Anim8or Community

Please login or register.

Login with username, password and session length
Advanced search  

News:

An update to Anim8or, v1.00b, is available with a few bug fixes. Get your copy HERE. See the "ReadMe" file for details.

Pages: [1] 2

Author Topic: Why objects should retain the options for shadows in Raytracing  (Read 8600 times)

VBSmiles

  • Full Member
  • ***
  • Posts: 203
    • View Profile
Why objects should retain the options for shadows in Raytracing
« on: November 02, 2008, 03:14:28 am »

The first image uses no shadows.

Its a great photo on it's own, BUT...

The second image used shadows.... note that the light source sits in the lamp. A big oops.

I took off the 'light' here to show what should be ( shadows with more emphisis than intended to bring focus to them )

If you ever decide to introduce self illuminating objects, you'll probably want to deal with this issue.

Oh,  I know how tough it would be to introduce shadows in the raytracer as it was in scanline. So don't blame ya if you never get it done  :-*
Logged

Steve

  • Administrator
  • Hero Member
  • *****
  • Posts: 1519
    • View Profile
Re: Why objects should retain the options for shadows in Raytracing
« Reply #1 on: November 03, 2008, 04:36:20 am »

I don't understand what you did for images 2 and 3.    Are they made with ART or the scanline renderer?  The missing feature from ART is the ability for each object to cast shadows or not.  They all cast shadows at 100% dark.  The scanline renderer allows them not to and to only cast a partial shadow.
Logged

VBSmiles

  • Full Member
  • ***
  • Posts: 203
    • View Profile
Re: Why objects should retain the options for shadows in Raytracing
« Reply #2 on: November 04, 2008, 01:57:35 am »

Sorry if I didn't state it clearly enough. All 3 photos used the ART renderer. And the missing feature in
ART is what I was refering too. Without this option it's pretty useless to use an object as a light source properly with shadows enabled.

in image 2 the light is inside the object with shadows enabled, ( which is to be expected in a lamp )
In image 3 I showed how it should be by taking out the object blocking all the light. ( or causing everything to be shadowed improperly )

As for casting shadows at 100% dark, I never noticed this to be the case.... thanks for the insight  :P
« Last Edit: November 04, 2008, 01:59:16 am by VBSmiles »
Logged

Steve

  • Administrator
  • Hero Member
  • *****
  • Posts: 1519
    • View Profile
Re: Why objects should retain the options for shadows in Raytracing
« Reply #3 on: November 04, 2008, 07:19:39 am »

I think I see.  You mean that the lamp in #2 has glass in the holes that is shadowing the light.  There are several ways to solve that.  By far the best one is to add photon mapping.  It is a very advanced way to model global lighting, probably the best practical technique known.  It could do caustics, glossy reflected light, diffuse irradiance, etc.  I would like to add that to ART in the near future but it would take about 3-6 months I think.

The second best way is to model transparent shadows.  It wouldn't handle dielectrics properly - they'd behave like transparent gels - and would slow down shadows.  Not nearly as difficult to do though.

The third way is to allow disabling of shadow casting by individual objects.  Not a very realistic solution - a real hack really - but fairly easy to do.  Would possibly slow down shadows a bit.
Logged

hihosilver

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1294
    • View Profile
Re: Why objects should retain the options for shadows in Raytracing
« Reply #4 on: November 04, 2008, 07:23:00 am »

I think being able to disable shadows for certain objects would be nice.  Even though it's not realistic, art often isn't realistic!
Of course photons, caustics, all that jazz would be amazing!
Logged

VBSmiles

  • Full Member
  • ***
  • Posts: 203
    • View Profile
Re: Why objects should retain the options for shadows in Raytracing
« Reply #5 on: November 04, 2008, 07:40:16 am »

You got the right idea Steven ( though the lamp itself is the glass in question :P )
photon mapping sounds pretty exciting :D
But yeah the hack would be ok also. Sounds weird that it would slow the shadows down rather than speed it up. Maybe just the way it is built that you would be basicly reversing the calculations of those objects?
Logged

floyd86

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1056
    • View Profile
    • http://youtube.com/profile?user=floyd386
Re: Why objects should retain the options for shadows in Raytracing
« Reply #6 on: November 04, 2008, 11:50:44 am »

Photons and caustics! It would be great if you could add those. But for a fast solution, i think disabling shadows for objects would help. Now renders take a very long time because every object is casting shadows, when maybe a few need too.

lynn22

  • Sr. Member
  • ****
  • Posts: 591
    • View Profile
    • 3D Animation
Re: Why objects should retain the options for shadows in Raytracing
« Reply #7 on: November 04, 2008, 08:07:11 pm »

I like to agree with Hiho, each object already has checkboxes for Cast and Receive shadows. If these boxes could be implemented in ART that would be very helpful.

Because of ART's improved rendering I'm currently restarting from scratch with my museum and I'm caught in a serious snag. In ART you cannot look through the windows anymore like you can in Scanline. ........  :-\

In Scanline you have this lovely reflection of the ceiling light in the top left pane but in ART there's nothing but near black faces. You can only see outside in ART when I take out the panes but then you also see that there are none.

Any suggestions are more than welcome.
« Last Edit: November 04, 2008, 08:10:36 pm by lynn22 »
Logged

Steve

  • Administrator
  • Hero Member
  • *****
  • Posts: 1519
    • View Profile
Re: Why objects should retain the options for shadows in Raytracing
« Reply #8 on: November 05, 2008, 06:55:46 am »

floyd86, renders do not take longer because every object casts a shadow.  Quite the opposite.  There is only one copy of the geometry this way and shadow rays don't have to find the closest hit.  Any hit means the ray is in a shadow.

The same is true for semi-transparent and colored transparency.  To do that each shadow ray would have to trace objects form the closest hit on until it got to the light or to a 100% opaque object.

lynn22, I know what you mean and I sympathize with you.  But if I waited until that was all working the ray tracer wouldn't be out yet.

Since this seems to be important I'll see what I can do.   Adding non-shadowing objects or materials won't be physically correct.
Logged

floyd86

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 1056
    • View Profile
    • http://youtube.com/profile?user=floyd386
Re: Why objects should retain the options for shadows in Raytracing
« Reply #9 on: November 05, 2008, 11:43:12 am »

oh, I was awfully wrong on that then :D

lynn22

  • Sr. Member
  • ****
  • Posts: 591
    • View Profile
    • 3D Animation
Re: Why objects should retain the options for shadows in Raytracing
« Reply #10 on: November 05, 2008, 05:37:13 pm »

Thank you Steve but there is no need to jump the queue of something else you are working on. I still have several months to go before I will start rendering animation tracks and who knows what changes/improvements you will make in the meantime.

I would really appreciate it though if you could find a way to code either shadows on/off or a (transparent) material attribute so that window panes do not throw shadows on their surroundings.

Many thanks in advance  :)
Logged

lynn22

  • Sr. Member
  • ****
  • Posts: 591
    • View Profile
    • 3D Animation
Re: Why objects should retain the options for shadows in Raytracing
« Reply #11 on: November 06, 2008, 01:26:39 am »

Steve I'm sorry that I was so quick to whine about the shadows in my project.
After some trial and error I found a solution : I increased the ambient and diffuse values to 0.900 in the material settings for the park images behind the windows and put a spotlight on each of them and .... tataaaaa, the shadows are gone  ;D
Logged

Steve

  • Administrator
  • Hero Member
  • *****
  • Posts: 1519
    • View Profile
Re: Why objects should retain the options for shadows in Raytracing
« Reply #12 on: November 06, 2008, 03:33:55 am »

floyd86, you never know just what thoses whacky programmers will do, eh?

lynn2, I didn't think you were whining.  It's a reasonable request.  (But you do need some furniture in that room.  Where are your guests gonna sit when they visit you?  On the floor?)
Logged

ENSONIQ5

  • Sr. Member
  • ****
  • Posts: 925
    • View Profile
    • Mission Backup Earth
Re: Why objects should retain the options for shadows in Raytracing
« Reply #13 on: November 06, 2008, 01:39:19 pm »

Lynn22:  Just a tip for the images behind the windows.  If you import the bitmap into the emissive texture field as well as the ambient and diffuse, and set the emissive value to 1, the image becomes always fully visible, and does not accept a shadow.  It is kinda like the image is printed on clear film placed on a light table.

On topic, it would certainly be nice to have more control over the ART shadows (photon mapping sounds seriously awesome... Anim8or will have it eventually no doubt.  Something to look forward to!) even if that control is just the boolean on/off in the cast/receive channels.  I admit I have no idea how renderers work, and things that sound simple to the layman rarely are, so like Lynn22 says, no need to jump the queue.  Everybody realises (I hope) that Anim8or is a work in progress, and its biggest attraction (to me at least) is that it is a simple, powerful modelling and animation platform upon which much functionality can be built.  Eventually it will be a serious rival to the commercial packages, and already it improves upon the best known of these in some crucial areas (wireframe editing and figure boning spring to mind).

We appreciate that the preview versions are a fast-tracked way of allowing us to play with the very latest developments without having to wait for a full reconstruct of the interface, and inevitably they will be incomplete and rudimentary in some respects.  The best is yet to come folks, be patient.
Logged

lynn22

  • Sr. Member
  • ****
  • Posts: 591
    • View Profile
    • 3D Animation
Re: Why objects should retain the options for shadows in Raytracing
« Reply #14 on: November 07, 2008, 01:22:06 am »

Thank you Steve. Well the visitors may need to stay on their feet, it's a museum ;)

VBSmiles, have you tried taking out the glass in the circles of your lamp and just keep the green cube ? Your image is rather dark so maybe you would get your shadows without anybody noticing that the glass is missing.

Ensoniq5, thanks for the suggestion, I tried it and it takes out the shadows but also the window panes. It's just too effective ;D
« Last Edit: November 07, 2008, 01:26:29 am by lynn22 »
Logged
Pages: [1] 2