When objects are close to the ground, part of the shadow seems to disappear underneath the ground material. For example, if I have a cube object resting on the ground with a spotlamp pointing at it at a 90 degree angle, I should get SOME shadow starting at the edge of the cube. Instead, I get this (see attached image).
Any fix to this? Or is this just a result of the “newness” of the shadow system?
-Sam
ive had this problem to, i find if you just shrink your scene then the shadow dosnt dissapear
My scene is already smaller than the typical blender scene, and shrinking things down will mess up plenty of physics and animation related things.
However, when I do put the light right next to the object it casts the correct shadow. Why would moving it far away (literally only about 6 blender units away) mess up the shadow that much?
lower the bias
I don’t know the answer to this issue. This seems to be a bug more than anything else.
“Shrink your scene”, “lower the bias”, I don’t think that those answers are appropriate.
“My wife and I sometimes disagree” -> Change your wife.
The goal is not to find solution at any cost even if it’s inappropriate, the goal is to find what is a bug or just a bad user setting…
In that case, I guess that there should be shadow there.
I was having this problem too, I lowered the bias setting and it resolved it without affecting the size of the scene. If you move the lamp closer to the object will do the same thing but then you have to change the spread of your spot. The best solution I can find is the lowering of the bias, it seems to be the forum consensus.
Finally! I’ve been looking for this answer for ages! XD
The bias is an offset in the shadow to correct shadow miscalculations. Just that, there’s nothing wrong in lowering it. If your shadow offset is too high you just lower the bias.
Ok, sorry for the mistake Valdark it seems that you were right.
I was just reacting to the fact that sometimes (often) we find “fixes” and not solutions on the forums.
Yours was a solution, thank you for sharing.
No, Cray was right, lowering the bias is not a good solution because this give you other problems as shown below.
As you can see, rising the bias is actually better.
I don’t know if this is a bug or not, but I found
a “better solution” is to simply extend the ‘clipping start’ to be closer to the object.
Bias and these “artifacts” are problems inherent with shadow mapping. I am new to Blender, couple of months now, and I love it. But I have used Lightwave primarily for the past 10 years, along with many other 3D programs.
Shadow mapped or buffered spotlights, even when not used in the game engine, usually have to be tweaked. Scale of the scene and proximity of the light to the object are things that have to be taken into account because of the way shadow mapped spots work.
Stencil mapped or shadow volumes are more accurate, but more expensive to render.
Not sure if I can post links here yet or not, but here goes. This link has plenty of information with regard to shadow techniques.
http://www.devmaster.net/articles/shadow_techniques/
EDIT: Looks like I can post links
PhilB, that is not a “bug”. That is the whole reason why the bias even exist. To correct those miscalculations inherit in how shadow buffering works. The article posted by dbigers explains that and so does the official blender docs at:
http://wiki.blender.org/index.php/Doc:Manual/Lighting/Lamps/Spot/Buffered_Shadows
You increase the bias to avoid that to happen. You decrease the bias to avoid SamBassador’s problem to happen. So you just keep it between too close and too far. The ideal values depends on your scene. So you just adjust it accordingly. There is no problem in doing so. That’s why the bias exists in the first place, to be adjusted according to your scene. This is very simple to understand.
You can also increase the shadow buffer size and softness to help offset the errors you see here.
Thanks for the link Vibrunazo I didn’t know that my problem was called Self Shadowing.
You’re right, I didn’t know that’s what it was designed to do.
But, since lowering the bias may lead to Self Shadowing Interferences.
Its more important to first adjust the clipping
since it will very likely solve Sam’s problem and it has benefits rather than potential issues.
Phil