the perspective transform finally looks right

camera.c

@@ -22,15 +22,14 @@ camera_new(
 	v3_t eye,
 	v3_t lookat,
 	v3_t up,
-	float fov,
+	float fov
-	float scale
 )
 {
 	camera_t * c = calloc(1, sizeof(*c));
 	if (!c)
 		return NULL;
 
-	camera_setup(c, eye, lookat, up, fov, scale);
+	camera_setup(c, eye, lookat, up, fov);
 	return c;
 }
 
@@ -41,8 +40,7 @@ camera_setup(
 	v3_t eye,
 	v3_t lookat,
 	v3_t up,
-	float fov,
+	float fov
-	float scale
 )
 {
 	// compute the basis for the camera
@@ -62,9 +60,9 @@ camera_setup(
 		{ u.p[2], v.p[2], w.p[2], 0 },
 		{ -v3_dot(u,eye), -v3_dot(v,eye), -v3_dot(w,eye), 1 },
 #else
-		{ u.p[0], u.p[1], u.p[2], -v3_dot(u,lookat) },
+		{ u.p[0], u.p[1], u.p[2], -v3_dot(u,eye) },
-		{ v.p[0], v.p[1], v.p[2], -v3_dot(v,lookat) },
+		{ v.p[0], v.p[1], v.p[2], -v3_dot(v,eye) },
-		{ w.p[0], w.p[1], w.p[2], -v3_dot(w,lookat) },
+		{ w.p[0], w.p[1], w.p[2], -v3_dot(w,eye) },
 		{ 0,      0,      0,      1 },
 #endif
 	};
@@ -80,7 +78,7 @@ camera_setup(
 
 	// now compute the perspective projection matrix
 	float s = 1.0 / tan(fov * M_PI / 180 / 2);
-	c->near = 1.0;
+	c->near = 4.0;
 	c->far = 20;
 	float f1 = - c->far / (c->far - c->near);
 	float f2 = - c->far * c->near / (c->far - c->near);
@@ -142,17 +140,28 @@ camera_project(
 		for (int j = 0 ; j < 4 ; j++)
 			p[i] += c->r[i][j] * v[j];
 
-	if(1) fprintf(stderr, "%.2f %.2f %.2f -> %.2f %.2f %.2f %.2f\n",
+	// what if p->p[4] == 0?
+	// pz < 0 == The point is behind us; do not display?
+	//if (p[2] < c->near || p[2] > c->far)
+	if (p[2] < 0)
+		return 0;
+
+	p[0] /= p[3];
+	p[1] /= p[3];
+/*
+	for (int i = 0 ; i < 3 ; i++)
+		p[i] /= p[3];
+	p[2] /= p[3];
+*/
+
+	if(0) fprintf(stderr, "%.2f %.2f %.2f -> %.2f %.2f %.2f %.2f\n",
 		v[0], v[1], v[2],
 		p[0], p[1], p[2], p[3]
 	);
 
 /*
-	for (int i = 0 ; i < 3 ; i++)
-		p[i] /= p[3];
 	p[0] *= -1;
 	p[1] *= -1;
-	p[2] /= p[3];
 */
 
 
@@ -162,10 +171,6 @@ camera_project(
 	v_out->p[1] = p[1];
 	v_out->p[2] = p[2];
 
-	// what if p->p[4] == 0?
-	// pz < 0 == The point is behind us; do not display?
-	if (p[2] < c->near || p[2] > c->far)
-		return 0;
 
 	return 1;
 }

camera.h

@@ -9,8 +9,7 @@ camera_new(
 	v3_t eye,
 	v3_t lookat,
 	v3_t up,
-	float fov,
+	float fov
-	float scale
 );
 
 extern void
@@ -19,8 +18,7 @@ camera_setup(
 	v3_t eye,
 	v3_t lookat,
 	v3_t up,
-	float fov,
+	float fov
-	float scale
 );
 
 /** Transform a XYZ point into a screen point.

hiddenwire.c

@@ -768,8 +768,10 @@ int onscreen(
 {
 	if (p->p[0] < -width/2 || width/2 < p->p[0])
 		return 0;
+/*
 	if (p->p[1] < -height/2 || height/2 < p->p[1])
 		return 0;
+*/
 /*
 	if (p->p[0] < 0 || width < p->p[0])
 		return 0;
@@ -868,7 +870,8 @@ int main(
 	}
 
 
-	const camera_t * const cam = camera_new(eye, lookat, up, fov, scale);
+	(void) scale;
+	const camera_t * const cam = camera_new(eye, lookat, up, fov);
 
 	printf("<svg xmlns=\"http://www.w3.org/2000/svg\" width=\"%.0fpx\" height=\"%.0fpx\" viewbox=\"0 0 %.0f %.0f\">\n", width, height, width, height);
 
@@ -897,18 +900,27 @@ int main(
 
 		for(int j = 0 ; j < 3 ; j++)
 		{
-			camera_project(cam, &stl->p[j], &s[j]);
+			// if any points are behind us, reject
+			// this one
+			if (!camera_project(cam, &stl->p[j], &s[j]))
+			{
+				behind++;
+				goto reject_early;
+			}
 		}
 
 		if(debug >= 2)
-		fprintf(stderr, "%.3f,%.3f,%.3f -> %.1f,%.1f,%.1f\n",
+		for(int j = 0 ; j < 3 ; j++)
-			stl->p[0].p[0],
+		{
-			stl->p[0].p[1],
+			fprintf(stderr, "%.3f %.3f %.3f -> %.3f %.3f %.3f\n",
-			stl->p[0].p[2],
+				stl->p[j].p[0],
-			s[0].p[0],
+				stl->p[j].p[1],
-			s[0].p[1],
+				stl->p[j].p[2],
-			s[0].p[2]
+				s[j].p[0],
-		);
+				s[j].p[1],
+				s[j].p[2]
+			);
+		}
 
 		tri_t * const tri = tri_new(s, stl->p);
 
@@ -962,6 +974,8 @@ tri_print(tri);
 
 reject:
 		tri_delete(tri);
+reject_early:
+		continue;
 	}
 
 	if (debug)

test.c

@@ -0,0 +1,25 @@
+#include <stdio.h>
+#include "camera.h"
+#include "v3.h"
+
+int main(void)
+{
+	v3_t lookat = {{0,0,0}};
+	v3_t eye = {{0,-20,0}};
+	v3_t up = {{0,0,1}};
+	float fov = 20;
+
+	camera_t * camera = camera_new(eye, lookat, up, fov);
+
+	for (float x = -5 ; x <= 5 ; x += 5)
+	for (float y = -25 ; y < 55 ; y += 5 )
+	{
+		v3_t v_in = {{ x, y, 5 }};
+		v3_t v_out;
+		int onscreen = camera_project(camera, &v_in, &v_out);
+		if (!onscreen && y > eye.p[1])
+			fprintf(stderr, "false positive\n");
+		if (onscreen && y < eye.p[1])
+			fprintf(stderr, "false negative\n");
+	}
+}