shithub: libgraphics

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add spotlight params and a light color shading routine. other things.

among these other things are clamping the color
channels to [0,1] internally, and adding a
modulation function for mixing colors/points.

--- a/graphics.h

+++ b/graphics.h

@@ -104,8 +104,12 @@

 struct LightSource

 {

 	Point3 p;

+	Point3 dir;

 	Color c;

 	int type;

+	/* spotlights */

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

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

 };

 struct Material

@@ -330,6 +334,8 @@

 /* util */

 double fmin(double, double);

 double fmax(double, double);

+Point2 modulapt2(Point2, Point2);

+Point3 modulapt3(Point3, Point3);

 Memimage *rgb(ulong);

 /* shadeop */

@@ -336,5 +342,6 @@

 double sign(double);

 double step(double, double);

 double smoothstep(double, double, double);

+Color getlightcolor(LightSource*, Point3);

 extern Rectangle UR;	/* unit rectangle */

--- a/render.c

+++ b/render.c

@@ -15,10 +15,10 @@

 {

 	uchar cbuf[4];

-	cbuf[0] = c.a*0xFF;

-	cbuf[1] = c.b*0xFF;

-	cbuf[2] = c.g*0xFF;

-	cbuf[3] = c.r*0xFF;

+	cbuf[0] = fclamp(c.a, 0, 1)*0xFF;

+	cbuf[1] = fclamp(c.b, 0, 1)*0xFF;

+	cbuf[2] = fclamp(c.g, 0, 1)*0xFF;

+	cbuf[3] = fclamp(c.r, 0, 1)*0xFF;

 	return cbuf[3]<<24 | cbuf[2]<<16 | cbuf[1]<<8 | cbuf[0];

 }

--- a/scene.c

+++ b/scene.c

@@ -159,18 +159,9 @@

 				if(mtl->name == nil)

 					sysfatal("strdup: %r");

 			}

-			mtl->ambient.r = objmtl->Ka.r;

-			mtl->ambient.g = objmtl->Ka.g;

-			mtl->ambient.b = objmtl->Ka.b;

-			mtl->ambient.a = 1;

-			mtl->diffuse.r = objmtl->Kd.r;

-			mtl->diffuse.g = objmtl->Kd.g;

-			mtl->diffuse.b = objmtl->Kd.b;

-			mtl->diffuse.a = 1;

-			mtl->specular.r = objmtl->Ks.r;

-			mtl->specular.g = objmtl->Ks.g;

-			mtl->specular.b = objmtl->Ks.b;

-			mtl->specular.a = 1;

+			mtl->ambient = Pt3(objmtl->Ka.r, objmtl->Ka.g, objmtl->Ka.b, 1);

+			mtl->diffuse = Pt3(objmtl->Kd.r, objmtl->Kd.g, objmtl->Kd.b, 1);

+			mtl->specular = Pt3(objmtl->Ks.r, objmtl->Ks.g, objmtl->Ks.b, 1);

 			mtl->shininess = objmtl->Ns;

 			if(objmtl->map_Kd != nil){

@@ -419,7 +410,6 @@

 clearscene(Scene *s)

 {

 	Entity *e, *ne;

-	int i;

 	for(e = s->ents.next; e != &s->ents; e = ne){

 		ne = e->next;

--- a/shadeop.c

+++ b/shadeop.c

@@ -30,3 +30,21 @@

 	t = fclamp((n-edge0)/(edge1-edge0), 0, 1);

 	return t*t * (3 - 2*t);

 }

+

+/* TODO apply attenuation for punctual lights */

+Color

+getlightcolor(LightSource *l, Point3 dir)

+{

+	double cθs, cθu, cθp, t;

+

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

+	if(l->type == LIGHT_SPOT){

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

+		cθu = cos(l->θu);

+		cθp = cos(l->θp);

+//		return mulpt3(l->c, smoothstep(cθu, cθp, cθs));

+		t = fclamp((cθs - cθu)/(cθp - cθu), 0, 1);

+		return mulpt3(l->c, t*t);

+	}

+	return l->c;

+}

--- a/util.c

+++ b/util.c

@@ -52,6 +52,18 @@

 	*b = t;

 }

+Point2

+modulapt2(Point2 a, Point2 b)

+{

+	return (Point2){a.x*b.x, a.y*b.y, a.w*b.w};

+}

+

+Point3

+modulapt3(Point3 a, Point3 b)

+{

+	return (Point3){a.x*b.x, a.y*b.y, a.z*b.z, a.w*b.w};

+}

+

 void

 memsetd(double *p, double v, usize len)

 {

--- a/vertex.c

+++ b/vertex.c

@@ -43,6 +43,9 @@

 	return nv;

 }

+/*

+ * linear attribute interpolation

+ */

 void

 lerpvertex(Vertex *v, Vertex *v0, Vertex *v1, double t)

 {

@@ -68,7 +71,7 @@

 }

 /*

- * perspective-correct barycentric attribute interpolation

+ * barycentric attribute interpolation

  */

 void

 berpvertex(Vertex *v, Vertex *v0, Vertex *v1, Vertex *v2, Point3 bc)