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pavel989

hello, i need a simply explanation

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Ok, so ive done a lot of research on Homogeneous Coordinates. and im still not sure what they are. ironically, im currently taking geometry (im in highschool) but don't really remember a lot of the functions and stuff. so, i need a simplyfied explanation of these. ive always thought that there would simply be an x,y, and z cordiante, and from my udnerstanding thats all that there is, so why is there a w. does it modify the location of an object. Im learning OpenGL, if that matters, but id assume that all libraries and stuffs have that concept.

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For most basic purposes, you can ignore W. The reason it is there is that OpenGL is based on matrix maths, and for an n-dimensional system you need to allow square matrices of size (n+1) to be able to represent translations. That is the reason that PostScript has a 3x3 transformation matrix (being a 2D environment) and the reason OpenGL has a 4x4 one (being 3D).

Now, once you have a 4x4 system you open the door to having the 4th coordinate (w) set to things other than 1, which can be very useful in certain circumstances (often to do with reflective texture mapping and 'environment mapping'). However, if all you are wanting to do is draw objects in a scene with static (or no) textures you can ignore w.

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