From: John Tsiombikas <nuclear@member.fsf.org>
Date: Tue, 27 Mar 2018 19:36:59 +0000 (+0300)
Subject: subtraction seems to work now
X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?a=commitdiff_plain;ds=inline;h=f4f8d2071921bb09ff0408fe70f0599cb1263319;hp=7abe0c51fc87e90674427c5ac5848f394af4575a;p=csgray

subtraction seems to work now
---

diff --git a/src/csgray.c b/src/csgray.c
index fe0228a..44c7eb9 100644
--- a/src/csgray.c
+++ b/src/csgray.c
@@ -350,7 +350,7 @@ static void shade(float *col, struct ray *ray, struct hit *hit)
 		sray.dy = ldir[1];
 		sray.dz = ldir[2];
 
-		if(1) {//!find_intersection(&sray, &tmphit) || tmphit.t > 1.0f) {
+		if(!find_intersection(&sray, &tmphit) || tmphit.t > 1.0f) {
 			if((len = sqrt(ldir[0] * ldir[0] + ldir[1] * ldir[1] + ldir[2] * ldir[2])) != 0.0f) {
 				float s = 1.0f / len;
 				ldir[0] *= s;
@@ -383,16 +383,32 @@ static void background(float *col, struct ray *ray)
 
 static int find_intersection(struct ray *ray, struct hit *best)
 {
+	int idx = 0;
 	csg_object *o;
-	struct hit *hit;
+	struct hinterv *hit, *it;
 
 	best->t = FLT_MAX;
 	best->o = 0;
 
 	o = oblist;
 	while(o) {
-		if((hit = ray_intersect(ray, o)) && hit->t < best->t) {
-			*best = *hit;
+		if((hit = ray_intersect(ray, o))) {
+			it = hit;
+			while(it) {
+				if(it->end[0].t > 1e-6) {
+					idx = 0;
+					break;
+				}
+				if(it->end[1].t > 1e-6) {
+					idx = 1;
+					break;
+				}
+				it = it->next;
+			}
+
+			if(it && it->end[idx].t < best->t) {
+				*best = it->end[idx];
+			}
 		}
 		free_hit_list(hit);
 		o = o->ob.next;
diff --git a/src/geom.c b/src/geom.c
index 1961aed..341e7c3 100644
--- a/src/geom.c
+++ b/src/geom.c
@@ -1,15 +1,20 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <math.h>
+#include <float.h>
 #include "geom.h"
 #include "matrix.h"
 
 #define EPSILON		1e-6f
 
+static struct hinterv *interval_union(struct hinterv *a, struct hinterv *b);
+static struct hinterv *interval_isect(struct hinterv *a, struct hinterv *b);
+static struct hinterv *interval_sub(struct hinterv *a, struct hinterv *b);
+
 /* TODO custom hit allocator */
-struct hit *alloc_hit(void)
+struct hinterv *alloc_hit(void)
 {
-	struct hit *hit = calloc(sizeof *hit, 1);
+	struct hinterv *hit = calloc(sizeof *hit, 1);
 	if(!hit) {
 		perror("failed to allocate ray hit node");
 		abort();
@@ -17,13 +22,13 @@ struct hit *alloc_hit(void)
 	return hit;
 }
 
-struct hit *alloc_hits(int n)
+struct hinterv *alloc_hits(int n)
 {
 	int i;
-	struct hit *list = 0;
+	struct hinterv *list = 0;
 
 	for(i=0; i<n; i++) {
-		struct hit *hit = alloc_hit();
+		struct hinterv *hit = alloc_hit();
 		hit->next = list;
 		list = hit;
 	}
@@ -31,21 +36,21 @@ struct hit *alloc_hits(int n)
 }
 
 
-void free_hit(struct hit *hit)
+void free_hit(struct hinterv *hit)
 {
 	free(hit);
 }
 
-void free_hit_list(struct hit *hit)
+void free_hit_list(struct hinterv *hit)
 {
 	while(hit) {
-		struct hit *tmp = hit;
+		struct hinterv *tmp = hit;
 		hit = hit->next;
 		free_hit(tmp);
 	}
 }
 
-struct hit *ray_intersect(struct ray *ray, csg_object *o)
+struct hinterv *ray_intersect(struct ray *ray, csg_object *o)
 {
 	switch(o->ob.type) {
 	case OB_SPHERE:
@@ -66,11 +71,11 @@ struct hit *ray_intersect(struct ray *ray, csg_object *o)
 	return 0;
 }
 
-struct hit *ray_sphere(struct ray *ray, csg_object *o)
+struct hinterv *ray_sphere(struct ray *ray, csg_object *o)
 {
 	int i;
 	float a, b, c, d, sqrt_d, t[2], sq_rad, tmp;
-	struct hit *hit, *hitlist;
+	struct hinterv *hit;
 	struct ray locray = *ray;
 
 	if(o->sph.rad == 0.0f) {
@@ -101,26 +106,31 @@ struct hit *ray_sphere(struct ray *ray, csg_object *o)
 		t[1] = tmp;
 	}
 
-	hitlist = hit = alloc_hits(2);
+	hit = alloc_hits(1);
+	hit->o = o;
 	for(i=0; i<2; i++) {
 		float c[3] = {0, 0, 0};
-		mat4_xform3(c, o->ob.xform, c);
+		float x, y, z;
 
-		hit->t = t[i];
-		hit->x = ray->x + ray->dx * t[i];
-		hit->y = ray->y + ray->dy * t[i];
-		hit->z = ray->z + ray->dz * t[i];
-		hit->nx = (hit->x - c[0]) / o->sph.rad;
-		hit->ny = (hit->y - c[1]) / o->sph.rad;
-		hit->nz = (hit->z - c[2]) / o->sph.rad;
-		hit->o = o;
+		mat4_xform3(c, o->ob.xform, c);
 
-		hit = hit->next;
+		x = ray->x + ray->dx * t[i];
+		y = ray->y + ray->dy * t[i];
+		z = ray->z + ray->dz * t[i];
+
+		hit->end[i].t = t[i];
+		hit->end[i].x = x;
+		hit->end[i].y = y;
+		hit->end[i].z = z;
+		hit->end[i].nx = (x - c[0]) / o->sph.rad;
+		hit->end[i].ny = (y - c[1]) / o->sph.rad;
+		hit->end[i].nz = (z - c[2]) / o->sph.rad;
+		hit->end[i].o = o;
 	}
-	return hitlist;
+	return hit;
 }
 
-struct hit *ray_cylinder(struct ray *ray, csg_object *o)
+struct hinterv *ray_cylinder(struct ray *ray, csg_object *o)
 {
 	struct ray locray = *ray;
 
@@ -128,10 +138,10 @@ struct hit *ray_cylinder(struct ray *ray, csg_object *o)
 	return 0;	/* TODO */
 }
 
-struct hit *ray_plane(struct ray *ray, csg_object *o)
+struct hinterv *ray_plane(struct ray *ray, csg_object *o)
 {
 	float vx, vy, vz, ndotv, ndotr, t;
-	struct hit *hit = 0;
+	struct hinterv *hit;
 	struct ray locray = *ray;
 
 	xform_ray(&locray, o->ob.inv_xform);
@@ -146,24 +156,31 @@ struct hit *ray_plane(struct ray *ray, csg_object *o)
 	ndotv = o->plane.nx * vx + o->plane.ny * vy + o->plane.nz * vz;
 
 	t = ndotv / ndotr;
-
-	if(t > EPSILON) {
-		hit = alloc_hits(1);
-		hit->t = t;
-		hit->x = ray->x + ray->dx * t;
-		hit->y = ray->y + ray->dy * t;
-		hit->z = ray->z + ray->dz * t;
-		hit->nx = o->plane.nx;
-		hit->ny = o->plane.ny;
-		hit->nz = o->plane.nz;
-		hit->o = o;
+	if(t < EPSILON) {
+		return 0;
 	}
+
+	hit = alloc_hits(1);
+	hit->o = hit->end[0].o = hit->end[1].o = o;
+	hit->end[0].t = t;
+	hit->end[0].x = ray->x + ray->dx * t;
+	hit->end[0].y = ray->y + ray->dy * t;
+	hit->end[0].z = ray->z + ray->dz * t;
+
+	hit->end[0].nx = hit->end[1].nx = o->plane.nx;
+	hit->end[0].ny = hit->end[1].ny = o->plane.ny;
+	hit->end[0].nz = hit->end[1].nz = o->plane.nz;
+
+	hit->end[1].t = FLT_MAX;
+	hit->end[1].x = ray->x + ray->dx * 10000.0f;
+	hit->end[1].y = ray->y + ray->dy * 10000.0f;
+	hit->end[1].z = ray->z + ray->dz * 10000.0f;
 	return hit;
 }
 
-struct hit *ray_csg_un(struct ray *ray, csg_object *o)
+struct hinterv *ray_csg_un(struct ray *ray, csg_object *o)
 {
-	struct hit *hita, *hitb;
+	struct hinterv *hita, *hitb, *res;
 
 	hita = ray_intersect(ray, o->un.a);
 	hitb = ray_intersect(ray, o->un.b);
@@ -171,73 +188,166 @@ struct hit *ray_csg_un(struct ray *ray, csg_object *o)
 	if(!hita) return hitb;
 	if(!hitb) return hita;
 
-	if(hita->t < hitb->t) {
+	res = interval_union(hita, hitb);
+	free_hit_list(hita);
+	free_hit_list(hitb);
+	return res;
+}
+
+struct hinterv *ray_csg_isect(struct ray *ray, csg_object *o)
+{
+	struct hinterv *hita, *hitb, *res;
+
+	hita = ray_intersect(ray, o->isect.a);
+	hitb = ray_intersect(ray, o->isect.b);
+
+	if(!hita || !hitb) {
+		free_hit_list(hita);
 		free_hit_list(hitb);
-		return hita;
+		return 0;
 	}
+
+	res = interval_isect(hita, hitb);
 	free_hit_list(hita);
-	return hitb;
+	free_hit_list(hitb);
+	return res;
 }
 
-struct hit *ray_csg_isect(struct ray *ray, csg_object *o)
+struct hinterv *ray_csg_sub(struct ray *ray, csg_object *o)
 {
-	return 0;
+	struct hinterv *hita, *hitb, *res;
+
+	hita = ray_intersect(ray, o->un.a);
+	hitb = ray_intersect(ray, o->un.b);
+
+	if(!hita) return 0;
+	if(!hitb) return hita;
+
+	res = interval_sub(hita, hitb);
+	free_hit_list(hita);
+	free_hit_list(hitb);
+	return res;
 }
 
-static struct hit *first(struct hit *hlist)
+
+void xform_ray(struct ray *ray, float *mat)
 {
-	return hlist;
+	float m3x3[16];
+
+	mat4_copy(m3x3, mat);
+	mat4_upper3x3(m3x3);
+
+	mat4_xform3(&ray->x, mat, &ray->x);
+	mat4_xform3(&ray->dx, m3x3, &ray->dx);
+}
+
+static void flip_hit(struct hit *hit)
+{
+	hit->nx = -hit->nx;
+	hit->ny = -hit->ny;
+	hit->nz = -hit->nz;
 }
 
-static struct hit *last(struct hit *hlist)
+static struct hinterv *interval_union(struct hinterv *a, struct hinterv *b)
 {
-	while(hlist->next) {
-		hlist = hlist->next;
+	struct hinterv *res, *res2;
+
+	if(a->end[0].t > b->end[1].t || a->end[1].t < b->end[0].t) {
+		/* disjoint */
+		res = alloc_hits(2);
+		res2 = res->next;
+
+		if(a->end[0].t < b->end[0].t) {
+			*res = *a;
+			*res2 = *b;
+		} else {
+			*res = *b;
+			*res2 = *a;
+		}
+		res->next = res2;
+		res2->next = 0;
+		return res;
 	}
-	return hlist;
+
+	res = alloc_hits(1);
+	res->end[0] = a->end[0].t <= b->end[0].t ? a->end[0] : b->end[0];
+	res->end[1] = a->end[1].t >= b->end[1].t ? a->end[1] : b->end[1];
+	return res;
 }
 
-struct hit *ray_csg_sub(struct ray *ray, csg_object *o)
+static struct hinterv *interval_isect(struct hinterv *a, struct hinterv *b)
 {
-	struct hit *hita, *hitb, *lasthit, tmp;
+	struct hinterv *res;
 
-	hita = ray_intersect(ray, o->sub.a);
-	hitb = ray_intersect(ray, o->sub.b);
+	if(a->end[0].t > b->end[1].t || a->end[1].t < b->end[0].t) {
+		/* disjoint */
+		return 0;
+	}
 
-	if(!hita) return 0;
-	if(!hitb) return hita;
+	res = alloc_hits(1);
 
-	if(first(hita)->t < first(hitb)->t) {
-		free_hit_list(hitb);
-		return hita;
+	if(a->end[0].t <= b->end[0].t && a->end[1].t >= b->end[1].t) {
+		/* B in A */
+		*res = *a;
+		res->next = 0;
+		return res;
+	}
+	if(a->end[0].t > b->end[0].t && a->end[1].t < b->end[1].t) {
+		/* A in B */
+		*res = *b;
+		res->next = 0;
+		return res;
 	}
-	if(first(hita)->t < (lasthit = last(hitb))->t) {
-		/* overlapping */
-		tmp = *hitb;
-		*hitb = *lasthit;
 
-		free_hit_list(tmp.next);
+	/* partial overlap */
+	if(a->end[0].t < b->end[1].t) {
+		res->end[0] = b->end[1];
+		res->end[1] = a->end[0];
+	} else {
+		res->end[0] = a->end[1];
+		res->end[1] = a->end[0];
+	}
+	return res;
+}
 
-		hitb->nx = -hitb->nx;
-		hitb->ny = -hitb->ny;
-		hitb->nz = -hitb->nz;
+static struct hinterv *interval_sub(struct hinterv *a, struct hinterv *b)
+{
+	struct hinterv *res;
 
-		free_hit_list(hita);
-		return hitb;
+	if(a->end[0].t >= b->end[0].t && a->end[1].t <= b->end[1].t) {
+		/* A in B */
+		return 0;
 	}
 
-	free_hit_list(hitb);
-	return hita;
-}
+	if(a->end[0].t < b->end[0].t && a->end[1].t > b->end[1].t) {
+		/* B in A */
+		res = alloc_hits(2);
+		res->end[0] = a->end[0];
+		res->end[1] = b->end[0];
+		res->next->end[0] = b->end[1];
+		res->next->end[1] = a->end[1];
+		return res;
+	}
 
+	res = alloc_hits(1);
 
-void xform_ray(struct ray *ray, float *mat)
-{
-	float m3x3[16];
+	if(a->end[0].t > b->end[1].t || a->end[1].t < b->end[0].t) {
+		/* disjoint */
+		*res = *a;
+		res->next = 0;
+		return res;
+	}
 
-	mat4_copy(m3x3, mat);
-	mat4_upper3x3(m3x3);
+	/* partial overlap */
+	if(a->end[0].t <= b->end[0].t) {
+		res->end[0] = a->end[0];
+		res->end[1] = b->end[0];
+	} else {
+		res->end[0] = b->end[1];
+		res->end[1] = a->end[1];
+	}
 
-	mat4_xform3(&ray->x, mat, &ray->x);
-	mat4_xform3(&ray->dx, m3x3, &ray->dx);
+	flip_hit(res->end + 0);
+	flip_hit(res->end + 1);
+	return res;
 }
diff --git a/src/geom.h b/src/geom.h
index 7405fa3..e3865d2 100644
--- a/src/geom.h
+++ b/src/geom.h
@@ -14,22 +14,28 @@ struct hit {
 	float x, y, z;
 	float nx, ny, nz;
 	csg_object *o;
+};
+
+struct hinterv {
+	struct hit end[2];
+	csg_object *o;
 
-	struct hit *next;
+	struct hinterv *next;
 };
 
-struct hit *alloc_hit(void);
-void free_hit(struct hit *hit);
-void free_hit_list(struct hit *hit);
 
-struct hit *ray_intersect(struct ray *ray, csg_object *o);
+struct hinterv *alloc_hits(int n);
+void free_hit(struct hinterv *hv);
+void free_hit_list(struct hinterv *hv);
+
+struct hinterv *ray_intersect(struct ray *ray, csg_object *o);
 
-struct hit *ray_sphere(struct ray *ray, csg_object *o);
-struct hit *ray_cylinder(struct ray *ray, csg_object *o);
-struct hit *ray_plane(struct ray *ray, csg_object *o);
-struct hit *ray_csg_un(struct ray *ray, csg_object *o);
-struct hit *ray_csg_isect(struct ray *ray, csg_object *o);
-struct hit *ray_csg_sub(struct ray *ray, csg_object *o);
+struct hinterv *ray_sphere(struct ray *ray, csg_object *o);
+struct hinterv *ray_cylinder(struct ray *ray, csg_object *o);
+struct hinterv *ray_plane(struct ray *ray, csg_object *o);
+struct hinterv *ray_csg_un(struct ray *ray, csg_object *o);
+struct hinterv *ray_csg_isect(struct ray *ray, csg_object *o);
+struct hinterv *ray_csg_sub(struct ray *ray, csg_object *o);
 
 void xform_ray(struct ray *ray, float *mat);
 
diff --git a/src/main.c b/src/main.c
index d6aac1c..301966f 100644
--- a/src/main.c
+++ b/src/main.c
@@ -48,7 +48,7 @@ int main(int argc, char **argv)
 	csg_color(obj, 0.4, 0.7, 0.4);
 	csg_add_object(obj);
 
-	obj = csg_null(-6, 10, 10);
+	obj = csg_null(-4, 10, 10);
 	csg_emission(obj, 80, 80, 80);
 	csg_add_object(obj);