Render Clipping Artefacts?

Hello all! I’m currently working on a fun short film involving kids on the run from a character based on an ‘Elite’ from the Xbox game, Halo…

The mesh was downloaded from the internet (presumably ripped from the game) and converted for blender. I thought this would be quicker than modelling from scratch, but actually I’ve spent a lot of time tweaking and error correcting since the conversion, and it still screams out ‘low poly’ when rendered…

Anyhoo, to my point…I’ve started another shot for my movie, the first where we see the character from the rear. The texturing is still in a draft stage, but for some reason, I keep getting black areas in the renders (see below)

http://www.filmsrus.euro1net.com/clipping.jpg

I presume it’s a clipping artefact, but I can’t see why. I’ve played with the lights a bit, but it doesn’t go away. I don’t want to change the lighting setup too much, as it might look odd compared with the other shots…

Here’s an animated testshowing the clipping artefacts. Pay particular attention to his right thigh, for example…

The thing is, I can turn off the ray tracing to lose the artefacts, but then I lose the ground shadows. I’m happy to make do without raytracing, but I need some shadows, even if they’re not 100% accurate - is there an alternative for this?

Sorting the isuue out but keeping ray tracing (there’s one transparent element on the character) would be ideal however, so any ideas would be appreciated.

Thanks in advance…

First things are to check for Doubles and Normals facing the wrong way. Then use Area Lamp(s) with sufficient Samples (and maybe Umbra). You don’t say which part has transparency but, in Materials, make sure ShadBuf is on and in Mirror Transp use RayTransp and set the IOR Depth higher than 0.00. Depending on which Shader you’re using, turning on Bias may help too.

(I’m not sure why it’s necessary to use Raytracing in a scene that has no obvious Mirror or Refraction elements)

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I think you hit the nail on the head with the sampling factor for area lights. I’ve been using them for the main shadowcasting, to get a more realistic soft edged shadow. When I increase the samples, the black areas on the model increase in size!

Unfortunately, even set on 1, the results are as in the video clip. However, if I set the character’s materials to not receive shadows, the clipping is gone! Not an ideal scenario, but much less distracting than the shadow artefacts…

Incidently, the only transparency is a glass dial on the wrist laser - however, the main reason for using ray tracing is to get an accurate shaped shadow on the ground floor. I would still be more than happy to avoid ray tracing (most of the textures are UV or image maps, etc) simply for the speed gain. I shall experiment with spotlights set at large distances to emulate sunlight…

Your help has definitely pointed me in the right direction - thanks!

Look at SoloCreator’s tips for BuffShadows here:

https://blenderartists.org/forum/viewtopic.php?t=54622

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A useful link, thank you.

My main problem is that if I use Zbuffer shadows, the base of the character’s shadow is weak - it should be the strongest part. I’ll experiment with extra shadow only lights to compensate…