why do some models have shadow faults ?

[Triadian]

Having a slight issue understanding why some models have shadow issues and some dont

the issue at hand can be seen in the demo example with the sydney model whereby sometimes her hand gives off a very distinct line in her shadow
an example of sydney in my world @ http://youtu.be/ydVm6pI-wmU

i created another example with my own model @ http://youtu.be/sqfO8pF79TE where the mouse pointer shows the line in the shadow on the top of his head

if i use the dwarf model @ http://youtu.be/gkQZRlSz9Ko no such shadow error exists

this leads to believe its an error with the models or possibly and error with the way shadows are made, i used my limited irrlicht knowledge to find out that shadows are made from creating a bounding box from the model and then using that to calculate the shadows, as the errors are from the extremities of the model i wondered if there was possibly a bug in creation of the bounding box either being too small or if the the shadow making routine has an error if there is a pixel of shadow on the very last pixel in the mask used to create it.

so i have 3 questions :-
how can edit my model to be more like the dwarf model and such that no pixel is on the edge of the shadow mask.

where can i increase the size of the bounding box before its sent to the mask making function'

where is the mask making function.

i filmed the videos using 1.8 but also tried it using the svn (rev 4555) and the issue still exists.

[CuteAlien]

The error in Sydney's hand is because the model is not closed there. Basically your model should be build in a way that you if you would fill it with water and nothing would leak out anywhere.

[Triadian]

is there any quick way of knowing where the hole could be in the model ?

using max 2010 or any other program.

[CuteAlien]

Not sure, there might be commands to weld vertices which avoid at least having 2 vertices at nearly identical positions accidentally.

[Triadian]

i went to our team member who made the model with your explaination he showed me how to find out if the model was water tight and we can both say definitevly it is water tight.

so with that in mind i loaded up the dwarf model and purposely made a hole in the model. exported the same way i did to our model and tested it in the world
The shadow remains complete with no errors.

could there be something other than watertightness that could be causing it ?

[Cube_]

Screwed up normals? Although that's unlikely as it would show up as large holes.
I don't actually know, I don't use stencil shadows ^^; (raytracing ftw!)

[Triadian]

is there a working example of some raytracing or other non-fps hogging semi-realistic shadows ?

[Cube_]

um... with non-fps hogging.. what hardware are you using? (and how complex are the scenes you intend to use, the more complex the higher the gain)

[Triadian]

well it would be a distributed game so hardware would vary based on people playing so assume general crappy specs type machines. scenes would get very busy lets say 250 of the characters with about 50 cuboid shaped objects quite a few overlaps in shadows etc multiple light sources (i am aware that some shadow systems limit the amount of closest lights etc)

[Cube_]

Hmm... I'd set a lower cap for minimum reqs, I get fairly decent results running a small 50 k triangle test using four 2048x2048 textures on an Athlon X2 64 with 2GB ram and a Mobility Radeon HD 3200 (no dedicated VRAM, I am suspecting the large textures causes the decent instead of good results on this silly machine)