sub D and ray-trace (solved : but if you need to keep talking use free ^^)

kitakoredaz

Hi rencently I render "sphere only" ^^; again and again, many times to learn shader builder and mixer,,
then I get simple question,,

When I render primitive sphere without sub-D, with one distant light
if I use ray-trace shadow , there is problem about border area bettween diffuse and dark

then I think,, if it is my render setting problem (I tweaked without intention,,)
or I need to check other parameter setting?

I know if I apply sub-D then increase poligons, the problem seems gone,
but it only happen when I set light with ray-trace shadow (usually we need ray trace,, I beleive)

Richard Haseltine

If you view the scene in wireframe I think you will find that those are the corners of polygons. Ray-traced shadows, being more precise, may be picking the differently angled faces up - I don't know if adjusting the Shadow Bias setting might help.

kitakoredaz

Hi Richard Yes I know it seems corner poligon edges, because when I set smooth OFF,
I can clear see each poligon edges ,,

then I felt if I cange driver setting (I tweaked many for other purpose before,,) Anti Alias etc,,
but it is same for you too?
the sphere primitive segments 60 sides 40, I thought it is Enough ,with apply smooth.,,,

Then thank you,,,:-)
light shadow bias setting actually worked for me :-)

I usually set it as default,,1.0 or more lower avlues,,,,, but when I turn it 1.5,
the dark part pligon edge beome weak, then if I turn shadow bias to 2.5
it seems almost gone away ( somehow blur effect?), though I care if it cause other unexpected effect,,,

Richard Haseltine

I think the problem is that the smoothing algorithm (not SubD, the one that adjusts the shading on flat surfaces to make them look curved) can't affect cast shadows - so where the angle of the planes is very close to the angle of the light you do get some casting shadows and some not. The effect would probably be less noticeable in a real scene, with environment light and/or more than one light source, and with less regular geometry.

AndyS

Hi Richard,

I noticed that problem too. When I got close to the face of my characters, I see some shodow peaks, especially round the nosetip and the cheeks.
You supposed to increase the shadow bias of the light as a workaround.
But:
If you have your characters clothed, i.e. shorts or T-Shirt, you need a shadow bias less then 0.2 . Otherwise the light shines through the clothes and fully illuminates the skin of legs and arms, if you look to the corresponding parts of your character from a special perspective.

So simply increasing shadow bias is no option.
The only option is to solve that bug in iRay !!

There are way more bugs in iRay!
I'm currently fighting with the not correctly working refraction and the related total reflection of the iRay Water shader.

I tested the same situations with 3Delight. Here everything works fine.

Yours
Andy

kitakoredaz

Hi thank you clear guide ^^ so I need not care much now. (and now I learn to remove problem)

(yes usually I do not need render only sphere etc , but felt strange, when I found it
I felt , there is more blick to change shadow,, etc,, but it was same when I apply daz default shaders,
then asked,,,):roll:

===========
smftrsd72>

If you have your characters clothed, i.e. shorts or T-Shirt, you need a shadow bias less then 0.2 . Otherwise the light shines through the clothes and fully illuminates the skin of legs and arms, if you look to the corresponding parts of your character from a special perspective.

yes I care it too. usually I use more low value (when I find problem)
may be we need to choose value for each purpose,,, there seems no best value about shadow biass
or I may need to apply sub-D for primitive (if you need such render for some purpose , )

CypherFOX

Greetings,

smftrsd72 said:

Hi Richard,

I noticed that problem too. When I got close to the face of my characters, I see some shodow peaks, especially round the nosetip and the cheeks.
You supposed to increase the shadow bias of the light as a workaround.
But:
If you have your characters clothed, i.e. shorts or T-Shirt, you need a shadow bias less then 0.2 . Otherwise the light shines through the clothes and fully illuminates the skin of legs and arms, if you look to the corresponding parts of your character from a special perspective.

So simply increasing shadow bias is no option.
The only option is to solve that bug in iRay !!

There are way more bugs in iRay!
I'm currently fighting with the not correctly working refraction and the related total reflection of the iRay Water shader.

I tested the same situations with 3Delight. Here everything works fine.

Yours
Andy

Wait, I didn't think lights in Iray have a shadow bias. In fact, I was pretty sure of it.

I don't think Iray has as many bugs as you think it does...

-- Morgan