// We can define our own vec3 struct
struct vec3{x,y,z;}
static modelMatrix[9];
() {
   cls(0x828282); // clear screen
   clz(1e32); // clear depth buffer
   setcam(0,0,-3,0,0); // set camera some units back

   // create two local arrays to hold rotation matrices
   double roty[9], rotz[9];

   static otim;
   tim=klock(0); dt=tim-otim; otim=tim;
   static degrees = 0;
   degrees+=200*dt;
   rads = degrees/180*pi;
   rotateZ( rotz, rads );
   rotateY( roty, rads );

   // evaldraw does support some GL-like drawing
   // modes, but any transformations must be done by hand
   // Here we use a global model matrix that
   // transforms vertices created by the myVertex function
   mult(modelMatrix, roty, rotz);
   glSetTex("cloud.png");
   drawcuboid(0,0,0,1,1,1);
}

drawcuboid(x,y,z,sx,sy,sz) {
   glBegin(GL_QUADS);
   setcol(192,32,32);
   glTexCoord(0,0); myVertex(x-sx,y-sy,z-sz);
   glTexCoord(1,0); myVertex(x+sx,y-sy,z-sz);
   glTexCoord(1,1); myVertex(x+sx,y+sy,z-sz);
   glTexCoord(0,1); myVertex(x-sx,y+sy,z-sz);

   setcol(32,192,32);
   glTexCoord(0,0); myVertex(x-sx,y-sy,z+sz);
   glTexCoord(1,0); myVertex(x-sx,y-sy,z-sz);
   glTexCoord(1,1); myVertex(x-sx,y+sy,z-sz);
   glTexCoord(0,1); myVertex(x-sx,y+sy,z+sz);

   setcol(32,32,192);
   glTexCoord(0,0); myVertex(x+sx,y-sy,z+sz);
   glTexCoord(1,0); myVertex(x-sx,y-sy,z+sz);
   glTexCoord(1,1); myVertex(x-sx,y+sy,z+sz);
   glTexCoord(0,1); myVertex(x+sx,y+sy,z+sz);

   setcol(192,192,32);
   glTexCoord(0,0); myVertex(x+sx,y-sy,z-sz);
   glTexCoord(1,0); myVertex(x+sx,y-sy,z+sz);
   glTexCoord(1,1); myVertex(x+sx,y+sy,z+sz);
   glTexCoord(0,1); myVertex(x+sx,y+sy,z-sz);

   setcol(192,32,192);
   glTexCoord(0,0); myVertex(x-sx,y-sy,z+sz);
   glTexCoord(1,0); myVertex(x+sx,y-sy,z+sz);
   glTexCoord(1,1); myVertex(x+sx,y-sy,z-sz);
   glTexCoord(0,1); myVertex(x-sx,y-sy,z-sz);

   setcol(32,192,192);
   glTexCoord(0,0); myVertex(x-sx,y+sy,z-sz);
   glTexCoord(1,0); myVertex(x+sx,y+sy,z-sz);
   glTexCoord(1,1); myVertex(x+sx,y+sy,z+sz);
   glTexCoord(0,1); myVertex(x-sx,y+sy,z+sz);
   glEnd();
}
myVertex(x,y,z) {
  // Initialize a struct value
  vec3 v = {x,y,z};

  // Apply global model matrix transformation
  transformPoint(v, modelMatrix);

  // Submit the vertex to draw list
  glVertex(v.x, v.y, v.z);
}
rotateY(m[9], r) {
   c = cos(r); s=sin(r);
   m[0] = c; m[1] = 0; m[2] = s;
   m[3] = 0; m[4] = 1;  m[5] = 0;
   m[6] = -s; m[7] = 0;  m[8] = c;
}

rotateZ(m[9], r) {
   c = cos(r); s=sin(r);
   m[0] = c; m[1] = -s; m[2] = 0;
   m[3] = s; m[4] = c;  m[5] = 0;
   m[6] = 0; m[7] = 0;  m[8] = 1;
}
transformPoint(vec3 v, m[9]) {
   x2 = v.x * m[0] + v.y * m[1] + v.z * m[2];
   y2 = v.x * m[3] + v.y * m[4] + v.z * m[5];
   z2 = v.x * m[6] + v.y * m[7] + v.z * m[8];
   // Mutate the struct v with new values
   v.x=x2; v.y=y2; v.z=z2;
}
mult(c[9],a[9],b[9]) { // C = AB
   // multiply a row in A with a column in B
   for(i=0; i<3; i++)
      for(j=0; j<3; j++) {
         sum = 0.0;
         for(k=0; k<3; k++) {
            sum += A[k*3+i] * B[k*3+j];
         }
         C[i*3+j] = sum;
      }
}