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Question about normal mapping in Ray tracingIt looks like al

Posted: Tue Jul 14, 2015 8:16 pm
by shiqiu1105
It looks like all the ray tracing renders I found online uses bump mapping, including me tuba mitsuba, PDRT and in all of the graphics courses taught at the Universies too.however real-time graphics uses normal mapping which is supposed to be better than bump mapping in terms of the ability to perturbed and normals. I wonder what is the reason behind this trend.

Re: Question about normal mapping in Ray tracingIt looks lik

Posted: Wed Jul 15, 2015 2:31 am
by friedlinguini
Typically normal maps are derived from bump maps. It's essentially a precomputation step that saves you from having to calculate surface derivatives at render time, which can be overly expensive when you only have a dozen or so milliseconds to display a frame. On the other hand, normal maps aren't very good for authoring purposes, as it's easy to generate physically implausible results. Normal maps also don't easily convert to displacement maps.

Re: Question about normal mapping in Ray tracingIt looks lik

Posted: Wed Jul 15, 2015 12:34 pm
by mrluzeiro
I believe "bump map" and "normal maps" are different things.
You will use "bump map" when you think about a texture (i.e the material properties of an object), it will fake some texture properties of the material.
You will use "normal map" when you think about geometry, it will fake geometry aspect of the object. That is why it is more used in games,etc so you can use a lower polygon count.

If you consider that raytracing is still a study subject and something only used for still final rendering (i.e not real time) then the propose is to render everything as much as the original designed detail and not fake it.
game engines: "how can we render it fast event if its a bit fake?"
raytracing: "how can we render it fast with all original information detail?"

Btw: raytracing is used to generate normal maps:
http://http.developer.nvidia.com/GPUGem ... _ch22.html

Maybe if raytracing continues to progress and start using for games, people will start investigate some more "fake" render options for raytracing.

Re: Question about normal mapping in Ray tracingIt looks lik

Posted: Wed Jul 15, 2015 1:48 pm
by stefan
mrluzeiro wrote:I believe "bump map" and "normal maps" are different things.
They're almost the same. They contain the same information, only in different format. A bump map contains height values that a render engine can use to calculate new normals from. A normal map contains the result of that calculation.

Re: Question about normal mapping in Ray tracingIt looks lik

Posted: Mon Jul 20, 2015 4:36 pm
by ultimatemau
shiqiu1105 wrote:It looks like all the ray tracing renders I found online uses bump mapping, including me tuba mitsuba, PDRT and in all of the graphics courses taught at the Universies too.however real-time graphics uses normal mapping which is supposed to be better than bump mapping in terms of the ability to perturbed and normals. I wonder what is the reason behind this trend.
Hi,

Definitely have a look at luxrender and/or SLG (GPU luxrender). I'm pretty sure they support both normal maps and bump maps.

Cheers

Re: Question about normal mapping in Ray tracingIt looks lik

Posted: Tue Jul 21, 2015 11:34 am
by m9105826
You could also check out Cycles. It has support for both normal and bump maps.

Re: Question about normal mapping in Ray tracingIt looks lik

Posted: Thu Jul 23, 2015 6:30 am
by cignox1
In my personal raytracer I've implemented normal maps. I don't really remember why those instead than bump maps (at the time I used to have PBRT as inspiration), but perhaps this is due to the fact that NP were mentioned everywhere on the forum I used to attend for proramming advices (gamedev.net).

Re: Question about normal mapping in Ray tracingIt looks lik

Posted: Thu Jul 23, 2015 7:33 am
by papaboo
A question to all of you out there using normal maps. How do you handle rays that intersect the surface on the front side, but are on the backside of the bumped normal?