GodotComponentTest/materials/shader/HexToTexture.gdshader

shader_type spatial;
render_mode specular_schlick_ggx, async_visible;

uniform sampler2D MapAlbedoTexture : hint_black_albedo;
uniform int TextureSize: hint_range(0, 1024, 4);
varying vec2 map_coord;

const mat2 _HexAffineInverse = mat2(vec2(1.333333, -0.6666667), vec2(0, -1.154701));

vec3 axial_to_cube(vec2 axial) {
	return vec3(axial.x, axial.y, -axial.x - axial.y);
}

ivec3 round_cube_coords(vec3 cube) {
	ivec3 rounded = ivec3(round(cube));
	
	vec3 diffs = abs(vec3(rounded) - cube);
	
	if (diffs.x > diffs.y && diffs.x > diffs.z) {
		rounded.x = -rounded.y - rounded.z;
	} else if (diffs.y > diffs.z) {
		rounded.y = -rounded.x - rounded.z;
	} else {
		 rounded.z = -rounded.x - rounded.y;
	}
	
	return rounded;
}

vec2 axial_to_offset(vec2 axial) {
	ivec3 cubeCoords = round_cube_coords(axial_to_cube(axial));
    int x = cubeCoords.x;
    int y = cubeCoords.y;
    int off_y = y + (x - (x % 2)) / 2;
    return vec2(float(x), float(off_y));
}

void vertex() {
// Input:2
	mat4 model_matrix = WORLD_MATRIX;

	vec3 origin = vec4(WORLD_MATRIX * vec4(0, 0, 0, 1)).xyz;
	vec3 axial_coords = vec3(_HexAffineInverse * origin.xz, 0);

	map_coord = origin.xz * 1. / float(TextureSize);
	map_coord = axial_to_offset(axial_coords.xy) / float(TextureSize) - vec2(0.5);
}

void fragment() {
	ALBEDO = texture(MapAlbedoTexture, map_coord).rgb;
}

void light() {
// Output:0

}