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#include <u.h>
#include <libc.h>
#include <thread.h>
#include <draw.h>
#include <memdraw.h>
#include <geometry.h>
#include "graphics.h"
#include "internal.h"
/*
* 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.
*/
Point3
clip2ndc(Point3 p)
{
p.w = p.w == 0? 0: 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.
*/
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;
}
Point3
viewport2ndc(Framebuf *fb, Point3 p)
{
p.x = 2*p.x/Dx(fb->r) - 1;
p.y = 1 - 2*p.y/Dy(fb->r);
p.z = 2*p.z - 1;
p.w = 1;
return p;
}
Point3
ndc2vcs(Camera *c, Point3 p)
{
Matrix3 invproj;
Point3 np;
memmove(invproj, c->proj, 4*4*sizeof(double));
invm3(invproj);
np = xform3(p, invproj);
np.w = np.w == 0? 0: 1.0/np.w;
np.x *= np.w;
np.y *= np.w;
np.z *= np.w;
np.w = 1;
return np;
}
Point3
viewport2vcs(Camera *c, Point3 p)
{
return ndc2vcs(c, viewport2ndc(c->view->getfb(c->view), p));
}
Point3
vcs2world(Camera *c, Point3 p)
{
return invrframexform3(p, *c);
}
Point3
viewport2world(Camera *c, Point3 p)
{
return vcs2world(c, viewport2vcs(c, p));
}
Point3
world2model(Entity *e, Point3 p)
{
return rframexform3(p, *e);
}
void
perspective(Matrix3 m, double fovy, double a, double n, double f)
{
double cotan;
cotan = 1/tan(fovy/2);
memset(m, 0, 4*4*sizeof(double));
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);
}
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