// A point p lies in the plotted set if evaluate(p) = 0. // You write the evaluate function! // This is GLSL v330. For basic usage, see https://en.wikibooks.org/wiki/GLSL_Programming/Vector_and_Matrix_Operations float evaluate(vec3 p){ float x = p.x; float y = p.y; float z = p.z; return 0.8 - length(p) -1.0 + abs(p.x) + abs(p.y) + abs(p.z); }

vec3 getColor(vec3 p, vec3 inDir){ // the width of a voxel float eps = 0.002; bool insideSurface = evaluate(p - eps * inDir) < 0.0; if(insideSurface){ // yellow return vec3(1.0, 0.9725, 0.4314); } else { // white return vec3(1.0, 1.0, 1.0); } }

lights all have radius 1/2.
*lights must be outside the sphere centered at the origin with radius 1/2 + sqrt(3)/2.