shithub: tinyrend

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Lesson 1: Triangle rasterization and back-face culling—Flat shading render

--- a/main.c

+++ b/main.c

@@ -346,6 +346,9 @@

 	Point3 bc;

 	int i;

 	uchar cbuf[4];

+	static Point3 light = {0,0,-1,1}; /* global point light */

+	Point3 n;

+	double intensity;

 	verts = model->vertdata[OBJVGeometric].verts;

@@ -370,10 +373,16 @@

 				if(bc.x < 0 || bc.y < 0 || bc.z < 0)

 					continue;

+				n = normvec3(crossvec3(subpt3(t.p2, t.p0), subpt3(t.p1, t.p0)));

+				intensity = dotvec3(n, light);

+				/* back-face culling */

+				if(intensity < 0)

+					continue;

+

 				cbuf[0] = 0xFF;

-				cbuf[1] = 0xFF*bc.x;

-				cbuf[2] = 0xFF*bc.y;

-				cbuf[3] = 0xFF*bc.z;

+				cbuf[1] = 0xFF*intensity;

+				cbuf[2] = 0xFF*intensity;

+				cbuf[3] = 0xFF*intensity;

 				memfillcolor(sp->frag, *(ulong*)cbuf);

 				return sp->frag;

@@ -392,6 +401,9 @@

 	Triangle st;

 	int i;

 	uchar cbuf[4];

+	static Point3 light = {0,0,-1,1}; /* global point light */

+	Point3 n;

+	double intensity;

 	verts = model->vertdata[OBJVGeometric].verts;

@@ -416,10 +428,16 @@

 				if(eqpt(st[0], st[1]) || eqpt(st[1], st[2]) || eqpt(st[2], st[0]))

 					continue;

+				n = normvec3(crossvec3(subpt3(t.p2, t.p0), subpt3(t.p1, t.p0)));

+				intensity = dotvec3(n, light);

+				/* back-face culling */

+				if(intensity < 0)

+					continue;

+

 				cbuf[0] = 0xFF;

-				cbuf[1] = 0xFF*frand();

-				cbuf[2] = 0xFF*frand();

-				cbuf[3] = 0xFF*frand();

+				cbuf[1] = 0xFF*intensity;

+				cbuf[2] = 0xFF*intensity;

+				cbuf[3] = 0xFF*intensity;

 				filltriangle(dst, st[0], st[1], st[2], rgb(*(ulong*)cbuf));

 			}

@@ -537,7 +555,7 @@

 	if(newwindow(nil) < 0)

 		sysfatal("newwindow: %r");

-	if(initdraw(nil, nil, nil) < 0)

+	if(initdraw(nil, nil, "tinyrend") < 0)

 		sysfatal("initdraw: %r");

 	if(memimageinit() != 0)

 		sysfatal("memimageinit: %r");