C语言圣诞树的实现示例

#define PI 3.14159265359f

float sx, sy;

typedef float Mat[4][4];typedef float Vec[4];

void scale(Mat* m, float s) {Mat temp = { {s,0,0,0}, {0,s,0,0 }, { 0,0,s,0 }, { 0,0,0,1 } };memcpy(m, &temp, sizeof(Mat));}

void rotateY(Mat* m, float t) {float c = cosf(t), s = sinf(t);Mat temp = { {c,0,s,0}, {0,1,0,0}, {-s,0,c,0}, {0,0,0,1} };memcpy(m, &temp, sizeof(Mat));}

void rotateZ(Mat* m, float t) {float c = cosf(t), s = sinf(t);Mat temp = { {c,-s,0,0}, {s,c,0,0}, {0,0,1,0}, {0,0,0,1} };memcpy(m, &temp, sizeof(Mat));}

void translate(Mat* m, float x, float y, float z) {Mat temp = { {1,0,0,x}, {0,1,0,y}, {0,0,1,z}, {0,0,0,1} };memcpy(m, &temp, sizeof(Mat));}

void mul(Mat* m, Mat a, Mat b) {Mat temp;for (int j = 0; j < 4; j++) for (int i = 0; i < 4; i++) {temp[j][i] = 0.0f;for (int k = 0; k < 4; k++) temp[j][i] += a[j][k] * b[k][i];}memcpy(m, &temp, sizeof(Mat));}

void transformPosition(Vec* r, Mat m, Vec v) {Vec temp = { 0, 0, 0, 0 };for (int j = 0; j < 4; j++) for (int i = 0; i < 4; i++) temp[j] += m[j][i] * v[i];memcpy(r, &temp, sizeof(Vec));}

float transformLength(Mat m, float r) {return sqrtf(m[0][0] * m[0][0] + m[0][1] * m[0][1] + m[0][2] * m[0][2]) * r;}

float sphere(Vec c, float r) {float dx = c[0] - sx, dy = c[1] - sy;float a = dx * dx + dy * dy;return a < r* r ? sqrtf(r * r - a) + c[2] : -1.0f;}

float opUnion(float z1, float z2) {return z1 > z2 ? z1 : z2;}

float f(Mat m, int n) {float z = -1.0f;for (float r = 0.0f; r < 0.8f; r += 0.02f) {Vec v = { 0.0f, r, 0.0f, 1.0f };transformPosition(&v, m, v);z = opUnion(z, sphere(v, transformLength(m, 0.05f * (0.95f - r))));}

if (n > 0) {Mat ry, rz, s, t, m2, m3;rotateZ(&rz, 1.8f);

for (int p = 0; p < 6; p++) {rotateY(&ry, p * (2 * PI / 6));mul(&m2, ry, rz);float ss = 0.45f;for (float r = 0.2f; r < 0.8f; r += 0.1f) {scale(&s, ss);translate(&t, 0.0f, r, 0.0f);mul(&m3, s, m2);mul(&m3, t, m3);mul(&m3, m, m3);z = opUnion(z, f(m3, n - 1));ss *= 0.8f;}}}

return z;}

float f0(float x, float y, int n) {sx = x;sy = y;Mat m;scale(&m, 1.0f);return f(m, n);}

int main(int argc, char* argv[]) {//这个里可以加打印信息哟，为他添加专属的printf