commit 66f483e9206060648b029a7e45759e77241eebc9
Author: Anton Lydike <me@antonlydike.de>
Date:   Thu Apr 23 15:17:52 2020 +0200

    Initial commit, basic shading

diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..3c9ded2
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "images"]
+	path = images
+	url = gitlab@git.datenvorr.at:anton/images.h.git
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..d53ca61
--- /dev/null
+++ b/README.md
@@ -0,0 +1,10 @@
+# Raymarching in C
+
+## Compiling:
+
+```fish
+# load requirements
+nix-shell
+# run gcc with flags
+gcc (pkg-config --cflags --libs gtk+-3.0 | string split " ") -lm -Wall -Wextra -o march.out main.c
+```
\ No newline at end of file
diff --git a/default.nix b/default.nix
new file mode 100644
index 0000000..ad62a24
--- /dev/null
+++ b/default.nix
@@ -0,0 +1,7 @@
+with import <nixpkgs> {};
+stdenv.mkDerivation {
+  name = "raymarcher-dev-env";
+  buildInputs = [
+    gtk3 pkgconfig gdb
+  ];
+}
\ No newline at end of file
diff --git a/images b/images
new file mode 160000
index 0000000..0ab4ae2
--- /dev/null
+++ b/images
@@ -0,0 +1 @@
+Subproject commit 0ab4ae2be9f993f26759fc03d3186a51d2770d45
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..9a22d72
--- /dev/null
+++ b/main.c
@@ -0,0 +1,71 @@
+#include <gtk/gtk.h> 
+#include <math.h>
+#include "images/images.h"
+#include "marcher.h"
+
+#define SCENE_MOD 2
+
+// this is the circle distance function definition
+double circle_dist(Point x, SceneObject *self) {
+    double r = self->args[0];
+    return pt_dist(pt_mod(x, SCENE_MOD), self->location) - r;
+}
+
+Color circle_color(Point hit, Point direction, SceneObject *self) {
+    Point obj_direction = self->location;
+
+    pt_sub(&obj_direction, pt_mod(hit, SCENE_MOD));
+
+    double angle = pt_angle(direction, obj_direction) / M_PI * 180;
+    Color color = self->color;
+
+    if (angle > 90) angle = 180 - angle ; // clamp angle to 0-90
+    color = color_mix(color, color_new(0,0,0), 1 - (angle / (double) 90));
+
+    return color;
+}
+
+SceneObject circle_new(Point loc, double radius) {
+    SceneObject so;
+    so.location = loc;
+    so.args = malloc(sizeof(double) * 2);
+    so.args[0] = radius;
+    so.distance = circle_dist;
+    so.get_color = circle_color;
+    so.color = color_new(255,0,0);
+    return so;
+}
+
+int main(int argc, char* argv[]) {
+    int threads = 1;
+    Camera cam;
+    cam.fov = 90;
+    camera_set_looking_at(&cam, pt_new(-.6,0,0), pt_new(-.5,1,0));
+
+    if (argc > 1) {
+        threads = atoi(argv[1]);
+    }
+
+    printf("threads: %d\n", threads);
+
+    // create basic scene with up to 10 objects
+    Scene scene = scene_new(800, 600, 10);
+    scene.max_steps = 64;
+    scene.threshold = 0.02;
+
+    scene_add_obj(&scene, circle_new(pt_new(0,1,0), .2));
+
+    //scene_add_obj(&scene, circle_new(pt_new(0,2,0), 0.5));
+    //scene_add_obj(&scene, circle_new(pt_new(0,-2,0), 0.5));
+    //scene_add_obj(&scene, circle_new(pt_new(0,-4,0), 0.5));
+
+    Image *img = render_scene(&scene, &cam, threads);
+
+    image_save_bmp(*img, "render.bmp");
+
+    image_destroy_shared(*img);
+    scene_destroy(scene);
+
+    return 0;  
+}
+
diff --git a/march.out b/march.out
new file mode 100755
index 0000000..812fa0d
Binary files /dev/null and b/march.out differ
diff --git a/marcher.h b/marcher.h
new file mode 100644
index 0000000..5a38355
--- /dev/null
+++ b/marcher.h
@@ -0,0 +1,83 @@
+#ifndef __MARCHER_H__
+#define __MARCHER_H__
+
+#include "images/images.h"
+
+// define pi if not available
+#ifndef M_PI
+#define M_PI 3.14159265358979323846
+#endif
+
+typedef struct __myvec {
+    double x;
+    double y;
+    double z;
+} Point;
+
+typedef struct __mymtrx {
+    double entries[9];
+} Matrix;
+
+inline Point pt_new(double x, double y, double z);
+Point pt_scale(Point pt, double length);
+inline Point pt_normalize(Point pt);
+inline double pt_length(Point pt);
+void pt_add(Point* pt, Point add);
+inline void pt_sub(Point* pt, Point sub);
+inline double pt_dist(Point p1, Point p2);
+inline Point pt_mod(Point pt, double mod);
+inline double pt_dot(Point a, Point b);
+inline Point pt_cross(Point a, Point b);
+inline double pt_angle(Point a, Point b);
+inline void pt_print(Point pt);
+inline void pt_print_n(const char* name, Point pt);
+
+
+typedef struct __mycam {
+    Point location;
+    Point direction;
+    unsigned int fov;
+} Camera;
+
+Camera camera_new(Point direction, unsigned int fov);
+void camera_set_looking_at(Camera *cam, Point origin, Point thing);
+
+// Scene objects have a position, some args, and a distance calculation function
+// the distance calc function has the following signature:
+// double distanceTo(Point myLocation, double * myArgs, Point externalPoint)
+// where myLocation is this.location, myArgs is this.args and externalPoint is the point from wich we want to know the distance
+// the get_color function takes args: point_hit, direction_hit, myArgs, MyLocation, MyColor
+typedef struct __myobject {
+    Point location;
+    double * args;
+    double (*distance)(Point, struct __myobject *); 
+    Color (*get_color)(Point, Point, struct __myobject *);
+    Color color;
+} SceneObject;
+
+typedef struct __myscene {
+    unsigned int width;
+    unsigned int height;
+    SceneObject * objects;
+    int object_count;
+    int allocated_space;
+    // some other settings
+    int max_steps;
+    double threshold;
+    // colors etc
+    Color background;
+} Scene;
+
+Image* render_scene(Scene *scene, Camera *camera, unsigned int threads);
+
+Scene scene_new(unsigned int width, unsigned int height, int obj_count);
+
+void scene_add_obj(Scene* scene, SceneObject object);
+
+void scene_destroy(Scene scene);
+
+#include "src/point.c"
+#include "src/camera.c"
+#include "src/scene.c"
+
+#endif
\ No newline at end of file
diff --git a/render.bmp b/render.bmp
new file mode 100644
index 0000000..32f011e
Binary files /dev/null and b/render.bmp differ
diff --git a/src/camera.c b/src/camera.c
new file mode 100644
index 0000000..3a79f2e
--- /dev/null
+++ b/src/camera.c
@@ -0,0 +1,172 @@
+#include "../marcher.h"
+#include <sys/wait.h>
+#include <sys/mman.h>
+
+
+Camera camera_new(Point direction, unsigned int fov) {
+    Camera camera;
+    camera.location = pt_new(0,0,0);
+    camera.fov = fov;
+
+    // normalize camera direction
+    camera.direction = pt_normalize(direction);
+
+    return camera;
+}
+
+void camera_set_looking_at(Camera *cam, Point origin, Point thing) {
+    cam->location = origin;
+    pt_sub(&thing, origin);
+    cam->direction = pt_normalize(thing);
+}
+
+void camera_iterate_rays_const_angle(Camera camera, int width, int height, int threads, void (*callback)(Point, int, int)) {
+    // negative threads => single threaded.
+    if (threads < 0) threads = 0;
+
+    Point span_z, span_xy;
+
+    // get rotation axis
+    pt_orthogonal_plane(camera.direction, &span_z, &span_xy);
+
+    printf("rendering %ix%i px", width, height);
+
+    pt_print_n("span_xy", span_xy);
+    pt_print_n("span_z", span_z);
+
+    // angle between rays
+    double angle_step = camera.fov / (double) (width - 1);
+
+    // rotation applied to reach the outmost end of the view
+    double angle_start_h = - (camera.fov / 2.0);
+    double angle_start_v = ((angle_step * (height - 1)) / 2) ;
+
+    printf("step: %f\nstart_h: %f\nstart_v: %f\n", angle_step, angle_start_h, angle_start_v);
+
+    // calculate both rotation matrices (expensive!)
+    Matrix rot_z = mtrx_rotation(span_z, angle_step);
+    Matrix rot_xy = mtrx_rotation(span_xy, -angle_step);
+
+    // rotate vector to starting location (bot left of screen)
+    // (very expensive!)
+    Point starting_point = mtrx_mult(
+        mtrx_rotation(span_xy, angle_start_v),
+        mtrx_mult(
+            mtrx_rotation(span_z, angle_start_h),
+            camera.direction
+        )
+    );
+
+    // initialize threads
+    int thread_id = 0;
+    for (int i = 0; i < threads - 1; i++) {
+        if (fork() == 0) {
+            thread_id = i + 1;
+            break;
+        }
+    }
+
+    printf("Thread %i reporting for duty\n", thread_id);
+
+    // this point is rotated for every pixel
+    Point curr_pt = starting_point;
+    // (0,0) screenspace is bottom left corner
+    for (int y = 0; y < height; y++) {
+        curr_pt = mtrx_mult(rot_xy, starting_point);
+        // move starting point one row down
+        starting_point = curr_pt;
+
+        if (y % threads != thread_id) continue;
+
+        for (int x = 0; x < width; x++) {
+            callback(curr_pt, x, y);
+            curr_pt = mtrx_mult(rot_z, curr_pt); // rotate point
+        }
+    }
+
+    if (thread_id != 0) {
+        printf("Thread %i is finished\n", thread_id);
+        exit(0);
+    }
+
+    int status;
+    for (int i = 0; i < threads - 1; i++) {
+        printf("Waiting for threads... %d/%d\n", i, threads);
+        while(wait(&status) > 0) {}
+    }
+
+    printf("got threads\n");
+}
+
+void camera_iterate_rays_const_dist(Camera camera, int width, int height, int threads, void (*callback)(Point, int, int)) {
+    // negative threads => single threaded.
+    if (threads < 0) threads = 0;
+
+    Point span_z, span_xy;
+
+    // get rotation axis
+    pt_orthogonal_plane(camera.direction, &span_z, &span_xy);
+
+    printf("rendering %ix%i px\n", width, height);
+
+    pt_print_n("span_xy", span_xy);
+    pt_print_n("span_z", span_z);
+
+
+    // distance each ray has from anothe on the ortogonal plane
+    double step_dist = 2 / (double) (width - 1);
+
+    // vectors to move on the projection plane
+    Point move_right = pt_scale(span_xy, step_dist);
+    Point move_up =    pt_scale(span_z,  step_dist);;
+
+    printf("step: %f\n", step_dist);
+    // set starting point
+    Point starting_point = pt_normalize(camera.direction);
+    
+    // rotate starting point to (0,0)
+    pt_add(&starting_point, pt_mult(move_right, - width / (double) 2));
+    pt_add(&starting_point, pt_mult(move_up, - height / (double) 2));
+
+    // initialize threads
+    int thread_id = 0;
+    for (int i = 0; i < threads - 1; i++) {
+        if (fork() == 0) {
+            thread_id = i + 1;
+            break;
+        }
+    }
+    printf("Thread %i reporting for duty\n", thread_id);
+
+    // this point is moved for every pixel
+    Point curr_pt = starting_point;
+
+    // (0,0) screenspace is bottom left corner
+    for (int y = 0; y < height; y++) {
+        // move one row up (this has to be done in every thread!)
+        pt_add(&starting_point, move_up);
+
+        // only render the lines this thread is responsible for
+        if (y % threads != thread_id) continue;
+        
+        // actually iterate this line
+        curr_pt = starting_point;
+        for (int x = 0; x < width; x++) {
+            callback(curr_pt, x, y);
+            pt_add(&curr_pt, move_right); // move pt right to next pt
+        }
+    }
+
+    if (thread_id != 0) {
+        printf("Thread %i is finished\n", thread_id);
+        exit(0);
+    }
+
+    int status;
+    for (int i = 0; i < threads - 1; i++) {
+        printf("Waiting for threads... %d/%d\n", i, threads);
+        while(wait(&status) > 0) {}
+    }
+
+    printf("got threads\n");
+}
\ No newline at end of file
diff --git a/src/point.c b/src/point.c
new file mode 100644
index 0000000..bfa2ecc
--- /dev/null
+++ b/src/point.c
@@ -0,0 +1,180 @@
+#include <math.h>
+#include <stdio.h>
+
+// basically a vector3
+inline Point pt_new(double x, double y, double z) {
+    Point pt;
+    pt.x = x;
+    pt.y = y;
+    pt.z = z;
+    return pt;
+}
+
+// scale vector to length
+Point pt_scale(Point pt, double length) {
+    double f = length / pt_length(pt);
+    return pt_new(
+        pt.x * f,
+        pt.y * f,
+        pt.z * f
+    );
+}
+
+inline Point pt_mult(Point pt, double scalar) {
+    return pt_new(
+        pt.x * scalar,
+        pt.y * scalar,
+        pt.z * scalar
+    );
+}
+
+// return internal angle between a and b
+inline double pt_angle(Point a, Point b) {
+    return acos(pt_dot(
+        pt_normalize(a),
+        pt_normalize(b)
+    ));
+}
+
+// get the length of vector
+inline double pt_length(Point pt) {
+    return sqrt((pt.x * pt.x) + (pt.y * pt.y) + (pt.z * pt.z));
+}
+
+// add the vector add to the vector pt
+void pt_add(Point* pt, Point add) {
+    pt->x = pt->x + add.x;
+    pt->y = pt->y + add.y;
+    pt->z = pt->z + add.z;
+}
+
+// add the vector add to the vector pt
+inline void pt_sub(Point* pt, Point sub) {
+    pt->x -= sub.x;
+    pt->y -= sub.y;
+    pt->z -= sub.z;
+}
+
+inline double pt_dist(Point p1, Point p2) {
+    pt_sub(&p1, p2);
+    return pt_length(p1);
+}
+
+// normalize a vector
+inline Point pt_normalize(Point pt) {
+    return pt_scale(pt, 1);
+}
+
+// dot product of two vectors
+inline double pt_dot(Point a, Point b) {
+    return a.x*b.x + a.y*b.y + a.z*b.z;
+}
+
+// cross product of two vectors
+inline Point pt_cross(Point a, Point b) {
+    return pt_new(
+        a.y*b.z - a.z*b.y, 
+        a.z*b.x - a.x*b.z,
+        a.x*b.y - a.y*b.x
+    );
+}
+
+inline void pt_print(Point pt) {
+    printf("(%f, %f, %f)\n", pt.x, pt.y, pt.z);
+}
+
+inline void pt_print_n(const char* name, Point pt) {
+    printf("%s: (%f, %f, %f)\n", name, pt.x, pt.y, pt.z);
+}
+
+// find two vectors that span the orthogonal plane, where 
+// span_xy is a vector lying on the xy-plane (and pointing left)
+// and span_z is orthogonal to span_xy pointing "upwards"
+void pt_orthogonal_plane(Point pt, Point *span_z, Point *span_xy) {
+    pt = pt_normalize(pt);
+
+    // get the vector lying on the xy axis
+    // this is done by 
+    *span_xy = pt_normalize(pt_cross(pt_new(0,0,1), pt)); // points to the "left" (of the viewing direction)
+
+    // now use this, to find the vector 
+    *span_z = pt_normalize(pt_cross(pt, *span_xy));
+}
+
+inline Point pt_mod(Point pt, double mod) {
+    return pt_new(
+        fmod(pt.x, mod),
+        fmod(pt.y, mod),
+        fmod(pt.z, mod)
+    );
+}
+
+
+///////////////////////////////
+////// Matrix operations //////
+///////////////////////////////
+
+
+/* create a new matrix with entries:
+    x1 x2 x3
+    y1 y2 y3
+    z1 z2 z3
+*/
+inline Matrix mtrx_new(double x1, double x2, double x3,
+                       double y1, double y2, double y3,
+                       double z1, double z2, double z3) 
+{
+    Matrix m;
+    m.entries[0] = x1;
+    m.entries[1] = y1;
+    m.entries[2] = z1;
+    m.entries[3] = x2;
+    m.entries[4] = y2;
+    m.entries[5] = z2;
+    m.entries[6] = x3;
+    m.entries[7] = y3;
+    m.entries[8] = z3;
+    return m;
+}
+
+inline Point mtrx_mult(Matrix mtrx, Point pt) {
+    Point result;
+
+    double *m = mtrx.entries;
+
+    result.x = m[0] * pt.x + m[3] * pt.y + m[6] * pt.z;
+    result.y = m[1] * pt.x + m[4] * pt.y + m[7] * pt.z;
+    result.z = m[2] * pt.x + m[5] * pt.y + m[8] * pt.z;
+
+    return result;
+}
+
+// create a rotation matrix around an axis given by the normalized axis vector (u)
+// taken from https://en.wikipedia.org/wiki/Rotation_matrix#Rotation_matrix_from_axis_and_angle
+Matrix mtrx_rotation(Point u, double theta) {
+    double theta_rad = theta * (M_PI / 180);
+    double cost = cos(theta_rad);
+    double sint = sin(theta_rad);
+
+    return mtrx_new(
+        cost+u.x*u.x*(1-cost),     u.x*u.y*(1-cost)-u.z*sint, u.x*u.z*(1-cost)+u.y*sint,
+        u.y*u.x*(1-cost)+u.z*sint, cost+u.y*u.y*(1-cost),     u.y*u.z*(1-cost)-u.x*sint,
+        u.z*u.x*(1-cost)-u.y*sint, u.z*u.y*(1-cost)+u.x*sint, cost+u.z*u.z*(1-cost)
+    );
+}
+
+void mtrx_print(Matrix mtrx) {
+    printf("  %8.2f %8.2f %8.2f\n  %8.2f %8.2f %8.2f\n  %8.2f %8.2f %8.2f\n",
+        mtrx.entries[0], mtrx.entries[3], mtrx.entries[6],
+        mtrx.entries[1], mtrx.entries[4], mtrx.entries[7],
+        mtrx.entries[2], mtrx.entries[5], mtrx.entries[8]
+    );
+}
+
+inline Matrix mtrx_outer_prod(Point a, Point b) {
+    return mtrx_new(
+        a.x*b.x, a.x*b.y, a.x*b.z,
+        a.y*b.x, a.y*b.y, a.y*b.z,
+        a.z*b.x, a.z*b.y, a.z*b.z
+    );
+}
\ No newline at end of file
diff --git a/src/scene.c b/src/scene.c
new file mode 100644
index 0000000..b6367ef
--- /dev/null
+++ b/src/scene.c
@@ -0,0 +1,121 @@
+#include "../marcher.h"
+#include "../images/images.h"
+
+#include <limits.h>
+
+static Image* current_image;
+static Scene* current_scene;
+static Camera* current_camera;
+
+Color march_ray(Point origin, Point direction, Scene* scene);
+void camera_iter_callback(Point direction, int x, int y);
+
+
+Scene scene_new(unsigned int width, unsigned int height, int obj_count) {
+    Scene scene;
+    scene.height = height;
+    scene.width = width;
+    scene.max_steps = 32;
+    scene.threshold = 0.02;
+    scene.object_count = 0;
+    scene.objects = malloc(obj_count * sizeof(SceneObject));
+    scene.allocated_space = obj_count;
+    scene.background = color_new(0,0,0);
+    return scene;
+}
+
+void scene_add_obj(Scene* scene, SceneObject object) {
+    if (scene->object_count >= scene->allocated_space) return; // limit reached
+    // TODO realloc
+
+    scene->objects[scene->object_count] = object;
+
+    scene->object_count++;
+}
+
+// render out the scene with threads
+// creates a shared image, so destroy with image_destroy_shared then free struct with free_shared_memory
+Image* render_scene(Scene *scene, Camera *camera, unsigned int threads) {
+    current_image = malloc(sizeof(Image));
+    current_scene = scene;
+    current_camera= camera;
+
+    // initialize shared pixel buffer
+    image_new_shared(scene->width, scene->height, current_image);
+
+    // iterate over the rays
+    camera_iterate_rays_const_dist(*camera, scene->width, scene->height, threads, camera_iter_callback);
+    // or camera_iterate_rays_const_angle for lense distortion (this might not work correctly tho)
+
+    // return the drawn image
+    return current_image;
+}
+
+// march the ray, set the color. repeated for each direction generated by the camera
+void camera_iter_callback(Point direction, int x, int y) {
+    Color c = march_ray(current_camera->location, direction, current_scene);
+    image_set_px_c(*current_image, x, y, c);
+}
+
+
+
+Color march_ray(Point origin, Point direction, Scene* scene) {
+    // some local variables
+    Point pos = origin;
+    double closest_encounter = DBL_MAX;
+    double dist = closest_encounter;
+    // the closest object we have
+    SceneObject* closest_obj = scene->objects;
+
+    // get steps, threshold from scene
+    int steps = scene->max_steps;
+    double threshold = scene->threshold;
+
+    // as long as we did not max out steps, or got very close to an object
+    while (steps > 0 && dist > threshold) {
+        dist = 100;
+
+        // find distance to closest object
+        for(int i = 0; i < scene->object_count; i++) {
+            // get pointer to scene obj
+            SceneObject* obj = scene->objects + i;
+            double curr_dist = scene->objects[i].distance(pos, obj);
+
+            // if we are close
+            if (curr_dist < dist) {
+                dist = curr_dist;
+                closest_obj = obj;
+            }
+        }
+
+        // write down our closest encounter
+        if (dist < closest_encounter) closest_encounter = dist;
+
+        // scale direction vector to distance, then add it to our position
+        Point step_vector = pt_scale(direction, dist);
+        pt_add(&pos, step_vector);
+
+        // one step taken...
+        steps--;
+    }
+
+    // check for a hit
+    if (dist <= threshold) {
+        // a hit!
+        return closest_obj->get_color(pos, direction, closest_obj);
+
+    } else {
+        // a miss :(
+        // this should be 0!
+        return scene->background;
+    }
+}
+
+void scene_destroy(Scene scene) {
+    for (int i = 0; i < scene.object_count; i++) {
+        // free args memory
+        free(scene.objects[i].args);
+    }
+    free(scene.objects);
+
+}
\ No newline at end of file