Lighting help

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Lighting help // Work in Progress

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Post by thescottishbloke // Apr 30, 2009, 7:40am

thescottishbloke
Total Posts: 56
Hi,


I need help please.


Ive started to work on a scene (no ground yet) but think ive got a few problems with lighting. When I use a image on the global illumination section part of my render comes in black and when I dont it looks a bit better. Also when I use the image my scene looks a bit blue. Can anyone help? Im using Vray. It aso looks as though there is a light in my building when I dont use a image.


Please :(

Post by TomG // Apr 30, 2009, 8:03am

TomG
Total Posts: 3397
Looks to me like there is a geometry error someplace - note the odd "shape" of lighting up top in the top image, and note in the second image this same area shows the texture while the rest is black.


This strongly suggests geometry errors that are confusing the renderer in both cases. Best would be to manually check for and fix those. Next best would be to try some automatic fixes, like using the Quadrify Polygons tool on the workspace side, or the "Try To Fix Bad Geometry" on the Model side.


I'm going to guess booleans were used to cut out the window shapes, and that these have left floating vertices - a search on this issue will turn up several detailed threads on the subject, and its also covered in one of our newsletters (http://www.caligari.com/news/news_200901/TipsNTricks_Ngon.html )


You could post a wireframe, or the actual scene too if it isn't protected, but I am 99% certain that geometry issues are the cause here rather than lighting issues.


HTH!

Tom

Post by Jack Edwards // Apr 30, 2009, 8:20am

Jack Edwards
Total Posts: 4062
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If you're using HDRI for your background image instead of a geometry based background like a plane, skycube, or skysphere, then the background will cast colored light onto your scene. If you lower the saturation in the HDRI parameter, you reduce the amount of color that the HDRI contributes to the scene. The default HDRI settings don't make any sense at all, so you'll want to set those back to more normal values, like 1.0 for intensity and saturation for starters.

Also I agree with Tom, that you've got bad geometry causing some problems.

Post by manxie // Apr 30, 2009, 9:25am

manxie
Total Posts: 76
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Hi Scottishbloke, producing buildings for an arch visual always requires boolean geometry and booleans can produce some really odd effects, I always save a scene before a boolean operation and only do one item boolean at a time and not a load of glued items which usually asks for trouble.

The lighting I always use is an area light with shadows and set the vray shadow value to around 800 as isle of man and scottish shadows are not well defined ie: sharp as we dont get sunshine like like spain or the amazon so keep it blurred for the reality effect.:D


Regards Manxie

Post by marcel // Apr 30, 2009, 9:44am

marcel
Total Posts: 569
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As tomG said i am sure at 99.99 per cent.
if you have not saved your scene before boolean operation you can try to repare the bad objet with news vertices between the corner of the windows or with triangulation. The solution depend of the real problem. We can't see it with these images. It is possible than the wrong geometry create bad normals on some face (the render show the colors which should be within the building).

Post by thescottishbloke // Apr 30, 2009, 10:39am

thescottishbloke
Total Posts: 56
Thanks people.


Where is the Try To Fix Bad Geometry tool?


Ive exported this model from autocad in a 3ds format for tuespace. Why does the bad geometry happen? Should I use another format?


:confused:

Post by Accu // Apr 30, 2009, 11:05am

Accu
Total Posts: 49
pic
Here's where you should find the Try to fix bad geometry tool on the model side...

Post by thescottishbloke // Apr 30, 2009, 11:18am

thescottishbloke
Total Posts: 56
I think im heading the correct way. Any comments? Is this heading towards a photorealistic image?

Post by TomG // Apr 30, 2009, 11:29am

TomG
Total Posts: 3397
Looking much better! The lighting does look pretty realistic to me, looking like late afternoon or so, on a sunny but relative cool or cold day.


There's a hint of bad geometry left up on the roof, and perhaps around one window.


If you want realism I would leave the lighting as is for now, and move to looking at texturing - some more variety and variation in the textures would be good. If the building is old, rather than completely brand new, you would want to add dirt, especially on the window frames and underneath those, and underneath the roof, perhaps some moss and other greenery on the brickwork under windows or around the base at ground level, etc.


If it is brand new you wouldn't want to add such aged dirt, but you would still need to add some "dirt" and variation so that not every brick looks the same (and not have it look like a repeating pattern).


It is looking really good though!


HTH!

Tom

Post by thescottishbloke // May 5, 2009, 10:21am

thescottishbloke
Total Posts: 56
Hi,


Ive developed my scene. Just one problem, im getting 2 shades of the same brick type of the one face of the building. Any suggestions? model, texture or lighting problem? Does anyone think this could be good enough for the competition and possibly get a mention on the web site for the finalists? I know the competition is tough :jumpy:


Any other tips would be greatfully accepted.

Post by Jack Edwards // May 5, 2009, 10:26am

Jack Edwards
Total Posts: 4062
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You definitely need to fix any render or geometry errors to get placed in the competition.

Not sure what the problem with the 2nd brick material, but it looks like you've added luminance to it and that it's "glowing". Could be that you have two overlapping polygons there.

You need a better concrete texture for the concrete part of the building.

Try Mayang's Free Textures:
http://mayang.com/textures/

And:
http://www.cgtextures.com/

Some other critiques, the image seems to lack contrast and the shadows don't have much depth at all. Make sure you don't have any ambient lights and that you're only using one infinite light to represent the sun light. Also there's some kind of funny yellow thing going on in the left side of the image.
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