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Allow camera position and target position to vary

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This commit is contained in:
Camden Dixie O'Brien
2025-09-23 15:36:08 +01:00
parent 75159e7223
commit c32c903d18
3 changed files with 32 additions and 25 deletions
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24
demo.c
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@@ -7,22 +7,23 @@
#define W 800 #define W 800
#define H 600 #define H 600
#define FOV 120 #define FOV 90
#define SAMPLES_PER_PIXEL 100 #define SAMPLES_PER_PIXEL 100
#define NELEMS(arr) (sizeof(arr) / sizeof(arr[0])) #define NELEMS(arr) (sizeof(arr) / sizeof(arr[0]))
static const vec3_t camera_pos = { 0.0, 0.0, 0.0 }; static const vec3_t camera_pos = { 0.0, 1.5, -2.0 };
static const vec3_t camera_target = { 0.0, 1.0, 1.0 };
static const obj_t scene[] = { static const obj_t scene[] = {
SPHERE(1.0, 0.0, -3.0, 1.0, LAMBERTIAN(0.6, 0.2, 0.8)), SPHERE(1.0, 1.0, 3.0, 1.0, LAMBERTIAN(0.6, 0.2, 0.8)),
SPHERE(-0.8, 0.0, -3.8, 1.0, LAMBERTIAN(1.0, 1.0, 1.0)), SPHERE(-0.8, 1.0, 3.8, 1.0, LAMBERTIAN(1.0, 1.0, 1.0)),
SPHERE(-1.0, -0.8, -2.6, 0.2, LAMBERTIAN(0.2, 0.9, 0.3)), SPHERE(-1.0, 0.2, 2.6, 0.2, LAMBERTIAN(0.2, 0.9, 0.3)),
SPHERE(0.3, -0.7, -1.8, 0.3, LAMBERTIAN(0.9, 0.6, 0.2)), SPHERE(0.3, 0.3, 1.8, 0.3, LAMBERTIAN(0.9, 0.6, 0.2)),
SPHERE(-1.6, -0.8, -2.0, 0.2, REFLECTIVE(1.0, 0.9, 0.4, 0.0)), SPHERE(-1.6, 0.2, 2.0, 0.2, REFLECTIVE(1.0, 0.9, 0.4, 0.0)),
SPHERE(-6.0, 5.0, -5.0, 6.0, REFLECTIVE(0.9, 0.9, 0.9, 0.05)), SPHERE(-6.0, 6.0, 5.0, 6.0, REFLECTIVE(0.9, 0.9, 0.9, 0.05)),
SPHERE(-0.7, -0.75, -1.5, 0.25, DIELECTRIC(1.5)), SPHERE(-0.7, 0.25, 1.5, 0.25, DIELECTRIC(1.5)),
SPHERE(0.0, -1001.0, 0.0, 1000.0, LAMBERTIAN(0.3, 0.3, 0.3)), SPHERE(0.0, -1000.0, 0.0, 1000.0, LAMBERTIAN(0.3, 0.3, 0.3)),
}; };
static pix_t pixbuf[W * H]; static pix_t pixbuf[W * H];
@@ -30,7 +31,8 @@ static pix_t pixbuf[W * H];
int main() int main()
{ {
img_t img = { .pix = pixbuf }; img_t img = { .pix = pixbuf };
camera_t camera = camera_init(camera_pos, FOV, W, H, SAMPLES_PER_PIXEL); camera_t camera = camera_init(
camera_pos, camera_target, FOV, W, H, SAMPLES_PER_PIXEL);
camera_render(&camera, scene, NELEMS(scene), &img); camera_render(&camera, scene, NELEMS(scene), &img);
ff_write(STDOUT_FILENO, img); ff_write(STDOUT_FILENO, img);

4
include/camera.h
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@@ -15,8 +15,8 @@ typedef struct {
} camera_t; } camera_t;
camera_t camera_init( camera_t camera_init(
vec3_t pos, double fov, uint32_t img_width, uint32_t img_height, vec3_t pos, vec3_t target, double fov, uint32_t img_width,
unsigned samples_per_pixel); uint32_t img_height, unsigned samples_per_pixel);
void camera_render( void camera_render(
const camera_t *camera, const obj_t *scene, unsigned scene_count, const camera_t *camera, const obj_t *scene, unsigned scene_count,

29
src/camera.c
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@@ -16,7 +16,6 @@
#define MAX_ITER 10 #define MAX_ITER 10
#define MIN_T 1e-6 #define MIN_T 1e-6
#define SAMPLE_STDDEV 0.333 #define SAMPLE_STDDEV 0.333
#define FOCAL_LEN 1.0
#define GAMMA 2.2 #define GAMMA 2.2
@@ -31,6 +30,8 @@ typedef struct {
atomic_uint *progress; atomic_uint *progress;
} work_slice_t; } work_slice_t;
static const vec3_t up = { 0.0, 1.0, 0.0 };
static const vec3_t lightblue = { 0.4, 0.6, 1.0 }; static const vec3_t lightblue = { 0.4, 0.6, 1.0 };
static const vec3_t white = { 1.0, 1.0, 1.0 }; static const vec3_t white = { 1.0, 1.0, 1.0 };
static const vec3_t black = { 0.0, 0.0, 0.0 }; static const vec3_t black = { 0.0, 0.0, 0.0 };
@@ -97,10 +98,11 @@ static int render_thread(void *arg)
const vec3_t offset = vec3_add( const vec3_t offset = vec3_add(
vec3_scale(camera->x_step, jitter.x), vec3_scale(camera->x_step, jitter.x),
vec3_scale(camera->y_step, jitter.y)); vec3_scale(camera->y_step, jitter.y));
const vec3_t jittered_pix = vec3_add(pix, offset);
const ray_t ray = { const ray_t ray = {
.orig = camera->pos, .orig = camera->pos,
.dir = vec3_unit(vec3_add(pix, offset)), .dir = vec3_unit(vec3_sub(jittered_pix, camera->pos)),
}; };
const vec3_t sample = trace( const vec3_t sample = trace(
ray, slice->scene, slice->scene_count, &slice->rng); ray, slice->scene, slice->scene_count, &slice->rng);
@@ -118,20 +120,23 @@ static int render_thread(void *arg)
} }
camera_t camera_init( camera_t camera_init(
vec3_t pos, double fov, uint32_t img_width, uint32_t img_height, vec3_t pos, vec3_t target, double fov, uint32_t img_width,
unsigned samples_per_pixel) uint32_t img_height, unsigned samples_per_pixel)
{ {
const double aspect = (double)img_width / (double)img_height;
const double fov_rad = M_PI * fov / 180.0; const double fov_rad = M_PI * fov / 180.0;
const double viewport_height = FOCAL_LEN * tan(fov_rad / 2); const double aspect = (double)img_width / (double)img_height;
const double viewport_height = tan(fov_rad / 2);
const double viewport_width = viewport_height * aspect; const double viewport_width = viewport_height * aspect;
const vec3_t viewport_disp = { 0, 0, FOCAL_LEN };
const vec3_t u = { viewport_width, 0, 0 }; const vec3_t w_hat = vec3_unit(vec3_sub(target, pos));
const vec3_t v = { 0, -viewport_height, 0 }; const vec3_t u_hat = vec3_unit(vec3_cross(up, w_hat));
const vec3_t topleft = vec3_sub( const vec3_t v_hat = vec3_unit(vec3_cross(w_hat, u_hat));
vec3_sub(pos, viewport_disp), vec3_scale(vec3_add(u, v), 0.5));
const vec3_t u = vec3_scale(u_hat, viewport_width);
const vec3_t v = vec3_scale(v_hat, -viewport_height);
const vec3_t topleft
= vec3_sub(vec3_add(pos, w_hat), vec3_scale(vec3_add(u, v), 0.5));
const vec3_t x_step = vec3_scale(u, 1.0 / (double)img_width); const vec3_t x_step = vec3_scale(u, 1.0 / (double)img_width);
const vec3_t y_step = vec3_scale(v, 1.0 / (double)img_height); const vec3_t y_step = vec3_scale(v, 1.0 / (double)img_height);