(Solved) Monte Carlo and DOF-Noise

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Offline Voulxe

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« on: April 26, 2020, 08:35:25 PM »
Hi,
me and yet another problem ;)

Probably there is an obvious setting that I am missing. When rendering a scene with vivid highlights from Orbit trap lights, the noise of the highlights cannot be smoothed by the Monte Carlo algorithm.
See attached image and the included scene.
Is there any approach to significantly reduce the noise except for postprocessing with the z-buffer?

Regards,
Voulxe

Code: [Select]
# Mandelbulber settings file
# version 2.21
# only modified parameters
[description]
Source: [youtube]SGXrnOZVk9M[/youtube]
TheBatjorge
https://fractal.batjorge.com/2019/11/07/how-to-do-organic-shapes-with-mandelbulber/
[main_parameters]
advanced_quality true;
ambient_occlusion_mode 1;
basic_fog_color 0000 0000 0000;
basic_fog_visibility 8,309109687805176;
camera -1,557104010228179 -7,27804983238102 1,221543854629269;
camera_distance_to_target 9,36238217353819;
camera_rotation 10,96180501736737 -9,362099503656667 4;
camera_top 0,03762598424409246 0,1725806883281127 0,9842764811402628;
DE_factor 0,5;
detail_level 0,5555555555555555;
DOF_enabled true;
DOF_focus 3,599015474319458;
DOF_max_noise 0,5;
DOF_min_samples 160;
DOF_monte_carlo true;
DOF_samples 800;
fake_lights_color c800 b100 9b00;
fake_lights_enabled true;
fake_lights_max_iter 8;
fake_lights_min_iter 2;
fake_lights_orbit_trap_shape circle;
fake_lights_thickness 2;
fake_lights_visibility 4;
fake_lights_visibility_size 3;
file_lightmap /home/volker/mandelbulber/textures/Equi_01.png;
flight_last_to_render 0;
fog_color_1 0000 0000 0000;
fog_color_2 b500 9c00 7f00;
fog_color_3 0000 0000 0000;
formula_1 73;
fov 20;
fractal_constant_factor 1,1 1 1,2;
glow_enabled false;
image_height 1080;
image_proportion 4;
image_width 1920;
julia_c 0,1984636319380371 -0,4236666666666666 -0,06426805482853225;
julia_mode true;
keyframe_last_to_render 0;
main_light_alpha -60,87;
main_light_beta 55,36;
main_light_colour e700 df00 de00;
mat1_file_color_texture /home/volker/mandelbulber/textures/envmap4.JPG;
mat1_fractal_coloring_algorithm 4;
mat1_fractal_coloring_extra_color_enabled_false true;
mat1_fractal_coloring_initial_color_value 0,9;
mat1_fractal_coloring_line_direction 8 -0,3981797935354395 0 0;
mat1_fractal_coloring_sphere_radius 0,5;
mat1_is_defined true;
mat1_metallic false;
mat1_rough_surface true;
mat1_shading 2;
mat1_specular 1,25;
mat1_specular_width 1,6;
mat1_surface_color ff00 ff00 ff00;
mat1_surface_color_gradient 0 fdfdfd 2184 555948 3613 ffffff 4884 1a769d 6953 ffffff 8424 3aaac3;
mat1_surface_roughness 0,16;
mat1_texture_center 0,8 0,5 0;
mat1_texture_fractalize true;
mat1_texture_fractalize_start_iteration 19;
mat1_texture_mapping_type 1;
mat1_use_color_texture true;
mat1_use_colors_from_palette false;
MC_soft_shadows_enable true;
raytraced_reflections true;
shadows_cone_angle 8;
target -3,313690169937846 1,791076155786678 -0,3014659410199156;
view_distance_max 143,8741610430438;
volumetric_fog_colour_1_distance 0,04024839333528404;
volumetric_fog_colour_2_distance 0,1609935733411362;
volumetric_fog_distance_factor 0,1609935733411362;
volumetric_fog_distance_from_surface 0,5;
volumetric_fog_enabled true;
[fractal_1]
mandelbox_scale 1,19;
transf_addition_constant_111 0,8 1,1 1;
transf_minimum_radius_05 0,025;
transf_rotation 1 9 -18;



Linkback: https://fractalforums.org/mandelbulber/14/monte-carlo-and-dof-noise/3447/
« Last Edit: April 26, 2020, 09:07:15 PM by Voulxe »

Offline buddhi

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    • Mandelbulber GitHub repository
« Reply #1 on: April 26, 2020, 09:01:38 PM »
This problem is caused by extremely bright and very small light sources. When very small and blight spot is in the area which is heavily blurred, then there is quite low probability that this light will be catch by random sample. But when will be it it will appear as bright single pixel (of brightness many times higher than maximum brightness visible on the screen). It causes heavy noise.
 This problem is difficult to avoid. Only solutions are:
- to increase minimum (50 is mostly enough) and maximum number of MC samples (in some cases it would be needed to calculate up to 1-5k of samples.
- to avoid using extremely bright spots with MC DOF
- to use post processing to eliminate noise.

Offline Voulxe

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« Reply #2 on: April 26, 2020, 09:06:55 PM »
Thanks for the quick reply.

Once I feel like doing postprocessing, I will take that approach then  ;) Just a sceond render without the Orbit trap lights and blending those two images should do the magic.

Have fun,
Voulxe


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