mirror(x,y,z)

context/mirror.lua

@@ -0,0 +1,16 @@
+
+local function apply_axis(ctx, axis, v)
+    assert(v <= 1)
+    if v == 1 then
+        -- invert axis
+        ctx.pos_factor[axis] = ctx.pos_factor[axis] * -1
+    end
+end
+
+function mtscad.Context:mirror(x, y, z)
+    local ctx = self:clone()
+    apply_axis(ctx, "x", x)
+    apply_axis(ctx, "y", y)
+    apply_axis(ctx, "z", z)
+    return ctx
+end

context/new.lua

@@ -13,6 +13,7 @@ function mtscad.create_context(opts)
 
     local self = {
         pos = opts.pos and vector.copy(opts.pos) or vector.zero(),
+        pos_factor = opts.pos_factor and vector.copy(opts.pos_factor) or vector.new(1,1,1),
         rotation = opts.rotation or mtscad.rotation_matrix_x(0),
         nodefactory = opts.nodefactory,
         param2 = opts.param2 or 0,

context/set_node.lua

@@ -4,6 +4,13 @@ function mtscad.Context:set_node()
         node.param2 = self.param2
     end
     local tnode = mtscad.transform_node(node, self.rotation)
+
+    if self.pos_factor.x == -1 or self.pos_factor.z == -1 then
+        tnode.param2 = mtscad.rotate_facedir(2, "y-", tnode.param2)
+    elseif self.pos_factor.y == -1 then
+        tnode.param2 = mtscad.rotate_facedir(2, "z-", tnode.param2)
+    end
+
     minetest.set_node(self.pos, tnode)
     mtscad.extents(self.session.min, self.session.max, self.pos)
     return self

context/translate.lua

@@ -7,7 +7,14 @@ function mtscad.Context:translate(x, y, z)
         z = z or 0
     }
     local ctx = self:clone()
+
+    -- rotate
     local m = mtscad.multiply_matrix(self.rotation, mtscad.pos_to_matrix(opos))
-    ctx.pos = vector.add(self.pos, mtscad.matrix_to_pos(m))
+    local rel_pos = mtscad.matrix_to_pos(m)
+
+    -- apply pos factor (mirror)
+    rel_pos = vector.multiply(self.pos_factor, rel_pos)
+
+    ctx.pos = vector.add(self.pos, rel_pos)
     return ctx
 end

init.lua

@@ -16,6 +16,7 @@ dofile(MP .. "/context/dome.lua")
 dofile(MP .. "/context/slope.lua")
 dofile(MP .. "/context/cylinder.lua")
 dofile(MP .. "/context/pattern.lua")
+dofile(MP .. "/context/mirror.lua")
 dofile(MP .. "/util/extents.lua")
 dofile(MP .. "/util/matrix.lua")
 dofile(MP .. "/util/origin.lua")

test/mod/init.lua

@@ -13,6 +13,7 @@ table.insert(jobs, loadfile(MP .. "/load_module.lua")({x=0, y=0, z=20}))
 table.insert(jobs, loadfile(MP .. "/draw_line.lua")({x=0, y=0, z=0}))
 table.insert(jobs, loadfile(MP .. "/draw_async.lua")({x=20, y=0, z=0}))
 table.insert(jobs, loadfile(MP .. "/translate_rotate.lua")({x=20, y=0, z=20}))
+table.insert(jobs, loadfile(MP .. "/mirror.lua")({x=-20, y=0, z=20}))
 
 local job_index = 1
 

test/mod/mirror.lua

@@ -0,0 +1,23 @@
+local origin = ...
+
+return function(callback)
+  print("mirror")
+
+  local ctx = mtscad.create_context({ pos = origin })
+  ctx.job_context.register_on_done(function(_, err_msg)
+    if err_msg then
+      error(err_msg)
+    end
+    assert(minetest.get_node(vector.add(origin, {x=5+2,y=5,z=5})).name == "default:mese")
+    assert(minetest.get_node(vector.add(origin, {x=5+2,y=5,z=5})).param2 == 3)
+    assert(minetest.get_node(vector.add(origin, {x=5-2,y=5,z=5})).name == "default:mese")
+    assert(minetest.get_node(vector.add(origin, {x=5-2,y=5,z=5})).param2 == 1)
+    callback()
+  end)
+
+  local mod = mtscad.load_module("mirror")
+  mod(ctx)
+
+  -- process async jobs
+  ctx.job_context.process()
+end

test/workspace/mirror.lua

@@ -0,0 +1,15 @@
+local function fn(ctx)
+    ctx
+    :translate(2, 0, 0)
+    :with("default:mese")
+    :slope(1, 1, 0)
+    :set_node()
+end
+
+return function(ctx)
+    ctx
+    :translate(5, 5, 5)
+    :execute(fn)
+    :mirror(1, 0, 0)
+    :execute(fn)
+end