Question about normal mapping in Ray tracingIt looks like al

Practical and theoretical implementation discussion.
shiqiu1105
Posts: 138
Joined: Sun May 27, 2012 4:42 pm

Question about normal mapping in Ray tracingIt looks like al

Postby shiqiu1105 » Tue Jul 14, 2015 8:16 pm

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.

friedlinguini
Posts: 82
Joined: Thu Apr 11, 2013 5:15 pm

Re: Question about normal mapping in Ray tracingIt looks lik

Postby friedlinguini » Wed Jul 15, 2015 2:31 am

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.

mrluzeiro
Posts: 28
Joined: Tue May 26, 2015 2:27 pm

Re: Question about normal mapping in Ray tracingIt looks lik

Postby mrluzeiro » Wed Jul 15, 2015 12:34 pm

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.

stefan
Posts: 45
Joined: Wed Dec 21, 2011 8:57 pm

Re: Question about normal mapping in Ray tracingIt looks lik

Postby stefan » Wed Jul 15, 2015 1:48 pm

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.

ultimatemau
Posts: 11
Joined: Wed Jan 08, 2014 9:48 am

Re: Question about normal mapping in Ray tracingIt looks lik

Postby ultimatemau » Mon Jul 20, 2015 4:36 pm

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

m9105826
Posts: 2
Joined: Sat Jul 18, 2015 1:01 am

Re: Question about normal mapping in Ray tracingIt looks lik

Postby m9105826 » Tue Jul 21, 2015 11:34 am

You could also check out Cycles. It has support for both normal and bump maps.

cignox1
Posts: 12
Joined: Mon Jan 30, 2012 10:11 am

Re: Question about normal mapping in Ray tracingIt looks lik

Postby cignox1 » Thu Jul 23, 2015 6:30 am

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).

papaboo
Posts: 41
Joined: Fri Jun 21, 2013 10:02 am
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Re: Question about normal mapping in Ray tracingIt looks lik

Postby papaboo » Thu Jul 23, 2015 7:33 am

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?


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