Trac #30613: Fix clipping issue for plots with small/large extents in Three.js

Plots that are very small/large in world-space coordinates can run into
clipping issues with the default near and far clipping distances set in
the Three.js viewer.

For example, the large "cool self-intersecting surface (Eppener
surface?)" near the bottom of the documentation for [https://doc.sagemat
h.org/html/en/reference/plot3d/sage/plot/plot3d/parametric_plot3d.html
Parametric Plots] appears completely blank due to far clipping:
{{{
#!python
sage: var('u,v')
sage: f_x = u - u^3/3 + u*v^2
sage: f_y = v - v^3/3 + v*u^2
sage: f_z = u^2 - v^2
sage: parametric_plot3d([f_x, f_y, f_z], (u,-25,25), (v,-25,25),
plot_points=[50,50], frame=False, color="green")
Graphics3d Object
}}}

...and the following small plot appears empty due to near clipping:
{{{
#!python
dodecahedron().scale(1/1000)
}}}

This ticket proposes to fix this problem by scaling both the near and
far clipping distances based on the overall size of the plot in world-
space coordinates.

URL: https://trac.sagemath.org/30613
Reported by: gh-jcamp0x2a
Ticket author(s): Joshua Campbell
Reviewer(s): Eric Gourgoulhon

Author: Release Manager

src/sage/ext_data/threejs/threejs_template.html

@@ -211,13 +211,17 @@
 
         var aspect = window.innerWidth / window.innerHeight;
 
+        // Scale the near and far clipping planes along with the overall plot size.
+        var nearClip = 0.01 * midToCorner;
+        var farClip = 100 * midToCorner;
+
         if ( options.projection === 'orthographic' ) {
-            var camera = new THREE.OrthographicCamera( -1, 1, 1, -1, -1000, 1000 );
+            var camera = new THREE.OrthographicCamera( -1, 1, 1, -1, -farClip, farClip );
             updateCameraAspect( camera, aspect );
             return camera;
         }
 
-        return new THREE.PerspectiveCamera( 45, aspect, 0.1, 1000 );
+        return new THREE.PerspectiveCamera( 45, aspect, nearClip, farClip );
 
     }