transparency in map mode

go.mod

@@ -34,7 +34,7 @@ require (
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/klauspost/compress v1.16.0 // indirect
-	github.com/minetest-go/colormapping v1.0.4
+	github.com/minetest-go/colormapping v1.0.5
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -17,6 +17,8 @@ github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWE
 github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
 github.com/minetest-go/colormapping v1.0.4 h1:EoIAvdjAyO7kUFcBipbPZmGFSOoSiHwDHpUeH4LSJ4k=
 github.com/minetest-go/colormapping v1.0.4/go.mod h1:oltuvIhwZBc5YMTCABzziVUHdOCkSOIHr46zDS23Ev0=
+github.com/minetest-go/colormapping v1.0.5 h1:axZm0xbOz0RQEIFvZmbxr3kuvebYiG0AAADPr8/ZQfg=
+github.com/minetest-go/colormapping v1.0.5/go.mod h1:6UVusIQTqfWbcru5HTktWwB2BCNHUE3W0VkkRBaMfcw=
 github.com/minetest-go/mapparser v1.0.0 h1:wQz0DNIb239YalZJr6cnZka+FurYo5sZB/IOfGq7Nno=
 github.com/minetest-go/mapparser v1.0.0/go.mod h1:MsLonoU5w+V57rQfPoVs9wx0GSyUuIXYC0meJg2HxDI=
 github.com/minetest-go/mtdb v1.1.48 h1:OWMbwH4Hq+RzK9UaW1nSIGWe2E+nZPGO5NDAZVdRWLw=

maprenderer.go

@@ -26,7 +26,7 @@ func RenderMap(na types.NodeAccessor, cr types.ColorResolver, from, to *types.Po
 	for x := from.X(); x <= to.X(); x++ {
 		for z := from.Z(); z <= to.Z(); z++ {
 			// top-down search
-			nodes, err := Probe(from, to, types.NewPos(x, to.Y(), z), search_dir, na, cr, true)
+			nodes, err := Probe(from, to, types.NewPos(x, to.Y(), z), search_dir, na, cr, false)
 			if err != nil {
 				return nil, err
 			}
@@ -35,32 +35,41 @@ func RenderMap(na types.NodeAccessor, cr types.ColorResolver, from, to *types.Po
 				continue
 			}
 
-			node := nodes[0]
+			top_node := nodes[0]
+			c := top_node.Color
 
-			c := cr(node.Name, node.Param2)
-			if c == nil {
-				continue
-			}
+			if len(nodes) == 1 && top_node.Color.A == 255 {
+				// a single opaque node, draw with shadows
 
-			// add shadows for view-blocking neighbors
-			for _, above_pos := range []*types.Pos{{-1, 1, 0}, {0, 1, 1}} {
-				nn, err := na(node.Pos.Add(above_pos))
-				if err != nil {
-					return nil, err
-				}
-				if nn != nil && cr(nn.Name, 0) != nil {
-					c = ColorAdjust(c, -10)
+				// add shadows for view-blocking neighbors
+				for _, above_pos := range []*types.Pos{{-1, 1, 0}, {0, 1, 1}} {
+					nn, err := na(top_node.Pos.Add(above_pos))
+					if err != nil {
+						return nil, err
+					}
+					if nn != nil && cr(nn.Name, 0) != nil {
+						c = ColorAdjust(c, -10)
+					}
 				}
-			}
 
-			// lighten up if no nodes directly nearby
-			for _, near_pos := range []*types.Pos{{-1, 0, 0}, {0, 0, 1}} {
-				nn, err := na(node.Pos.Add(near_pos))
-				if err != nil {
-					return nil, err
+				// lighten up if no nodes directly nearby
+				for _, near_pos := range []*types.Pos{{-1, 0, 0}, {0, 0, 1}} {
+					nn, err := na(top_node.Pos.Add(near_pos))
+					if err != nil {
+						return nil, err
+					}
+					if nn == nil || cr(nn.Name, 0) == nil {
+						c = ColorAdjust(c, 10)
+					}
 				}
-				if nn == nil || cr(nn.Name, 0) == nil {
-					c = ColorAdjust(c, 10)
+			} else {
+				// multiple nodes with alpha channel
+				c = nodes[len(nodes)-1].Color
+
+				// bottom up color blending
+				for i := len(nodes) - 2; i >= 0; i-- {
+					node := nodes[i]
+					c = BlendColor(c, node.Color)
 				}
 			}
 

maprenderer_test.go

@@ -23,7 +23,7 @@ func TestRenderMap(t *testing.T) {
 	err = cm.LoadDefaults()
 	assert.NoError(t, err)
 
-	from := types.NewPos(-10, -20, -10)
+	from := types.NewPos(0, -20, 0)
 	to := types.NewPos(100, 50, 100)
 	opts := &maprenderer.MapRenderOpts{}
 

iso_utils.go → utils.go

@@ -111,3 +111,15 @@ func ColorAdjust(c *color.RGBA, value int) *color.RGBA {
 		A: c.A,
 	}
 }
+
+func BlendColor(bg, fg *color.RGBA) *color.RGBA {
+	a := float64(fg.A) / 255
+	ai := 1 - a
+
+	return &color.RGBA{
+		R: uint8((float64(fg.R) * a) + (float64(bg.R) * ai)),
+		G: uint8((float64(fg.G) * a) + (float64(bg.G) * ai)),
+		B: uint8((float64(fg.B) * a) + (float64(bg.B) * ai)),
+		A: max(bg.A, fg.A),
+	}
+}