About shadows with ZBrush:Please Matthew an answer.

[Le Discot]

Why don't we have drop shadows of the object which the light is under see in the picture below????

Why don't we can place lights in real depht???
And why don't they have a direct interation with objects drop shadows forms???
http://www2.zbrushcentral.com/uploaded_from_zbc/200309/user_image-1063874882hhh.jpg

[cameyo]

Hi LeDiscot,
As Marcel explain in his last post, the shadow are a bit "strange" in Z...it allows to see where it should be, but you must enforce it with painting.
I have tried for long time to understand the Light palette, but with no luck.
I hope some guru explain this and other light's problem.

cameyo

[Frenchy Pilou]

Maybe page 219, 220 of the Manual 1.55B :)
Maybe ! :rolleyes:
Pilou

[aurick]

http://www2.zbrushcentral.com/uploaded_from_zbc/200309/user_image-1063903481guv.jpg

ZBrush is fully capable of handling such effects -- but you need to have a good understanding of how lights work in order to accomplish it. It's actually not very complicated.

Here's how I set it up:

1) Point lights don't cast shadows very well over really long distances, so if I'm going to use them I make sure to keep my objects as close together in depth as is practical. A good way to guarantee success is to put the background on a separate layer from the object that will be casting the shadows onto it. I can then easily adjust that layer's depth later if I need to.

2) To place the point light, I first use the Light>Position>P button and drag out from it onto the canvas. I release it on top of the back surface of my shadow casting object, as close as possible to the proper XY coordinates. By releasing over top of the back face, that places it at the back depth of the object.

3) I then move the Light>Position>Z slider to a slightly lower value, to move the light back toward the camera.

Note: An even easier approach, if you have put the shadow-casting object on its own layer, is to move that layer to a depth of 0. This will put the center of the object at 0, so you can also set the light depth to 0. :)

4) Also in the Position menu, increase the Radius value. I used 4 here, since that represents the total depth of the scene.

5) In the Shadow menu, turn on Z mode, and crank the Length all the way up. Leave the Rays and Aperture alone for the moment and do a test render.

6) You will see very jagged shadows appearing throughout your scene. That's fine, since you will be resolving them in a moment. The key is to see that the shadows ARE actually appearing on the objects where they're wanted. If they aren't, try moving the layers closer together, or change the Light>Intensity Curve by raising the left side (filling the curve in even more).

7) Once you have shadows falling where you want them, it's time to make them look pretty. This is accomplished by increasing your Rays value so that more shadow-casting rays are emitted from the light. The more rays you have, the more likely it is that they will be stopped by your foreground object, resulting in that object casting an accurate shadow. At the same time, you need to decrease the Aperture setting in order to give the shadows good definition. (Aperture is basically the thickness of the light ray. The thicker it is, the more of it will get past your shadow-casting object, obscuring the shadows.) A little trial and error is always necessary to get a nice balance between Rays and Aperture.

8) Even with the best of settings, you can still get some artifacts. This is due to the fact that once an object is snapshot to the canvas it is no longer fully 3D. ZBrush then has to "guess" a little bit when it comes to filling in anything that lies behind a foreground object. You can see that in my example above, where the foreground rings create holes in the shadow cast by the background rings. To finish the scene, you would want to bake the layer or re-import it and then use the Shading Enhancer brush to quickly and easily clean things up a bit. I didn't do that here because I wanted you to be able to see what's to be expected.

Here is the light setup that I used for this scene:

http://www2.zbrushcentral.com/uploaded_from_zbc/200309/user_image-1063904803qbw.jpg


Hope that helps!

[Frenchy Pilou]

Enlighting :cool: :)
Pilou

[Le Discot]

Ohhh thanks a lot for this thread Mr Aurick. ;) :)

But...Hemmmmm...Do not be angry after me,but the result of drop shadows rendering is not realy...nice...
I'm never satified with the lights placement in ZBrush.

I can propose you something like the "giro light buffer":
It's a sort of mini lay out wich allow you placing lights in a real x,y,z positions in front or under or back the object.
It is no necessary to have a so big previsualisation of lights icones...It should be more interesting to have a bigger one for the light placement and effects on the object.

Tell me what you think about it and if it is possible to upgrade the actual system of lights placement.

Thx ;) :)

http://www2.zbrushcentral.com/uploaded_from_zbc/200309/user_image-1063908444jcp.jpg

[aurick]

The new version is currently in beta testing, which is the wrong time to be adding new features. The proper time to request a feature such as this would be when the Wish List is opened again. At that time, we will be seeking such input, and able to give each suggestion the attention that it deserves.

[Bonecradle]

Thanks for the explanation Aurick - it always helps to know the theory behind the practice.

I was doing similar acrobatics with the picture below. In the end I dropped the light on the back edge of the dome and played with the sliders, but perspective added complications.

It's not quite what you illustrated Olivier, but there is also Digit's Light an brush (http://www.pixolator.com/zbc-bin/ultimatebb.cgi?ubb=get_topic&f=1&t=010476) zscript for helping to place lights. You basically draw a sphere on a separate layer, put it where you want the light and then hit a button that places the light, I assume, at the sphere's centre.

http://www2.zbrushcentral.com/uploaded_from_zbc/200309/user_image-1063924370ddz.jpg

[cameyo]

Thank you Aurick :tu: :tu:
Some 'light' on lights...

cameyo

[PusGhetty]

Great tips Aurick!
Very insightful!

[Le Discot]

Another question about drop shadows:

The script of Digit is more effective for the lights placements. :) ;) A great job!!!

But the drop shadows results are not logical.

See the pict below:
Point lights who are placed under objects generate a non sens drop shadows or do not generate good drop shadows.
http://www2.zbrushcentral.com/uploaded_from_zbc/200309/user_image-1063954343ije.jpg

[Frenchy Pilou]

Maybe it's an ambiance light :)
Pilou

[aurick]

Hi there. Please check your Shadow settings. It looks to me like ZMode is not active for point light 2.

As for point light 1, are you sure that it's below the lower plane, and not slightly above it?