ref: 764afe37e2438498bcace9de56b9618565b7cd34
dir: libgraphics/render.c
#include <u.h>
#include <libc.h>
#include <thread.h>
#include <draw.h>
#include <memdraw.h>
#include <geometry.h>
#include "libobj/obj.h"
#include "graphics.h"
#include "internal.h"
Rectangle UR = {0,0,1,1};
static ulong
col2ul(Color c)
{
uchar cbuf[4];
cbuf[0] = c.a*0xFF;
cbuf[1] = c.b*0xFF;
cbuf[2] = c.g*0xFF;
cbuf[3] = c.r*0xFF;
return cbuf[3]<<24 | cbuf[2]<<16 | cbuf[1]<<8 | cbuf[0];
}
static void
pixel(Memimage *dst, Point p, Memimage *src)
{
if(dst == nil || src == nil)
return;
memimagedraw(dst, rectaddpt(UR, p), src, ZP, nil, ZP, SoverD);
}
static int
isvisible(Point3 p)
{
if(p.x < -p.w || p.x > p.w ||
p.y < -p.w || p.y > p.w ||
p.z < -p.w || p.z > p.w)
return 0;
return 1;
}
static int
isfacingback(Triangle t)
{
double sa; /* signed area */
sa = t[0].p.x * t[1].p.y - t[0].p.y * t[1].p.x +
t[1].p.x * t[2].p.y - t[1].p.y * t[2].p.x +
t[2].p.x * t[0].p.y - t[2].p.y * t[0].p.x;
return sa <= 0;
}
static void
mulsdm(double r[6], double m[6][4], Point3 p)
{
int i;
for(i = 0; i < 6; i++)
r[i] = m[i][0]*p.x + m[i][1]*p.y + m[i][2]*p.z + m[i][3]*p.w;
}
typedef struct
{
Vertex *v;
ulong n;
ulong cap;
} Polygon;
static int
addvert(Polygon *p, Vertex v)
{
if(++p->n > p->cap)
p->v = erealloc(p->v, (p->cap = p->n)*sizeof(*p->v));
p->v[p->n-1] = v;
return p->n;
}
static void
swappoly(Polygon *a, Polygon *b)
{
Polygon tmp;
tmp = *a;
*a = *b;
*b = tmp;
}
static void
cleanpoly(Polygon *p)
{
int i;
for(i = 0; i < p->n; i++)
delvattrs(&p->v[i]);
p->n = 0;
}
/*
* references:
* - James F. Blinn, Martin E. Newell, “Clipping Using Homogeneous Coordinates”,
* SIGGRAPH '78, pp. 245-251
* - https://cs418.cs.illinois.edu/website/text/clipping.html
* - https://github.com/aap/librw/blob/14dab85dcae6f3762fb2b1eda4d58d8e67541330/tools/playground/tl_tests.cpp#L522
*/
static int
cliptriangle(Triangle *t)
{
/* signed distance from each clipping plane */
static double sdm[6][4] = {
1, 0, 0, 1, /* l */
-1, 0, 0, 1, /* r */
0, 1, 0, 1, /* b */
0, -1, 0, 1, /* t */
0, 0, 1, 1, /* f */
0, 0, -1, 1, /* n */
};
double sd0[6], sd1[6];
double d0, d1, perc;
Polygon Vin, Vout;
Vertex *v0, *v1, v; /* edge verts and new vertex (line-plane intersection) */
int i, j, nt;
nt = 0;
memset(&Vin, 0, sizeof Vin);
memset(&Vout, 0, sizeof Vout);
for(i = 0; i < 3; i++)
addvert(&Vin, t[0][i]);
for(j = 0; j < 6 && Vin.n > 0; j++){
for(i = 0; i < Vin.n; i++){
v0 = &Vin.v[i];
v1 = &Vin.v[(i+1) % Vin.n];
mulsdm(sd0, sdm, v0->p);
mulsdm(sd1, sdm, v1->p);
if(sd0[j] < 0 && sd1[j] < 0)
continue;
if(sd0[j] >= 0 && sd1[j] >= 0)
goto allin;
d0 = (j&1) == 0? sd0[j]: -sd0[j];
d1 = (j&1) == 0? sd1[j]: -sd1[j];
perc = d0/(d0 - d1);
lerpvertex(&v, v0, v1, perc);
addvert(&Vout, v);
if(sd1[j] >= 0){
allin:
addvert(&Vout, dupvertex(v1));
}
}
cleanpoly(&Vin);
if(j < 6-1)
swappoly(&Vin, &Vout);
}
/* triangulate */
if(Vout.n < 3)
cleanpoly(&Vout);
else
for(i = 0; i < Vout.n-2; i++, nt++){
/*
* when performing fan triangulation, indices 0 and 2
* are referenced on every triangle, so duplicate them
* to avoid complications during rasterization.
*/
t[nt][0] = i < Vout.n-2-1? dupvertex(&Vout.v[0]): Vout.v[0];
t[nt][1] = Vout.v[i+1];
t[nt][2] = i < Vout.n-2-1? dupvertex(&Vout.v[i+2]): Vout.v[i+2];
}
free(Vout.v);
free(Vin.v);
return nt;
}
/*
* transforms p from e's reference frame into
* the world.
*/
Point3
model2world(Entity *e, Point3 p)
{
return invrframexform3(p, *e);
}
/*
* transforms p from the world reference frame
* to c's one (aka Viewing Coordinate System).
*/
Point3
world2vcs(Camera *c, Point3 p)
{
return rframexform3(p, *c);
}
/*
* projects p from the VCS to clip space, placing
* p.[xyz] ∈ (-∞,-w)∪[-w,w]∪(w,∞) where [-w,w]
* represents the visibility volume.
*
* the clipping planes are:
*
* | -w | w |
* +----------------+
* | left | right |
* | bottom | top |
* | far | near |
*/
Point3
vcs2clip(Camera *c, Point3 p)
{
return xform3(p, c->proj);
}
Point3
world2clip(Camera *c, Point3 p)
{
return vcs2clip(c, world2vcs(c, p));
}
/*
* performs the perspective division, placing
* p.[xyz] ∈ [-1,1] and p.w = 1/z
* (aka Normalized Device Coordinates).
*
* p.w is kept as z⁻¹ so we can later do
* perspective-correct attribute interpolation.
*/
static Point3
clip2ndc(Point3 p)
{
p.w = p.w == 0? 1: 1.0/p.w;
p.x *= p.w;
p.y *= p.w;
p.z *= p.w;
return p;
}
/*
* scales p to fit the destination viewport,
* placing p.x ∈ [0,width], p.y ∈ [0,height],
* p.z ∈ [0,1] and leaving p.w intact.
*/
static Point3
ndc2viewport(Framebuf *fb, Point3 p)
{
Matrix3 view = {
Dx(fb->r)/2.0, 0, 0, Dx(fb->r)/2.0,
0, -Dy(fb->r)/2.0, 0, Dy(fb->r)/2.0,
0, 0, 1.0/2.0, 1.0/2.0,
0, 0, 0, 1,
};
double w;
w = p.w;
p.w = 1;
p = xform3(p, view);
p.w = w;
return p;
}
void
perspective(Matrix3 m, double fov, double a, double n, double f)
{
double cotan;
cotan = 1/tan(fov/2);
identity3(m);
m[0][0] = cotan/a;
m[1][1] = cotan;
m[2][2] = (f+n)/(f-n);
m[2][3] = -2*f*n/(f-n);
m[3][2] = -1;
}
void
orthographic(Matrix3 m, double l, double r, double b, double t, double n, double f)
{
identity3(m);
m[0][0] = 2/(r - l);
m[1][1] = 2/(t - b);
m[2][2] = -2/(f - n);
m[0][3] = -(r + l)/(r - l);
m[1][3] = -(t + b)/(t - b);
m[2][3] = -(f + n)/(f - n);
}
static void
rasterize(SUparams *params, Triangle t)
{
FSparams fsp;
Triangle2 t₂;
Rectangle bbox;
Point p;
Point3 bc;
Color c;
double z, depth;
t₂.p0 = Pt2(t[0].p.x, t[0].p.y, 1);
t₂.p1 = Pt2(t[1].p.x, t[1].p.y, 1);
t₂.p2 = Pt2(t[2].p.x, t[2].p.y, 1);
/* find the triangle's bbox and clip it against the fb */
bbox = Rect(
min(min(t₂.p0.x, t₂.p1.x), t₂.p2.x), min(min(t₂.p0.y, t₂.p1.y), t₂.p2.y),
max(max(t₂.p0.x, t₂.p1.x), t₂.p2.x)+1, max(max(t₂.p0.y, t₂.p1.y), t₂.p2.y)+1
);
bbox.min.x = max(bbox.min.x, params->fb->r.min.x);
bbox.min.y = max(bbox.min.y, params->fb->r.min.y);
bbox.max.x = min(bbox.max.x, params->fb->r.max.x);
bbox.max.y = min(bbox.max.y, params->fb->r.max.y);
fsp.su = params;
memset(&fsp.v, 0, sizeof fsp.v);
for(p.y = bbox.min.y; p.y < bbox.max.y; p.y++)
for(p.x = bbox.min.x; p.x < bbox.max.x; p.x++){
bc = barycoords(t₂, Pt2(p.x,p.y,1));
if(bc.x < 0 || bc.y < 0 || bc.z < 0)
continue;
z = fberp(t[0].p.z, t[1].p.z, t[2].p.z, bc);
depth = fclamp(z, 0, 1);
lock(¶ms->fb->zbuflk);
if(depth <= params->fb->zbuf[p.x + p.y*Dx(params->fb->r)]){
unlock(¶ms->fb->zbuflk);
continue;
}
params->fb->zbuf[p.x + p.y*Dx(params->fb->r)] = depth;
unlock(¶ms->fb->zbuflk);
/* interpolate z⁻¹ and get actual z */
z = fberp(t[0].p.w, t[1].p.w, t[2].p.w, bc);
z = 1.0/(z < 1e-5? 1e-5: z);
/* perspective-correct attribute interpolation */
bc.x *= t[0].p.w;
bc.y *= t[1].p.w;
bc.z *= t[2].p.w;
bc = mulpt3(bc, z);
berpvertex(&fsp.v, &t[0], &t[1], &t[2], bc);
fsp.p = p;
c = params->fshader(&fsp);
memfillcolor(params->frag, col2ul(c));
pixel(params->fb->cb, p, params->frag);
delvattrs(&fsp.v);
}
}
static void
shaderunit(void *arg)
{
SUparams *params;
VSparams vsp;
OBJVertex *verts, *tverts, *nverts; /* geometric, texture and normals vertices */
OBJIndexArray *idxtab;
OBJElem **ep, **eb, **ee;
Point3 n; /* surface normal */
Triangle *t; /* triangles to raster */
int i, nt;
params = arg;
vsp.su = params;
threadsetname("shader unit #%d", params->id);
t = emalloc(sizeof(*t)*16);
verts = params->entity->mdl->obj->vertdata[OBJVGeometric].verts;
tverts = params->entity->mdl->obj->vertdata[OBJVTexture].verts;
nverts = params->entity->mdl->obj->vertdata[OBJVNormal].verts;
eb = params->entity->mdl->elems;
ee = eb + params->entity->mdl->nelems;
for(ep = eb; ep != ee; ep++){
nt = 1; /* start with one. after clipping it might change */
idxtab = &(*ep)->indextab[OBJVGeometric];
t[0][0].p = Pt3(verts[idxtab->indices[0]].x,
verts[idxtab->indices[0]].y,
verts[idxtab->indices[0]].z,
verts[idxtab->indices[0]].w);
t[0][1].p = Pt3(verts[idxtab->indices[1]].x,
verts[idxtab->indices[1]].y,
verts[idxtab->indices[1]].z,
verts[idxtab->indices[1]].w);
t[0][2].p = Pt3(verts[idxtab->indices[2]].x,
verts[idxtab->indices[2]].y,
verts[idxtab->indices[2]].z,
verts[idxtab->indices[2]].w);
idxtab = &(*ep)->indextab[OBJVNormal];
if(idxtab->nindex == 3){
t[0][0].n = Vec3(nverts[idxtab->indices[0]].i,
nverts[idxtab->indices[0]].j,
nverts[idxtab->indices[0]].k);
t[0][0].n = normvec3(t[0][0].n);
t[0][1].n = Vec3(nverts[idxtab->indices[1]].i,
nverts[idxtab->indices[1]].j,
nverts[idxtab->indices[1]].k);
t[0][1].n = normvec3(t[0][1].n);
t[0][2].n = Vec3(nverts[idxtab->indices[2]].i,
nverts[idxtab->indices[2]].j,
nverts[idxtab->indices[2]].k);
t[0][2].n = normvec3(t[0][2].n);
}else{
/* TODO build a list of per-vertex normals earlier */
n = normvec3(crossvec3(subpt3(t[0][1].p, t[0][0].p), subpt3(t[0][2].p, t[0][0].p)));
t[0][0].n = t[0][1].n = t[0][2].n = n;
}
idxtab = &(*ep)->indextab[OBJVTexture];
if(idxtab->nindex == 3){
t[0][0].uv = Pt2(tverts[idxtab->indices[0]].u,
tverts[idxtab->indices[0]].v, 1);
t[0][1].uv = Pt2(tverts[idxtab->indices[1]].u,
tverts[idxtab->indices[1]].v, 1);
t[0][2].uv = Pt2(tverts[idxtab->indices[2]].u,
tverts[idxtab->indices[2]].v, 1);
}else{
t[0][0].uv = t[0][1].uv = t[0][2].uv = Vec2(0,0);
}
for(i = 0; i < 3; i++){
t[0][i].c = Pt3(1,1,1,1);
t[0][i].mtl = (*ep)->mtl;
t[0][i].attrs = nil;
t[0][i].nattrs = 0;
}
vsp.v = &t[0][0];
vsp.idx = 0;
t[0][0].p = params->vshader(&vsp);
vsp.v = &t[0][1];
vsp.idx = 1;
t[0][1].p = params->vshader(&vsp);
vsp.v = &t[0][2];
vsp.idx = 2;
t[0][2].p = params->vshader(&vsp);
if(!isvisible(t[0][0].p) || !isvisible(t[0][1].p) || !isvisible(t[0][2].p))
nt = cliptriangle(t);
while(nt--){
t[nt][0].p = clip2ndc(t[nt][0].p);
t[nt][1].p = clip2ndc(t[nt][1].p);
t[nt][2].p = clip2ndc(t[nt][2].p);
/* culling */
// if(isfacingback(t[nt]))
// goto skiptri;
t[nt][0].p = ndc2viewport(params->fb, t[nt][0].p);
t[nt][1].p = ndc2viewport(params->fb, t[nt][1].p);
t[nt][2].p = ndc2viewport(params->fb, t[nt][2].p);
rasterize(params, t[nt]);
//skiptri:
delvattrs(&t[nt][0]);
delvattrs(&t[nt][1]);
delvattrs(&t[nt][2]);
}
}
free(t);
sendp(params->donec, params);
threadexits(nil);
}
void
shade(Framebuf *fb, Scene *sc, Shader *s)
{
int i;
uvlong time;
Entity *ent;
SUparams *params;
Channel *donec;
time = nanosec();
donec = chancreate(sizeof(void*), 0);
/* TODO come up with an actual concurrent architecture */
for(i = 0, ent = sc->ents.next; i < sc->nents; i++, ent = ent->next){
params = emalloc(sizeof *params);
params->fb = fb;
params->id = i;
params->frag = rgb(DBlack);
params->donec = donec;
params->entity = ent;
params->uni_time = time;
params->vshader = s->vshader;
params->fshader = s->fshader;
proccreate(shaderunit, params, mainstacksize);
}
while(i--){
params = recvp(donec);
freememimage(params->frag);
free(params);
}
chanfree(donec);
}