Fix math

src/math.zig

@@ -79,5 +79,5 @@ pub inline fn wideMulDivFloor(a: i32, mul: i32, div: i32) i32 {
 }
 
 pub inline fn wideMulDivCeil(a: i32, mul: i32, div: i32) i32 {
-    return @intCast(@divFloor(@as(i64, a) * @as(i64, mul) + @as(i64, div) - 1, div));
+    return @intCast(@divFloor(@as(i64, a) * @as(i64, mul) + @as(i64, div) - std.math.sign(div), div));
 }

src/voxels.zig

@@ -1,12 +1,44 @@
+const std = @import("std");
+
+const c = @import("const.zig");
+
 const Materials = @import("assets/Materials.zig");
 
 pub const Orientation = enum(u3) {
-    negative_x,
-    positive_x,
-    negative_y,
-    positive_y,
-    negative_z,
-    positive_z,
+    negative_x = 0b111,
+    positive_x = 0b000,
+    negative_y = 0b110,
+    positive_y = 0b001,
+    negative_z = 0b101,
+    positive_z = 0b010,
+
+    pub fn initSignIndex(sign: i2, index: u2) Orientation {
+        std.debug.assert(sign == -1 or sign == 1);
+        std.debug.assert(index < 3);
+        const value: u3 = (if (sign > 0) @as(u3, 0b100) else @as(u3, 0b000)) | index;
+        return @enumFromInt(value);
+    }
+
+    /// 0 for ±X
+    /// 1 for ±Y
+    /// 2 for ±Z
+    pub fn getIndex(self: Orientation) u2 {
+        return if (@intFromEnum(self) & 0b100 != 0) @intCast(~@intFromEnum(self)) else @intCast(@intFromEnum(self));
+    }
+
+    /// +1 for positive
+    /// -1 for negative
+    pub fn getSign(self: Orientation) i2 {
+        return if (@intFromEnum(self) & 0b100 != 0) -1 else 1;
+    }
+
+    pub fn getOffsetVx(self: Orientation) i32 {
+        return if (@intFromEnum(self) & 0b100 != 0) 1 else 0;
+    }
+
+    pub fn getOffsetSv(self: Orientation) i32 {
+        return if (@intFromEnum(self) & 0b100 != 0) c.sv_per_vx else 0;
+    }
 };
 
 pub const Transform = enum(u3) {