求大佬告知哪里错了？

Question

#include<stdio.h>

#include<math.h>

 

 float f(float x,float y,float z)

 {

     float a=x*x+9.0f/4.0f*y*y+z*z-1;

     return a*a*a-x*x*z*z*z-9.0f/80.0f*y*y*z*z*z;

 }

float h(float x,float z){

   for(float y=1.0f;y>=0.0f;y-=0.001f)

     if(f(x,y,z)<=0.0f)

  return y;

   return 0.0f;

}

int main(){

   for(float z=1.5f;z>-1.5f;z-=0.05f){

     for(float x=-1.5f;x<1.5f;x+=0.025f){

  float v=f(x,0.0f,z);

  if(v<=0.0f){

    float y0=h(x,z);

float ny=0.01f;

float nx=h(x+ny,z)-y0;

float nz=h(x,z+ny)-y0;

float nd=1.0f/sqrtf(nx*nx+ny*ny+nz*nz);

float d=(nx+ny-nz)*nd*0.5f+0.5f;

putchar(".:-=+*#%@"[(int)(d*5.0f)]);

  }

  else

    putchar('');

}

putchar('\n');

   }

}