구차니의 잡동사니 모음

#define __glPi 3.14159265358979323846

void GLAPIENTRY

gluPerspective(GLdouble fovy, GLdouble aspect, GLdouble zNear, GLdouble zFar)

{

GLdouble m[4][4];

double sine, cotangent, deltaZ;

double radians = fovy / 2 * __glPi / 180;

deltaZ = zFar - zNear;

sine = sin(radians);

if ((deltaZ == 0) || (sine == 0) || (aspect == 0)) {

    return;

}

cotangent = COS(radians) / sine;

__gluMakeIdentityd(&m[0][0]);

m[0][0] = cotangent / aspect;

m[1][1] = cotangent;

m[2][2] = -(zFar + zNear) / deltaZ;

m[2][3] = -1;

m[3][2] = -2 * zNear * zFar / deltaZ;

m[3][3] = 0;

glMultMatrixd(&m[0][0]);

}

void GLAPIENTRY

gluLookAt(GLdouble eyex, GLdouble eyey, GLdouble eyez, GLdouble centerx,

     GLdouble centery, GLdouble centerz, GLdouble upx, GLdouble upy,

     GLdouble upz)

{

float forward[3], side[3], up[3];

GLfloat m[4][4];

forward[0] = centerx - eyex;

forward[1] = centery - eyey;

forward[2] = centerz - eyez;

up[0] = upx;

up[1] = upy;

up[2] = upz;

normalize(forward);

/* Side = forward x up */

cross(forward, up, side);

normalize(side);

/* Recompute up as: up = side x forward */

cross(side, forward, up);

__gluMakeIdentityf(&m[0][0]);

m[0][0] = side[0];

m[1][0] = side[1];

m[2][0] = side[2];

m[0][1] = up[0];

m[1][1] = up[1];

m[2][1] = up[2];

m[0][2] = -forward[0];

m[1][2] = -forward[1];

m[2][2] = -forward[2];

glMultMatrixf(&m[0][0]);

glTranslated(-eyex, -eyey, -eyez);

}

Specifies the distance from the viewer to the near clipping plane (always positive).

Specifies the distance from the viewer to the far clipping plane (always positive).

Notes

Depth buffer precision is affected by the values specified for zNear and zFar. The greater the ratio of zFar to zNear is, the less effective the depth buffer will be at distinguishing between surfaces that are near each other. If

r = zFar zNear

roughly log 2 ⁡ r bits of depth buffer precision are lost. Because r approaches infinity as zNear approaches 0, zNear must never be set to 0.