From 8a2544f72e40383844404ebd7c9b222600b5f983 Mon Sep 17 00:00:00 2001
From: BuckarooBanzay <BuckarooBanzay@users.noreply.github.com>
Date: Sun, 30 Jun 2024 11:17:54 +0200
Subject: [PATCH] isometric tile renderer

---
 isotilerenderer.go      | 69 +++++++++++++++++++++++++++++++++++++++++
 isotilerenderer_test.go | 41 ++++++++++++++++++++++++
 2 files changed, 110 insertions(+)
 create mode 100644 isotilerenderer.go
 create mode 100644 isotilerenderer_test.go

diff --git a/isotilerenderer.go b/isotilerenderer.go
new file mode 100644
index 0000000..ff217e8
--- /dev/null
+++ b/isotilerenderer.go
@@ -0,0 +1,69 @@
+package maprenderer
+
+import (
+	"fmt"
+	"image"
+	"slices"
+
+	"github.com/minetest-go/types"
+)
+
+type IsoTileRenderOpts struct {
+	CubeLen int
+}
+
+func NewDefaultIsoTileRenderOpts() *IsoTileRenderOpts {
+	return &IsoTileRenderOpts{
+		CubeLen: 8,
+	}
+}
+
+func RenderIsometricTile(na types.NodeAccessor, cr types.ColorResolver, from, to *types.Pos, opts *IsoTileRenderOpts) (image.Image, error) {
+	if opts == nil {
+		opts = NewDefaultIsoTileRenderOpts()
+	}
+
+	min, max := types.SortPos(from, to)
+	size := to.Subtract(from).Add(types.NewPos(1, 1, 1))
+	top_size := types.NewPos(size.X(), 1, size.Z())
+
+	width, height := GetIsometricImageSize(top_size, opts.CubeLen)
+	center_x, center_y := GetIsoCenterCubeOffset(size, opts.CubeLen)
+	img := image.NewRGBA(image.Rectangle{Min: image.Point{}, Max: image.Point{X: width, Y: height}})
+
+	ipos := types.NewPos(1, -1, 1)
+
+	nodes := []*NodeWithColor{}
+
+	// top layer
+	for x := min.X(); x <= max.X(); x++ {
+		for z := min.Z(); z <= max.Z(); z++ {
+			pnodes, err := Probe(min, max, types.NewPos(x, max.Y(), z), ipos, na, cr, true)
+			if err != nil {
+				return nil, fmt.Errorf("probe error, top layer: %v", err)
+			}
+			nodes = append(nodes, pnodes...)
+		}
+	}
+
+	slices.SortFunc(nodes, SortNodesWithColor)
+
+	for _, n := range nodes {
+		rel_pos := n.Pos.Subtract(min)
+		c1 := ColorAdjust(n.Color, 0)
+		// disable alpha channel
+		c1.A = 255
+
+		// brighter/darker colors for the other sides
+		c2 := ColorAdjust(c1, -10)
+		c3 := ColorAdjust(c1, 10)
+
+		x, y := GetIsoCubePosition(center_x, center_y, opts.CubeLen, rel_pos)
+		err := DrawIsoCube(img, opts.CubeLen, x, y, c1, c2, c3)
+		if err != nil {
+			return nil, fmt.Errorf("DrawIsoCube error: %v", err)
+		}
+	}
+
+	return img, nil
+}
diff --git a/isotilerenderer_test.go b/isotilerenderer_test.go
new file mode 100644
index 0000000..29adda4
--- /dev/null
+++ b/isotilerenderer_test.go
@@ -0,0 +1,41 @@
+package maprenderer_test
+
+import (
+	"image/png"
+	"os"
+	"testing"
+
+	"github.com/minetest-go/colormapping"
+	"github.com/minetest-go/maprenderer"
+	"github.com/minetest-go/types"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIsoTileRenderer(t *testing.T) {
+	m := NewMap()
+	err := m.Load("testdata/map.csv")
+	assert.NoError(t, err)
+
+	cm := colormapping.NewColorMapping()
+	assert.NotNil(t, cm)
+
+	//load defaults
+	err = cm.LoadDefaults()
+	assert.NoError(t, err)
+
+	from := types.NewPos(0, 0, 0)
+	to := types.NewPos(15, 30, 15)
+	opts := &maprenderer.IsoTileRenderOpts{
+		CubeLen: 16,
+	}
+
+	img, err := maprenderer.RenderIsometricTile(m.GetNode, cm.GetColor, from, to, opts)
+	assert.NoError(t, err)
+	assert.NotNil(t, img)
+
+	f, err := os.OpenFile("output/iso-tile-test.png", os.O_CREATE|os.O_RDWR, 0755)
+	assert.NoError(t, err)
+
+	err = png.Encode(f, img)
+	assert.NoError(t, err)
+}