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Shader variables and expressions

M

mole_man99

Messages
172
Hi All

Getting into P3d V4.

I am trying to be clever with shader variables through PTA tool. PTA's own explanation of shader variables and expressions is a bit thin. I can not find in the SDK where the variables may be listed and explained.

Simple example from PTA
(saturate(1.0 - cb_Altitude/2438))

As PTA explain, this changes the saturation level above 2438m, but changes from what to what? Does the minus mean above or below the variable? Sometimes it is a plus symbol. Not sure how and when to use which.

Anybody know where it is hidden in the SDK learning centre, if there at all? I am assuming it's part of the P3D system, and not PTA specific.

Cheers

Graeme
 
As per the MS DX SDK HLSL documentation, the saturate function clamps the x parameter within the range of 0 to 1. The input value is 1.0 - cb_Altitude/2438 so the value of cb_Altitude is in meters. if altitude is < 2438, divide by 2438 will give you a value between 0 and 1. 1.0 - 0.6 for example will give a value of 0.4. If altitude exceeds 2438, you will get a value of > 1. Therefore 1.0 - 1.2 for example will give -0.2. A value of -0.2 passed to the saturate function will be clamped to 0.
 
Wow that's way beyond me.

I was wondering where the docs were, so they are in the DX SDK. I'll try downloading and see how I get on.

Thanks for the reply.
 
After my 15th read (and a helpful chap at AVSIM), the penny dropped. Thanks. Just downloading the docs to see about clamping a rigid value to a certain alt then having it reduce.

What a varied hobby this is.
 
Would be interested in seeing the post at avsim...link?
 
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