ref: d3516b11559657935d70829c672f29393e857b8e
parent: 6e461add61d35d23f733cffb5064a286419b79b0
author: rodri <rgl@antares-labs.eu>
date: Mon May 20 16:20:48 EDT 2024
fix the perspective projection and add inverse xform functions.
--- a/graphics.h
+++ b/graphics.h
@@ -276,10 +276,19 @@
/* render */
Renderer *initgraphics(void);
+
+/* xform */
Point3 model2world(Entity*, Point3);
Point3 world2vcs(Camera*, Point3);
Point3 vcs2clip(Camera*, Point3);
Point3 world2clip(Camera*, Point3);
+Point3 clip2ndc(Point3);
+Point3 ndc2viewport(Framebuf*, Point3);
+Point3 viewport2ndc(Framebuf*, Point3);
+Point3 ndc2vcs(Camera*, Point3);
+Point3 viewport2vcs(Camera*, Point3);
+Point3 vcs2world(Camera*, Point3);
+Point3 viewport2world(Camera*, Point3);
void perspective(Matrix3, double, double, double, double);
void orthographic(Matrix3, double, double, double, double, double, double);
--- a/mkfile
+++ b/mkfile
@@ -6,6 +6,7 @@
viewport.$O\
render.$O\
clip.$O\
+ xform.$O\
scene.$O\
vertex.$O\
texture.$O\
--- a/render.c
+++ b/render.c
@@ -52,118 +52,6 @@
return sa <= 0;
}
-/*
- * 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(Rastertask *task)
{--- /dev/null
+++ b/xform.c
@@ -1,0 +1,167 @@
+#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"
+
+/*
+ * 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? 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.
+ */
+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->vp->getfb(c->vp), p));
+}
+
+Point3
+vcs2world(Camera *c, Point3 p)
+{+ return invrframexform3(p, *c);
+}
+
+Point3
+viewport2world(Camera *c, Point3 p)
+{+ return vcs2world(c, viewport2vcs(c, p));
+}
+
+void
+perspective(Matrix3 m, double fovy, double a, double n, double f)
+{+ double cotan;
+
+ cotan = 1/tan(fovy/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;
+ m[3][3] = 0;
+}
+
+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);
+}