Update audio_amp_envelope.c

* add  audio_amp_envelope example

* Change 1.0f to env->sustainLevel in case the user
release the spacebar before attack state done

examples/audio/audio_amp_envelope.c

@@ -0,0 +1,238 @@
+/*******************************************************************************************
+*
+*   raylib [audio] example - amp envelope
+*
+*   Example complexity rating: [★☆☆☆] 1/4
+*
+*   Example originally created with raylib 6.0, last time updated with raylib 6.0
+*
+*   Example contributed by Arbinda Rizki Muhammad (@arbipink) and reviewed by Ramon Santamaria (@raysan5)
+*
+*   Example licensed under an unmodified zlib/libpng license, which is an OSI-certified,
+*   BSD-like license that allows static linking with closed source software
+*
+*   Copyright (c) 2026 Arbinda Rizki Muhammad (@arbipink)
+*
+********************************************************************************************/
+
+#include "raylib.h"
+
+#define RAYGUI_IMPLEMENTATION
+#include "raygui.h"
+
+#include <math.h>           // Required for: sinf()
+
+#define BUFFER_SIZE      4096
+#define SAMPLE_RATE     44100
+
+// Wave state
+typedef enum {
+    IDLE,
+    ATTACK,
+    DECAY,
+    SUSTAIN,
+    RELEASE
+} ADSRState;
+
+// Grouping all ADSR parameters and state into a struct
+typedef struct {
+    float attackTime;
+    float decayTime;
+    float sustainLevel;
+    float releaseTime;
+    float currentValue;
+    ADSRState state;
+} Envelope;
+
+//------------------------------------------------------------------------------------
+// Module Functions Declaration
+//------------------------------------------------------------------------------------
+static void FillAudioBuffer(int i, float *buffer, float envelopeValue, float *audioTime);
+static void UpdateEnvelope(Envelope *env);
+static void DrawADSRGraph(Envelope *env, Rectangle bounds);
+
+//------------------------------------------------------------------------------------
+// Program main entry point
+//------------------------------------------------------------------------------------
+int main(void)
+{
+    // Initialization
+    //--------------------------------------------------------------------------------------
+    const int screenWidth = 800;
+    const int screenHeight = 450;
+
+    InitWindow(screenWidth, screenHeight, "raylib [audio] example - amp envelope");
+
+    InitAudioDevice();
+
+    // Set the number of samples the stream will keep in memory at a time to BUFFER_SIZE
+    SetAudioStreamBufferSizeDefault(BUFFER_SIZE);
+    float buffer[BUFFER_SIZE] = { 0 };
+
+    // Init raw audio stream (sample rate: 44100, sample size: 32bit-float, channels: 1-mono)
+    AudioStream stream = LoadAudioStream(SAMPLE_RATE, 32, 1);
+
+    // Init Phase
+    float audioTime = 0.0f;
+
+    // Initialize the struct
+    Envelope env = {
+        .attackTime = 1.0f,
+        .decayTime = 1.0f,
+        .sustainLevel = 0.5f,
+        .releaseTime = 1.0f,
+        .currentValue = 0.0f,
+        .state = IDLE
+    };
+
+    SetTargetFPS(60);
+    //--------------------------------------------------------------------------------------
+
+    // Main game loop
+    while (!WindowShouldClose())
+    {
+        // Update
+        //----------------------------------------------------------------------------------
+        if (IsKeyPressed(KEY_SPACE)) env.state = ATTACK;
+
+        if (IsKeyReleased(KEY_SPACE) && (env.state != IDLE)) env.state = RELEASE;
+
+        if (IsAudioStreamProcessed(stream))
+        {
+            if ((env.state != IDLE) || (env.currentValue > 0.0f))
+            {
+                for (int i = 0; i < BUFFER_SIZE; i++)
+                {
+                    UpdateEnvelope(&env);
+                    FillAudioBuffer(i, buffer, env.currentValue, &audioTime);
+                }
+            }
+            else
+            {
+                // Clear buffer if silent to avoid looping noise
+                for (int i = 0; i < BUFFER_SIZE; i++) buffer[i] = 0;
+                audioTime = 0.0f;
+            }
+
+            UpdateAudioStream(stream, buffer, BUFFER_SIZE);
+        }
+
+        if (!IsAudioStreamPlaying(stream)) PlayAudioStream(stream);
+        //----------------------------------------------------------------------------------
+
+        // Draw
+        //----------------------------------------------------------------------------------
+        BeginDrawing();
+
+            ClearBackground(RAYWHITE);
+
+            GuiSliderBar((Rectangle){ 100, 60, 400, 30 }, "Attack (s)", TextFormat("%2.2fs", env.attackTime), &env.attackTime, 0.1f, 3.0f);
+            GuiSliderBar((Rectangle){ 100, 100, 400, 30 }, "Decay (s)", TextFormat("%2.2fs", env.decayTime), &env.decayTime, 0.1f, 3.0f);
+            GuiSliderBar((Rectangle){ 100, 140, 400, 30 }, "Sustain", TextFormat("%2.2f", env.sustainLevel), &env.sustainLevel, 0.0f, 1.0f);
+            GuiSliderBar((Rectangle){ 100, 180, 400, 30 }, "Release (s)", TextFormat("%2.2fs", env.releaseTime), &env.releaseTime, 0.1f, 3.0f);
+
+            DrawADSRGraph(&env, (Rectangle){ 100, 250, 400, 100 });
+
+            DrawCircleV((Vector2){ 520, 350 - (env.currentValue * 100) }, 5, MAROON);
+            DrawText(TextFormat("Current Gain: %2.2f", env.currentValue), 535, 345 - (env.currentValue * 100), 10, MAROON);
+
+            DrawText("Press SPACE to PLAY the sound!", 200, 400, 20, LIGHTGRAY);
+
+        EndDrawing();
+        //----------------------------------------------------------------------------------
+    }
+
+    // De-Initialization
+    //--------------------------------------------------------------------------------------
+    UnloadAudioStream(stream);
+    CloseAudioDevice();
+
+    CloseWindow();
+    //--------------------------------------------------------------------------------------
+
+    return 0;
+}
+
+//------------------------------------------------------------------------------------
+// Module Functions Definition
+//------------------------------------------------------------------------------------
+static void FillAudioBuffer(int i, float *buffer, float envelopeValue, float *audioTime)
+{
+    int frequency = 440;
+    buffer[i] = envelopeValue*sinf(2.0f*PI*frequency*(*audioTime));
+    *audioTime += (1.0f/SAMPLE_RATE);
+}
+
+static void UpdateEnvelope(Envelope *env)
+{
+    // Calculate the time delta for ONE sample (1/44100)
+    float sampleTime = 1.0f/SAMPLE_RATE;
+
+    switch(env->state)
+    {
+        case ATTACK:
+        {
+            env->currentValue += (1.0f/env->attackTime)*sampleTime;
+            if (env->currentValue >= 1.0f)
+            {
+                env->currentValue = 1.0f;
+                env->state = DECAY;
+            }
+
+        } break;
+        case DECAY:
+        {
+            env->currentValue -= ((1.0f - env->sustainLevel)/env->decayTime)*sampleTime;
+            if (env->currentValue <= env->sustainLevel)
+            {
+                env->currentValue = env->sustainLevel;
+                env->state = SUSTAIN;
+            }
+
+        } break;
+        case SUSTAIN:
+        {
+            env->currentValue = env->sustainLevel;
+
+        } break;
+        case RELEASE:
+        {
+            env->currentValue -= (env->sustainLevel/env->releaseTime)*sampleTime;
+            if (env->currentValue <= 0.001f) // Use a small threshold to avoid infinite tail
+            {
+                env->currentValue = 0.0f;
+                env->state = IDLE;
+            }
+
+        } break;
+        default: break;
+    }
+}
+
+static void DrawADSRGraph(Envelope *env, Rectangle bounds)
+{
+    DrawRectangleRec(bounds, Fade(LIGHTGRAY, 0.3f));
+    DrawRectangleLinesEx(bounds, 1, GRAY);
+
+    // Fixed visual width for sustain stage since it's an amplitude not a time value
+    float sustainWidth = 1.0f;
+
+    // Total time to visualize (sum of A, D, R + a padding for Sustain)
+    float totalTime = env->attackTime + env->decayTime + sustainWidth + env->releaseTime;
+
+    float scaleX = bounds.width/totalTime;
+    float scaleY = bounds.height;
+
+    Vector2 start = { bounds.x, bounds.y + bounds.height };
+    Vector2 peak = { start.x + (env->attackTime*scaleX), bounds.y };
+    Vector2 sustain = { peak.x + (env->decayTime*scaleX), bounds.y + (1.0f - env->sustainLevel)*scaleY };
+    Vector2 rel = { sustain.x + (sustainWidth*scaleX), sustain.y };
+    Vector2 end = { rel.x + (env->releaseTime*scaleX), bounds.y + bounds.height };
+
+    DrawLineV(start, peak, SKYBLUE);
+    DrawLineV(peak, sustain, BLUE);
+    DrawLineV(sustain, rel, DARKBLUE);
+    DrawLineV(rel, end, ORANGE);
+
+    DrawText("ADSR Visualizer", bounds.x, bounds.y - 20, 10, DARKGRAY);
+}