diff --git a/src/render.c b/src/render.c
index de0d798..663798d 100644
--- a/src/render.c
+++ b/src/render.c
@@ -26,7 +26,7 @@ double integrand_r(double *xy, size_t dim, void *integrand_params_void) {
   double rgb[3] = {0};
   double theta_phi[2] = {theta, phi};
   integrand_params->system->angle_to_pixel(theta_phi, rgb);
-  return rgb[0]*gsl_spline_eval_deriv(integrand_params->spline_data->spline, cotpsi, integrand_params->spline_data->acc);
+  return rgb[0]*fabs(gsl_spline_eval_deriv(integrand_params->spline_data->spline, cotpsi, integrand_params->spline_data->acc));
 }
 
 double integrand_g(double *xy, size_t dim, void *integrand_params_void) {
@@ -38,7 +38,7 @@ double integrand_g(double *xy, size_t dim, void *integrand_params_void) {
   double rgb[3] = {0};
   double theta_phi[2] = {theta, phi};
   integrand_params->system->angle_to_pixel(theta_phi, rgb);
-  return rgb[1]*gsl_spline_eval_deriv(integrand_params->spline_data->spline, cotpsi, integrand_params->spline_data->acc);
+  return rgb[1]*fabs(gsl_spline_eval_deriv(integrand_params->spline_data->spline, cotpsi, integrand_params->spline_data->acc));
 }
 
 double integrand_b(double *xy, size_t dim, void *integrand_params_void) {
@@ -50,7 +50,7 @@ double integrand_b(double *xy, size_t dim, void *integrand_params_void) {
   double rgb[3] = {0};
   double theta_phi[2] = {theta, phi};
   integrand_params->system->angle_to_pixel(theta_phi, rgb);
-  return rgb[2]*gsl_spline_eval_deriv(integrand_params->spline_data->spline, cotpsi, integrand_params->spline_data->acc);
+  return rgb[2]*fabs(gsl_spline_eval_deriv(integrand_params->spline_data->spline, cotpsi, integrand_params->spline_data->acc));
 }
 
 int MC_pixel_render(const System *system, int i, int j, const Spline_data spline_data, double *rgb, int pixel_render_max, double pixel_render_err, gsl_rng *r){