How it worksDrop a triangle on the screen and every pixel inside it gets three numbers — how much it belongs to each corner — that always add up to one. At a corner that corner's weight is one and the others zero; along the opposite edge it falls to zero. Show them as red/green/blue and you read each weight directly. Hand the triangle a value per corner and those same weights blend it smoothly across the face — that is all 'interpolation' is. The contour view draws lines of equal weight: evenly spaced and parallel to each edge, which is the visible proof the weights vary perfectly linearly.
