Ray Trace settings Help X6


Gawdzira
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Jintu - I will try that.  But it shold not be happening.  ALso, How did you get rid of the red tint?  Same answer?

 

I think there is a bit of a misconception as to how Raytrace functions. It is not some type of auto finction that you would find on most digital cameras. It's the equivalent of operating your camera in manual mode only. Ratrace computes a scene based soley upon the light settings you define and the interaction of the light rays as they strike and reflect off of the surfaces within their path. If the results are unsatisfactory then either the lighting must be adjusted or the material properties that the light is  refelecting off of needs adjusting. It's one or the other or a combination of both. When Raytracing one needs to take off their designer hat and put on their photograpers cap.

 

Graham

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Graham - I understand.  HOWEVER, Why is the sun going THROUGH the wall and reflecting/bouncing off the back of furniture?

Can you splain that to me??  And why should I have to change the direction of the sun angle to fix the problem?

Been with Chief since 97 and know that it is not a flip the switch procedure but I and others are still not happy with how

light bleeds in certain situations.  Things have come a long way but still need improving.  IMHO

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Dennis - from my playing around I don't believe the light is actually leaking through the wall, it only appears to be. From what I can deduce it is actually the result of reflected light rays concentrating in shadowed regions. These shadow regions occur where two surfaces are perpendicular to each other, such as a wall ceiling intersect, wall corners, window/door casings and furniture placed against the wall. Raytrace only assigns so many rays to compute for each type of light, under extreme or difficult lighting situations the reflected rays striking these shaded intersect regions show up as pure bright white points. As you continue to render, more passes, Raytrace tries to smooth out the transition between the bright regions and the surrounding shadowed regions. Unfortunately it can only do so much with this. When you change the sun angle or intensity you are altering how and where the light rays strike the shadow region intersects.The colour cast that can also occur is the result of the reflected light being influenced by the material it is being reflected off of. In your scene it is aggravated by the furniture and window shutter colour/material properties. Brown contains a significant RGB red component, the originating light entering the room is white, upon striking these surfaces the reflected light will be altered from white and shifted to incorporate some of the material colour properties. Now the light striking the shadow regions is not white and therefore it appears as a colour cast.

 

That's the best that I can deduce.

 

Graham

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Dennis - In your defense when you state that this should not happen. I did during some of my research encounter an article that evaluated the Chief rendering plug-in. Overall they gave it a high ranking but did specifically comment that they felt there were some short comings in the way the plug-in dealt with lighting entering a room from exterior sources. Possibly we are experiencing this when the lighting conditions are not ideal. Will try to find the article again and post a link.

 

Would be interesting to know if those who upload their scenes to the full version of Pov-Ray experience the same issue.

 

Graham

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Dennis - had a chance to upload X8 so I took a look at your plan.

 

Though my camera position is different the effect of my adjustments demonstrate the effect.

 

The first two pics are as per your settings, only difference is the sun angle. The first is a 1 pass result and the 2nd is after 15 passes.

 

The two following pics, 1 pass & 15 passes, are after making a few adjustments. The only adjustments made were to the interior light intensity & balance and a few materials in respect to their emmisivity & roughness. The sun intensity & environment intensity is as per your original plan.

 

The light bleed has been brought under control and the reddish colour cast has almost been completely eliminated, would just need a little more fine tuning.

 

The output is also much cleaner with improved dynamic range.

 

Hope this helps to demonstrate that all is not lost when that light bleed and colour casting rears it's ugly head.

 

Graham

 

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Dennis - from my playing around I don't believe the light is actually leaking through the wall, it only appears to be. From what I can deduce it is actually the result of reflected light rays concentrating in shadowed regions. These shadow regions occur where two surfaces are perpendicular to each other, such as a wall ceiling intersect, wall corners, window/door casings and furniture placed against the wall. Raytrace only assigns so many rays to compute for each type of light, under extreme or difficult lighting situations the reflected rays striking these shaded intersect regions show up as pure bright white points. As you continue to render, more passes, Raytrace tries to smooth out the transition between the bright regions and the surrounding shadowed regions. Unfortunately it can only do so much with this. When you change the sun angle or intensity you are altering how and where the light rays strike the shadow region intersects.The colour cast that can also occur is the result of the reflected light being influenced by the material it is being reflected off of. In your scene it is aggravated by the furniture and window shutter colour/material properties. Brown contains a significant RGB red component, the originating light entering the room is white, upon striking these surfaces the reflected light will be altered from white and shifted to incorporate some of the material colour properties. Now the light striking the shadow regions is not white and therefore it appears as a colour cast.

 

That's the best that I can deduce.

 

Graham

That my friend is very clever!! I appreciate how you explained the science. Please keep up the good works. Your researches can help chief to improve.

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Thanks Yusuf.

 

I don't claim to be 100% correct on this but I am reasonably confident that the general principle(s) are applicable. I, like so many other users have really struggled to get acceptable Raytraces on a consistent basis, usually more on a hit and miss basis. As I started to dig deeper it eventually dawned on me to think about it from a photography perspective. Upon doing so my approach to lighting and material property adjustments changed significantly, this in turn resulted in much higher quality Raytraces in lower pass time. The other benefit was that when things don't come out right I can fairly quickly identify the culprit and make predictable adjustments. Not perfect but a huge improvement.

 

Many Thanks,

Graham

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My biggest frustration with ray traces is that we can always make them work, but as you have suggested, its similar to photography...we play with lighting and materials to get the desired affect.  Problem is that I personally don't want it to "look good" all the time.  What I'm after is realism, and often times the realistic settings are the ones that result in the light bleed, spottiness, and other various issues.  Once adjusted to alleviate the aforementioned issues, the scene is often flat, artificial feeling, or otherwise simply unrealistic.    

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Agee Michael - It's definitely a challenge to impart that sense of realism. And to your point Raytraces can have that "flat" look. I don't believe this can be fully accomplished using just standard light placement. Most likely 3D cameras will need to be strategically placed and adjust to create shadows and highlites within the scene. Often done in photography were a light might be placed behind say a couch to create a soft glow backdrop to impart a sense of depth. There may also be the need to perform post processing in PhotoShop if your going to crank-up the level of realism. Not many photographs go straight from the camera to print without significant post processing.

 

Graham

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Graham - appreciate your sticking with this.  I did not initially try some of those things as I did not think the light bleed

was related to the things you pointed out.  Wrong again..........

IAE, you got the immediate problem fixed.  Good lesson for all of us.  Thanks again!

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I'm having problems in interiors with no sun also, this bath with no windows, only two 100w spot lights, I'm having a shadow in the top part of the walls that dont' know what produces it, also the light bleed in corners. Don't know what to fix.

Make sun intensity Zero.

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Make sun intensity Zero.

 

Sun to zero solved the light bleed, so is a solution in interiors with no sun light. So the light bleed is produced by sun light only and it filters trough the ceilings and corners maybe?

 

the strange shadow in walls was solved erasing and placing again the the lights, it seems that there was a problem with them.

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