another newbie light question

[sara]

I have just started playing around with 3D rendering and am having trouble with an interior shot. I've placed a point light in the center of the room, but the ceiling, which is white, keeps coming in grey in renderworks. I've bumped the brightness up and had a better result, except then the walls are getting washed out. Does anyone have any suggestions about how to use light on an interior rendering? Thank you for any help you can give.

[Guest]

White's are going to render as grey depending on how few lights you have and the direction of the light.

If you want the ceiling to light up brighter, point a light towards the ceiling.

Lights pointing down or at an angle, do not reflect on the ceiling and have it render white.

In a normal room in the real world, the ceiling is always a shade of gray because most light is difused down.

[bclydeb]

Lights and colors you don't expect things to be.

I think we all idealize the look we want to see in a room or ? However lighting in the real world does things we hardly notice until we try to light our CAD models. To help you anticipate light effects you will get in VW 3D - spend some focus time observing how rooms actually light up. Ceilings with lights mounted on them which are shining down are darker - because the ceiling is above the light source and only gets reflected light from other room sources.

Ceilings with Up-Down lighting have "pools" of light and shadow depending on the fall off of he light pattern between fixtures.

Think about how light actually bounces (straight line bounce based on angle of reflection = angle of incidence) - and that it falls off in brightness with the square of the distance. 1 lumen at one foot is 1/100th lumen at 10 feet.

Experiment a little with secondary light sources which produce a reflective bounce on your ceiling.

With VW and renderworks you can actually experiment with lighting scheme effects using multiple fixtures and light types.

If your room has a window - and the sun is "shining" you will get other effects. Setting the "bounce" factors in the views/rendering/custom render settings for ray tracing recursions give more realistic lighting. However I recommend you stay away from recursion levels greater than 2 for more complex rooms or areas. Shadow mapped shadows further enhace realism.

Experimenting with the ambiant light controls in a narrow range - say 40 to 60% may also help get the effect you envision. However use care to base your vision on the reality of light - or you get a very disappointed client!

Finally I reiterate - go to the real source of lighting - the world around you and take a deeper look at how lights, reflections, outside light and "brightness" levels affect spaces. Then come back to VW and apply what you have learned.

[MikeB]

Also remeber that RW is a RayTrace Renderer,it cannot "bounce" light. What this means in your rendering is if you have sunlight coming thru a window or a spot light shining down on to a reflective floor RW will not bounce that light back up to the walls and ceiling, so while the floor may be well lit, the ceiling will still be black, You have to set secondary light sources to fake the natural light works, or rather to fake the "bounce".

Like bclydeb said, look carefully around you and you will begin to notice how often things a lit indirectly by objects around them.

Most of the higher end rendering packages have Radiosity Rendering engins in addition to a ray trace engine, The radiosity engins can more accuratly render the characterists of natural light and can bounce light, but they can easily add hours or days to the time it takes to render a scene

What I'm trying to get at is, particularly with interior rendering, you have to fake the way natrual light works to get the scene to better represent reality.

Good Luck

[Dave Donley]

Hello Sara:

Here is an example of an interior with secondary point lights added. I added ones just above the bright patches on the floor to re-emit the light up to the walls and onto the column. Without these secondary lights only the floor would be lit and everything else would a single brightness (the layer ambient value) and flat-looking. The point lights were set to have a "Sharp" falloff so that their effects are localized to the area near the floor. When using Sharp falloff you usually have to bump up the light brightness a lot to see any effect from the light.

http://www.nemetschek.net/gallery/res_build/donley.html

[sara]

Thanks for all the advise. I've been working all morning with greater success, and a better understanding of what to expect. I appriciate everyone's help.

[Jershaun]

Hi Sara

One thing I have found that works to give me a better white finish is increasing the ambient light figure and also use a texture that has ambient set on high.

I agree with MikeB as well (light bouncing of surfaces). Maybe NNA should look into this for improving the renderworks engine.

Shaun