1 files changed, 147 insertions, 0 deletions
diff --git a/src/libs/din/din.c b/src/libs/din/din.c
new file mode 100644
index 0000000..2293c30
--- /dev/null
+++ b/src/libs/din/din.c
@@ -0,0 +1,147 @@
+/* implements a classical perlin noise function */
+/* https://en.wikipedia.org/wiki/Perlin_noise */
+
+#include <stdlib.h>
+
+#include "din.h"
+#include "v3f.h"
+
+typedef struct din_t {
+	int	width, height, depth;
+	v3f_t	grid[];
+} din_t;
+
+
+/* return random number between -1 and +1 */
+static inline float randf(void)
+{
+	return 2.f / RAND_MAX * rand() - 1.f;
+}
+
+
+void din_randomize(din_t *din)
+{
+	int	x, y, z;
+
+	for (z = 0; z < din->depth; z++) {
+		for (y = 0; y < din->height; y++) {
+			for (x = 0; x < din->width; x++) {
+				v3f_t	r;
+
+				r.x = randf();
+				r.y = randf();
+				r.z = randf();
+
+				din->grid[z * din->width * din->height + y * din->width + x] = v3f_normalize(&r);
+			}
+		}
+	}
+}
+
+
+din_t * din_new(int width, int height, int depth)
+{
+	din_t	*din;
+
+	din = calloc(1, sizeof(din_t) + (sizeof(v3f_t) * (width * height * depth)));
+	if (!din)
+		return NULL;
+
+	din->width = width;
+	din->height = height;
+	din->depth = depth;
+
+	din_randomize(din);
+
+	return din;
+}
+
+
+void din_free(din_t *din)
+{
+	free(din);
+}
+
+
+static inline float dotgradient(const din_t *din, int x, int y, int z, const v3f_t coordinate)
+{
+	v3f_t	distance = v3f_sub(&coordinate, &(v3f_t){.x = x, .y = y, .z = z});
+
+	return v3f_dot(&din->grid[z * din->width * din->height + y * din->width + x], &distance);
+}
+
+
+static inline float lerp(float a, float b, float t)
+{
+	return (1.0f - t) * a + t * b;
+}
+
+
+static inline float clamp(float x, float lowerlimit, float upperlimit) {
+	if (x < lowerlimit)
+		x = lowerlimit;
+
+	if (x > upperlimit)
+		x = upperlimit;
+
+	return x;
+}
+
+
+static inline float smootherstep(float edge0, float edge1, float x) {
+	x = clamp((x - edge0) / (edge1 - edge0), 0.f, 1.f);
+
+	return x * x * x * (x * (x * 6.f - 15.f) + 10.f);
+}
+
+
+/* coordinate is in a unit cube of -1...+1 */
+float din(din_t *din, v3f_t coordinate)
+{
+	int	x0, y0, z0, x1, y1, z1;
+	float	i1, i2, ii1, ii2;
+	float	tx, ty, tz;
+	float	n0, n1;
+
+	coordinate.x = 1.f + (coordinate.x * .5f + .5f) * (float)(din->width - 2);
+	coordinate.y = 1.f + (coordinate.y * .5f + .5f) * (float)(din->height - 2);
+	coordinate.z = 1.f + (coordinate.z * .5f + .5f) * (float)(din->depth - 2);
+
+	x0 = floorf(coordinate.x);
+	y0 = floorf(coordinate.y);
+	z0 = floorf(coordinate.z);
+
+	x1 = x0 + 1.f;
+	y1 = y0 + 1.f;
+	z1 = z0 + 1.f;
+
+	tx = coordinate.x - (float)x0;
+	ty = coordinate.y - (float)y0;
+	tz = coordinate.z - (float)z0;
+
+	n0 = dotgradient(din, x0, y0, z0, coordinate);
+	n1 = dotgradient(din, x1, y0, z0, coordinate);
+	tx = smootherstep(0.f, 1.f, tx);
+	i1 = lerp(n0, n1, tx);
+
+	n0 = dotgradient(din, x0, y1, z0, coordinate);
+	n1 = dotgradient(din, x1, y1, z0, coordinate);
+	i2 = lerp(n0, n1, tx);
+
+	ty = smootherstep(0.f, 1.f, ty);
+	ii1 = lerp(i1, i2, ty);
+
+	n0 = dotgradient(din, x0, y0, z1, coordinate);
+	n1 = dotgradient(din, x1, y0, z1, coordinate);
+	i1 = lerp(n0, n1, tx);
+
+	n0 = dotgradient(din, x0, y1, z1, coordinate);
+	n1 = dotgradient(din, x1, y1, z1, coordinate);
+	i2 = lerp(n0, n1, tx);
+
+	ii2 = lerp(i1, i2, ty);
+
+	tz = smootherstep(0.f, 1.f, tz);
+
+	return lerp(ii1, ii2, tz);
+}