shithub: libgraphics

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control cutoff distance from the lights themselves

--- a/graphics.h

+++ b/graphics.h

@@ -143,10 +143,11 @@

 struct LightSource

 {

+	int type;

 	Point3 p;

 	Point3 dir;

 	Color c;

-	int type;

+	double cutoff;	/* distance */

 	/* spotlights */

 	double θu;	/* umbra angle. anything beyond is unlit */

 	double θp;	/* penumbra angle. anything within is fully lit */

--- a/shadeop.c

+++ b/shadeop.c

@@ -32,10 +32,12 @@

 /* see Equation 5.16, Real-Time Rendering 4th ed. § 5.2.2 */

 static double

-dfalloff(double d)

+dfalloff(LightSource *l, double d)

 {

-	enum { RMAX = 3000 };	/* cutoff distance */

-	d = d/RMAX;

+	if(l->cutoff <= 0)

+		return 0;

+

+	d = d/l->cutoff;

 	d *= d;

 	d = max(0, 1 - d);

 	return d*d;

@@ -53,17 +55,17 @@

 	ldir = divpt3(ldir, r);

 	switch(l->type){

+	case LightDirectional:

+		t = max(0, dotvec3(mulpt3(l->dir, -1), n));

+		c = mulpt3(l->c, t);

+		break;

 	case LightPoint:

 		t = max(0, dotvec3(ldir, n));

 		c = mulpt3(l->c, t);

 		/* attenuation */

-		c = mulpt3(c, dfalloff(r));

+		c = mulpt3(c, dfalloff(l, r));

 		break;

-	case LightDirectional:

-		t = max(0, dotvec3(mulpt3(l->dir, -1), n));

-		c = mulpt3(l->c, t);

-		break;

 	case LightSpot:

 		/* see “Spotlights”, Real-Time Rendering 4th ed. § 5.2.2 */

 		cθs = dotvec3(mulpt3(ldir, -1), l->dir);

@@ -76,7 +78,7 @@

 		c = mulpt3(l->c, t*t);

 		/* attenuation */

-		c = mulpt3(c, dfalloff(r));

+		c = mulpt3(c, dfalloff(l, r));

 		break;

 	default: sysfatal("alien light form detected");

 	}