Isometric/axonometric tile engine with height maps, terrain transitions, and A* pathfinding integration. More...

#include <math.h>
#include <stdio.h>
#include "nilorea/n_astar.h"
#include "nilorea/n_iso_engine.h"
#include <allegro5/allegro.h>
#include <allegro5/allegro_primitives.h>

Include dependency graph for n_iso_engine.c:

Go to the source code of this file.

Functions
static int	_cmp_draw_entry (const void a, const void b)

static ALLEGRO_COLOR	_compute_tile_tint (int seg_top, int max_height, float intensity, float ambient_r, float ambient_g, float ambient_b, float dyn_r, float dyn_g, float dyn_b)

static void	_draw_height_borders (const ISO_MAP *map, int mx, int my, int seg_idx, int seg_bottom, int seg_top, int has_underside_face, const float vx[4], const float vy[4], float lift)
	Draw black border outlines on the diamond edges of an elevated tile.

static void	_draw_segment_sides (const ISO_MAP *map, float east_x, float east_y, float south_x, float south_y, float west_x, float west_y, int mx, int my, int seg_bottom, int seg_top, float lift, float height_brightness, int wall_terrain_override)
	Draw cliff side faces for a single segment {seg_bottom..seg_top}.

static void	_draw_segment_underside (ALLEGRO_BITMAP *bmp, float base_dx, float base_dy, float phw, float phh, float tile_draw_w, float tile_draw_h, int tile_w, int tile_h)
	Draw the underside face of a floating segment at 65% brightness.

static void	_draw_tile_warped (ALLEGRO_BITMAP *bmp, const float vx[4], const float vy[4], int tile_w, int tile_h, ALLEGRO_COLOR tint)
	Draw a tile bitmap warped to 4 pre-computed screen vertices.

static ALLEGRO_COLOR	_height_tint (int seg_top, int max_height, float intensity)
	Compute a brightness tint color for a segment at a given height.

static void	_iso_corner_to_screen (float hw, float hh, float tl, int cx, int cy, float fh, float cam_px, float cam_py, float zoom, float sx, float sy)
	Project a tile corner to screen coordinates (canonical formula).

static int	_iso_object_check_occlusion (const ISO_MAP map, float obj_fx, float obj_fy, float obj_fz, float obj_sx, float obj_sy, float sprite_h, float sprite_half_w, float cam_px, float cam_py, float zoom, float out_clip_y)
	Check if an object is occluded by tiles drawn in front of it.

static float	_iso_preset_angle (int preset)
	Get the angle in degrees for a projection preset.

static float	_smooth_neighbor_h (const ISO_MAP *map, float h_self, int nx, int ny)
	Helper: clamp neighbor height for smooth slope rendering.

static int	_tile_covers_height (const ISO_MAP *map, int mx, int my, int z)
	Check if a tile has geometry covering height level z.

int	camera_to_map (MAP **map, int tx, int ty, int x, int y)
	Center Map on given map coordinate, with x & y offset.

int	camera_to_scr (MAP **map, int x, int y)
	Center Map on given screen coordinate.

int	create_empty_map (MAP *map, const char name, int XSIZE, int YSIZE, int TILEW, int TILEH, int nbmaxobjects, int nbmaxgroup, int nbmaxanims, int nbtiles, int nbanims)
	Create an empty map.

int	draw_map (MAP map, ALLEGRO_BITMAP bmp, int destx, int desty, int mode)
	Draw a MAP map on the ALLEGRO_BITMAP bmp.

int	free_map (MAP **map)
	Free the map.

int	get_value (MAP *map, int type, int x, int y)
	Get a the tilenumber of a cell item.

void	iso_corner_to_screen (const ISO_MAP map, int cx, int cy, float fh, float cam_px, float cam_py, float zoom, float sx, float *sy)
	Project a tile corner to screen coordinates (canonical formula).

float	iso_diamond_dist (int px, int py, int tile_w, int tile_h)
	Distance from pixel to the diamond edge.

void	iso_generate_transition_masks (ALLEGRO_BITMAP **masks, int tile_w, int tile_h)
	Generate the 32 procedural transition alpha masks (16 edge + 16 corner).

void	iso_generate_transition_tiles (ALLEGRO_BITMAP *tiles, ALLEGRO_BITMAP masks, ALLEGRO_BITMAP **tile_bitmaps, int num_terrains, int tile_w, int tile_h)
	Pre-composite transition tiles (terrain texture * alpha mask).

int	iso_is_in_diamond (int px, int py, int tile_w, int tile_h)
	Test if pixel (px,py) is inside the isometric diamond.

int	iso_map_build_draw_order (const ISO_MAP map, ISO_DRAW_ENTRY out, int max_entries)
	Build the draw order for segment-sorted rendering.

void	iso_map_calc_transitions (const ISO_MAP map, int mx, int my, int edge_bits, int *corner_bits)
	Compute terrain transition bitmasks for a cell (Article 934).

void	iso_map_calc_transitions_full (const ISO_MAP map, int mx, int my, int edge_bits, int *corner_bits)
	Compute per-terrain transition bitmasks with height filtering.

void	iso_map_corner_heights (const ISO_MAP map, int mx, int my, float h_n, float h_e, float h_s, float *h_w)
	Compute average corner heights for smooth tile rendering (Article 2026).

void	iso_map_draw (const ISO_MAP map, ALLEGRO_BITMAP tile_bitmaps, ALLEGRO_BITMAP transition_tiles, int num_masks, ALLEGRO_BITMAP overlay_bitmaps, int num_overlay_tiles, float cam_px, float cam_py, float zoom, int screen_w, int screen_h, int player_mode, N_ISO_OBJECT *objects, int num_objects)
	Draw the full ISO_MAP with segment-sorted rendering.

void	iso_map_free (ISO_MAP **map_ptr)
	Free an ISO_MAP and set the pointer to NULL.

int	iso_map_get_ability (const ISO_MAP *map, int mx, int my)
	Get the ability at a cell.

int	iso_map_get_height (const ISO_MAP *map, int mx, int my)
	Get the height at a cell.

const ISO_TILE_SEGMENTS *	iso_map_get_segments (const ISO_MAP *map, int mx, int my)
	get per-tile segments.

int	iso_map_get_terrain (const ISO_MAP *map, int mx, int my)
	Get the terrain type at a cell.

ISO_VISIBLE_EDGES	iso_map_get_visible_edges (const ISO_MAP *map, int mx, int my)
	Compute which diamond edges of tile (mx,my) need a height border.

ISO_VISIBLE_EDGES	iso_map_get_visible_edges_segment (const ISO_MAP *map, int mx, int my, int seg_idx)
	Per-segment edge visibility with adjacency + occlusion.

float	iso_map_interpolate_height (const ISO_MAP *map, float fx, float fy)
	Bilinear height interpolation at fractional map coordinates.

void	iso_map_lerp_projection (ISO_MAP *map, float dt)
	Smoothly interpolate the projection angle toward the target.

ISO_MAP *	iso_map_load (const char *filename)
	Load ISO_MAP from a binary file.

ISO_MAP *	iso_map_new (int width, int height, int num_terrains, int max_height)
	Create a new height-aware isometric map.

void	iso_map_randomize (ISO_MAP *map)
	Randomize terrain and height for testing/demo purposes.

int	iso_map_save (const ISO_MAP map, const char filename)
	Save ISO_MAP to a binary file.

void	iso_map_set_ability (ISO_MAP *map, int mx, int my, int ab)
	Set the ability at a cell.

void	iso_map_set_height (ISO_MAP *map, int mx, int my, int h)
	Set the height at a cell (clamped to [0, max_height])

void	iso_map_set_projection (ISO_MAP *map, int preset, float tile_width)
	Set projection parameters from a preset and tile width.

void	iso_map_set_projection_custom (ISO_MAP *map, float half_w, float half_h, float tile_lift)
	Set custom projection parameters directly.

void	iso_map_set_projection_target (ISO_MAP *map, int preset)
	Set the target projection for smooth interpolation.

int	iso_map_set_segments (ISO_MAP map, int mx, int my, const ISO_TILE_SEGMENT segs, int count)
	set per-tile segments on an ISO_MAP.

void	iso_map_set_terrain (ISO_MAP *map, int mx, int my, int terrain)
	Set the terrain type at a cell.

int	iso_map_should_transition (const ISO_MAP *map, int mx1, int my1, int mx2, int my2)
	Check if terrain blending should occur between two adjacent cells.

int	iso_map_should_transition_smooth (const ISO_MAP *map, int mx1, int my1, int mx2, int my2)
	Check if terrain transition should render between two cells (height-aware).

void	iso_map_smooth_corner_heights (const ISO_MAP map, int mx, int my, float h_n, float h_e, float h_s, float *h_w)
	Compute smooth corner heights with slope clamping.

void	iso_map_to_screen (const ISO_MAP map, int mx, int my, int h, float screen_x, float *screen_y)
	Convert map tile coordinates to screen pixel coordinates.

void	iso_map_to_screen_f (const ISO_MAP map, float fmx, float fmy, float h, float screen_x, float *screen_y)
	Convert map coordinates to screen coordinates (float version).

void	iso_mask_tile_to_diamond (ALLEGRO_BITMAP *bmp, int tile_w, int tile_h)
	Mask a tile bitmap to the isometric diamond shape.

const char *	iso_projection_name (int preset)
	Get the display name for a projection preset.

void	iso_screen_to_map (const ISO_MAP map, float screen_x, float screen_y, int mx, int *my)
	Convert screen pixel coordinates to map tile coordinates.

void	iso_screen_to_map_height (const ISO_MAP map, float screen_x, float screen_y, int tile_w, int tile_h, int mx, int *my)
	Height-aware screen-to-map conversion with diamond hit testing.

void	iso_screen_to_map_height_f (const ISO_MAP map, float screen_x, float screen_y, int tile_w, int tile_h, int mx, int my, float out_fx, float *out_fy)
	Height-aware screen-to-map conversion returning fractional tile coordinates.

int	load_map (MAP *map, char filename)
	Load the map from filename.

void	n_iso_camera_center_on (N_ISO_CAMERA *cam, float world_x, float world_y, int screen_w, int screen_h)
	Center the camera so that a world point is at screen center.

void	n_iso_camera_follow (N_ISO_CAMERA *cam, float target_x, float target_y, int screen_w, int screen_h, float smoothing, float dt)
	Smoothly follow a world-space target.

void	n_iso_camera_free (N_ISO_CAMERA **cam)
	Free a camera and set the pointer to NULL.

N_ISO_CAMERA *	n_iso_camera_new (float zoom_min, float zoom_max)
	Create a new 2D isometric camera.

void	n_iso_camera_screen_to_world (const N_ISO_CAMERA cam, float sx, float sy, float wx, float *wy)
	Convert screen pixel coordinates to world coordinates.

void	n_iso_camera_scroll (N_ISO_CAMERA *cam, float dx, float dy)
	Scroll the camera by (dx, dy) world units.

void	n_iso_camera_world_to_screen (const N_ISO_CAMERA cam, float wx, float wy, float sx, float *sy)
	Convert world coordinates to screen pixel coordinates.

void	n_iso_camera_zoom (N_ISO_CAMERA *cam, float dz, float mouse_x, float mouse_y)
	Zoom the camera toward a screen-space point.

int	save_map (MAP map, char filename)
	Save the map to filename.

int	ScreenToMap (int mx, int my, int Tilex, int Tiley, ALLEGRO_BITMAP *mousemap)
	Convert screen coordinate to map coordinate.

int	set_value (MAP *map, int type, int x, int y, int value)
	Set the value of a cell in a map.

Detailed Description

Isometric/axonometric tile engine with height maps, terrain transitions, and A* pathfinding integration.

Author: Castagnier Mickael

Version: 2.0

Date: 01/03/2026

Definition in file n_iso_engine.c.

Function Documentation

◆ _cmp_draw_entry()

static int _cmp_draw_entry	(	const void *	a,
		const void *	b
	)

static

Definition at line 1506 of file n_iso_engine.c.

References ISO_DRAW_ENTRY::bottom, ISO_DRAW_ENTRY::mx, and ISO_DRAW_ENTRY::my.

Referenced by iso_map_build_draw_order().

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◆ _compute_tile_tint()

static ALLEGRO_COLOR _compute_tile_tint	(	int	seg_top,
		int	max_height,
		float	intensity,
		float	ambient_r,
		float	ambient_g,
		float	ambient_b,
		float	dyn_r,
		float	dyn_g,
		float	dyn_b
	)

inlinestatic

Definition at line 2033 of file n_iso_engine.c.

Referenced by iso_map_draw().

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◆ _draw_height_borders()

static void _draw_height_borders	(	const ISO_MAP *	map,
		int	mx,
		int	my,
		int	seg_idx,
		int	seg_bottom,
		int	seg_top,
		int	has_underside_face,
		const float	vx[4],
		const float	vy[4],
		float	lift
	)

static

Draw black border outlines on the diamond edges of an elevated tile.

Rules:

Only draws edges where height difference > 1 or neighbor missing.
NEVER draws the top vertex (N) where NW and NE edges meet — it is always hidden behind the tile surface itself.
At corners E, S, W where two drawn edges meet, they join naturally.
Occlusion is handled by painter's algorithm: tiles drawn later (closer to camera) paint over borders of earlier tiles.

Diamond vertices: N=vx[0] (top), E=vx[1] (right), S=vx[2] (bottom), W=vx[3] (left)

Definition at line 2348 of file n_iso_engine.c.

References ISO_VISIBLE_EDGES::draw_ne, ISO_VISIBLE_EDGES::draw_nw, ISO_VISIBLE_EDGES::draw_se, ISO_VISIBLE_EDGES::draw_sw, ISO_VISIBLE_EDGES::draw_underside, iso_map_get_visible_edges_segment(), ISO_VISIBLE_EDGES::neighbor_top_ne, ISO_VISIBLE_EDGES::neighbor_top_nw, ISO_VISIBLE_EDGES::neighbor_top_se, and ISO_VISIBLE_EDGES::neighbor_top_sw.

Referenced by iso_map_draw().

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◆ _draw_segment_sides()

static void _draw_segment_sides	(	const ISO_MAP *	map,
		float	east_x,
		float	east_y,
		float	south_x,
		float	south_y,
		float	west_x,
		float	west_y,
		int	mx,
		int	my,
		int	seg_bottom,
		int	seg_top,
		float	lift,
		float	height_brightness,
		int	wall_terrain_override
	)

static

Draw cliff side faces for a single segment {seg_bottom..seg_top}.

For ground segments (seg_bottom==0) uses neighbor-aware wall height. For floating segments (seg_bottom>0) draws full segment height.

Definition at line 2123 of file n_iso_engine.c.

References iso_map_get_height(), and iso_map_get_terrain().

Referenced by iso_map_draw().

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◆ _draw_segment_underside()

static void _draw_segment_underside	(	ALLEGRO_BITMAP *	bmp,
		float	base_dx,
		float	base_dy,
		float	phw,
		float	phh,
		float	tile_draw_w,
		float	tile_draw_h,
		int	tile_w,
		int	tile_h
	)

static

Draw the underside face of a floating segment at 65% brightness.

The underside is a diamond drawn at the segment's bottom height.

Definition at line 2224 of file n_iso_engine.c.

Referenced by iso_map_draw().

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◆ _draw_tile_warped()

static void _draw_tile_warped	(	ALLEGRO_BITMAP *	bmp,
		const float	vx[4],
		const float	vy[4],
		int	tile_w,
		int	tile_h,
		ALLEGRO_COLOR	tint
	)

static

Draw a tile bitmap warped to 4 pre-computed screen vertices.

Uses two textured triangles mapped to the warped diamond shape. Vertices must come from _iso_corner_to_screen for bit-identical shared edges between adjacent tiles.

Definition at line 2067 of file n_iso_engine.c.

Referenced by iso_map_draw().

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◆ _height_tint()

static ALLEGRO_COLOR _height_tint	(	int	seg_top,
		int	max_height,
		float	intensity
	)

inlinestatic

Compute a brightness tint color for a segment at a given height.

Higher segments are brighter (closer to white), lower segments are darker.

Parameters

seg_top	top height of the segment
max_height	maximum height in the map (0 = no scaling)
intensity	tint intensity (0.0 = no tint/white, 1.0 = full range)

Returns: ALLEGRO_COLOR to use as multiply tint

Definition at line 2019 of file n_iso_engine.c.

◆ _iso_corner_to_screen()

static void _iso_corner_to_screen	(	float	hw,
		float	hh,
		float	tl,
		int	cx,
		int	cy,
		float	fh,
		float	cam_px,
		float	cam_py,
		float	zoom,
		float *	sx,
		float *	sy
	)

inlinestatic

Project a tile corner to screen coordinates (canonical formula).

Every screen vertex in the renderer must come from this function so that two tiles sharing a corner get bit-identical screen positions regardless of which tile's draw call is computing the vertex.

The camera offset (cam_px, cam_py) must be integer-snapped pixel offsets computed as floor(cam_x * zoom), floor(cam_y * zoom). This ensures the fractional pixel position of each vertex comes only from (wx * zoom), which is constant per vertex, eliminating sub-pixel aliasing shimmer during camera movement.

Parameters

hw	map->proj.half_w (unzoomed)
hh	map->proj.half_h (unzoomed)
tl	map->proj.tile_lift (unzoomed)
cx	corner X in tile grid (e.g. mx+1 for the East corner)
cy	corner Y in tile grid
fh	height (float, supports smooth-height interpolation)
cam_px	integer-snapped camera pixel X: floor(cam_x * zoom)
cam_py	integer-snapped camera pixel Y: floor(cam_y * zoom)
zoom	zoom factor
sx	output screen X
sy	output screen Y

Definition at line 2004 of file n_iso_engine.c.

Referenced by _iso_object_check_occlusion(), and iso_map_draw().

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◆ _iso_object_check_occlusion()

static int _iso_object_check_occlusion	(	const ISO_MAP *	map,
		float	obj_fx,
		float	obj_fy,
		float	obj_fz,
		float	obj_sx,
		float	obj_sy,
		float	sprite_h,
		float	sprite_half_w,
		float	cam_px,
		float	cam_py,
		float	zoom,
		float *	out_clip_y
	)

static

Check if an object is occluded by tiles drawn in front of it.

Tests tiles at higher depth (mx+my) in a forward cone to see if any elevated tile's screen area overlaps the object's screen position.

Parameters

map	the map
obj_fx	object fractional map X
obj_fy	object fractional map Y
obj_fz	object height
obj_sx	object screen X (camera-transformed)
obj_sy	object screen Y (camera-transformed)
sprite_h	sprite height used for occlusion bounding
cam_px	camera X offset in pixels
cam_py	camera Y offset in pixels
zoom	current zoom

Returns: 1 if occluded, 0 if visible

Definition at line 2259 of file n_iso_engine.c.

References _iso_corner_to_screen(), ISO_PROJECTION::half_h, ISO_PROJECTION::half_w, ISO_MAP::height, iso_map_get_height(), iso_map_to_screen(), ISO_MAP::max_height, ISO_MAP::proj, ISO_PROJECTION::tile_lift, and ISO_MAP::width.

Referenced by iso_map_draw().

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◆ _iso_preset_angle()

static float _iso_preset_angle ( int preset )

static

Get the angle in degrees for a projection preset.

Parameters

preset one of ISO_PROJ_CLASSIC, ISO_PROJ_ISOMETRIC, ISO_PROJ_STAGGERED, ISO_PROJ_MILITARY

Returns: angle in degrees

Definition at line 696 of file n_iso_engine.c.

References ISO_PROJ_CLASSIC, ISO_PROJ_ISOMETRIC, ISO_PROJ_MILITARY, and ISO_PROJ_STAGGERED.

Referenced by iso_map_set_projection(), and iso_map_set_projection_target().

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◆ _smooth_neighbor_h()

static float _smooth_neighbor_h	(	const ISO_MAP *	map,
		float	h_self,
		int	nx,
		int	ny
	)

inlinestatic

Helper: clamp neighbor height for smooth slope rendering.

If the height difference exceeds smooth_slope_max, return self height (creating a cliff instead of a slope).

Definition at line 1426 of file n_iso_engine.c.

References iso_map_get_height(), and ISO_MAP::smooth_slope_max.

Referenced by iso_map_smooth_corner_heights().

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◆ _tile_covers_height()

static int _tile_covers_height	(	const ISO_MAP *	map,
		int	mx,
		int	my,
		int	z
	)

static

Check if a tile has geometry covering height level z.

Returns 1 if any segment of (mx,my) has bottom <= z AND top > z, meaning the tile's wall/surface extends strictly above z. Used for occlusion: a tile drawn later in painter order covers edges of earlier tiles when its wall passes above the edge height.

Requires the occluding tile to be at least 2 height units taller (top > z + 1) so that single-step stairs (+1 per tile) do not suppress the NW/NE borders — the step only partially covers the edge, and painter order handles the overlap visually.

Definition at line 1824 of file n_iso_engine.c.

References ISO_TILE_SEGMENT::bottom, ISO_TILE_SEGMENTS::count, ISO_MAP::height, iso_map_get_height(), iso_map_get_segments(), ISO_TILE_SEGMENTS::segs, ISO_TILE_SEGMENT::top, and ISO_MAP::width.

Referenced by iso_map_get_visible_edges_segment().

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Functions

Detailed Description

Function Documentation

◆ _cmp_draw_entry()

◆ _compute_tile_tint()

◆ _draw_height_borders()

◆ _draw_segment_sides()

◆ _draw_segment_underside()

◆ _draw_tile_warped()

◆ _height_tint()

◆ _iso_corner_to_screen()

◆ _iso_object_check_occlusion()

◆ _iso_preset_angle()

◆ _smooth_neighbor_h()

◆ _tile_covers_height()