delatin/delatin.min.js

JavaScript terrain mesh generation tool

export default class Delatin{constructor(e,t,s=t){this.data=e,this.width=t,this.height=s,this.coords=[],this.triangles=[],this._halfedges=[],this._candidates=[],this._queueIndices=[],this._queue=[],this._errors=[],this._pending=[],this._pendingLen=0,this._rmsdSum=0,this._init()}run(e=1){for(;this.getMaxError()>e;)this.refine()}refine(){this._step(),this._flush()}getMaxError(){return this._errors[0]}getRMSD(){return Math.sqrt(this._rmsdSum/this._errors.length)}heightAt(e,t){return this.data[this.width*t+e]}_init(){const e=this.width-1,t=this.height-1,s=this._addPoint(0,0),i=this._addPoint(e,0),h=this._addPoint(0,t),n=this._addPoint(e,t),r=this._addTriangle(n,s,h,-1,-1,-1);this._addTriangle(s,n,i,r,-1,-1),this._flush()}_flush(){const e=this.coords;for(let t=0;t<this._pendingLen;t++){const s=this._pending[t],i=2*this.triangles[3*s+0],h=2*this.triangles[3*s+1],n=2*this.triangles[3*s+2];this._findCandidate(e[i],e[i+1],e[h],e[h+1],e[n],e[n+1],s)}this._pendingLen=0}_findCandidate(e,t,s,i,h,n,r){const a=Math.min(e,s,h),_=Math.min(t,i,n),d=Math.max(e,s,h),o=Math.max(t,i,n);let l=orient(s,i,h,n,a,_),u=orient(h,n,e,t,a,_),g=orient(e,t,s,i,a,_);const c=i-t,f=e-s,q=n-i,p=s-h,m=t-n,w=h-e,M=orient(e,t,s,i,h,n),T=this.heightAt(e,t)/M,P=this.heightAt(s,i)/M,z=this.heightAt(h,n)/M;let S=0,x=0,L=0;for(let e=_;e<=o;e++){let t=0;l<0&&0!==q&&(t=Math.max(t,Math.floor(-l/q))),u<0&&0!==m&&(t=Math.max(t,Math.floor(-u/m))),g<0&&0!==c&&(t=Math.max(t,Math.floor(-g/c)));let s=l+q*t,i=u+m*t,h=g+c*t,n=!1;for(let r=a+t;r<=d;r++){if(s>=0&&i>=0&&h>=0){n=!0;const t=T*s+P*i+z*h,a=Math.abs(t-this.heightAt(r,e));a>S&&(S=a,x=r,L=e)}else if(n)break;s+=q,i+=m,h+=c}l+=p,u+=w,g+=f}(x===e&&L===t||x===s&&L===i||x===h&&L===n)&&(S=0),this._candidates[2*r]=x,this._candidates[2*r+1]=L,this._queuePush(r,S)}_step(){const e=this._queuePop(),t=3*e+0,s=3*e+1,i=3*e+2,h=this.triangles[t],n=this.triangles[s],r=this.triangles[i],a=this.coords[2*h],_=this.coords[2*h+1],d=this.coords[2*n],o=this.coords[2*n+1],l=this.coords[2*r],u=this.coords[2*r+1],g=this._candidates[2*e],c=this._candidates[2*e+1],f=this._addPoint(g,c);if(0===orient(a,_,d,o,g,c))this._handleCollinear(f,t);else if(0===orient(d,o,l,u,g,c))this._handleCollinear(f,s);else if(0===orient(l,u,a,_,g,c))this._handleCollinear(f,i);else{const e=this._halfedges[t],a=this._halfedges[s],_=this._halfedges[i],d=this._addTriangle(h,n,f,e,-1,-1,t),o=this._addTriangle(n,r,f,a,-1,d+1),l=this._addTriangle(r,h,f,_,d+2,o+1);this._legalize(d),this._legalize(o),this._legalize(l)}}_addPoint(e,t){const s=this.coords.length>>1;return this.coords.push(e,t),s}_addTriangle(e,t,s,i,h,n,r=this.triangles.length){const a=r/3;return this.triangles[r+0]=e,this.triangles[r+1]=t,this.triangles[r+2]=s,this._halfedges[r+0]=i,this._halfedges[r+1]=h,this._halfedges[r+2]=n,i>=0&&(this._halfedges[i]=r+0),h>=0&&(this._halfedges[h]=r+1),n>=0&&(this._halfedges[n]=r+2),this._candidates[2*a+0]=0,this._candidates[2*a+1]=0,this._queueIndices[a]=-1,this._pending[this._pendingLen++]=a,r}_legalize(e){const t=this._halfedges[e];if(t<0)return;const s=e-e%3,i=t-t%3,h=s+(e+1)%3,n=s+(e+2)%3,r=i+(t+2)%3,a=i+(t+1)%3,_=this.triangles[n],d=this.triangles[e],o=this.triangles[h],l=this.triangles[r],u=this.coords;if(!inCircle(u[2*_],u[2*_+1],u[2*d],u[2*d+1],u[2*o],u[2*o+1],u[2*l],u[2*l+1]))return;const g=this._halfedges[h],c=this._halfedges[n],f=this._halfedges[r],q=this._halfedges[a];this._queueRemove(s/3),this._queueRemove(i/3);const p=this._addTriangle(_,l,o,-1,f,g,s),m=this._addTriangle(l,_,d,p,c,q,i);this._legalize(p+1),this._legalize(m+2)}_handleCollinear(e,t){const s=t-t%3,i=s+(t+1)%3,h=s+(t+2)%3,n=this.triangles[h],r=this.triangles[t],a=this.triangles[i],_=this._halfedges[i],d=this._halfedges[h],o=this._halfedges[t];if(o<0){const t=this._addTriangle(e,n,r,-1,d,-1,s),i=this._addTriangle(n,e,a,t,-1,_);return this._legalize(t+1),void this._legalize(i+2)}const l=o-o%3,u=l+(o+2)%3,g=l+(o+1)%3,c=this.triangles[u],f=this._halfedges[u],q=this._halfedges[g];this._queueRemove(l/3);const p=this._addTriangle(n,r,e,d,-1,-1,s),m=this._addTriangle(r,c,e,q,-1,p+1,l),w=this._addTriangle(c,a,e,f,-1,m+1),M=this._addTriangle(a,n,e,_,p+2,w+1);this._legalize(p),this._legalize(m),this._legalize(w),this._legalize(M)}_queuePush(e,t){const s=this._queue.length;this._queueIndices[e]=s,this._queue.push(e),this._errors.push(t),this._rmsdSum+=t*t,this._queueUp(s)}_queuePop(){const e=this._queue.length-1;return this._queueSwap(0,e),this._queueDown(0,e),this._queuePopBack()}_queuePopBack(){const e=this._queue.pop(),t=this._errors.pop();return this._rmsdSum-=t*t,this._queueIndices[e]=-1,e}_queueRemove(e){const t=this._queueIndices[e];if(t<0){const t=this._pending.indexOf(e);if(-1===t)throw new Error("Broken triangulation (something went wrong).");return void(this._pending[t]=this._pending[--this._pendingLen])}const s=this._queue.length-1;s!==t&&(this._queueSwap(t,s),this._queueDown(t,s)||this._queueUp(t)),this._queuePopBack()}_queueLess(e,t){return this._errors[e]>this._errors[t]}_queueSwap(e,t){const s=this._queue[e],i=this._queue[t];this._queue[e]=i,this._queue[t]=s,this._queueIndices[s]=t,this._queueIndices[i]=e;const h=this._errors[e];this._errors[e]=this._errors[t],this._errors[t]=h}_queueUp(e){let t=e;for(;;){const e=t-1>>1;if(e===t||!this._queueLess(t,e))break;this._queueSwap(e,t),t=e}}_queueDown(e,t){let s=e;for(;;){const e=2*s+1;if(e>=t||e<0)break;const i=e+1;let h=e;if(i<t&&this._queueLess(i,e)&&(h=i),!this._queueLess(h,s))break;this._queueSwap(s,h),s=h}return s>e}}function orient(e,t,s,i,h,n){return(s-h)*(t-n)-(i-n)*(e-h)}function inCircle(e,t,s,i,h,n,r,a){const _=e-r,d=t-a,o=s-r,l=i-a,u=h-r,g=n-a,c=o*o+l*l,f=u*u+g*g;return _*(l*f-c*g)-d*(o*f-c*u)+(_*_+d*d)*(o*g-l*u)<0}