Quelques changements :

• Le sol plane.
• L'éclairage avec une area_light.
• Une texture toute simple pour l'isosurface.

Le code :

// --------------------------------------------------------------------------
// --- LIGHTING -------------------------------------------------------------
// --------------------------------------------------------------------------

// --- area_light size is power of 2 plus 1
// --- 2^2+1 = 5, 2^3+1 = 9, 2^4+1 = 17, 2^5+1=33, 2^6+1=65...
#macro makeAreaLight(AreaSize,AreaLevel)
	#local n=1+pow(2,AreaLevel);
	area_light -*0.50, +*0.50, n, n
	adaptive 1
	jitter 
	orient 
	circular 
#end


		
light_source {
	p2r(15, 60, 100, false)
	colour rgb 1
	#if (useAreaLights)
		makeAreaLight(100,3)
	#end
	}



// --------------------------------------------------------------------------
// --- ISOSURFACE -----------------------------------------------------------
// --------------------------------------------------------------------------
#declare transmitValue = 0.00;
#if (useTransmit)
	#declare transmitValue = 0.25;
#end

#declare myColorMap = color_map {
	[ 0.00 rgb < 1.00000, 0.50000, 1.00000> transmit transmitValue ]
	[ 0.10 rgb < 1.00000, 0.50000, 1.00000> transmit transmitValue ]
	[ 0.20 rgb < 0.50000, 0.50000, 1.00000> transmit transmitValue ]
	[ 0.30 rgb < 0.20000, 0.20000, 1.00000> transmit transmitValue ]
	[ 0.40 rgb < 0.20000, 1.00000, 1.00000> transmit transmitValue ]
	[ 0.50 rgb < 0.20000, 1.00000, 0.20000> transmit transmitValue ]
	[ 0.60 rgb < 1.00000, 1.00000, 0.20000> transmit transmitValue ]
	[ 0.70 rgb < 1.00000, 0.50000, 0.20000> transmit transmitValue ]
	[ 0.80 rgb < 1.00000, 0.20000, 0.20000> transmit transmitValue ]
	[ 0.90 rgb < 1.00000, 0.20000, 0.20000> transmit transmitValue ]
	[ 1.00 rgb < 1.00000, 0.50000, 1.00000> transmit transmitValue ]
	}


isosurface {
	function {
		f_helical_torus (x, y, z, 1, 9, 5, 0.25, 0.10, -0.15, 0, 1, 1,  0)
		}          
	contained_by {
		box { <-1.5,-1.0, -1.5>, <1.5, 1.0, 1.5> }
		}
	max_gradient 10
	texture {
		pigment {
			#if(useColorsMap)
				radial
				color_map { myColorMap }
			#else
				color Sienna
			#end
			}
		finish {
			emission 0.10
			diffuse 0.50
			specular 0.10
			roughness 0.10
			phong 0.20
			#if(!SimpleTexture)
				reflection 0.20
			#end
			}
		}
	#if(!SimpleTexture)
		interior {
			ior 1.50
			}
	#end
	rotate<0,0,0>
	scale 1
	translate< 0, dH, 0>
	}


// --------------------------------------------------------------------------
// --- PLANE ----------------------------------------------------------------
// --------------------------------------------------------------------------
plane {
	y, 0
	pigment {
		checker rgb 0.60, rgb 0.80
		rotate -45*y
		}
	normal {
		checker 0.50
		rotate -45*y
		}
	finish {
		emission 0.20
		diffuse 0.80
		reflection 0.30
		}
	}

La variable transmitValue et la table de couleurs myColorMap seront utilisées un peu plus loin.


Ce qui nous donne :