prisms

engine/hexprisms.go

@@ -1,10 +0,0 @@
-package engine
-
-type HexPrismMap struct {
-	Map map[Point3]*HexPrism
-}
-
-type HexPrism struct {
-	pos Point3
-	hpm *HexPrismMap
-}

engine/prisms.go

@@ -0,0 +1,53 @@
+package engine
+
+import (
+	"image"
+
+	"github.com/hajimehoshi/ebiten/v2"
+)
+
+type PrismMap struct {
+	Map           map[Point3]*Prism
+	DrawOrderBias image.Point // dot with (X,Y) = bias
+	DrawOffset    image.Point // offset to apply to whole map
+	DrawZStride   image.Point // (X,Y) draw translation for each unit in Z
+	PrismSize     Point3
+	Sheet         Sheet
+}
+
+func (m *PrismMap) Prepare(*Game) error {
+	for v, p := range m.Map {
+		p.pos = v
+		p.pm = m
+	}
+	return nil
+}
+
+func (m *PrismMap) Transform(pt Transform) (tf Transform) {
+	tf.Opts.GeoM.Translate(cfloat(m.DrawOffset))
+	return tf.Concat(pt)
+}
+
+type Prism struct {
+	Cell int
+
+	pos Point3
+	pm  *PrismMap
+}
+
+func (p *Prism) Draw(screen *ebiten.Image, tf *Transform) {
+	screen.DrawImage(p.pm.Sheet.SubImage(p.Cell), &tf.Opts)
+}
+
+func (p *Prism) DrawOrder() (int, int) {
+	return p.pos.Z * p.pm.PrismSize.Z,
+		dot(p.pos.XY(), p.pm.DrawOrderBias)
+}
+
+func (p *Prism) Transform(pt Transform) (tf Transform) {
+	v := p.pos.CMul(p.pm.PrismSize)
+	tf.Opts.GeoM.Translate(cfloat(
+		v.XY().Add(p.pm.DrawZStride.Mul(v.Z)),
+	))
+	return tf.Concat(pt)
+}

engine/projection.go

@@ -1,6 +1,6 @@
 package engine
 
-const (
+var (
 	// Oblique projections
 	CabinetProjection  = ParallelProjection{0.5, 0.5}
 	CavalierProjection = ParallelProjection{1, 1}