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/* revision 7 */
/* @2010 Kamil Kaminski
*
* math3d.c
*
*/
#include "math3d.h"
void m3dFindNormalf(M3DVector3f result, const M3DVector3f point1,
const M3DVector3f point2, const M3DVector3f point3)
{
M3DVector3f v1, v2;
/* calculate two vectors from the three points, assumes
* counter clockwise winding
*/
v1[0] = point1[0] - point2[0];
v1[1] = point1[1] - point2[1];
v1[2] = point1[2] - point2[2];
v2[0] = point2[0] - point3[0];
v2[1] = point2[1] - point3[1];
v2[2] = point2[2] - point3[2];
/* take the cross product of the two vectors to get the normal vector */
m3dCrossProductf(result, v1, v2);
}
void m3dLoadIdentity33f(M3DMatrix33f m)
{
/* don't be fooled, this is still column major */
static M3DMatrix33f identity = { 1.0f, 0.0f, 0.0f,
0.0f, 1.0f, 0.0f,
0.0f, 0.0f, 1.0f };
memcpy(m, identity, sizeof(M3DMatrix33f));
}
void m3dLoadIdentity44f(M3DMatrix44f m) /* 4x4 float */
{
/* don't be fooled, this is still column major */
static M3DMatrix44f identity = { 1.0f, 0.0f, 0.0f, 0.0f,
0.0f, 1.0f, 0.0f, 0.0f,
0.0f, 0.0f, 1.0f, 0.0f,
0.0f, 0.0f, 0.0f, 1.0f };
memcpy(m, identity, sizeof(M3DMatrix44f));
}
/* calculate the plane equation of the plane that the three specified points lay in
* the points are given in clockwise winding order, with normal pointing out of clockwise face
* planeEq contains the a, b, c, and d of the plane equation coefficients
*/
void m3dGetPlaneEquationf(M3DVector4f planeEq, const M3DVector3f p1,
const M3DVector3f p2, const M3DVector3f p3)
{
/* get two vectors... do the cross product */
M3DVector3f v1, v2;
/* v1 = p3 - p1 */
v1[0] = p3[0] - p1[0];
v1[1] = p3[1] - p1[1];
v1[2] = p3[2] - p1[2];
/* v2 = p2 - p1 */
v2[0] = p2[0] - p1[0];
v2[1] = p2[1] - p1[1];
v2[2] = p2[2] - p1[2];
/* unit normal to plane - Not sure which is the best way here */
m3dCrossProductf(planeEq, v1, v2);
m3dNormalizeVectorf(planeEq);
/* back substitute to get d */
planeEq[3] = -(planeEq[0] * p3[0] + planeEq[1] * p3[1] + planeEq[2] * p3[2]);
}
/* creates a 4x4 rotation matrix, takes radians not degrees */
void m3dRotationMatrix44f(M3DMatrix44f m, float angle, float x, float y, float z)
{
float mag, s, c;
float xx, yy, zz, xy, yz, zx, xs, ys, zs, one_c;
s = (float) (sin(angle));
c = (float) (cos(angle));
mag = (float) (sqrt(x*x + y*y + z*z));
/* identity matrix */
if (mag == 0.0f)
{
m3dLoadIdentity44f(m);
return;
}
/* rotation matrix is normalized */
x /= mag;
y /= mag;
z /= mag;
#define M(row,col) m[col*4+row]
xx = x * x;
yy = y * y;
zz = z * z;
xy = x * y;
yz = y * z;
zx = z * x;
xs = x * s;
ys = y * s;
zs = z * s;
one_c = 1.0f - c;
M(0,0) = (one_c * xx) + c;
M(0,1) = (one_c * xy) - zs;
M(0,2) = (one_c * zx) + ys;
M(0,3) = 0.0f;
M(1,0) = (one_c * xy) + zs;
M(1,1) = (one_c * yy) + c;
M(1,2) = (one_c * yz) - xs;
M(1,3) = 0.0f;
M(2,0) = (one_c * zx) - ys;
M(2,1) = (one_c * yz) + xs;
M(2,2) = (one_c * zz) + c;
M(2,3) = 0.0f;
M(3,0) = 0.0f;
M(3,1) = 0.0f;
M(3,2) = 0.0f;
M(3,3) = 1.0f;
#undef M
}
/* create a projection to "squish" an object into the plane.
* use m3dGetPlaneEquationf(planeEq, point1, point2, point3); to get a plane equation
*/
void m3dMakePlanarShadowMatrixf(M3DMatrix44f proj, const M3DVector4f planeEq,
const M3DVector3f vLightPos)
{
/* these just make the code below easier to read */
float a = planeEq[0];
float b = planeEq[1];
float c = planeEq[2];
float d = planeEq[3];
float dx = -vLightPos[0];
float dy = -vLightPos[1];
float dz = -vLightPos[2];
/* now build the projection matrix */
proj[0] = b * dy + c * dz;
proj[1] = -a * dy;
proj[2] = -a * dz;
proj[3] = 0.0;
proj[4] = -b * dx;
proj[5] = a * dx + c * dz;
proj[6] = -b * dz;
proj[7] = 0.0;
proj[8] = -c * dx;
proj[9] = -c * dy;
proj[10] = a * dx + b * dy;
proj[11] = 0.0;
proj[12] = -d * dx;
proj[13] = -d * dy;
proj[14] = -d * dz;
proj[15] = a * dx + b * dy + c * dz;
/* shadow matrix ready */
}
/* hmm not sure if defines could reside outside of a function as they did */
void m3dMatrixMultiply44f(M3DMatrix44f product, const M3DMatrix44f a,
const M3DMatrix44f b)
{
#define A(row,col) a[(col<<2)+row]
#define B(row,col) b[(col<<2)+row]
#define P(row,col) product[(col<<2)+row]
int i;
for (i = 0; i < 4; i++)
{
float ai0 = A(i, 0), ai1 = A(i, 1), ai2 = A(i, 2), ai3 = A(i, 3);
P(i, 0) = ai0 * B(0, 0) + ai1 * B(1, 0) + ai2 * B(2, 0) + ai3 * B(3, 0);
P(i, 1) = ai0 * B(0, 1) + ai1 * B(1, 1) + ai2 * B(2, 1) + ai3 * B(3, 1);
P(i, 2) = ai0 * B(0, 2) + ai1 * B(1, 2) + ai2 * B(2, 2) + ai3 * B(3, 2);
P(i, 3) = ai0 * B(0, 3) + ai1 * B(1, 3) + ai2 * B(2, 3) + ai3 * B(3, 3);
}
#undef A
#undef B
#undef P
}
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