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enable backface culling

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This commit is contained in:
Trammell hudson 2017-09-26 22:59:09 -04:00
parent 6c13b35255
commit a3815d7c4e
Failed to extract signature
3 changed files with 59 additions and 27 deletions
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14
camera.c
View File

@ -12,14 +12,14 @@
struct _camera_t
{
float zoom;
float eye_z;
v3_t eye;
float r[3][3];
};
camera_t *
camera_new(
float eye_z,
v3_t eye,
float phi,
float theta,
float psi
@ -29,8 +29,8 @@ camera_new(
if (!c)
return NULL;
c->zoom = 1024;
camera_setup(c, eye_z, phi, theta, psi);
c->zoom = 4096;
camera_setup(c, eye, phi, theta, psi);
return c;
}
@ -38,7 +38,7 @@ camera_new(
void
camera_setup(
camera_t * const c,
float eye_z,
v3_t eye,
float phi,
float theta,
float psi
@ -63,7 +63,7 @@ camera_setup(
c->r[2][1] = sx * cy;
c->r[2][2] = cx * cy;
c->eye_z = eye_z;
c->eye = eye;
}
@ -78,7 +78,7 @@ camera_project(
v3_t * const v_out
)
{
v3_t p = { .p = { 0, 0, c->eye_z } };
v3_t p = c->eye;
for (int i = 0 ; i < 3 ; i++)
for (int j = 0 ; j < 3 ; j++)

4
camera.h
View File

@ -6,7 +6,7 @@ typedef struct _camera_t camera_t;
extern camera_t *
camera_new(
float eye_z,
v3_t eye,
float phi,
float theta,
float psi
@ -15,7 +15,7 @@ camera_new(
extern void
camera_setup(
camera_t * const c,
float eye_z,
v3_t eye,
float phi,
float theta,
float psi

62
hiddenwire.c
View File

@ -17,8 +17,7 @@
#define M_PI 3.1415926535897932384
#endif
static int debug = 0;
static int draw_labels = 0;
static int debug = 1;
typedef struct
{
@ -111,7 +110,7 @@ svg_line(
{
if (!dash)
{
printf("<line x1=\"%f\" y1=\"%f\" x2=\"%f\" y2=\"%f\" stroke=\"%s\" stroke-width=\"0.1px\"/>\n",
printf("<line x1=\"%f\" y1=\"%f\" x2=\"%f\" y2=\"%f\" stroke=\"%s\" stroke-width=\"0.5px\"/>\n",
p1[0],
p1[1],
p2[0],
@ -716,11 +715,18 @@ stl2faces(
#endif
int main(void)
int main(
int argc,
char ** argv
)
{
const size_t max_len = 1 << 20;
const size_t max_len = 32 << 20;
uint8_t * const buf = calloc(max_len, 1);
float phi = argc > 1 ? atof(argv[1]) * M_PI/180 : 0;
float theta = argc > 2 ? atof(argv[2]) * M_PI/180 : 0;
float psi = argc > 3 ? atof(argv[3]) * M_PI/180 : 0;
ssize_t rc = read(0, buf, max_len);
if (rc == -1)
return EXIT_FAILURE;
@ -729,38 +735,64 @@ int main(void)
const stl_face_t * const stl_faces = (const void*)(hdr+1);
const int num_triangles = hdr->num_triangles;
if(debug)
{
fprintf(stderr, "header: '%s'\n", hdr->header);
fprintf(stderr, "num: %d\n", num_triangles);
}
// looking at (0,0,0)
const camera_t * const cam = camera_new(400, 0, M_PI/2, M_PI);
v3_t eye = { { 0, 0, 400 } };
const camera_t * const cam = camera_new(eye, phi, theta, psi);
// translate each face into lines
printf("<svg xmlns=\"http://www.w3.org/2000/svg\">\n");
printf("<g>\n");
// convert the stl triangles into faces
float off_x = 500;
float off_y = 500;
printf("<g transform=\"translate(%f %f)\">\n", off_x, off_y);
int rejected = 0;
for (int i = 0 ; i < num_triangles ; i++)
{
const stl_face_t * const stl = &stl_faces[i];
int reject = 0;
v3_t s[3];
for(int j = 0 ; j < 3 ; j++)
camera_project(cam, &stl->p[j], &s[j]);
// reject this face if any of them are behind us
for(int j = 0 ; j < 3 ; j++)
if (s[j].p[2] <= 0)
reject = 1;
// do a back-face cull to determine if this triangle
// is not facing us. we have to determine the orientation
// from the winding of the new projection
v3_t normal = v3_cross(
v3_sub(s[1], s[0]),
v3_sub(s[2], s[1])
);
if (normal.p[2] <= 0)
reject = 1;
if (reject)
{
rejected++;
continue;
}
// draw each of the three lines
for(int j = 0 ; j < 3 ; j++)
{
if (s[j].p[2] <= 0)
continue;
if (s[(j+1) % 3].p[2] <= 0)
continue;
svg_line("#FF0000", s[j].p, s[(j+1) % 3].p, 0);
}
}
if (debug)
fprintf(stderr, "Rejected %d triangles\n", rejected);
#if 0
face_t * const faces = stl2faces(stl_faces, num_triangles);