perlin2d, sample terrain render

src/game_api.h

@@ -7,6 +7,7 @@
 #include "rendering.h"
 #include "audio.h"
 #include "util.h"
+#include "procgen.h"
 
 /* application provided */
 extern void game_tick(void);

src/procgen.h

@@ -0,0 +1,6 @@
+#ifndef PROCGEN_H
+#define PROCGEN_H
+
+#include "procgen/perlin.h"
+
+#endif

src/procgen/perlin.h

@@ -0,0 +1,10 @@
+#ifndef PROCGEN_PERLIN_H
+#define PROCGEN_PERLIN_H
+
+#include "../vec.h"
+
+void set_perlin_2d_seed(uint32_t seed);
+
+float sample_perlin_2d(t_fvec2 position, float frequency, uint8_t octaves);
+
+#endif

src/procgen/perlin2d.c

@@ -0,0 +1,70 @@
+#include "perlin.h"
+#include "../vec.h"
+
+static uint32_t seed = 0;
+
+static const uint8_t hash[] = { 208,34,231,213,32,248,233,56,161,78,24,140,71,48,140,254,245,255,247,247,40,
+                                185,248,251,245,28,124,204,204,76,36,1,107,28,234,163,202,224,245,128,167,204,
+                                9,92,217,54,239,174,173,102,193,189,190,121,100,108,167,44,43,77,180,204,8,81,
+                                70,223,11,38,24,254,210,210,177,32,81,195,243,125,8,169,112,32,97,53,195,13,
+                                203,9,47,104,125,117,114,124,165,203,181,235,193,206,70,180,174,0,167,181,41,
+                                164,30,116,127,198,245,146,87,224,149,206,57,4,192,210,65,210,129,240,178,105,
+                                228,108,245,148,140,40,35,195,38,58,65,207,215,253,65,85,208,76,62,3,237,55,89,
+                                232,50,217,64,244,157,199,121,252,90,17,212,203,149,152,140,187,234,177,73,174,
+                                193,100,192,143,97,53,145,135,19,103,13,90,135,151,199,91,239,247,33,39,145,
+                                101,120,99,3,186,86,99,41,237,203,111,79,220,135,158,42,30,154,120,67,87,167,
+                                135,176,183,191,253,115,184,21,233,58,129,233,142,39,128,211,118,137,139,255,
+                                114,20,218,113,154,27,127,246,250,1,8,198,250,209,92,222,173,21,88,102,219 };
+
+void set_perlin_2d_seed(uint32_t s) {
+    seed = s;
+}
+
+static int32_t noise2(int x, int y)
+{
+    int tmp = hash[(y + seed) % 256];
+    return hash[(tmp + x) % 256];
+}
+
+static float lin_inter(float x, float y, float s)
+{
+    return x + s * (y-x);
+}
+
+static float smooth_inter(float x, float y, float s)
+{
+    return lin_inter(x, y, s * s * (3-2*s));
+}
+
+static float noise2d(float x, float y)
+{
+    int32_t x_int = (int32_t)x;
+    int32_t y_int = (int32_t)y;
+    float x_frac = x - (float)x_int;
+    float y_frac = y - (float)y_int;
+    int32_t s = noise2(x_int, y_int);
+    int32_t t = noise2(x_int + 1, y_int);
+    int32_t u = noise2(x_int, y_int + 1);
+    int v = noise2(x_int + 1, y_int + 1);
+    float low = smooth_inter((float)s, (float)t, x_frac);
+    float high = smooth_inter((float)u, (float)v, x_frac);
+    return smooth_inter(low, high, y_frac);
+}
+
+/* https://gist.github.com/nowl/828013 */
+float sample_perlin_2d(t_fvec2 position, float frequency, uint8_t octaves) {
+    t_fvec2 a = m_vec_scale(position, frequency);
+    float amp = 1.0;
+    float fin = 0;
+    float div = 0.0;
+
+    for(uint8_t i = 0; i < octaves; i++)
+    {
+        div += 256 * amp;
+        fin += noise2d(a.x, a.y) * amp;
+        amp /= 2;
+        a = m_vec_scale(a, 2);
+    }
+
+    return fin/div;
+}

src/vec.h

@@ -70,6 +70,10 @@ static inline t_fvec3 fvec3_sub(t_fvec3 a, t_fvec3 b) {
     return (t_fvec3) { a.x - b.x, a.y - b.y, a.z - b.z };
 }
 
+static inline t_fvec2 fvec2_scale(t_fvec2 a, float s) {
+    return (t_fvec2) { a.x * s, a.y * s };
+}
+
 static inline t_fvec3 fvec3_scale(t_fvec3 a, float s) {
     return (t_fvec3) { a.x * s, a.y * s, a.z * s };
 }
@@ -103,6 +107,7 @@ static inline t_fvec3 fvec3_norm(t_fvec3 a) {
                                 )(p_any_vec0, p_any_vec1))
 
 #define m_vec_scale(p_any_vec, p_any_scalar) (_Generic((p_any_vec),     \
+                                    t_fvec2:   fvec2_scale,             \
                                     t_fvec3:   fvec3_scale              \
                                 )(p_any_vec, p_any_scalar))