HLSL: What represents the 4th component in a float4/vector?

OnyxIdol · Post by **OnyxIdol** » Sat Jan 31, 2009 12:26 pm

Ok, the internet didn't turn anything up on this, maybe its just too obvious. What, exactly, represents the 4th component in a float4/vector variable?

I am currently writing a shader, using Nvidia FxComposer(Great tool btw) and setting the 4th component of my global variables to zero produces some strange effects, such as stretching an object to infinity in case of a position vector. Setting it to 1 seems straightforward enough, yet I'd like to know what I'm dealing with.

Mel · Post by **Mel** » Sat Jan 31, 2009 12:32 pm

Normally, in position vectors it is always 1. In fact float4() is a flexible object, and thus, the 4th component can be used in many ways. for example, in colors, the 4th component is the alpha channel. So, if you want to use position vectors, just stick to the 3 first, and ignore the 4th. It will work well in any case

OnyxIdol · Post by **OnyxIdol** » Sat Jan 31, 2009 12:40 pm

Thx for the answer. But As I said, setting the 4th component in a position Vector creates really strange effects, i.e. it must have some meaning in a position vector as well.

BlindSide · Post by **BlindSide** » Sat Jan 31, 2009 12:47 pm

It has to do with perspective projection. It's called the W component. Read up on that.

OnyxIdol · Post by **OnyxIdol** » Sat Jan 31, 2009 12:50 pm

I will do that. Thank You.

Edit:
This thread can now be considered closed.

Acki · Post by **Acki** » Sat Jan 31, 2009 5:51 pm

OnyxIdol wrote:some strange effects, such as stretching an object to infinity in case of a position vector. Setting it to 1 seems straightforward enough

I'm just guessing, but this sounds to me that in your case the 4th number could be a scale factor !?!?!

Irrlicht Engine

HLSL: What represents the 4th component in a float4/vector?

HLSL: What represents the 4th component in a float4/vector?

Re: HLSL: What represents the 4th component in a float4/vect