transparency support

canvas.lua

@@ -8,6 +8,22 @@ function Canvas:get_index(x, y)
     return (self.width * y) + x + 1
 end
 
+function Canvas:add_pixel(x, y, fg)
+    fg.a = fg.a or 255
+
+    local i = self:get_index(x, y)
+    local bg = self.png_data[i]
+    local a = fg.a / 255
+    local ai = 1 - a
+
+    self.png_data[i] = {
+        r = ((fg.r * a) + (bg.r * ai)),
+        g = ((fg.g * a) + (bg.g * ai)),
+        b = ((fg.b * a) + (bg.b * ai)),
+        a = math.max(bg.a, fg.a)
+    }
+end
+
 function Canvas:set_pixel(x, y, colorspec)
     local i = self:get_index(x, y)
     self.png_data[i] = colorspec

common.lua

@@ -40,14 +40,29 @@ function isogen.get_cube_position(center_x, center_y, cube_len, _, pos)
     return x, y
 end
 
-function isogen.probe_position(min, max, pos, ipos)
+function isogen.probe_position(min, max, pos, ipos, list)
+    list = list or {}
     while vector.in_area(pos, min, max) do
         local node = minetest.get_node(pos)
-        if node.name ~= "air" and node.name ~= "ignore" then
+        local color = isogen.get_color(node)
-            return node, pos
+        if color then
+            local rel_pos = vector.subtract(pos, min)
+            local rel_max = vector.subtract(max, min)
+            local order =
+                (rel_pos.y * (rel_max.x * rel_max.z)) +
+                (rel_max.x - rel_pos.x) +
+                (rel_max.z - rel_pos.z)
+
+            table.insert(list, {
+                pos = pos,
+                color = color,
+                order = order,
+                node = node
+            })
         end
         pos = vector.add(pos, ipos)
     end
+    return list
 end
 
 local function flip_pos(pos, max, axis)

draw.lua

@@ -1,22 +1,4 @@
 
-local function probe_and_add(list, min, max, pos, ipos)
-    local node, npos = isogen.probe_position(min, max, pos, ipos)
-    if node then
-        local rel_pos = vector.subtract(npos, min)
-        local rel_max = vector.subtract(max, min)
-        local order =
-            (rel_pos.y * (rel_max.x * rel_max.z)) +
-            (rel_max.x - rel_pos.x) +
-            (rel_max.z - rel_pos.z)
-
-        table.insert(list, {
-            node = node,
-            pos = npos,
-            order = order
-        })
-    end
-end
-
 local function clamp(v, min, max)
     if v > max then
         return max
@@ -53,21 +35,21 @@ function isogen.draw(pos1, pos2, cube_len)
     -- top layer
     for x=min.x, max.x do
         for z=min.z, max.z do
-            probe_and_add(list, min, max, vector.new(x, max.y, z), ipos)
+            isogen.probe_position(min, max, vector.new(x, max.y, z), ipos, list)
         end
     end
 
     -- left layer (without top stride)
     for x=min.x, max.x do
         for y=min.y, max.y-1 do
-            probe_and_add(list, min, max, vector.new(x, y, min.z), ipos)
+            isogen.probe_position(min, max, vector.new(x, y, min.z), ipos, list)
         end
     end
 
     -- right layer (without top and left stride)
     for z=min.z+1, max.z do
         for y=min.y, max.y-1 do
-            probe_and_add(list, min, max, vector.new(min.x, y, z), ipos)
+            isogen.probe_position(min, max, vector.new(min.x, y, z), ipos, list)
         end
     end
 
@@ -77,12 +59,10 @@ function isogen.draw(pos1, pos2, cube_len)
 
     for _, entry in ipairs(list) do
         local rel_pos = vector.subtract(entry.pos, min)
-        local color = isogen.get_color(entry.node)
+        local color = entry.color
-        if color then
         local x, y = isogen.get_cube_position(center_x, center_y, cube_len, 0, rel_pos)
         isogen.draw_cube(canvas, cube_len, x, y, color, color_adjust(color, -10), color_adjust(color, 10))
     end
-    end
 
     return canvas:png()
 end

draw_cube.lua

@@ -11,9 +11,9 @@ function isogen.draw_cube(canvas, cube_len, x_offset, y_offset, color1, color2,
     for x=0,half_len_zero_indexed do
         for y=0,half_len_zero_indexed do
             -- left
-            canvas:set_pixel(x_offset+x, y_offset+y+quarter_len+yo, color1)
+            canvas:add_pixel(x_offset+x, y_offset+y+quarter_len+yo, color1)
             -- right
-            canvas:set_pixel(x_offset+cube_len-1-x, y_offset+y+quarter_len+yo, color2)
+            canvas:add_pixel(x_offset+cube_len-1-x, y_offset+y+quarter_len+yo, color2)
         end
         if x % 2 == 0 then
             yo = yo + 1
@@ -26,9 +26,9 @@ function isogen.draw_cube(canvas, cube_len, x_offset, y_offset, color1, color2,
     for x=0,half_len_zero_indexed-1 do
         for y=0,yl do
             -- left
-            canvas:set_pixel(x_offset+1+x, y_offset+quarter_len-1-yo+y, color3)
+            canvas:add_pixel(x_offset+1+x, y_offset+quarter_len-1-yo+y, color3)
             -- right
-            canvas:set_pixel(x_offset+cube_len-2-x, y_offset+quarter_len-1-yo+y, color3)
+            canvas:add_pixel(x_offset+cube_len-2-x, y_offset+quarter_len-1-yo+y, color3)
         end
         if x % 2 ~= 0 then
             yo = yo + 1