fx2d-physics-engine

Raylib Renderer — FxRylbRenderer

The FxRylbRenderer class drives the real-time render loop using raylib and Dear ImGui (via rlImGui). Include via:

#include "Fx2D/Core.h"

---

Construction

FxRylbRenderer(FxScene& scene, int fps = 60, unsigned int scale = 100);

Parameter	Description
scene	Reference to a FxScene to render and simulate
fps	Target frames per second (default: 60)
scale	Pixels per physics unit (default: 100)

auto scene = FxYAML::buildScene("./Scene.yml");
FxRylbRenderer renderer(scene, 60, 100);

---

Running the Simulation

void run(bool play = true);

Starts the window and enters the render loop. Returns when the window is closed.

• If play = false, the simulation starts paused — useful for inspecting the initial state.

renderer.run();         // start playing immediately
renderer.run(false);    // start paused

---

Background

void set_background(const FxVec4ui8& color);       // solid RGBA color
void set_background(const std::string& filepath);  // image/texture file

renderer.set_background(FxVec4ui8(30, 30, 30, 255));   // dark grey
renderer.set_background("./assets/background.png");

---

Real-Time Factor

Controls how fast the simulation runs relative to wall-clock time.

void   set_real_time_factor(const double& rt_factor);
double get_real_time_factor() const;

• 1.0 — real time (default)
• 0.5 — half speed (slow motion)
• 2.0 — double speed

The value is clamped to [0.01, 10.0]; values outside this range are rejected with a warning and clamped.

renderer.set_real_time_factor(0.5);

---

ImGui Panel

While running, an ImGui overlay is displayed with:

• Play / Pause toggle
• Real-time factor control
• Simulation time

---

Fixed Timestep Integration

The renderer uses a fixed-timestep accumulator pattern:

1. Wall-clock elapsed time × real-time factor is accumulated each frame (raw frame time is capped at 0.2 s to prevent spiral-of-death).
2. Each drain step uses dt = clamp(m_fixed_dt × real_time_factor, 1e-3, 0.06) — so the effective step size scales with the real-time factor.
3. scene.step(dt) is called repeatedly until the accumulator is drained.

This decouples rendering frame rate from physics stability.

---

Texture Caching

Entity textures are loaded lazily on first draw and cached in an internal std::unordered_map<std::string, Texture2D>. Repeated references to the same file path incur no extra GPU uploads.

This site is open source. Improve this page.