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The Black Diamond

Posted: Tue Oct 02, 2018 6:06 pm
by SurfingNerd
Hello,
i just started with blender and LuxRenderer,
and i am stuck with a rendering:
Rendering.png
(The diamond is laying on a plane)
i am trying to create a rendering of a diamond,
thanks to some tutorials i came already pretty far.
i am very satisfied with the dispersion and refraction of the lightrays on the ground,
but the diamond itself appears very dark.
any idea ?
there are 2 spotlights shining on the diamond.

blender version 2.79b
LuxCoreRenderer 2.0
Ubuntu 18.04
Diamond_material.png
LuxCoreSettings.png

Re: The Black Diamond

Posted: Tue Oct 02, 2018 6:09 pm
by Dade
SurfingNerd wrote:
Tue Oct 02, 2018 6:06 pm
but the diamond itself appears very dark.
any idea ?
This is likely to happen because of the black background (reflected by the diamond). Try to use an HDR background or just a white one.

Re: The Black Diamond

Posted: Tue Oct 02, 2018 7:54 pm
by SurfingNerd
thx for the answer.
here the scene in a brighter light:
rendering_white_color.png
settings_world.png
settings_world.png (11 KiB) Viewed 695 times
the diamond is indeed reflecting the world box colors.
but it shouldn't it reflect/refract the light from above as well ?
shouldn't the concentrated light on the ground be reflected back into the crystal as well ?

Re: The Black Diamond

Posted: Tue Oct 02, 2018 10:01 pm
by Dade
It looks like you have to increase the "gain" a lot (may be to 10.0, try to do some test).

What main light source type are you using ? A point light ? Try also to replace the point light with 1-3 quads emitting light. You probably want to simulate a studio-like light setup.

Re: The Black Diamond

Posted: Thu Oct 04, 2018 9:03 am
by SurfingNerd
Thank you for your help! :)
I had used spotlights from above in the scene.

I have done further experiments and now i have a deeper understanding of the issue:
Light direct from a lightsource get ignored by the camera.
I have set up a scene here with some point lights and replaced the ground with a mirror.
Maybe there is a trick or a setting to stop this ignorance ?
scene_lots_of_lots.png
Here the layout of the Spot lights and the new Point Lights
rendering_lots_of_lights.png
Even the scene is full of lights with direct camera hits, most of the scene stays dark
rendering_lots_of_lights_with_matte_ground.png
What you can observe if you replace the Mirror ground with a matte ground.

Re: The Black Diamond

Posted: Thu Oct 04, 2018 9:48 am
by Dade
SurfingNerd wrote:
Thu Oct 04, 2018 9:03 am
I have done further experiments and now i have a deeper understanding of the issue:
Light direct from a lightsource get ignored by the camera.
I have set up a scene here with some point lights and replaced the ground with a mirror.
Point lights have no extension so they are not visible if you look at them (or trough a mirror). It is the reason why I was suggesting to use a quad area lights so they are visible.