with new parameters if you manage your own framebuffers).

Construction

Constructors

Renderer()

Constructs a renderer.

GPU resources are not created until Initialize is called.

Renderer::Renderer(const Renderer::Parameters& params);

Parameter	Description
params	Initialization parameters for constructing the renderer.

Types

Renderer::Parameters struct

Parameters for constructing a Renderer object.

Parameter	Description
framebuffer_width int	Current framebuffer width in pixels.
framebuffer_height int	Current framebuffer height in pixels.
sample_count int	Antialiasing level (e.g., 4x MSAA).
clear_color Color	Clear color used at the start of a frame.

Functions

CreateTextureFromRenderTarget() std::shared_ptr<Texture2D>

Returns the color texture associated with an offscreen render target.

When rendering to a RenderTarget the renderer attaches a 2D texture that receives the color output of the frame. This method retrieves that texture so it can be bound in subsequent passes.

The returned pointer is shared with the render target and remains valid as long as both the renderer and the render target are alive. If target is null or does not have an associated color texture an empty pointer is returned.

std::shared_ptr<Texture2D> Renderer::CreateTextureFromRenderTarget(RenderTarget* target);

Parameter	Description
target	Render target whose color texture should be retrieved.

Initialize() std::expected<void, std::string>

Initializes GPU state and allocates required resources.

std::expected<void, std::string> Renderer::Initialize();

operator=() Renderer&

Renderer& Renderer::operator=(Renderer& &) noexcept;

Parameter	Description

Render() void

Renders the given scene from the specified camera.

The scene is expected to be in a consistent state for rendering. If you are using the runtime path, this is handled automatically. In direct initialization flows, call tye per-frame update routine Scene::Advance prior to rendering.

void Renderer::Render(Scene* scene, Camera* camera, RenderTarget* target=nullptr);

Parameter	Description
scene	Pointer to the scene to render.
camera	Pointer to the active camera.
target

RenderedObjectsPerFrame() size_t

Returns the number of renderable objects drawn in the last frame.

Intended for statistics overlays and debugging.

size_t Renderer::RenderedObjectsPerFrame() const;

SetClearColor() void

Sets the clear color for subsequent frames.

The color is applied at the start of each frame when the framebuffer is cleared. Typically used to define the background color of the rendering surface.

void Renderer::SetClearColor(const Color& color);

Parameter	Description
color	Clear color in RGB format.

SetViewport() void

Sets the active viewport rectangle in pixels.

Adjusts the area of the framebuffer that subsequent draw calls will target. This should be called whenever the window or framebuffer size changes, or when rendering to a specific sub-region of the target surface.

When using the runtime-managed rendering path, the viewport is updated automatically. In manual initialization flows, you are responsible for calling this method whenever the framebuffer dimensions change.

void Renderer::SetViewport(int x, int y, int width, int height);

Parameter	Description
x	Left pixel of the viewport.
y	Bottom pixel of the viewport.
width	Viewport width in pixels.
height	Viewport height in pixels.