static void bezier_split_up_down(VECTOR (*Patch)[4][4], VECTOR (*Bottom_Patch)[4][4], VECTOR (*Top_Patch)[4][4])
{
int i, j;
VECTOR Temp1[4], Temp2[4];
VECTOR Half;
for (i = 0; i < 4; i++)
{
Assign_Vector(Temp1[0], (*Patch)[i][0]);
VHalf(Temp1[1], (*Patch)[i][0], (*Patch)[i][1]);
VHalf(Half, (*Patch)[i][1], (*Patch)[i][2]);
VHalf(Temp1[2], Temp1[1], Half);
VHalf(Temp2[2], (*Patch)[i][2], (*Patch)[i][3]);
VHalf(Temp2[1], Half, Temp2[2]);
VHalf(Temp1[3], Temp1[2], Temp2[1]);
Assign_Vector(Temp2[0], Temp1[3]);
Assign_Vector(Temp2[3], (*Patch)[i][3]);
for (j = 0; j < 4; j++)
{
Assign_Vector((*Bottom_Patch)[i][j], Temp1[j]);
Assign_Vector((*Top_Patch)[i][j] , Temp2[j]);
}
}
}
static void bezier_split_left_right(VECTOR (*Patch)[4][4], VECTOR (*Left_Patch)[4][4], VECTOR (*Right_Patch)[4][4])
{
int i, j;
VECTOR Half;
VECTOR Temp1[4], Temp2[4];
for (i = 0; i < 4; i++)
{
Assign_Vector(Temp1[0], (*Patch)[0][i]);
VHalf(Temp1[1], (*Patch)[0][i], (*Patch)[1][i]);
VHalf(Half, (*Patch)[1][i], (*Patch)[2][i]);
VHalf(Temp1[2], Temp1[1], Half);
VHalf(Temp2[2], (*Patch)[2][i], (*Patch)[3][i]);
VHalf(Temp2[1], Half, Temp2[2]);
VHalf(Temp1[3], Temp1[2], Temp2[1]);
Assign_Vector(Temp2[0], Temp1[3]);
Assign_Vector(Temp2[3], (*Patch)[3][i]);
for (j = 0; j < 4; j++)
{
Assign_Vector((*Left_Patch)[j][i], Temp1[j]);
Assign_Vector((*Right_Patch)[j][i], Temp2[j]);
}
}
}
static DBL ground_fog(RAY *Ray, DBL Depth, DBL Width, FOG *Fog, COLOUR Colour)
{
DBL fog_density, delta;
DBL start, end;
DBL y1, y2, k;
VECTOR P, P1, P2;
/* Get start point. */
VEvaluateRay(P1, Ray->Initial, Depth, Ray->Direction);
/* Get end point. */
VLinComb2(P2, 1.0, P1, Width, Ray->Direction);
/*
* Could preform transfomation here to translate Start and End
* points into ground fog space.
*/
VDot(y1, P1, Fog->Up);
VDot(y2, P2, Fog->Up);
start = (y1 - Fog->Offset) / Fog->Alt;
end = (y2 - Fog->Offset) / Fog->Alt;
/* Get integral along y-axis from start to end. */
if (start <= 0.0)
{
if (end <= 0.0)
{
fog_density = 1.0;
}
else
{
fog_density = (atan(end) - start) / (end - start);
}
}
else
{
if (end <= 0.0)
{
fog_density = (atan(start) - end) / (start - end);
}
else
{
delta = start - end;
if (fabs(delta) > EPSILON)
{
fog_density = (atan(start) - atan(end)) / delta;
}
else
{
fog_density = 1.0 / (Sqr(start) + 1.0);
}
}
}
/* Apply turbulence. */
if (Fog->Turb != NULL)
{
VHalf(P, P1, P2);
VEvaluateEq(P, Fog->Turb->Turbulence);
/* The further away the less influence turbulence has. */
k = exp(-Width / Fog->Distance);
Width *= 1.0 - k * min(1.0, Turbulence(P, Fog->Turb, NULL)*Fog->Turb_Depth);
}
Assign_Colour(Colour, Fog->Colour);
return (exp(-Width * fog_density / Fog->Distance));
}
