Initial commit.

5 files changed, 1524 insertions, 0 deletions

diff --git a/src/common.h b/src/common.h
new file mode 100644
index 0000000..ee9c3fe
--- /dev/null
+++ b/src/common.h
@@ -0,0 +1,256 @@
+#include <stdlib.h>
+#include <inttypes.h>
+#include <string.h>  
+#include <assert.h>
+#include <stdbool.h>
+#include <math.h>
+#include <SDL2/SDL.h>
+
+#define PROGRAM_NAME "Symulator pól elektromagnetycznych"
+
+#include <stdio.h>
+#define con_printf printf
+
+#define max2(a, b) ((a) > (b) ? (a) : (b))
+#define max3(a, b, c) (max2(max2(a, b), c))
+#define min2(a, b) ((a) < (b) ? (a) : (b))
+#define min3(a, b, c) (min2(min2(a, b), c))
+
+// main
+
+char *va(const char *fmt, ...);
+int64_t get_time(void);
+
+// math
+
+typedef float vec_t;
+typedef vec_t vec2_t[2];   
+typedef vec_t vec3_t[3];    
+typedef vec_t vec4_t[4];
+typedef vec_t mst2_t[4];
+/* mst2_t is a 3x3 scale&translate matrix (only 4 components are needed):
+ * [ dw  0   dx ]
+ * [ 0   dh  dy ]
+ * [ 0   0   1  ]
+ */
+
+static inline void v2_copy(vec_t *R, vec_t *A)
+{
+	R[0] = A[0];
+	R[1] = A[1];
+}
+
+static inline void v3_copy(vec_t *R, vec_t *A)
+{
+	R[0] = A[0];
+	R[1] = A[1];
+	R[2] = A[2];
+}
+
+static inline void v4_copy(vec_t *R, vec_t *A)
+{
+	R[0] = A[0];
+	R[1] = A[1];
+	R[2] = A[2];
+	R[3] = A[3];
+}
+
+static inline void v2_set(vec_t *R, vec_t a, vec_t b)
+{
+	R[0] = a;
+	R[1] = b;
+}
+
+static inline void v3_set(vec_t *R, vec_t a, vec_t b, vec_t c)
+{
+	R[0] = a;
+	R[1] = b;
+	R[2] = c;
+}
+
+static inline void v2_add(vec_t *R, vec_t *A, vec_t *B)
+{
+	R[0] = A[0] + B[0];
+	R[1] = A[1] + B[1];
+}
+
+static inline void v2_sub(vec_t *R, vec_t *A, vec_t *B)
+{
+	R[0] = A[0] - B[0];
+	R[1] = A[1] - B[1];
+}
+
+static inline void v2_mul(vec_t *R, vec_t *A, vec_t b)
+{
+	R[0] = A[0] * b;
+	R[1] = A[1] * b;
+}
+
+static inline void mst2_set_identity(mst2_t R)
+{
+	R[0] = 0;
+	R[1] = 0;
+	R[2] = 1;
+	R[3] = 1;
+}
+
+static inline void mst2_set(mst2_t R, vec_t dx, vec_t dy, vec_t dw, vec_t dh)
+{
+	R[0] = dx;
+	R[1] = dy;
+	R[2] = dw;
+	R[3] = dh;
+}
+
+static inline void mst2_inv(mst2_t R, mst2_t A)
+{
+	mst2_t copy = {A[0], A[1], A[2], A[3]};
+
+	R[0] = -copy[0] / copy[2];
+	R[1] = -copy[1] / copy[3];
+	R[2] = 1 / copy[2];
+	R[3] = 1 / copy[3];
+}
+
+static inline void v2_mul_mst2(vec_t *R, vec_t *A, mst2_t M)
+{
+	R[0] = M[0] + A[0] * M[2];
+	R[1] = M[1] + A[1] * M[3];
+}
+
+static inline void v2_div_mst2(vec_t *R, vec_t *A, mst2_t M)
+{
+	mst2_t inv;
+
+	mst2_inv(inv, M);
+	v2_mul_mst2(R, A, inv);
+}
+
+// v2_mul_mst2 but without translation
+static inline void v2_mul_mst2_nt(vec_t *R, vec_t *A, mst2_t M)
+{
+	R[0] = A[0] * M[2];
+	R[1] = A[1] * M[3];
+}
+
+// v2_div_mst2 but without translation
+static inline void v2_div_mst2_nt(vec_t *R, vec_t *A, mst2_t M)
+{
+	mst2_t inv;
+
+	mst2_inv(inv, M);
+	v2_mul_mst2_nt(R, A, inv);
+}
+
+static inline void mst2_dump(mst2_t M)
+{
+	printf("[%f\t%f\t%f]\n", M[2], 0.0, M[0]);
+	printf("[%f\t%f\t%f]\n", 0.0, M[3], M[1]);
+	printf("[%f\t%f\t%f]\n", 0.0, 0.0, 1.0);
+}
+
+// physics
+
+typedef struct {
+	size_t width, height, depth;
+	size_t zstr, ystr, xstr, size; // strides in no. of points (not bytes)
+	size_t zstr1, ystr1, xstr1, size1; // same as above but for associated
+	                                   // scalar fields
+	float spacing; // in meters
+} phy_field_info;
+
+typedef struct {
+	float *E;
+	float *H;
+} phy_field_em;
+
+/*
+typedef struct {
+	int num;
+	void *data;
+} phy_command;
+*/
+
+typedef struct {
+	phy_field_info field_info;
+	phy_field_em fields[3];
+	float *field_eps, *field_mu; //permittivity and permeability
+	float time;
+
+	SDL_mutex *rotate_lock;
+} phy_sim;
+
+void phy_sim_destroy(phy_sim *sim);
+int phy_sim_create(phy_sim *sim);
+void phy_sim_compute_const_fields(phy_sim *sim);
+void phy_sim_step(phy_sim *sim, float dt);
+
+int phy_thread(phy_sim *sim);
+
+// renderer
+
+extern float r_color_white[4];
+extern float r_color_black[4];
+extern float r_color_red[4];
+extern float r_color_blue[4];
+
+typedef struct r_window_s r_window;
+struct r_window_s {
+	SDL_Window *window;
+	SDL_Renderer *renderer;
+	SDL_Texture *font_texture;
+
+	r_window *prev, *next;
+};
+
+int r_init(void);
+void r_quit(void);
+
+r_window *r_window_create(void);
+void r_window_destroy(r_window *rw);
+
+void r_clear(r_window *rw, float *color);
+void r_flip(r_window *rw);
+
+void r_clip_enable(r_window *rw, float x, float y, float w, float h);
+void r_clip_disable(r_window *rw);
+void r_draw_line(r_window *rw, float x0, float y0, float x1, float y1,
+                 float *color);
+void r_draw_rect(r_window *rw, float x, float y, float w, float h,
+                 float *color);
+
+#define TEXT_CENTERX     0x0001
+#define TEXT_RIGHTX      0x0002
+float r_text_width(float h, char *text);
+void r_draw_text(r_window *rw, float x, float y, float h, char *text,
+                 float *color, int flags);
+
+typedef enum {
+	XSECTION_XY,
+	XSECTION_XZ,
+	XSECTION_YZ
+} r_xsection_type;
+
+typedef struct {
+	SDL_Texture *texture;
+	float aspect_ratio;
+} r_xsection;
+
+void r_xsection_create(r_xsection *xsection);
+void r_xsection_destroy(r_xsection *xsection);
+int r_xsection_update(r_window *rw, r_xsection *xsection,
+                      phy_field_info *fi, float *field,
+                      r_xsection_type type, float frac);
+void r_xsection_draw(r_window *rw, r_xsection *xsection,
+                     float x, float y, float w, float h);
+
+// ui
+
+int ui_init(void);
+void ui_quit(void);
+
+void ui_renderer_window_register(r_window *rw);
+
+void ui_event(SDL_Event *event);
+void ui_draw(phy_sim *sim);
+
diff --git a/src/main.c b/src/main.c
new file mode 100644
index 0000000..65a7ab3
--- /dev/null
+++ b/src/main.c
@@ -0,0 +1,90 @@
+#include "common.h"
+#include <signal.h>
+#include <time.h>
+
+char *va(const char *fmt, ...)
+{
+	va_list vl;
+	static char buffer[4096];
+
+	va_start(vl, fmt);
+	vsnprintf(buffer, sizeof(buffer), fmt, vl);
+	va_end(vl);
+
+	return buffer;
+}
+
+int64_t get_time(void)
+{
+	struct timespec ts;
+	clock_gettime(CLOCK_MONOTONIC, &ts);
+	return ts.tv_sec * 1000000000 + ts.tv_nsec;
+}
+
+int main(void)
+{
+	int rv = 0;
+	r_window *first_window;
+	phy_sim sim;
+	SDL_Thread *sim_thread;
+
+	if (r_init()) {
+		con_printf("fatal error: renderer initialization failed\n");
+		rv = 1;
+		goto quit;
+	}
+
+	if (ui_init()) {
+		con_printf("fatal error: UI initialization failed\n");
+		rv = 1;
+		goto quit;
+	}
+
+	signal(SIGINT, SIG_DFL);
+	signal(SIGTERM, SIG_DFL);
+
+	first_window = r_window_create();
+	if (!first_window) {
+		con_printf("fatal error: couldn't open first window\n");
+		rv = 1;
+		goto quit;
+	}
+
+	ui_renderer_window_register(first_window);
+
+	if (phy_sim_create(&sim)) {
+		con_printf("fatal error: phy_sim_create failed\n");
+		rv = 1;
+		goto quit;
+	}
+
+	sim_thread = SDL_CreateThread((SDL_ThreadFunction)phy_thread,
+	                              "phy_thread", &sim);
+	if (!sim_thread) {
+		con_printf("fatal error: SDL_CreateThread failed: %s\n",
+		           SDL_GetError());
+		rv = 1;
+		goto quit;
+	}
+
+	while (1) {
+		SDL_Event event;
+
+		while (SDL_PollEvent(&event)) {
+			if (event.type == SDL_QUIT)
+				goto quit;
+			else
+				ui_event(&event);
+		}
+
+		ui_draw(&sim);
+	}
+
+quit:
+	con_printf("main: exitting, rv=%i\n", rv);
+  	phy_sim_destroy(&sim);
+	ui_quit();
+	r_quit();
+	SDL_Quit();
+	return rv;
+}
diff --git a/src/physics.c b/src/physics.c
new file mode 100644
index 0000000..be6a426
--- /dev/null
+++ b/src/physics.c
@@ -0,0 +1,244 @@
+#include "common.h"
+
+void phy_sim_destroy(phy_sim *sim) {
+	size_t i;
+
+	SDL_DestroyMutex(sim->rotate_lock);
+
+	for (i = 0; i < 3; i++) {
+		free(sim->fields[i].E);
+		free(sim->fields[i].H);
+	}
+}
+
+int phy_sim_create(phy_sim *sim) {
+	size_t i;
+	phy_field_info *fi;
+
+	memset(sim, 0, sizeof(phy_sim));
+
+	fi = &sim->field_info;
+
+	fi->width = 30;
+	fi->height = 30;
+	fi->depth = 30;
+	fi->spacing = 1.5e10 / max3(fi->width, fi->height, fi->depth);
+
+	fi->xstr = 3;
+	fi->ystr = fi->xstr * fi->width;
+	fi->zstr = fi->ystr * fi->height;
+	fi->size = fi->zstr * fi->depth;
+
+	fi->xstr1 = 1;
+	fi->ystr1 = fi->xstr1 * fi->width;
+	fi->zstr1 = fi->ystr1 * fi->height;
+	fi->size1 = fi->zstr1 * fi->depth;
+
+	for (i = 0; i < 3; i++) { 
+		sim->fields[i].E = calloc(fi->size, sizeof(float));
+		sim->fields[i].H = calloc(fi->size, sizeof(float));
+		if (!sim->fields[i].E || !sim->fields[i].H) {
+			con_printf("phy_sim_create: out of memory\n");
+			goto error;
+		}
+	}
+
+	sim->field_eps = calloc(fi->size1, sizeof(float));
+	sim->field_mu = calloc(fi->size1, sizeof(float));
+
+	phy_sim_compute_const_fields(sim);
+
+	sim->rotate_lock = SDL_CreateMutex();
+	assert(sim->rotate_lock);
+
+	return 0;
+
+error:
+	phy_sim_destroy(sim);
+	return 1;
+}
+
+void phy_sim_compute_const_fields(phy_sim *sim)
+{
+	size_t x, y, z;
+	phy_field_info *fi = &sim->field_info;
+	size_t border_width;
+
+	border_width = 3;
+
+	for (z = 0; z < fi->depth; z++)
+	for (y = 0; y < fi->height; y++)
+	for (x = 0; x < fi->width; x++) {
+		float *eps, *mu;
+		float border_fx, border_fy, border_fz, border_f;
+
+		eps = sim->field_eps + z * fi->zstr1 + y * fi->ystr1 +
+		      x * fi->xstr1;
+		mu = sim->field_mu + z * fi->zstr1 + y * fi->ystr1 +
+		     x * fi->xstr1;
+
+		*eps = 1.129409066837282e+11;
+		*mu = -7.957747154594767e+5;
+
+/*
+		if (x < border_width) {
+			border_fx = (float)x / border_width;
+		} else if (x >= fi->width - border_width) {
+			border_fx = 1.0f - ((float)x - fi->width + border_width + 1) / border_width;
+		} else {
+			border_fx = 1.0f;
+		}
+
+		if (y < border_width) {
+			border_fy = (float)y / border_width;
+		} else if (y >= fi->height - border_width) {
+			border_fy = 1.0f - ((float)y - fi->height + border_width + 1) / border_width;
+		} else {
+			border_fy = 1.0f;
+		}
+
+		if (z < border_width) {
+			border_fz = (float)y / border_width;
+		} else if (z >= fi->depth - border_width) {
+			border_fz = 1.0f - ((float)z - fi->depth + border_width + 1) / border_width;
+		} else {
+			border_fz = 1.0f;
+		}
+
+		border_f = min3(border_fx, border_fy, border_fz);
+
+		*eps *= border_f;
+		*mu *= border_f;*/
+	}
+}
+
+void phy_sim_step_1(phy_field_info *fi, float dt, float *mul_const,
+                    const float *L0, float *L2, const float *R)
+{
+	size_t x, y, z;
+
+#define AT(F, x, y, z) ((F) + (z) * fi->zstr + (y) * fi->ystr + (x) * fi->xstr)
+#define AT1(F, x, y, z) ((F)[(z) * fi->zstr1 + (y) * fi->ystr1 + \
+                         (x) * fi->xstr1])
+
+	// X
+	for (z = 1; z < fi->depth - 1; z++)
+	for (y = 1; y < fi->height - 1; y++)
+	for (x = 0; x < fi->width; x++) {
+		float dRzdy, dRydz, dLxdt;
+
+		dRzdy = AT(R, x, y + 1, z)[2] - AT(R, x, y - 1, z)[2];
+		dRzdy /= 2 * fi->spacing;
+
+		dRydz = AT(R, x, y, z + 1)[1] - AT(R, x, y, z - 1)[1];
+		dRydz /= 2 * fi->spacing;
+
+		dLxdt = AT1(mul_const, x, y, z) * (dRzdy - dRydz);
+
+		AT(L2, x, y, z)[0] = AT(L0, x, y, z)[0] + dLxdt * dt;
+	}
+
+	// Y
+	for (z = 1; z < fi->depth - 1; z++)
+	for (y = 0; y < fi->height; y++)
+	for (x = 1; x < fi->width - 1; x++) {
+		float dRxdz, dRzdx, dLydt;
+
+		dRxdz = AT(R, x, y, z + 1)[0] - AT(R, x, y, z - 1)[0];
+		dRxdz /= 2 * fi->spacing;
+
+		dRzdx = AT(R, x + 1, y, z)[2] - AT(R, x - 1, y, z)[2];
+		dRzdx /= 2 * fi->spacing;
+
+		dLydt = AT1(mul_const, x, y, z) * (dRxdz - dRzdx);
+
+		AT(L2, x, y, z)[1] = AT(L0, x, y, z)[1] + dLydt * dt;
+	}
+
+	// Z
+	for (z = 0; z < fi->depth; z++)
+	for (y = 1; y < fi->height - 1; y++)
+	for (x = 1; x < fi->width - 1; x++) {
+		float dRydx, dRxdy, dLzdt;
+
+		dRydx = AT(R, x + 1, y, z)[1] - AT(R, x - 1, y, z)[1];
+		dRydx /= 2 * fi->spacing;
+
+		dRxdy = AT(R, x, y + 1, z)[0] - AT(R, x, y - 1, z)[0];
+		dRxdy /= 2 * fi->spacing;
+
+		dLzdt = AT1(mul_const, x, y, z) * (dRydx - dRxdy);
+
+		AT(L2, x, y, z)[2] = AT(L0, x, y, z)[2] + dLzdt * dt;
+	}
+#undef AT
+#undef AT1
+}
+
+void phy_sim_add_sources(phy_sim *sim)
+{
+	phy_field_info *fi = &sim->field_info;
+	size_t x, y, z;
+
+	for (z = 0; z < fi->depth; z++)
+	for (y = 0; y < fi->height; y++)
+	for (x = 0; x < fi->width; x++) {
+		float *E, *H, fx, fy, fz, chuj;
+
+		fx = (float)x / fi->width * 2 - 1;
+		fy = (float)y / fi->height * 2 - 1;
+		fz = (float)z / fi->depth * 2 - 1;
+
+		E = sim->fields[2].E + z * fi->zstr + y * fi->ystr + x * fi->xstr;
+		H = sim->fields[2].H + z * fi->zstr + y * fi->ystr + x * fi->xstr;
+
+		chuj = (0.3 - sqrt(fx * fx + fy * fy + fz * fz)) / 0.3;
+		if (chuj < 0)
+			chuj = 0;
+
+		chuj *= sin(sim->time) * 10;
+		//chuj *= exp(-10.0f * pow(sim->time - 0.5, 2)) * 2;
+		E[0] += chuj;
+	}
+}
+
+void phy_sim_step(phy_sim *sim, float dt) {
+	phy_field_info *fi = &sim->field_info;
+	phy_field_em *fields = sim->fields;
+
+	size_t i, size_in_bytes;
+
+	phy_sim_add_sources(sim);
+
+	size_in_bytes = fi->size * sizeof(float);
+
+	SDL_mutexP(sim->rotate_lock);
+	for (i = 0; i < 2; i++) {
+		// TODO: avoid copying, just switch around pointers
+		memcpy(fields[i].E, fields[i + 1].E, size_in_bytes);
+		memcpy(fields[i].H, fields[i + 1].H, size_in_bytes);
+	}
+	SDL_mutexV(sim->rotate_lock);
+
+	phy_sim_step_1(fi, dt, sim->field_eps,
+	               fields[0].E, fields[2].E, fields[1].H);
+	phy_sim_step_1(fi, dt, sim->field_mu,
+	               fields[0].H, fields[2].H, fields[1].E);
+
+	sim->time += dt;
+}
+
+/*
+void phy_control(phy_command cmd, void *data)
+
+}     */
+
+int phy_thread(phy_sim *sim)
+{
+	while (1) {
+		phy_sim_step(sim, 0.1);
+	}
+
+	printf("phy_thread: quitting\n");
+}
+
diff --git a/src/renderer.c b/src/renderer.c
new file mode 100644
index 0000000..11c3706
--- /dev/null
+++ b/src/renderer.c
@@ -0,0 +1,473 @@
+#define _RENDERER_C
+#include "common.h"
+#include <SDL2/SDL_image.h>
+
+#define FONT_FILE "assets/font.png"
+
+float r_color_white[4] = {1, 1, 1, 1};
+float r_color_black[4] = {0, 0, 0, 1};
+float r_color_red[4] = {1, 0, 0, 1};     
+float r_color_blue[4] = {0, 0, 1, 1};
+
+static struct {
+	SDL_Surface *font;
+	float font_aspect_ratio;
+
+	r_window *windows;
+} rs;
+
+int r_init(void)
+{
+	memset(&rs, 0, sizeof(rs));
+
+	con_printf("r_init: initializing SDL...\n");
+	if (SDL_Init(SDL_INIT_VIDEO) == -1) {
+		con_printf("r_init: SDL_Init(SDL_INIT_VIDEO) failed: %s\n",
+		           SDL_GetError());
+		goto error;
+	}
+
+	con_printf("r_init: initializing SDL_image...\n");
+	if (IMG_Init(IMG_INIT_JPG | IMG_INIT_PNG) !=
+	    (IMG_INIT_JPG | IMG_INIT_PNG)) {
+		con_printf("r_init: IMG_Init failed: %s\n", SDL_GetError());
+		goto error;
+	}
+
+	SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "2");
+
+	con_printf("r_init: loading font \""FONT_FILE"\"...\n");
+	rs.font = IMG_Load("assets/font.png");
+	if (!rs.font) {
+		con_printf("r_init: IMG_Load failed: %s\n",
+		           IMG_GetError());
+		goto error;
+	}
+
+	rs.font_aspect_ratio = (float)rs.font->w / rs.font->h;
+
+	con_printf("r_init: renderer init complete\n");
+	return 0;
+
+error:
+	r_quit();
+	return 1;
+}
+
+r_window *r_window_create(void)
+{
+	r_window *rw;
+
+	rw = calloc(1, sizeof(r_window));
+	if (!rw)
+		abort();
+
+	rw->prev = NULL;
+	if (rs.windows)
+		rs.windows->prev = rw;
+	rw->next = rs.windows;
+	rs.windows = rw;
+	
+	rw->window = SDL_CreateWindow(PROGRAM_NAME, SDL_WINDOWPOS_CENTERED,
+		                      SDL_WINDOWPOS_CENTERED, 300, 300,
+		                      SDL_WINDOW_RESIZABLE);
+	if (!rw->window) {
+		con_printf("r_window_create: SDL_CreateWindow failed: %s\n",
+		           SDL_GetError());
+		goto error;
+	}
+
+	rw->renderer = SDL_CreateRenderer(rw->window, -1,
+	                                  SDL_RENDERER_ACCELERATED |
+	                                  SDL_RENDERER_PRESENTVSYNC);
+	if (!rw->renderer) {
+		con_printf("r_window_create: SDL_CreateRenderer failed: %s\n",
+		           SDL_GetError());
+		goto error;
+	}
+
+	SDL_SetRenderDrawBlendMode(rw->renderer, SDL_BLENDMODE_BLEND);
+
+	rw->font_texture = SDL_CreateTextureFromSurface(rw->renderer, rs.font);
+	if (!rw->font_texture) {
+		con_printf("r_window_create: SDL_CreateTextureFromSurface"
+		           " failed: %s\n", SDL_GetError());
+		goto error;
+	}
+
+	con_printf("r_window_create: created window #%i\n",
+	           SDL_GetWindowID(rw->window));
+
+	return rw;
+
+error:
+	r_window_destroy(rw);
+	return NULL;
+}
+
+void r_window_destroy(r_window *rw)
+{
+	SDL_DestroyTexture(rw->font_texture);
+	SDL_DestroyRenderer(rw->renderer);
+	SDL_DestroyWindow(rw->window);
+
+	if (rw->prev)
+		rw->prev->next = rw->next;
+	if (rw->next)
+		rw->next->prev = rw->prev;
+
+	if (rs.windows == rw)
+		rs.windows = rw->next;
+
+	free(rw);
+}
+
+
+void r_quit(void)
+{
+	con_printf("r_quit: renderer is quitting\n");
+
+	while (rs.windows)
+		r_window_destroy(rs.windows);
+
+	SDL_FreeSurface(rs.font);
+	IMG_Quit();
+}
+
+static void r_set_color(SDL_Renderer *renderer, float *color)
+{
+	SDL_SetRenderDrawColor(renderer, color[0] * 255, color[1] * 255,
+	                       color[2] * 255, color[3] * 255);
+}
+
+
+void r_clear(r_window *rw, float *color)
+{
+	r_set_color(rw->renderer, color);
+	SDL_RenderClear(rw->renderer);
+}
+
+void r_flip(r_window *rw)
+{
+	SDL_RenderPresent(rw->renderer);
+}
+
+void r_clip_enable(r_window *rw, float x, float y, float w, float h)
+{
+	SDL_Rect rect = {x, y, w, h};
+	SDL_RenderSetClipRect(rw->renderer, &rect);
+}
+
+void r_clip_disable(r_window *rw)
+{
+	SDL_RenderSetClipRect(rw->renderer, NULL);
+}
+
+void r_draw_line(r_window *rw, float x0, float y0, float x1, float y1,
+                 float *color)
+{
+
+	r_set_color(rw->renderer, color);
+	SDL_RenderDrawLine(rw->renderer, x0, y0, x1, y1);
+}
+
+void r_draw_rect(r_window *rw, float x, float y, float w, float h, float *color)
+{
+	SDL_Rect rect = {x, y, w, h};
+	r_set_color(rw->renderer, color);
+	SDL_RenderFillRect(rw->renderer, &rect);
+}
+
+static int r_iterate_chars(char **p)
+{
+	int rv;
+
+	if ((*p)[0] == '\0') {
+		return -1;
+	} else if (((*p)[0] & 0b10000000) == 0b00000000) {
+		rv = (*p)[0];
+		(*p)++;
+		return rv;
+	} else if (((*p)[0] & 0b11100000) == 0b11000000) {
+		if ((*p)[1] == '\0')
+			return -1;
+
+		rv = (((*p)[0] & 0b00011111) << 6) | ((*p)[1] & 0b00111111);
+		(*p) += 2;
+		return rv;
+	} else {
+		(*p)++;
+		return 0;
+	}
+}
+
+static int r_font_find_glyph(int ch)
+{
+	if (ch < 128)
+		return ch;
+
+	switch (ch) {
+		case 0x105: return 128; // ą
+		case 0xE4:  return 129; // ä
+		case 0x107: return 130; // ć
+		case 0x119: return 131; // ę
+		case 0xEB:  return 132; // ë
+		case 0x142: return 133; // ł
+		case 0x144: return 134; // ń
+		case 0xF3:  return 135; // ó
+		case 0xF6:  return 136; // ö
+		case 0x15B: return 137; // ś
+		case 0xFC:  return 138; // ü
+		case 0x17C: return 139; // ż
+		case 0x17A: return 140; // ź
+		//case 0x: return 141; // free
+		//case 0x: return 142; // free
+		//case 0x: return 143; // free
+		case 0x104: return 144; // Ą
+		case 0xC4:  return 145; // Ä
+		case 0x106: return 146; // Ć
+		case 0x118: return 147; // Ę
+		case 0xCB:  return 148; // Ë
+		case 0x141: return 149; // Ł
+		case 0x143: return 150; // Ń
+		case 0xD3:  return 151; // Ó
+		case 0xD6:  return 152; // Ö
+		case 0x15A: return 153; // Ś
+		case 0xDC:  return 154; // Ü
+		case 0x17B: return 155; // Ż
+		case 0x179: return 156; // Ź
+		//case 0x: return 157; // free
+		//case 0x: return 158; // free
+		//case 0x: return 159; // free
+	}
+
+	// lowercase greek
+	if (ch >= 0x3B1 && ch <= 0x3C1)
+		return ch - 0x3B1 + 160;
+	else if (ch >= 0x3C3 && ch <= 0x3C9)
+		return ch - 0x3C3 + 177;
+
+	// uppercase greek
+	if (ch >= 0x391 && ch <= 0x3A1)
+		return ch - 0x391 + 192;
+	else if (ch >= 0x3A3 && ch <= 0x3A9)
+		return ch - 0x3A3 + 209;
+
+	return 0;
+}
+
+float r_text_width(float h, char *text)
+{
+	char *p = text;
+	float rv = 0;
+
+	while(r_iterate_chars(&p) != -1) 
+		rv += h * rs.font_aspect_ratio;
+
+	return rv;
+}
+
+void r_draw_text(r_window *rw, float x, float y, float h, char *text,
+                 float *color, int flags)
+{
+	char *p = text;
+	float w = h * rs.font_aspect_ratio;
+	int ch;
+	float total_width;
+
+	if (flags & (TEXT_CENTERX | TEXT_RIGHTX)) {
+		total_width = r_text_width(h, text);
+
+		if (flags & TEXT_CENTERX)
+			x -= total_width / 2;
+		else
+			x -= total_width;
+	}
+
+	SDL_SetTextureColorMod(rw->font_texture, color[0] * 255, color[1] * 255,
+		               color[2] * 255);
+	SDL_SetTextureAlphaMod(rw->font_texture, color[3] * 255);
+	
+	while ((ch = r_iterate_chars(&p)) != -1) {
+		int glyph, glyph_x, glyph_y;
+		SDL_Rect src, dst;
+
+		glyph = r_font_find_glyph(ch);
+		glyph_x = glyph % 16;
+		glyph_y = glyph / 16;
+		src.x = rs.font->w / 16 * glyph_x;
+		src.y = rs.font->h / 16 * glyph_y;
+		src.w = rs.font->w / 16;
+		src.h = rs.font->h / 16;
+
+		dst.x = x;
+		dst.y = y;
+		dst.w = w;
+		dst.h = h;
+
+		SDL_RenderCopy(rw->renderer, rw->font_texture, &src, &dst);
+
+		x += w;
+	}
+}
+
+static uint8_t r_float_to_u8(float num)
+{
+	if (num >= 1.0f)
+		return 255;
+	else if (num <= -1.0f)
+		return 0;
+	else
+		return floor((num + 1.0f) * 0.5f * 256.0f);
+}
+
+static int r_xsection_alloc(SDL_Renderer *renderer, SDL_Texture **texture,
+                            size_t width, size_t height)
+{
+	int old_width, old_height;
+
+	if (*texture) {
+		SDL_QueryTexture(*texture, NULL, NULL, &old_width, &old_height);
+
+		if (old_width != width || old_height != height) {
+			SDL_DestroyTexture(*texture);
+			*texture = NULL;
+		}
+	}
+
+	if (!*texture) {
+		*texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_BGR888,
+		                             SDL_TEXTUREACCESS_STREAMING,
+		                             width, height);
+		if (!*texture) {
+			con_printf("r_xsection_alloc: SDL_CreateTexture failed"
+			           ": %s\n", SDL_GetError());
+			return 1;
+		}
+	}
+
+	return 0;
+}
+
+void r_xsection_create(r_xsection *xsection)
+{
+	memset(xsection, 0, sizeof(r_xsection));
+}
+
+void r_xsection_destroy(r_xsection *xsection)
+{
+	SDL_DestroyTexture(xsection->texture);
+}
+
+int r_xsection_update(r_window *rw, r_xsection *xsection,
+                      phy_field_info *fi, float *field,
+                      r_xsection_type type, float frac)
+{
+	size_t width, height, x, y, z;
+	uint8_t *pixels;
+	int pitch;
+
+	switch (type) {
+	case XSECTION_XY:
+		width = fi->width;
+		height = fi->height;
+		break;
+
+	case XSECTION_XZ:
+		width = fi->width;
+		height = fi->depth;
+		break;
+
+	case XSECTION_YZ:
+		width = fi->height;
+		height = fi->depth;
+		break;
+	}
+
+	if (frac < 0.0f)
+		frac = 0.0f;
+	else if (frac > 1.0f)
+		frac = 1.0f;
+
+	if (r_xsection_alloc(rw->renderer, &xsection->texture,
+	                     width, height)) {
+		return 1;
+	}
+
+	SDL_LockTexture(xsection->texture, NULL, (void**)&pixels, &pitch);
+
+	switch (type) {
+	case XSECTION_XY:
+		z = frac * fi->depth;       
+		if (z >= fi->depth)
+			z = fi->depth - 1;
+
+		for (y = 0; y < fi->height; y++)
+		for (x = 0; x < fi->width; x++) {
+			uint8_t *pixel;
+			float *point;
+
+			pixel = pixels + (y * pitch + x * 4);
+			point = field + z * fi->zstr + y * fi->ystr +
+			        x * fi->xstr;
+
+			pixel[0] = r_float_to_u8(point[0]);
+			pixel[1] = r_float_to_u8(point[1]);
+			pixel[2] = r_float_to_u8(point[2]);
+		}
+		break;
+
+	case XSECTION_XZ:
+		y = frac * fi->height;
+		if (y >= fi->height)
+			y = fi->height - 1;
+
+		for (z = 0; z < fi->depth; z++)
+		for (x = 0; x < fi->width; x++) {
+			uint8_t *pixel;
+			float *point;
+
+			pixel = pixels + (z * pitch + x * 4);
+			point = field + z * fi->zstr + y * fi->ystr +
+			        x * fi->xstr;
+
+			pixel[0] = r_float_to_u8(point[0]);
+			pixel[1] = r_float_to_u8(point[1]);
+			pixel[2] = r_float_to_u8(point[2]);
+		}
+		break;
+
+	case XSECTION_YZ:
+		x = frac * fi->width;
+		if (x >= fi->width)
+			x = fi->width - 1;
+
+		for (z = 0; z < fi->depth; z++)
+		for (y = 0; y < fi->height; y++) {
+			uint8_t *pixel;
+			float *point;
+
+			pixel = pixels + (z * pitch + y * 4);
+			point = field + z * fi->zstr + y * fi->ystr +
+			        x * fi->xstr;
+
+			pixel[0] = r_float_to_u8(point[0]);
+			pixel[1] = r_float_to_u8(point[1]);
+			pixel[2] = r_float_to_u8(point[2]);
+		}
+		break;
+	}
+
+	SDL_UnlockTexture(xsection->texture);
+
+	xsection->aspect_ratio = (float)width / height;
+
+	return 0;
+}
+
+void r_xsection_draw(r_window *rw, r_xsection *xsection,
+                     float x, float y, float w, float h)
+{
+	SDL_Rect dst = {x, y, w, h};
+	SDL_RenderCopy(rw->renderer, xsection->texture, NULL, &dst);
+}
diff --git a/src/ui.c b/src/ui.c
new file mode 100644
index 0000000..0f4477b
--- /dev/null
+++ b/src/ui.c
@@ -0,0 +1,461 @@
+#include "common.h"
+
+struct {
+	float font_size;
+	float color_text[4];    
+	float color_text_light[4];
+	float color_background[4]; 
+	float color_main[4];
+	float color_info[4];
+	float color_selection[4];
+} theme =
+{
+	.font_size = 20,
+	.color_text = {0, 0, 0, 1},   
+	.color_text_light = {0.5, 0.5, 0.5, 1},
+	.color_background = {0.1, 0.1, 0.1, 1},  
+	.color_main = {0.75, 0.75, 0.75, 1},
+	.color_info = {1, 1, 1, 1},
+	.color_selection = {1, 0, 0, 1}
+};
+
+#define MAX_INFO 1024
+
+typedef struct {
+	bool dragging;
+	r_xsection_type xsection_type;
+	float xsection_frac;
+	bool selected;
+	vec3_t selection;
+
+	bool info_valid;
+	int64_t info_time;
+	char info[MAX_INFO];
+
+	float margin_bottom, margin_top;
+
+	mst2_t origin, scale; // in virtual space
+	mst2_t tf_v2s, tf_x2s;
+	r_xsection xsection;
+} ui_simview;
+
+typedef enum {
+	UI_WINDOW_SIMVIEW
+} ui_window_type;
+
+typedef struct ui_window_s ui_window;
+struct ui_window_s {
+	int w, h;
+	r_window *rw;
+	ui_window *prev, *next;
+
+	bool initialized;
+	int64_t last_frame;
+	size_t frame_count;
+	vec2_t mouse;
+
+	ui_window_type type;
+	ui_simview simview;
+};
+
+static struct {
+	ui_window *windows;
+
+	bool use_window_open_timer;
+	int64_t window_open_timer;
+} uis;
+
+
+int ui_init(void)
+{
+	return 0;
+}
+
+static void ui_window_destroy(ui_window *uiw)
+{
+	con_printf("ui_window_destroy: destroying uiw=%p\n", uiw);
+	
+	if (uiw->prev)
+		uiw->prev->next = uiw->next;
+	if (uiw->next)
+		uiw->next->prev = uiw->prev;
+
+	if (uis.windows == uiw)
+		uis.windows = uiw->next;
+
+	r_xsection_destroy(&uiw->simview.xsection);
+
+	free(uiw);
+}
+
+void ui_quit(void)
+{
+	while (uis.windows)
+		ui_window_destroy(uis.windows);
+}
+
+void ui_renderer_window_register(r_window *rw)
+{
+	ui_window *uiw;
+
+	uiw = calloc(1, sizeof(ui_window));
+	if (!uiw)
+		abort();
+
+	uiw->prev = NULL;
+	if (uis.windows)
+		uis.windows->prev = uiw;
+	uiw->next = uis.windows;
+	uis.windows = uiw;
+
+	uiw->rw = rw;
+
+	con_printf("ui_renderer_window_register: registered window #%i"
+	           ", uiw = %p\n", SDL_GetWindowID(rw->window), uiw);
+
+	r_xsection_create(&uiw->simview.xsection);
+}
+
+static ui_window *ui_find_window(int id)
+{
+	ui_window *uiw;
+
+	for (uiw = uis.windows; uiw; uiw = uiw->next)
+		if (SDL_GetWindowID(uiw->rw->window) == id)
+			return uiw;
+
+	return NULL;
+}
+
+void ui_infof(ui_window *uiw, const char *fmt, ...)
+{
+	va_list vl;
+
+	va_start(vl, fmt);
+	vsnprintf(uiw->simview.info, MAX_INFO, fmt, vl);
+	va_end(vl);
+
+	uiw->simview.info_valid = true;
+	uiw->simview.info_time = get_time();
+}
+
+static void ui_simview_set_selection(ui_simview *sv, vec2_t sel_2d)
+{
+	if (sel_2d[0] < 0.0f || sel_2d[0] > 1.0f ||
+	    sel_2d[1] < 0.0f || sel_2d[1] > 1.0f) {
+		sv->selected = false;
+		return;
+	}
+
+	switch (sv->xsection_type) {
+	case XSECTION_XY:
+		v3_set(sv->selection, sel_2d[0], sel_2d[1], sv->xsection_frac);
+		break;
+
+	case XSECTION_XZ:
+		v3_set(sv->selection, sel_2d[0], sv->xsection_frac, sel_2d[1]);
+		break;
+
+	case XSECTION_YZ:
+		v3_set(sv->selection, sv->xsection_frac, sel_2d[0], sel_2d[1]);
+		break;
+	}
+
+	sv->selected = true;
+}
+
+void ui_event_window(SDL_Event *event, ui_window *uiw)
+{
+	ui_simview *sv = &uiw->simview;
+
+	if (!uiw->initialized)
+		return;
+
+	switch (event->type) {
+	case SDL_MOUSEWHEEL:
+		{
+			vec2_t mouse_v;
+			float delta;
+
+			v2_div_mst2(mouse_v, uiw->mouse, sv->tf_v2s);
+
+			delta = pow(1.1, event->wheel.y);
+
+			v2_mul(sv->scale, sv->scale, delta);
+
+			v2_sub(sv->origin, sv->origin, mouse_v);
+			v2_mul(sv->origin, sv->origin, delta);
+			v2_add(sv->origin, sv->origin, mouse_v);
+		}
+		break;
+
+	case SDL_MOUSEBUTTONDOWN:
+		if (event->button.button == SDL_BUTTON_LEFT &&
+		    event->button.y > sv->margin_top &&
+		    event->button.y < uiw->h - sv->margin_bottom)
+			sv->dragging = true;
+
+		if (event->button.button == SDL_BUTTON_RIGHT) {
+			vec2_t sel_2d;
+
+			v2_div_mst2(sel_2d, uiw->mouse, sv->tf_x2s);
+			ui_simview_set_selection(sv, sel_2d);
+		}
+		break;
+
+	case SDL_MOUSEBUTTONUP:
+		if (event->button.button == SDL_BUTTON_LEFT)
+			sv->dragging = false;
+		break;
+
+	case SDL_MOUSEMOTION:
+		uiw->mouse[0] = event->motion.x;
+		uiw->mouse[1] = event->motion.y;
+
+		if (sv->dragging) {
+			vec2_t delta_v;
+
+			v2_set(delta_v, event->motion.xrel, event->motion.yrel);
+			v2_div_mst2_nt(delta_v, delta_v, sv->tf_v2s);
+			v2_add(sv->origin, sv->origin, delta_v);
+		}
+		break;
+
+	case SDL_KEYDOWN:
+		switch (event->key.keysym.sym) {
+		case SDLK_1:
+			sv->xsection_type = XSECTION_XY;
+			break;
+
+		case SDLK_2:
+			sv->xsection_type = XSECTION_XZ;
+			break;
+
+		case SDLK_3:
+			sv->xsection_type = XSECTION_YZ;
+			break;
+
+		case SDLK_w:
+			sv->xsection_frac += 0.1f;
+			if (sv->xsection_frac > 1.0f)
+				sv->xsection_frac = 1.0f;
+			break;
+
+		case SDLK_s:
+			sv->xsection_frac -= 0.1f;
+			if (sv->xsection_frac < 0.0f)
+				sv->xsection_frac = 0.0f;
+			break;
+		}
+	}
+}
+
+void ui_event(SDL_Event *event)
+{
+	if (event->type == SDL_KEYDOWN &&
+	    event->key.keysym.sym == SDLK_RETURN) {
+
+		if (!uis.use_window_open_timer ||
+		    uis.window_open_timer + 500000000 <= get_time()) {
+			r_window *rw;
+
+			uis.use_window_open_timer = true;
+			uis.window_open_timer = get_time();
+
+			rw = r_window_create();
+			if (rw)
+				ui_renderer_window_register(rw);
+		}
+	} else if (event->type == SDL_WINDOWEVENT &&
+	           event->window.event == SDL_WINDOWEVENT_CLOSE) {
+			ui_window *uiw;
+
+			uiw = ui_find_window(event->window.windowID);
+			if (!uiw)
+				con_printf("WARNING: ui_event: SDL_WINDOWEVENT_"
+				           "CLOSE for a window not registered"
+				           " by ui\n");
+			else {
+				r_window_destroy(uiw->rw);
+				ui_window_destroy(uiw);
+			}
+	} else {
+		ui_window *uiw;
+
+		// SDL sends some SDL_WINDOWEVENTs after a window's been closed
+
+		uiw = ui_find_window(event->window.windowID);
+		if (uiw)
+			ui_event_window(event, uiw);
+	}
+}
+
+void ui_animate_exp(float *val, float targ, float lambda, float dt)
+{
+	*val = targ + (*val - targ) * exp(-lambda * dt);
+}
+
+void ui_draw_window_simview(ui_window *uiw, phy_sim *sim, int64_t time,
+                            float dt)
+{
+	ui_simview *sv = &uiw->simview;
+	float aspect_ratio;
+	vec2_t origin_s, scale_s;
+	phy_field_em *field_em = sim->fields + 2;
+
+	const char *xsection_type_strings[] = {
+		"Przekrój XY przez Z",
+		"Przekrój XZ przez Y",
+		"Przekrój YZ przez X"
+	};
+
+	// xsection
+
+	SDL_mutexP(sim->rotate_lock);
+	r_xsection_update(uiw->rw, &sv->xsection, &sim->field_info,
+	                  field_em->E, sv->xsection_type, sv->xsection_frac);
+	SDL_mutexV(sim->rotate_lock);
+
+	aspect_ratio = sv->xsection.aspect_ratio;
+
+	if (uiw->w > uiw->h * aspect_ratio)
+		mst2_set(sv->tf_v2s, (uiw->w - uiw->h * aspect_ratio) / 2.0f, 0,
+		         uiw->h * aspect_ratio, uiw->h);
+	else
+		mst2_set(sv->tf_v2s, 0, (uiw->h - uiw->w / aspect_ratio) / 2.0f,
+		         uiw->w, uiw->w / aspect_ratio);
+
+	v2_mul_mst2(origin_s, sv->origin, sv->tf_v2s);
+	v2_mul_mst2_nt(scale_s, sv->scale, sv->tf_v2s);
+
+	mst2_set(sv->tf_x2s, origin_s[0], origin_s[1],
+	         scale_s[0], scale_s[1]);
+
+	r_xsection_draw(uiw->rw, &sv->xsection, origin_s[0], origin_s[1],
+	                scale_s[0], scale_s[1]);
+
+	// xsection - selection
+
+	if (sv->selected)
+	{
+		vec2_t selection_s;
+
+		switch (sv->xsection_type) {
+		case XSECTION_XY:
+			v2_set(selection_s, sv->selection[0], sv->selection[1]);
+			break;
+
+		case XSECTION_XZ:
+			v2_set(selection_s, sv->selection[0], sv->selection[2]);
+			break;
+
+		case XSECTION_YZ:
+			v2_set(selection_s, sv->selection[1], sv->selection[2]);
+			break;
+		}
+
+		v2_mul_mst2(selection_s, selection_s, sv->tf_x2s);    
+
+		r_draw_line(uiw->rw, selection_s[0], 0, selection_s[0], uiw->h,
+		            theme.color_selection);
+		r_draw_line(uiw->rw, 0, selection_s[1], uiw->w, selection_s[1],
+		            theme.color_selection);
+
+
+		r_draw_rect(uiw->rw, 0, uiw->h - theme.font_size,
+		            uiw->w, theme.font_size, theme.color_main);
+
+		r_draw_text(uiw->rw, 0, uiw->h - theme.font_size,
+		            theme.font_size,
+		            va("x = [%f %f %f]", sv->selection[0],
+		            sv->selection[1], sv->selection[2]),
+		            theme.color_text, 0); 
+
+		sv->margin_bottom = 1 * theme.font_size;
+	}
+	else
+		sv->margin_bottom = 0;
+
+	// status
+
+	r_draw_rect(uiw->rw, 0, 0, uiw->w, theme.font_size, theme.color_main);
+
+	r_draw_text(uiw->rw, uiw->w, 0, theme.font_size,
+	            va("%.0fkl./s %04zu", 1.0f / dt, uiw->frame_count % 10000),
+	            theme.color_text_light, TEXT_RIGHTX);
+
+	r_draw_text(uiw->rw, 0, 0, theme.font_size,
+	            va("%s = %f", xsection_type_strings[sv->xsection_type],
+	            sv->xsection_frac),
+	            theme.color_text, 0);
+
+	// info text
+
+	if (sv->info_valid && sv->info_time + 2000000000ll > time)
+	{
+		vec4_t color;
+
+		if (sv->info_time + 1000000000ll >= time)
+			color[3] = 1.0f;
+		else
+			color[3] = 1.0f - (time - sv->info_time - 1000000000ll)
+			           / 1.0e9f;
+
+		v3_copy(color, theme.color_info);
+
+		r_draw_rect(uiw->rw, 0, theme.font_size, uiw->w,
+		            theme.font_size, color);
+
+		v3_copy(color, theme.color_text);
+
+		r_draw_text(uiw->rw, uiw->w / 2.0f, theme.font_size,
+		            theme.font_size, sv->info, color, TEXT_CENTERX);
+	}
+}
+
+void ui_draw_window(ui_window *uiw, phy_sim *sim)
+{
+	ui_simview *sv = &uiw->simview;
+	int64_t time;
+	float dt;
+
+	time = get_time();
+
+	if (!uiw->initialized) {
+		uiw->initialized = true;
+		uiw->last_frame = time;
+
+		v2_set(sv->origin, 0, 0);
+		v2_set(sv->scale, 1, 1);
+		sv->xsection_type = XSECTION_XY;
+		sv->xsection_frac = 0.5f;
+
+		sv->selected = false;
+		sv->margin_top = theme.font_size;
+		sv->margin_bottom = 0;
+
+		sv->info_valid = false;
+
+		r_clear(uiw->rw, r_color_black);
+		return;
+	}
+
+	dt = (get_time() - uiw->last_frame) * 1.0e-9;
+
+	r_clear(uiw->rw, r_color_black);
+	ui_draw_window_simview(uiw, sim, time, dt);
+	r_flip(uiw->rw);
+
+	uiw->last_frame = time;
+}
+
+void ui_draw(phy_sim *sim)
+{
+	ui_window *uiw;
+
+	for (uiw = uis.windows; uiw; uiw = uiw->next) {
+		SDL_GetWindowSize(uiw->rw->window, &uiw->w, &uiw->h);
+		ui_draw_window(uiw, sim);
+		uiw->frame_count++;
+	}
+}