diff options
Diffstat (limited to 'src/mesa/swrast/s_aatriangle.c')
| -rw-r--r-- | src/mesa/swrast/s_aatriangle.c | 17 |
1 files changed, 12 insertions, 5 deletions
diff --git a/src/mesa/swrast/s_aatriangle.c b/src/mesa/swrast/s_aatriangle.c index 5f0a5c76012..dde2c89f76d 100644 --- a/src/mesa/swrast/s_aatriangle.c +++ b/src/mesa/swrast/s_aatriangle.c @@ -1,4 +1,4 @@ -/* $Id: s_aatriangle.c,v 1.20 2001/11/13 00:26:39 brianp Exp $ */ +/* $Id: s_aatriangle.c,v 1.21 2001/12/17 04:54:35 brianp Exp $ */ /* * Mesa 3-D graphics library @@ -40,6 +40,7 @@ /* * Compute coefficients of a plane using the X,Y coords of the v0, v1, v2 * vertices and the given Z values. + * A point (x,y,z) lies on plane iff a*x+b*y+c*z+d = 0. */ static INLINE void compute_plane(const GLfloat v0[], const GLfloat v1[], const GLfloat v2[], @@ -53,9 +54,15 @@ compute_plane(const GLfloat v0[], const GLfloat v1[], const GLfloat v2[], const GLfloat qy = v2[1] - v0[1]; const GLfloat qz = z2 - z0; + /* Crossproduct "(a,b,c):= dv1 x dv2" is orthogonal to plane. */ const GLfloat a = py * qz - pz * qy; const GLfloat b = pz * qx - px * qz; const GLfloat c = px * qy - py * qx; + /* Point on the plane = "r*(a,b,c) + w", with fixed "r" depending + on the distance of plane from origin and arbitrary "w" parallel + to the plane. */ + /* The scalar product "(r*(a,b,c)+w)*(a,b,c)" is "r*(a^2+b^2+c^2)", + which is equal to "-d" below. */ const GLfloat d = -(a * v0[0] + b * v0[1] + c * z0); plane[0] = a; @@ -93,8 +100,8 @@ do { \ static INLINE GLfloat solve_plane(GLfloat x, GLfloat y, const GLfloat plane[4]) { - const GLfloat z = (plane[3] + plane[0] * x + plane[1] * y) / -plane[2]; - return z; + ASSERT(plane[2] != 0.0F); + return (plane[3] + plane[0] * x + plane[1] * y) / -plane[2]; } @@ -193,7 +200,7 @@ compute_coveragef(const GLfloat v0[3], const GLfloat v1[3], #ifdef DEBUG { const GLfloat area = dx0 * dy1 - dx1 * dy0; - assert(area >= 0.0); + ASSERT(area >= 0.0); } #endif @@ -276,7 +283,7 @@ compute_coveragei(const GLfloat v0[3], const GLfloat v1[3], #ifdef DEBUG { const GLfloat area = dx0 * dy1 - dx1 * dy0; - assert(area >= 0.0); + ASSERT(area >= 0.0); } #endif |