From 37244d7f690919566b0f917b06b18b6c26eaae75 Mon Sep 17 00:00:00 2001
From: Andrey Stepanov <standmit@yandex.ru>
Date: Sat, 2 Nov 2024 21:24:01 +0500
Subject: [PATCH] transparency

---
 mapblockrenderer/renderer.go | 83 +++++++++++++++++++++++++-----------
 1 file changed, 59 insertions(+), 24 deletions(-)

diff --git a/mapblockrenderer/renderer.go b/mapblockrenderer/renderer.go
index cae4b72..2007348 100644
--- a/mapblockrenderer/renderer.go
+++ b/mapblockrenderer/renderer.go
@@ -73,6 +73,31 @@ func addColorComponent(c *color.RGBA, value int) *color.RGBA {
 	}
 }
 
+func clamp_ratio(ratio float32) float32 {
+	if ratio < 0 {
+		return 0
+	}
+
+	if ratio > 1 {
+		return 1
+	}
+
+	return ratio
+}
+
+func interp_value(min uint8, max uint8, ratio float32) uint8 {
+	return min + uint8(float32(max-min)*clamp_ratio(ratio))
+}
+
+func blend_colors(lower color.RGBA, upper color.RGBA) (blended color.RGBA) {
+	ratio := float32(upper.A) / float32(255)
+	blended.R = interp_value(lower.R, upper.R, ratio)
+	blended.G = interp_value(lower.G, upper.G, ratio)
+	blended.B = interp_value(lower.B, upper.B, ratio)
+	blended.A = 255
+	return
+}
+
 func (r *MapBlockRenderer) Render(pos1, pos2 *types.MapBlockCoords) (*image.NRGBA, error) {
 	if pos1.X != pos2.X {
 		return nil, errors.New("x does not line up")
@@ -124,6 +149,8 @@ func (r *MapBlockRenderer) Render(pos1, pos2 *types.MapBlockCoords) (*image.NRGB
 
 		for x := 0; x < 16; x++ {
 			for z := 0; z < 16; z++ {
+				var colors_stack [15]color.RGBA
+				var visible_nodes_count uint8 = 0
 				for y := 15; y >= 0; y-- {
 					if xzOccupationMap[x][z] {
 						break
@@ -142,9 +169,6 @@ func (r *MapBlockRenderer) Render(pos1, pos2 *types.MapBlockCoords) (*image.NRGB
 						continue
 					}
 
-					// clamp alpha channel to max
-					c.A = 255
-
 					if r.enableShadow {
 						var left, leftAbove, top, topAbove string
 
@@ -209,35 +233,46 @@ func (r *MapBlockRenderer) Render(pos1, pos2 *types.MapBlockCoords) (*image.NRGB
 						}
 					}
 
-					imgX := x * IMG_SCALE
-					imgY := (15 - z) * IMG_SCALE
+					colors_stack[visible_nodes_count] = *c
+					visible_nodes_count++
 
-					r32, g32, b32, a32 := c.RGBA()
-					r8, g8, b8, a8 := uint8(r32), uint8(g32), uint8(b32), uint8(a32)
-					for Y := imgY; Y < imgY+IMG_SCALE; Y++ {
-						ix := (Y*IMG_SIZE + imgX) << 2
-						for X := 0; X < IMG_SCALE; X++ {
-							img.Pix[ix] = r8
-							ix++
-							img.Pix[ix] = g8
-							ix++
-							img.Pix[ix] = b8
-							ix++
-							img.Pix[ix] = a8
-							ix++
-						}
-					}
-
-					if c.A != 0xFF || !r.enableTransparency {
+					if c.A == 0xFF || !r.enableTransparency {
 						//not transparent, mark as rendered
 						foundBlocks++
 						xzOccupationMap[x][z] = true
 					}
+				}
 
-					if foundBlocks == EXPECTED_BLOCKS_PER_FLAT_MAPBLOCK {
-						return img, nil
+				visible_nodes_count--
+				result_color := colors_stack[visible_nodes_count]
+				if visible_nodes_count > 0 {
+					for layer := visible_nodes_count; layer > 0; layer-- {
+						result_color = blend_colors(result_color, colors_stack[layer-1])
 					}
 				}
+
+				imgX := x * IMG_SCALE
+				imgY := (15 - z) * IMG_SCALE
+
+				r32, g32, b32, a32 := result_color.RGBA()
+				r8, g8, b8, a8 := uint8(r32), uint8(g32), uint8(b32), uint8(a32)
+				for Y := imgY; Y < imgY+IMG_SCALE; Y++ {
+					ix := (Y*IMG_SIZE + imgX) << 2
+					for X := 0; X < IMG_SCALE; X++ {
+						img.Pix[ix] = r8
+						ix++
+						img.Pix[ix] = g8
+						ix++
+						img.Pix[ix] = b8
+						ix++
+						img.Pix[ix] = a8
+						ix++
+					}
+				}
+
+				if foundBlocks == EXPECTED_BLOCKS_PER_FLAT_MAPBLOCK {
+					return img, nil
+				}
 			}
 		}
 	}