Timeline for What does the graphics card do with the fourth element of a vector as the final position?
Current License: CC BY-SA 3.0
9 events
| when toggle format | what | by | license | comment | |
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| Oct 2, 2011 at 14:34 | vote | accept | CommunityBot | ||
| Oct 2, 2011 at 14:34 | comment | added | user5399 | @Nathan, I can see clearly now the purpose of the fourth element, and how the information it contains is used by the rasterizer. Thanks a lot! | |
| Oct 2, 2011 at 10:13 | comment | added | FxIII | @NathanReed I hope that my post helps to clarify the point, anyway a large part of my point is upon definitions and the misuse of the term vector plus the primacy of linear algebra over the standard 3D library terminology. Of course both are debatable as every definition and primacy claim is | |
| Oct 1, 2011 at 23:11 | comment | added | Nathan Reed | @FxIII and Nicol Bolas: I disagree. You really do encode vectors as w = 0 - including both vectors that just represent a direction, and actual vectors where the length is important. For instance, you can transform the angular velocity vector (direction = rotation axis, length = speed) of an object between local space and world space using the object's matrix. You don't want the angular velocity to get the object's translation added to it; you only want it to be rotated. So you set w = 0. I don't see the problem? | |
| Oct 1, 2011 at 21:57 | comment | added | Nicol Bolas | @FxIII: Corrected. It was confusing to use "vector" in the standard math sense and as a synonym for "direction" in the same post. | |
| Oct 1, 2011 at 21:56 | history | edited | Nicol Bolas | CC BY-SA 3.0 | added 12 characters in body |
| Oct 1, 2011 at 21:17 | comment | added | FxIII | Once again is slightly incorrect to talk about vectors and points in those terms since there is an isomorphism between points and vectors (the point and the vector that move the origin to that point are the same entity). Would be more correct to talk about points/vectors (w!=0) and (projective)directions (w=0). Anyway the misuse of the term "vector" is a quite consolidated standard in the 3d libraries language. | |
| Oct 1, 2011 at 16:09 | history | edited | Nathan Reed | CC BY-SA 3.0 | added 197 characters in body |
| Oct 1, 2011 at 15:59 | history | answered | Nathan Reed | CC BY-SA 3.0 |