Ray Trace Contrast

[Tomhinz57]

Version X6. How do you control the contrast of the shadows on a ray trace? Tom

[Barton_Brown]

Discussion of the Image Properties Panel starts on page 928 in the X6 Reference Manual. Once a Ray Trace has been started, these settings can be modified.  The panel includes brightness, contrast, saturation.

 

While the Image Properties Panel allows one to change characteristics of the existing image, it is working with the lighting of the existing image, if the lighting is poor, correcting the image with the Image Properties Panel will be a struggle.

 

On page 926 of the Reference Manual is the discussion of the lighting options in the Ray Trace Options dbx - altering values in the dbx can have a huge impact on the contrast of the ray trace image.

 

Question: are you doing indoor or outdoor ray traces? The values of 'direct sunlight' and 'ambient light' can both effect how much contrast exists in your 'default' image (ie, image not modified by the Images Properties Panel).

 

Obviously, if the image is outdoor, the sun intensity value has a big impact and should be much larger than the 'ambient light' values. 

 

If you are doing indoor images, the more lights you have on, the brighter (better contrast) will be your image. Also, the more passes you let the ray trace run, the better will be the image. If you happen to make your walls, ceilings, or floors slightly emissive because you don't have enough lights, then your image contrast will look 'flat' compared to a scene without emissive walls, floors, or ceilings.

[Barton_Brown]

Tom, if you have some specific examples of contrast situations you would like to control, please provide some details. The details will help responders to your question provide more specific answers. Thanks.

[Dennis_Gavin]

Tom - For interiors pay attention to what BArton suggested regarding the ambient light setting. I find that in some situations I need to crank up the ambient light. It looks too bright in standard render but when ray traces the results are much better. There can also be a big sifference when using photons versus not using photons. Play around with trying it with small screen sizes (another setting) to get a quicker peek.

[IanPellant]

Some tips:

Set the North and Sun Ngles to get a balance of light and shade on the facade

Go to 3D View Defaults <Ctrl> <1> and zero out all of the Lighting Options... these Default lights play havoc with the Ray Tracer

In the Ray Trace Options, set Uniform Intensity to 0.5; Direct Sunlight to 5.0; Environment Light to 0.5

If you have some outdoor light fittings turned on... Use Photon Mapping; otherwise leave Photons Off for quick Ray Traces

 

The ray trace wizard is not good for outdoor traces.

 

The key that took me ages to find was that Chief has Default Lights that ensure internal perspective renders will be illuminated.... these settings confound outdoor ray tracing... So zero out the 3D View Lighting Options before doing a Ray Trace. Reset them back to high Ambients for workaday camera views.