57 replies to this topic

[pixo]

I confirm chingchong, i was just trying to say that cycle was fairly good.
By the way the terminator issue is not a big problem, subdivision correct it,by the way when you model properly your surface you don't need to subd a lot.
Kind

[michalis]

Subdivisions makes it less visible. It's there however.

[pixo]

Nope it doesn't happen that much in most path tracer.
At least not the ones that i tested 3 without cycle.

It happens only if you are using oldschool lights.
The one that emit infinite energy from one point, aka spot,omni,etc light without any size.
With most probably a very old shadow function.

If you need these kind of lights ,you should probably use a Reyes with micropolygon subd it will be better.
Especially because you have way to offset the ray(bias) in an intelligent way .

Kind

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[michalis]

It happens only if you are using oldschool lights.

Old school lights? lol
You probably mean hard lights. Like sun in an exterior for instance. It's a problem for architectural visualization. It kills smoothed bevels under a certain angle of sunlight.
Indeed, using large lights-smooth shadow casting helps a lot. But you need hard lighting in half of the cases.

[pixo]

For Sun light you can use IBL with MIS you can get easily sharp shadows without this problem.I did it many times.
Of course you will get more realistic result too.

[pixo]

By the way if you really want to use old school lights , just bias you ray and it works.

[pixo]

just to make you happy.
I did path tracing with a REYES and Raytrace, directionnal light with a shadow at 0.5 degree raytraced shadow of course.
The sphere is really low poly, i just have to bias a little bit the ray and there's is no problem.Old school method for old school problem.

Take care.

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[michalis]

Thanks pixo.
But, cycles is not a biased renderer. Neither octane.
Another older unbiased renderer is Kerkythea. And thea. They found a biased solution on this problem though.

[pixo]

Bias mean offset the ray in this case, i m not talking about convergence of the integral.
I used a biased Reyes ,and an unbiased Raytracer to show you that's working in both situation.
By the way you can do path tracing in both ,Raytracer and Reyes,and use unbiased render method in both type of renderers.
You probably misunderstood the unbiased meaning .

[michalis]

How low poly the sphere is, I can see (in the shadow casting)
I wonder, is it so simple? I keep complaining on this, in blenderartists forum, among other users. Cycles can't do it. For the moment. Neither octane can.
Are these methods support GPU-cuda or maybe OCL? Are you sure? This GPU support became a bottle neck on development.

[pixo]

Yes Michalis it's that simple hopefully for us 2 .

You just need to add a raytrace bias to your objects if cycle consider per object attributes or to your shadow light function which mean to your light attribute .
If you don't find it , just complain to don't have shadow raytrace bias or raytracing bias.

Hope it can help you.
Take care

[pixo]

Are these methods support GPU-cuda or maybe OCL? Are you sure? This GPU support became a bottle neck on development.

For sure since it's nothing else than displacing the position of the ray origin along the normals.
I insist your result will not be biased at all in term of render.

[michalis]

Now, I have to post such ideas on blenderartists forum. They will eat my alive but it won't be the first time LOL

[pixo]

If cycle doesn't have it , you are right to ask them since every render have this at least all that i tested.
It doesn't solve everything but it helps a lot.

[michalis]

Basically it's a dirty trick. Not for purists, if you know what I mean LOL.
But, who cares...

[pixo]

It's isn't a dirty trick...or subdivide your model to the micro-polygon level.

Actually if you are such a path tracer's fanatic you would never use these kind of lights .
Even solid angle consider this kind of what you call "trick", and they are the hardest fanatic that i saw,they didn't even consider "bake" or "PTC" as a solution .
Using a light with infinite energy that your are multiplying by a shadow function with a different distribution than the surface brdf ,it is not what i call path tracing purism.
So there's no purist in production at least ..... IMHO if you wants to go further ,path tracing should be very used for exterior shots with IBL and MIS this is the only case where it's really efficient (my 2 cents biased renderers does it very well for less computation time).
But for serious things like interior ,you should use BPT cause it's predictable without any bias and far more faster than PT.
MLT is elegant, converge faster but doesn't allow a fast preview since you have a start-up "bias",the problem is that your lighters will wait more before to have a proper scene lighting preview , for instance Maxwell renderer use on a thumbnail , for me it is not enough.
My 2 cents, just keep in mind that we hopefully have tools that help us .We should use them properly.
I can give so many cases where path tracing can't do something at reasonable cost ,this is the same for the others methods.
There's not today an absolute method that's it .
Keep in mind that PT with MIS is very old at least older than the modern software.

Take care
Pixo

[michalis]

Dirty is not what I think. It's what cycles developers think about it.
I like dirt.

[TimmyZDesign]

Very interesting thread. Thank you for the information about rendering!