Render Artifacts Wonder Why

[Marcel]

It's a 'moire' pattern, fine lines close to eachother start to create weird patterns.

http://en.wikipedia.org/wiki/Moir%C3%A9_pattern

The solution is to increase your sampling while rendering. Are you rendering with the default rendering or with Mental ray?

[ASWDesign]

Hey Marcel!
Can always count on you for solid replies!
Rendering with the default render just for tests would mental ray help this problem?
Not only do i think the problem is 3d, i think it has to do with Illustrator and or Photoshop, you see i get this exact same effect when i am making the texture.

I made the outer swirl (vinyl record is one single swirl inwards) in Illutrator and i still get this effect when zoomed out to about 100% and downwards, and i exported it into photoshop and still got this problem.... The illustrator "Swirl Tool" isnt very good so i think that and the settings i used is the problem but i cant seem to find a better way to make it?

I dont think increasing the texture size will help at all infact it has made the pattern worse.

Is there anyway to get close lines togeather and swirl into the centre with out getting this Moiré pattern

Any suggestions?

Using Maya Build 7.5 is there anyway i could even model it that wouldn't be so time consuming?

Thanks once again for the perfect responce hope you return back.

Regards
ASW

[Marcel]

Good to know you appreciate the help :)

You will see the same problem in Photoshop because when you zoom out it downsamples the image in a way that is as quick as possible (you wouldn't want to wait a few second everytime you zoom in and out). I think if you used Image->Image Size to make you image smaller (set it to Bicubic Smoother) then you probably wouldn't see the Moire pattern.

It's all about how Photoshop or Maya samples the texture. Lets say for example that your render is 500 pixels wide, and your texture 2000 pixels. This means that your texture is 4 times as dense as the render. When Maya needs to draw the texture on your model, it samples the colour from your texture. But because the lines in the texture are so close together and the resolution is higher, it is pretty random if it returns a block or a white colour. It could sample a black pixel, but if it would sample only a fraction to the left or right it might see a white pixel.

Normally this is not a problem, because textures are pretty smooth. But when you have a texture with a lot of small details, you can get these kind of patterns, or in animation you get horrible flickering noise.

The solution is to let Maya not sample just once for each pixel in the render, but many times. When it samples 8 or 16 times from the texture and takes the average from all these samples, the result will be much more accurate. It'll take longer to render, but in this case you do not have a choice.

You can set the sampling rate for the render at the global render settings (Render Options Window->Antialiasing Quality->Shading). There should also be options to set it at a texture level, but I can't seem to find it now. Another option is to render out your image at a ridiculous size (so big you start to see the individual threads of the record) and scale it back in Photoshop.

There are tons of articles on sampling, here is one for Mental Ray:

http://www.impresszio.hu/szabolcs/MentalRay/MentalRaySampling.htm

(Read the bit about how the sample setting relates to the actual number of samples, it tells you important things like 'do not go above 3 samples in MR unless you have a lot of coffee in store :thumbsup: )

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