* Added Noise Cubic oscillator

- White noise with cubic interpolation

Author: kennethdmiller3

Wave.cpp

@@ -27,7 +27,8 @@ WaveEvaluate const wave_evaluate[WAVE_COUNT] =
 	OscillatorTriangle,		// WAVE_TRIANGLE,
 	OscillatorNoise,		// WAVE_NOISE,
 	OscillatorNoiseHold,	// WAVE_NOISE_HOLD
-	OscillatorNoiseSlope,	// WAVE_NOISE_SLOPE
+	OscillatorNoiseLinear,	// WAVE_NOISE_LINEAR
+	OscillatorNoiseCubic,	// WAVE_NOISE_CUBIC
 	OscillatorPoly,			// WAVE_POLY4,
 	OscillatorPoly,			// WAVE_POLY5,
 	OscillatorPoly,			// WAVE_PERIOD93,
@@ -47,7 +48,8 @@ char const * const wave_name[WAVE_COUNT] =
 	"Triangle",		// WAVE_TRIANGLE,
 	"Noise",		// WAVE_NOISE,
 	"Noise Hold",	// WAVE_NOISE_HOLD
-	"Noise Slope",	// WAVE_NOISE_SLOPE
+	"Noise Linear",	// WAVE_NOISE_LINEAR
+	"Noise Cubic",	// WAVE_NOISE_CUBIC
 	"Poly4",		// WAVE_POLY4,
 	"Poly5",		// WAVE_POLY5,
 	"Period-93",	// WAVE_PERIOD93,
@@ -70,7 +72,8 @@ float const wave_adjust_frequency[WAVE_COUNT] =
 	1.0f,					// WAVE_TRIANGLE,
 	1.0f, 					// WAVE_NOISE,
 	1.0f,					// WAVE_NOISE_HOLD,
-	1.0f,					// WAVE_NOISE_SLOPE,
+	1.0f,					// WAVE_NOISE_LINEAR,
+	1.0f,					// WAVE_NOISE_CUBIC,
 	2.0f * 15.0f / 16.0f,	// WAVE_POLY4,
 	2.0f * 31.0f / 32.0f,	// WAVE_POLY5,
 	2.0f * 93.0f / 128.0f,	// WAVE_PERIOD93,
@@ -91,7 +94,8 @@ int const wave_loop_cycle[WAVE_COUNT] =
 	INT_MAX,					// WAVE_TRIANGLE,
 	INT_MAX,					// WAVE_NOISE,
 	ARRAY_SIZE(noise),			// WAVE_NOISE_HOLD
-	ARRAY_SIZE(noise),			// WAVE_NOISE_SLOPE
+	ARRAY_SIZE(noise),			// WAVE_NOISE_LINEAR
+	ARRAY_SIZE(noise),			// WAVE_NOISE_CUBIC
 	ARRAY_SIZE(poly4),			// WAVE_POLY4,
 	ARRAY_SIZE(poly5),			// WAVE_POLY5,
 	ARRAY_SIZE(period93),		// WAVE_PERIOD93,

Wave.h

@@ -20,8 +20,9 @@ enum Wave
 	WAVE_SAWTOOTH,
 	WAVE_TRIANGLE,
 	WAVE_NOISE,
-	WAVE_NOISE_HOLD,
-	WAVE_NOISE_SLOPE,
+	WAVE_NOISE_HOLD,	// noise with sample and hold
+	WAVE_NOISE_LINEAR,	// noise with linear interpolation
+	WAVE_NOISE_CUBIC,	// noise with cubic interpolation
 
 	WAVE_POLY4,			// Atari POKEY AUDC 12
 	WAVE_POLY5,			// Atari TIA AUDC 7 or 9

WaveHold.cpp

@@ -108,6 +108,28 @@ static float OscillatorLerp(OscillatorConfig const &config, OscillatorState &sta
 	return value;
 }
 
+// shared data oscillator
+static float OscillatorCubic(OscillatorConfig const &config, OscillatorState &state, float data[], int cycle, float step)
+{
+	if (step > 0.5f * cycle)
+		return 0;
+
+	// four consecutive wavetable values
+	register float const value0 = data[state.index];
+	register float const value1 = data[(state.index + 1) & (cycle - 1)];
+	register float const value2 = data[(state.index + 2) & (cycle - 1)];
+	register float const value3 = data[(state.index + 3) & (cycle - 1)];
+
+	// cubic interpolation
+	// (Catmull-Rom spline)
+	register float value = 
+		value1 + 
+		state.phase * 0.5 * (value2 - value0 +
+		state.phase * (2.0 * value0 - 5.0 * value1 + 4.0 * value2 - value3 + 
+		state.phase * (3.0 * (value1 - value2) + value3 - value0)));
+
+	return value;
+}
 
 // sample-and-hold noise
 float OscillatorNoiseHold(OscillatorConfig const &config, OscillatorState &state, float step)
@@ -116,7 +138,13 @@ float OscillatorNoiseHold(OscillatorConfig const &config, OscillatorState &state
 }
 
 // linear interpolated noise
-float OscillatorNoiseSlope(OscillatorConfig const &config, OscillatorState &state, float step)
+float OscillatorNoiseLinear(OscillatorConfig const &config, OscillatorState &state, float step)
 {
 	return OscillatorLerp(config, state, noise, ARRAY_SIZE(noise), step);
 }
+
+// cubic interpolated noise
+float OscillatorNoiseCubic(OscillatorConfig const &config, OscillatorState &state, float step)
+{
+	return OscillatorCubic(config, state, noise, ARRAY_SIZE(noise), step);
+}

WaveHold.h

@@ -8,4 +8,5 @@ extern void InitNoise();
 
 // sample-and-hold noise
 extern float OscillatorNoiseHold(OscillatorConfig const &config, OscillatorState &state, float step);
-extern float OscillatorNoiseSlope(OscillatorConfig const &config, OscillatorState &state, float step);
+extern float OscillatorNoiseLinear(OscillatorConfig const &config, OscillatorState &state, float step);
+extern float OscillatorNoiseCubic(OscillatorConfig const &config, OscillatorState &state, float step);

WavePoly.cpp

@@ -32,7 +32,8 @@ static char const * const poly_data[WAVE_COUNT] =
 	NULL,			// WAVE_TRIANGLE,
 	NULL,			// WAVE_NOISE,
 	NULL,			// WAVE_NOISE_HOLD,
-	NULL,			// WAVE_NOISE_SLOPE,
+	NULL,			// WAVE_NOISE_LINEAR,
+	NULL,			// WAVE_NOISE_CUBIC,
 	poly4,			// WAVE_POLY4,
 	poly5,			// WAVE_POLY5,
 	period93,		// WAVE_PERIOD93,