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#version 330 core
layout (location = 0) in vec3 in_quad;
layout (std140) uniform Matrices {
mat4 proj;
mat4 view;
};
// world chunk position
const int CHUNK_SIZE = 16;
uniform ivec3 chunk_position;
const int MAX_FACES = CHUNK_SIZE * CHUNK_SIZE * CHUNK_SIZE;
layout (std140) uniform Face {
// normaly a uint but std140 layout
// requires 16-byte alignment
uvec4 face_data[MAX_FACES / 4];
};
flat out uvec2 pass_data;
out float pass_ao;
const mat3 ROT90 = mat3(
0.0, 0.0, 1.0,
0.0, 1.0, 0.0,
-1.0, 0.0, 0.0
);
uint get_half(int index)
{
int arr_index = index / 4;
int vec_index = index % 4;
return face_data[arr_index][vec_index];
}
uvec2 get_data(int index)
{
uint lower = get_half(index * 2);
uint upper = get_half(index * 2 + 1);
return uvec2(lower, upper);
}
bool get_ao_rotate(uint data)
{
vec4 ao;
ao.x = (data >> 0) & 3u;
ao.y = (data >> 2) & 3u;
ao.z = (data >> 4) & 3u;
ao.w = (data >> 6) & 3u;
float a = abs(ao.x - ao.w);
float b = abs(ao.y - ao.z);
return a > b;
}
float get_ao(uint data, uint face)
{
vec4 ao;
ao.x = (data >> 0) & 3u;
ao.y = (data >> 2) & 3u;
ao.z = (data >> 4) & 3u;
ao.w = (data >> 6) & 3u;
switch (face) {
case 0u: // PX
case 2u: // PY
case 4u: // PZ
ao = ao.xywz;
if (get_ao_rotate(data))
ao = ao.wxyz;
break;
case 1u: // NX
case 3u: // NY
case 5u: // NZ
if (get_ao_rotate(data))
ao = ao.ywxz;
ao = ao.wzxy;
break;
}
return ao[gl_VertexID];
}
vec3 rotate(vec3 v, uint face)
{
switch(face) {
case 0u: // PX
case 1u: // NX
v = vec3(v.x, v.z, -v.y + 1);
break;
case 2u: // PY
case 3u: // NY
v = vec3(-v.z + 1, v.y, v.x);
break;
case 4u: // PZ
case 5u: // NZ
v = vec3(v.y, -v.x + 1, v.z);
break;
}
return v;
}
vec3 get_quad(uint face, uint width, uint height)
{
vec3 quad = in_quad;
quad.x *= width;
quad.y *= height;
switch(face) {
case 0u: // PX
quad = quad.yzx + vec3(1, 0, 0);
break;
case 1u: // NX
quad = quad.yxz;
break;
case 2u: // PY
quad = quad.xyz + vec3(0, 1, 0);
break;
case 3u: // NY
quad = quad.zyx;
break;
case 4u: // PZ
quad = quad.zxy + vec3(0, 0, 1);
break;
case 5u: // NZ
quad = quad.xzy;
break;
}
return quad;
}
void main(void)
{
// get face data
uvec2 data = get_data(gl_InstanceID);
uint x = (data.x >> 0) & 31u;
uint y = (data.x >> 5) & 31u;
uint z = (data.x >> 10) & 31u;
uint width = (data.x >> 15) & 31u;
uint height = (data.x >> 20) & 31u;
uint face = (data.x >> 25) & 7u;
// get quad verts
vec3 quad = get_quad(face, width, height);
if (get_ao_rotate(data.y))
quad = rotate(quad, face);
// get position
vec3 position = vec3(x, y, z);
position += chunk_position * CHUNK_SIZE;
position += quad;
// draw
gl_Position = proj * view * vec4(position, 1.0);
// fragment input
pass_data = data;
pass_ao = get_ao(data.y, face);
}
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