Formalise a bit in each cell as an "IsActive()" bit

cmd/view-map/main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"flag"
+	"fmt"
 	"log"
 	"math"
 	"os"
@@ -112,26 +113,28 @@ func (e *env) run() {
 	})
 }
 
-func (e *env) getSprite(palette []string, ref maps.ObjRef) *conv.Sprite {
+func (e *env) getSprite(palette []string, ref maps.ObjRef) (*conv.Sprite, error) {
+	// There seems to be an active bit that hides many sins
+	if !ref.IsActive() {
+		return nil, nil
+	}
+
 	if ref.Index() >= len(palette) {
-		log.Printf("Palette too small: %v requested", ref.Index())
+		return nil, fmt.Errorf("Palette too small: %v requested", ref.Index())
-		return nil
 	}
 
 	name := palette[ref.Index()]
 
 	obj := e.objects[name]
 	if obj == nil {
-		log.Printf("Failed to find surface sprite %#v -> %q", ref, name)
+		return nil, fmt.Errorf("Failed to find surface sprite %#v -> %q", ref, name)
-		return nil
 	}
 
-	if ref.Frame() >= len(obj.Sprites) {
+	if ref.Sprite() >= len(obj.Sprites) {
-		log.Printf("Out-of-index sprite %v requested for %v", ref.Frame(), name)
+		return nil, fmt.Errorf("Out-of-index sprite %v requested for %v", ref.Sprite(), name)
-		return nil
 	}
 
-	return &obj.Sprites[ref.Frame()]
+	return &obj.Sprites[ref.Sprite()], nil
 }
 
 // TODO: build all the sprites in the set into a single spritesheet so we can
@@ -171,14 +174,29 @@ func (s *state) renderCell(x, y, z int, pWin *pixelgl.Window) {
 
 	cell := s.env.gameMap.Cells.At(x, y, z)
 
-	sprites = append(sprites, s.env.getSprite(s.env.set.Palette, cell.Surface))
+	if spr, err := s.env.getSprite(s.env.set.Palette, cell.Surface); err != nil {
+		log.Printf("%v %v %v surface: %v", x, y, z, err)
+	} else {
+		sprites = append(sprites, spr)
+	}
 
-	sprites = append(
+	if spr, err := s.env.getSprite(s.env.set.Palette, cell.Center); err != nil {
-		sprites,
+		log.Printf("%v %v %v center: %v", x, y, z, err)
-		s.env.getSprite(s.env.set.Palette, cell.Center),
+	} else {
-		s.env.getSprite(s.env.set.Palette, cell.Left),
+		sprites = append(sprites, spr)
-		s.env.getSprite(s.env.set.Palette, cell.Right),
+	}
-	)
+
+	if spr, err := s.env.getSprite(s.env.set.Palette, cell.Left); err != nil {
+		log.Printf("%v %v %v left: %v", x, y, z, err)
+	} else {
+		sprites = append(sprites, spr)
+	}
+
+	if spr, err := s.env.getSprite(s.env.set.Palette, cell.Right); err != nil {
+		log.Printf("%v %v %v right: %v", x, y, z, err)
+	} else {
+		sprites = append(sprites, spr)
+	}
 
 	// Taking the Z index away *seems* to draw the object in the correct place.
 	// FIXME: There are some artifacts, investigate more
@@ -227,11 +245,14 @@ func (s *state) handleKeys(pWin *pixelgl.Window) {
 	// FIXME: this suggests we should pass the next state into here and
 	// modify it instead
 	if pWin.JustPressed(pixelgl.MouseButton1) {
-		cell := s.pixToCell(s.cam.Unproject(pWin.MousePosition()))
 		if s.zIdx != 0 {
 			log.Printf("WARNING: z-index not yet taken into account")
 		}
-		log.Printf("X=%v Y=%v, zIdx=%v", cell.X, cell.Y, s.zIdx)
+
+		pos := s.pixToCell(s.cam.Unproject(pWin.MousePosition()))
+		cell := s.env.gameMap.Cells.At(int(pos.X), int(pos.Y), s.zIdx)
+		log.Printf("X=%v Y=%v, zIdx=%v", pos.X, pos.Y, s.zIdx)
+		log.Printf("Cell=%#v", cell)
 	}
 
 	if pWin.Pressed(pixelgl.KeyLeft) {

doc/formats/maps.md

@@ -400,15 +400,15 @@ Investigation has so far suggested the following:
     *  0x40: Animated object
 * `Cell[2]` hasn't been seen with a value > 0 yet
 * `Cell[3]` Object 0 (Surface) Area (Sets/*.set lookup)
-* `Cell[4]` Object 0 (Surface) Sprite + ???
+* `Cell[4]` Object 0 (Surface) Sprite + active flag
     * Bottom bits encode the sprite (frame number in the .obj file)
     * 0x80 is set too. A flag?
 * `Cell[5]` Object 1 (Left) Area (Sets/*.set lookup)
-* `Cell[6]` Object 1 (Surface) Sprite + ???
+* `Cell[6]` Object 1 (Surface) Sprite + active flag
 * `Cell[7]` Object 2 (Right) Area (Sets/*.set lookup)
-* `Cell[6]` Object 2 (Right) Sprite + ???
+* `Cell[6]` Object 2 (Right) Sprite + active flag
 * `Cell[9]` Object 3 (Center) Area (Sets/*.set lookup)
-* `Cell[10]` Object 3 (Right) Sprite + ???
+* `Cell[10]` Object 3 (Right) Sprite + active flag
 * `Cell[11]` all 255?
 * `Cell[12]` all 0?
 * `Cell[13]` all 0?
@@ -436,6 +436,12 @@ So `CellIdx == 9` points to the center object's Area, looked up in the set file!
 It seems the area numbers are absolute indexes into the set, rather than having
 a new set of indices for each type.
 
+We have to remove 0x80 from the sprite byte to get a valid reference. This seems
+to act as an "active" flag - without it, Chapter01.MAP has a "ghost" of the
+template close to the 0,0 boundary. Theory: the devs originally started at 0,0
+but then they decided to center smaller maps rather than being there, so the
+layout got moved!
+
 With this information, we can render a given Z index for a map quite easily,
 using the new `view-map` binary. It draws the four objects for every cell, and
 gives results like this:

internal/conv/object.go

@@ -52,7 +52,7 @@ var transparent = color.RGBA{0, 0, 0, 0}
 func spriteToPic(name string, idx int, sprite *data.Sprite) *pixel.PictureData {
 	pic := pixel.MakePictureData(pixel.R(float64(0), float64(0), float64(sprite.Width), float64(sprite.Height)))
 
-	log.Printf("%v %v: width=%v height=%v", name, idx, sprite.Width, sprite.Height)
+	//log.Printf("%v %v: width=%v height=%v", name, idx, sprite.Width, sprite.Height)
 
 	for y := 0; y < int(sprite.Height); y++ {
 		// Start with all bytes transparent
@@ -61,7 +61,7 @@ func spriteToPic(name string, idx int, sprite *data.Sprite) *pixel.PictureData {
 		}
 
 		row := sprite.Rows[y]
-		log.Printf("%#v", row)
+		//log.Printf("%#v", row)
 		pixels := row[0 : len(row)-1] // Strip off the record separator (0x00)
 
 		// Not really clear on what this does yet. Aligned with sprite width in
@@ -79,7 +79,7 @@ func spriteToPic(name string, idx int, sprite *data.Sprite) *pixel.PictureData {
 
 		// Do nothing if we're out of pixels
 		if u0 == 0x80 {
-			log.Printf("Handling 0x80: %#v", pixels)
+			//log.Printf("Handling 0x80: %#v", pixels)
 			xOffset = int(pixels[0])
 			pixels = pixels[1:len(pixels)]
 
@@ -98,10 +98,10 @@ func spriteToPic(name string, idx int, sprite *data.Sprite) *pixel.PictureData {
 			}
 		}
 
-		log.Printf(
+		//log.Printf(
-			"%v %d: len(row)=%v, len(pixels)=%v sprWidth=%v u0=%v xOffset=%v",
+		//	"%v %d: len(row)=%v, len(pixels)=%v sprWidth=%v u0=%v xOffset=%v",
-			name, idx, len(row), len(pixels), sprite.Width, u0, xOffset,
+		//	name, idx, len(row), len(pixels), sprite.Width, u0, xOffset,
-		)
+		//)
 
 		for x, b := range pixels {
 			vec := pixel.V(float64(xOffset+x), float64(y))

internal/maps/maps.go

@@ -69,8 +69,8 @@ func (h Header) MapSetFilename() string {
 }
 
 type ObjRef struct {
-	AreaByte            byte
+	AreaByte          byte
-	FrameAndUnknownByte byte
+	SpriteAndFlagByte byte
 }
 
 // The index into a set palette to retrieve the object
@@ -78,8 +78,14 @@ func (o ObjRef) Index() int {
 	return int(o.AreaByte)
 }
 
-func (o ObjRef) Frame() int {
+func (o ObjRef) Sprite() int {
-	return int(o.FrameAndUnknownByte - 0x80)
+	// The top bit seems to be a flag of some kind
+	return int(o.SpriteAndFlagByte & 0x7f)
+}
+
+// The top bit seems to say whether we should draw or not.
+func (o ObjRef) IsActive() bool {
+	return (o.SpriteAndFlagByte & 0x80) == 0x80
 }
 
 type Cell struct {
@@ -108,19 +114,19 @@ func (c *Cell) At(n int) byte {
 	case 3:
 		return c.Surface.AreaByte
 	case 4:
-		return c.Surface.FrameAndUnknownByte
+		return c.Surface.SpriteAndFlagByte
 	case 5:
 		return c.Left.AreaByte
 	case 6:
-		return c.Left.FrameAndUnknownByte
+		return c.Left.SpriteAndFlagByte
 	case 7:
 		return c.Right.AreaByte
 	case 8:
-		return c.Right.FrameAndUnknownByte
+		return c.Right.SpriteAndFlagByte
 	case 9:
 		return c.Center.AreaByte
 	case 10:
-		return c.Center.FrameAndUnknownByte
+		return c.Center.SpriteAndFlagByte
 	case 11:
 		return c.Unknown11
 	case 12:
@@ -139,7 +145,6 @@ func (c *Cell) At(n int) byte {
 // Cells is always a fixed size; use At to get a cell according to x,y,z
 type Cells []Cell
 
-// FIXME: Ordering may be incorrect? I assume z,y,x for now...
 func (c Cells) At(x, y, z int) Cell {
 	return c[(z*MaxLength*MaxWidth)+(y*MaxWidth)+x]
 }