std_data.cpp

#include"std_data.h"

glm::vec2 eng::vec2_lerp(glm::vec2 start_value, glm::vec2 end_value, float t) {
	return glm::vec2(
		start_value.x + (end_value.x - start_value.x) * t,
		start_value.y + (end_value.y - start_value.y) * t
	);
}

glm::vec3 eng::vec3_lerp(glm::vec3 start_value, glm::vec3 end_value, float t) {
	return glm::vec3(
		start_value.x + (end_value.x - start_value.x) * t,
		start_value.y + (end_value.y - start_value.y) * t,
		start_value.z + (end_value.z - start_value.z) * t
	);
}

glm::vec2 random_gradient(int ix, int iy) {
	const unsigned w = 8 * sizeof(unsigned);
	const unsigned s = w / 2;
	unsigned a = ix, b = iy;
	a *= 3284157443;

	b ^= a << s | a >> w - s;
	b *= 1911520717;

	a ^= b << s | b >> w - s;
	a *= 2048419325;
	float random = a * (3.14159265 / ~(~0u >> 1));

	glm::vec2 v;
	v.x = sin(random);
	v.y = cos(random);

	return v;
}
float dot_grid_gradient(int ix, int iy, float x, float y) {
	glm::vec2 gradient = random_gradient(ix, iy);

	float dx = x - (float)ix;
	float dy = y - (float)iy;

	return (dx * gradient.x + dy * gradient.y);
}
float interpolate(float a0, float a1, float w) {
	return ((a1 - a0) * (3.0 - w * 2.0) * w * w + a0);
}
float eng::perlin(float x, float y) {
	int x0 = (int)x;
	int y0 = (int)y;
	int x1 = x0 + 1;
	int y1 = y0 + 1;

	float sx = x - (float)x0;
	float sy = y - (float)y0;

	float n0 = dot_grid_gradient(x0, y0, x, y);
	float n1 = dot_grid_gradient(x1, y0, x, y);
	float ix0 = interpolate(n0, n1, sx);

	n0 = dot_grid_gradient(x0, y1, x, y);
	n1 = dot_grid_gradient(x1, y1, x, y);
	float ix1 = interpolate(n0, n1, sx);

	float value = interpolate(ix0, ix1, sy);

	return value;
}