Talk:3D projection/Archive 1

Untitled

Archived on 11-09-2007 to coincide with new article text.

I think, the "Third step: perspective transform" is very hard to understand. It actually lacks explanations of how the formulas/projection matrix are created! The simplified version does not help about this issue, as here the formulas are missing as well, so you cannot conclude from the simple version to the projection matrix. Flipflix 19:07, 20 January 2007 (UTC)[reply]

1/tan = cot

Sorry, i changed the perspective disortion representation matrix a little bit, because i wanted to print it this way. If it's uncommon in computer graphics to use $\cot$ instead of ${\frac {1}{tan}}$ then i'll change it back.

please explain!

Projection onto 2D plane needs to explained more

I've been looking at the "simple version" of the projection onto a 2D plane and I don't understand why you say DX/DY is the distance on the XY plane and then give the two equations with the partial differentials in them without explaining how to get them from the distance formula. —The preceding unsigned comment was added by Maxvt103 (talk • contribs) 18:09, 18 February 2007 (UTC).[reply]

Field of view

Under the heading "Third step: perspective transform" the parameters mu and nu are introduced. Is it appropriate to say that these parameters refer to the camera's "field of view"? If so, it would be helpful to mention that and link to the field of view article. —The preceding unsigned comment was added by Alexdow (talk • contribs) 19:51, 21 February 2007 (UTC).[reply]

What's this doing here?

It almost seems like a better candidate for WikiBooks. --Thenickdude 10:39, 14 June 2007 (UTC)[reply]

I agree for large parts of the article. The "3 steps" section apparently describes one single method of 3D projection, but not 3D projection in general. There is no point explaining the multiplication of the three one-axis rotation matrices twice, but not mentioning that there are other ways to arrive at the transformation matrix (vectors, quaternions, ...) - (or not using any matrices at all). Maybe the world transform should just be mentioned, as it's not really that relevant for "3d projection" - it's more a specific detail you need (or not) depending on details of the 3d engine used. Also the "data necessary" section forgets to mention the camera specification data, which is crucial. But I don't want to just make big changes to the article unless everyone agrees that big changes are needed. --Allefant 09:52, 25 July 2007 (UTC)[reply]

I agree. This reads more like an article on DirectX rendering transforms than general 3D Projection. I would advise cutting out the world transformation, and refactoring this section to be relevant to a camera viewing 3d points in a generalised language. This should result in a much clearer and more useful article. Stestagg 17:45, 12 August 2007 (UTC)[reply]