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#include <stdio.h>
#include <stdlib.h>
#define CGLTF_IMPLEMENTATION
#include "cgltf.h"
typedef struct {
unsigned short p, n, t;
} Vertex;
struct {
int vc, pc, nc, tc;
int* p, * n, * t;
Vertex* verts;
} result = { 0 };
struct {
unsigned short* ind;
float* p, * n, * t;
int ic, pc, nc, tc;
} intern = { 0 };
void parse_attrib(
float** d,
int* c,
int ec,
const cgltf_accessor* a
) {
int count, es = ec * 4;
const cgltf_buffer_view* v = a->buffer_view;
if (a->component_type != cgltf_component_type_r_32f) {
fprintf(stderr, "Only float attributes are supported.\n");
exit(33);
}
if (ec * 4 != a->stride) {
fprintf(stderr, "Attribute stride doesn't match component count.\n");
exit(34);
}
count = *c + a->count;
*d = realloc(*d, count * es);
memcpy(
&(*d)[*c],
&((char*)v->buffer->data)[v->offset],
a->count * es
);
*c = count;
}
void parse_prim_attribs(const cgltf_primitive* p) {
int i;
unsigned m = 0;
for (i = 0; i < p->attributes_count; i++) {
const cgltf_attribute* a = &p->attributes[i];
switch (a->type) {
case cgltf_attribute_type_position:
parse_attrib(&intern.p, &intern.pc, 3, a->data);
m |= 0x1;
break;
case cgltf_attribute_type_normal:
parse_attrib(&intern.n, &intern.nc, 3, a->data);
m |= 0x2;
break;
case cgltf_attribute_type_texcoord:
parse_attrib(&intern.t, &intern.tc, 2, a->data);
m |= 0x4;
break;
default: break;
}
}
if (m != 0x7) {
fprintf(stderr, "Not all attributes were provided.\n");
exit(32);
}
}
void parse_prim(const cgltf_primitive* p) {
int i, c, s;
const cgltf_accessor* a;
const cgltf_buffer_view* v;
if (p->type != cgltf_primitive_type_triangles) {
fprintf(stderr, "Only triangle meshes are supported.\n");
exit(30);
}
a = p->indices;
if (!a) {
fprintf(stderr, "Meshes must be indexed.\n");
exit(35);
}
if (a->stride != 2) {
fprintf(stderr, "Only two byte indices are supported.\n");
exit(31);
}
v = a->buffer_view;
c = intern.ic + a->count;
intern.ind = realloc(intern.ind, c * sizeof *intern.ind);
memcpy(
&intern.ind[intern.ic],
&((char*)v->buffer->data)[v->offset],
a->count * sizeof *intern.ind
);
intern.ic = c;
parse_prim_attribs(p);
}
void parse_mesh(const cgltf_mesh* m) {
int i;
for (i = 0; i < m->primitives_count; i++)
parse_prim(&m->primitives[i]);
}
int parse(const char* name) {
int i;
cgltf_options opt = { 0 };
cgltf_data* d;
cgltf_result r;
r = cgltf_parse_file(&opt, name, &d);
if (r) return r;
r = cgltf_load_buffers(&opt, d, name);
if (r) return r;
for (i = 0; i < d->meshes_count; i++)
parse_mesh(&d->meshes[i]);
cgltf_free(d);
return 0;
}
int to_fixed(float v) {
return (int)(v * 512.0f);
}
int attrib_eq(float* a, int* b, int ec) {
int i;
for (i = 0; i < ec; i++) {
int fpv = to_fixed(a[i]);
if (fpv != b[i])
return 0;
}
return 1;
}
void convert_attrib(
float* s,
int ec,
unsigned short* di,
int* dc,
int* d
) {
int i, idx, c = *dc;
for (i = 0; i < c; i++) {
int ei = i * ec;
if (attrib_eq(s, &d[ei], ec)) {
*di = i;
return;
}
}
idx = c++;
*dc = c;
*di = (unsigned short)idx;
for (i = 0; i < ec; i++) {
int iidx = i + idx * ec;
d[iidx] = to_fixed(s[i]);
}
}
void convert_vert(int i) {
Vertex* d = &result.verts[result.vc++];
int idx = intern.ind[i];
convert_attrib(
&intern.p[idx * 3],
3,
&d->p,
&result.pc,
result.p
);
convert_attrib(
&intern.n[idx * 3],
3,
&d->n,
&result.nc,
result.n
);
convert_attrib(
&intern.t[idx * 2],
2,
&d->t,
&result.tc,
result.t
);
}
void convert(void) {
int i;
result.p = malloc(intern.pc * sizeof *result.p * 3);
result.n = malloc(intern.nc * sizeof *result.n * 3);
result.t = malloc(intern.tc * sizeof *result.t * 2);
result.verts = malloc(intern.ic * sizeof *result.verts);
for (i = 0; i < intern.ic; i++) {
convert_vert(i);
}
}
void dump(const char* name) {
FILE* outfile = fopen(name, "wb");
if (!outfile) {
fprintf(stderr, "Failed to open %s\n", name);
exit(35);
}
fwrite(&result, 1, sizeof result, outfile);
fwrite(result.p, result.pc, sizeof* result.p * 3, outfile);
fwrite(result.n, result.nc, sizeof* result.n * 3, outfile);
fwrite(result.t, result.tc, sizeof* result.t * 2, outfile);
fwrite(result.verts, result.vc, sizeof* result.verts, outfile);
}
int main(int argc, const char** argv) {
int r;
if (argc < 3) {
fprintf(
stderr,
"Usage: %s infile outfile\n",
argv[0]
);
return 1;
}
r = parse(argv[1]);
if (r) return r;
convert();
dump(argv[2]);
return 0;
}
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