int outSize = 201; field#1(2)[] F = ctmr ⊛ load("../../data/ddro-115.nrrd"); strand sample (int ui, int vi) { real uu = lerp(0.0, 1.0, -0.5, real(ui), real(outSize)-0.5); real vv = lerp(0.0, 1.0, -0.5, real(vi), real(outSize)-0.5); vec2 pos = [uu, vv]; output vec3 out = [nan,nan,nan]; update { vec2 grad = ∇F(pos) if (inside(pos,F)) else [2000.0,0.0]; out = [grad[0], grad[1], |grad|]; stabilize; } } initially [ sample(ui, vi) | vi in 0..(outSize-1), ui in 0..(outSize-1) ];