myk45

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1. Visualizing Perspective projection

Thanks a lot max343
2. Visualizing Perspective projection

Hi max343, Wonderful reply! Thanks a lot! [i]Scaling a set of lines in a singular way is like identifying subsets of lines (in a non-singular way you just pack them closer or farther apart). For instance, if you have two different lines [x:y:z:w] and [x:y:z:w'] with w!=w', then scaling by [1,1,1,0] identifies these two lines. This correlates to projecting points in 3D space onto a plane, as many different points go to the same point on the plane.[/i] I had some difficulty following this. Could you please explain what you meant by "scaling by [1,1,1,0]"? Also, could you please point me to some book/link that talks about the exact same thing you posted about? Most books i've read do not go into these details [i]Also, a true projection matrix is indeed singular with a zeroed last column, as is yours. Projection matrices in graphics applications are a bit different, as they also compute the local coordinates of the point on the projection plane (up to the division factor) and preserve the depth information. However, these two operations have nothing to do with the projection per se.[/i] Yes, well i was not referring to the typical projection matrix defined by OpenGL. @alvaro No problem, Thanks
3. Visualizing Perspective projection

This is w.r.t Perspective projection and homogeneous coordinates. I have read that we use homogeneous coordinates when it comes to perspective projection. So, the very simple matrix is as follows:(to project a 3D point on a 2D plane) [1 0 0 0] [0 1 0 0] [0 0 1 0] [0 0 1/d 0] Where d = distance of plane onto which the projection is made. So, now i understand the following: 1) Use the matrix above to obtain a 4D homogeneous coordinate. 2) Do a perspective divide, thus obtaining the complete projection. Now, my question is this: What i do not understand is, what exactly is the result we get after step (1)? i.e how exactly do i visualize [x, y, z, z/d] as? I'm not able to figure this out. Can anyone please help me out on this? Thanks in advance!
4. Modelling Objects in a scene

Thanks a lot for the reply EndersGames. That was a lot of information. Just what i wanted to know. Well i actually am trying to build a scene. It involves a terrain and multiple objects too and with user movement. What would you suggest? Is it better i render the entire terrain? OR Shall i split the terrain into pieces and render them separately as you had suggested(ie depending on the user's location). >>>You only need to load 3 and draw them multiple times on the road Will that work fast? i mean rendering them multiple times? Thanks. [b] [/b] [b] [url="../../user/176637-endersgames/"] [/url][/b]
5. Modelling Objects in a scene

Hello Everyone, Well, last year, we had a course in Computer Graphics (with OpenGL as the API). i have some experience programming in OpenGL. Now here is my doubt: i was recently playing GTA SanAndreas.(Nice game!). i was wondering how the scene is handled. What i mean is, there is so much data including 3D models in the scene. How are they exactly rendered. For eg: this is what i generally do: /* set up projection and modelview matrix */ // now specify vertices. /* Finish */ Well, in a huge game like San Andreas, we have so many models(lets assume they are .obj files). Is this how it is done? /* set up projection and modelview matrix */ /* model object 1 */ /* model object 2 */ /* model object 3 */ /* model object 4 */ /* model object 5 */ /* Finish */ But aren't there so many models to be loaded? Are all models loaded at once and rendered? But that would mean huge amounts of data right? Can anyone please clarify how exactly its done? Thanks.