add RevolutionSurface to surfaces demo

peteroupc · peteroupc · commit 87eb85c07e31 · 2015-04-13T13:07:19.000-04:00
diff --git a/glutil-eval.js b/glutil-eval.js
@@ -648,8 +648,17 @@ SurfaceEval.prototype.evaluate=function(mesh,u,v){
    GLMath.vec3scaleInPlace(vv,1.0/dv);
    GLMath.vec3normInPlace(vu);
    GLMath.vec3normInPlace(vv);
-   vu=GLMath.vec3cross(vu,vv);
-   GLMath.vec3normInPlace(vu);
+   if(GLMath.vec3length(vu)==0){
+    // partial derivative of u is degenerate
+    //console.log([vu,vv]+" u degen")
+    vu=vv;
+   } else if(GLMath.vec3length(vv)!=0){
+    vu=GLMath.vec3cross(vu,vv);
+    GLMath.vec3normInPlace(vu);
+   } else {
+    // partial derivative of v is degenerate
+    //console.log([vu,vv]+" v degen")
+   }
    mesh.normal3(vu[0],vu[1],vu[2]);
   } else if(normal){
    mesh.normal3(normal[0],normal[1],normal[2]);
diff --git a/glutil_min.js b/glutil_min.js
diff --git a/surfaces.html b/surfaces.html
@@ -6,7 +6,9 @@
 <body>
 <a href="javascript:link1()">Ellipsoid</a>,
 <a href="javascript:link2()">Klein bottle</a>,
-<a href="javascript:link3()">M&ouml;bius strip</a>
+<a href="javascript:link3()">M&ouml;bius strip</a>,
+<a href="javascript:link4()">Surface of revolution for f(x) = sin x</a>
+<a href="javascript:link5()">Surface of revolution for f(x) = x<sup>2</sup></a>
 <br>
 <canvas width="600" height="450" id=canvas></canvas>
 <script id="demo">
@@ -34,6 +36,22 @@
  }
 }
 
+var RevolutionSurface=function(func,minval,maxval){
+ this.func=func
+ this.minval=minval
+ this.maxval=maxval
+ this.evaluate=function(u,v,output){
+  v=1-v;
+  v*=Math.PI*2;
+  u=minval+(maxval-minval)*u;
+  var r=this.func(u);
+  output[0]=u;
+  output[1]=r*Math.cos(v);
+  output[2]=r*Math.sin(v);
+  return 3;
+ }
+}
+
 var KleinBottle=function(){
  this.evaluate=function(u,v,output){
   u*=Math.PI*2;
@@ -82,8 +100,6 @@
  }
 }
 
-
-
 var ColorGradient={
 evaluate:function(u,v,output){
  output[0]=1.0-u;
@@ -100,7 +116,6 @@
     .color(ColorGradient)
     .setAutoNormal(true)
     .evalSurface(mesh,Mesh.TRIANGLES,50,50);
-  console.log(mesh)
   return mesh;
 }
 
@@ -119,6 +134,26 @@
  scene.addShape(shape=scene.makeShape(makeMesh(new MoebiusStrip())));
 }
 
+function link4(){
+ scene.removeShape(shape);
+ scene.addShape(shape=scene.makeShape(makeMesh(new RevolutionSurface(function(x){
+  return Math.sin(x)
+ },-Math.PI,Math.PI))));
+}
+
+function link5(){
+ scene.removeShape(shape);
+ scene.addShape(shape=scene.makeShape(makeMesh(new RevolutionSurface(function(x){
+  return x*x
+ },-1,1))));
+}
+
+function link5(){
+ scene.removeShape(shape);
+ scene.addShape(shape=scene.makeShape(makeMesh(new RevolutionSurface(function(x){
+  return x*x
+ },-1,1))));
+}
 
   // Create the 3D scene; find the HTML canvas and pass it
   // to Scene3D.
