LuxCore + Sun = no shadow ?

[spoan]

Hi all,

i have an object, matte, simple square (note that the same issue happens to me with the real purpose of my tests, which is with a glass object, to see the caustic shadows).
when i use a spot light, i get shadows (though the scene is dark).
when I use a sun, no shadows at all... (and scene super bright).
i'm to the point that i would love even if anyone can share the most simple scene with a horizontal plane and a square above it, and the sun light above facing down, where i can get the caustic shadow...
i've been struggling for some days now, tried different YT videos and asked around, can't find any answer.
here some screenshots and my blender file, can anyone support to let me know what did i do wrong ?

so in summary, in the file
luxcore+(cube or CAT_Poisson)+sun = no shadow
luxcore+CAT_Poisson+spot = shadow (of a cat image)

what i want is to have a shadow whenever i use the sun (for the cube, a "normal" shadow, and the CAT_Poisson, a caustic shadow of a cat image that should be perfectly clear and sharp).

i only get this issue with LuxCoreRender as the render engine

thank you in advance

[CodeHD]

Hi,

in your file, your Sun light is set to the "Distant" type with a half-angle of 41.35 degrees. So you have an extremely wide, diffuse light source, which just blurs the shadow.

Create a new Sun light with its default settings, and your cat appears

[spoan]

thanks for your answer @CodeHD

side note, actually i saw this post of yours (viewtopic.php?t=943) and this is what motivated me to post my question here

so i removed the sun, added a new one, and with sun type = sun, i indeed see the cat now, thanks for that first step !
it is blurry, unsure how to fix that, i tried moving it closer to the plane, same result, and further away makes it more distorted

but with sun type = distant, it still doesnt work. is it normal behavior ? can i fix it somehow ? could it be that by making it work with type = distant, the caustic will be sharper ?

EDIT : oh ! with distant and size = 0, now the image is perfect and clear !
thank you

[CodeHD]

Uh, old topic, I don't remember that one in particular I should say

About your scene:
1) Moving the sun lamp closer or further away (assuming that is what you mean) doesn't change anything. The Sun/Distant lamp are assumed to be at infinity. Only the orientation angle matters, not the position in the 3D viewport!
2) Note that the default size of the Distant light is 10 degrees (half-angle)! This is much larger than the sun, which is about 1/4 of a degree. Note also that the two types have different units (Sun is relative to this value) and Distant is absolute degrees. Also according to that old topic you can't make the Sun relative size smaller than 1, so try Distant with size = 0.05 or something like that.
3) You might want to use the Laser light instead (it is an option to the Area light). Then you have size=0. There may be other implications depending on the scene, not sure how aware you are of this light or such details. (Also, the laser is position dependent, unlike the Sun!)

[spoan]

thanks for the help and details, it was quite easy fix thanks to you. I put distant size to 0 and it worked instantly. all clear now

the laser light i will give it a try, could be useful probably for something even more sharp, but i want to really simulate the sun to see if that would work well.

again, thank you ! so relieved to finally have it fixed