# Planetside Software Forums

## General => Terragen Discussion => Topic started by: Thelby on July 27, 2009, 10:37:32 pm

Title: A Bug Maybe?
Post by: Thelby on July 27, 2009, 10:37:32 pm
I was showing someone how the bump (Displacement) worked in TG2 and discovered a shadow that popped up when using a negative value. However it does not start until the 1 crosses the decimal point on the left. Example: Default value displacement is 0.01, make it negative -0.01 and is OK. It is OK at -.1 also, but make it -1 and the problem starts.
The first image is Default Displacement 0.01.
The second is with -1 Displacement.
Title: Re: A Bug Maybe?
Post by: Matt on July 27, 2009, 10:58:08 pm
The shadow tracer doesn't recognise displacements on objects (only on planets, spheres and planes). Displacement should be kept to small values and should always be positive to prevent the surface from sinking into regions of shadow.

(Sometimes a small negative displacement is OK, but it's safer to avoid it completely.)

Matt
Title: Re: A Bug Maybe?
Post by: Thelby on July 27, 2009, 11:04:21 pm
Will that change in the future at some point? I mean having displacement on an object, say a house is essential to the realism of the scene. Just asking!!!
Title: Re: A Bug Maybe?
Post by: Matt on July 27, 2009, 11:10:08 pm
Yes, some day :)

You can already use displacement, and it affects the shading of the surface, it's just that the shadows don't see it.

Matt
Title: Re: A Bug Maybe?
Post by: Thelby on July 27, 2009, 11:13:07 pm
So instead of using a bump map that needed a negative value it would be better to invert it before using it to avoid this altogether.
Title: Re: A Bug Maybe?
Post by: Matt on July 28, 2009, 02:22:14 am
You can use a negative displacement amount if you compensate with a positive displacement offset. If you need a displacement of -1, set the displacement offset to +1.

Matt