/apps/examples/circle-raster: simple code for grid-centered circle rasterization

apps/examples/circle-raster/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.21)
+
+project(circle-raster LANGUAGES C)
+
+if(NOT CMAKE_BUILD_TYPE)
+        set(CMAKE_BUILD_TYPE Debug)
+endif()
+
+add_subdirectory($ENV{TWNROOT} $ENV{TWNROOT}/build)
+
+set(SOURCE_FILES
+        game.c
+        state.h
+)
+
+use_townengine(${PROJECT_NAME} "${SOURCE_FILES}" ${CMAKE_CURRENT_SOURCE_DIR})

apps/examples/circle-raster/data/twn.toml

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+# This file contains everything about the engine and your game that can be
+# configured before it runs.
+#
+# Optional settings are commented out, with their default values shown.
+# Invalid values in these settings will be ignored.
+
+# Data about your game as an application
+[about]
+title = "Template"
+developer = "You"
+app_id = "template"
+dev_id = "you"
+
+# Game runtime details
+[game]
+resolution = [ 640, 480 ]
+#debug = true
+
+# Engine tweaks. You probably don't need to change these
+[engine]
+#ticks_per_second = 60 # minimum of 8
+#keybind_slots = 3 # minimum of 1
+#texture_atlas_size = 2048 # minimum of 32
+#font_texture_size = 2048 # minimum of 1024
+#font_oversampling = 4 # minimum of 0
+#font_filtering = "linear" # possible values: "nearest", "linear"

apps/examples/circle-raster/game.c

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+#include "twn_game_api.h"
+#include "state.h"
+
+#include <malloc.h>
+#include <math.h>
+
+
+/* Emits `x` and `y` for every intersecting cell */
+/* We snap position to the nearest corner, which means there's no aliasing */
+/* It works great for integer radii */
+#define m_iter_circle_pixels(p_center_x, p_center_y, p_radius) \
+    for (float y = (p_center_y + ceilf(p_radius)) - 1; y > (p_center_y - ceilf(p_radius)) - 1; --y) \
+        for (float x = p_center_x - ceilf(sqrtf(p_radius * p_radius - (y - p_center_y + (y <= p_center_y)) * (y - p_center_y + (y <= p_center_y)))); x < p_center_x + ceilf(sqrtf(p_radius * p_radius - (y - p_center_y + (y <= p_center_y)) * (y - p_center_y + (y <= p_center_y)))); ++x)
+
+
+void game_tick(void) {
+    if (ctx.initialization_needed) {
+        if (!ctx.udata) {
+            ctx.udata = ccalloc(1, sizeof (struct state));
+            struct state *state = ctx.udata;
+            state->r = 10;
+        }
+    }
+
+    struct state *state = ctx.udata;
+
+    Vec2 const mouse_snap = {floorf(ctx.mouse_position.x / 8) * 8, floorf(ctx.mouse_position.y / 8) * 8};
+
+    input_action("up", CONTROL_LEFT_MOUSE);
+    input_action("down", CONTROL_RIGHT_MOUSE);
+
+    if (input_action_just_pressed("up"))
+        state->r += 1;
+    if (input_action_just_pressed("down"))
+        state->r -= 1;
+
+    float const rs = state->r * state->r;
+    float const cr = ceilf(state->r);
+    for (float iy = cr - 1; iy > -cr - 1; --iy) {
+        float const dx = ceilf(sqrtf(rs - (iy + (iy <= 0)) * (iy + (iy <= 0))));
+        for (float ix = -dx; ix < dx; ++ix) {
+            draw_box((Rect){mouse_snap.x + ix * 8, mouse_snap.y + iy * 8, 8, 8}, 1, (Color){255, 0, 0, 125});
+        }
+    }
+
+    draw_circle(mouse_snap, state->r * 8, (Color){125, 125, 125, 125});
+}
+
+
+void game_end(void) {
+    /* do your deinitialization here */
+    struct state *state = ctx.udata;
+    free(state);
+}

apps/examples/circle-raster/state.h

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+#ifndef STATE_H
+#define STATE_H
+
+#include "twn_game_api.h"
+
+struct state {
+    float r;
+};
+
+
+#endif