# ArnoAtWork

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1. ## Butterfly to Voronoi

Hello guys, I would like to tesselate a non-uniform patch resulting of a Delaunay triangulation. Unfortunately, the result is non uniform and Butterfly Tesselation can not be used. It seems that Voronoi algorithm can be used for this case. Unfortunately, I did not find any documentation. Do you know where to find it? Thanks very much, Arno.
2. ## Smooth

Hey guys, Do you know an algorithm to smooth an object with non-uniform faces(different size) but able to generate a result with fixed size faces? The only algorithm I see for this stuff is tesselation carring on subdividing edges until anyone is smaller than a specified size. However, it should be possible to convert this uniform vertex list into a patch of fixed size quad. Arno.
3. ## convert altmetry points into heightmap

Hey guys! In the system I am implemeting, I have to load a list of altimetry points. At first, I tried using Delaunay triangulation + tesselation. However tesselation is not uniform so I have faces of different size. However, I would like to have a heightmap. So how smoothing at specified step? Thanks for your help.
4. ## Hermite patch

Quote:Original post by griffin2000 You will need a border region of unused points along the edge of your surface however. Heu,...no. As you define your surface with only 4 vertices at time, there is no problem. In fact, with Hermite, you cut your patch in a subpatch of 2x2 vertices to generate the surface. For this reason, editing a control point means recalculating 4 subpatches around this control point. Quote:Original post by Basiror You want to have a look at natural cubic splines. I don't know a lot of surface type(only Bezier, Nurbs and Hermite). So this one seems good because you have controls points on surface. However I think that Hermite has an advantage. A control point can have 2 tangents per direction(u or v). It's then easy to "break" the surface curvature. Quote:Original post by griffin2000 True but they are (as I understanding by quickly skimming the link :-) ) less GPU friendly In my case it's not really the problem. But it's a good point however ;) Arno. [Edited by - ArnoAtWork on June 9, 2006 4:41:34 AM]
5. ## Hermite patch

"The patch goes trough the corner control points of the Bezier patch and the rest of the control points define the normals" The control points do not only define the normals but the behaviour of the curve. In Hermite case the patch go through all control points because you define a patch of four points and the calculation is done using position and tangents of each of these four control points...
6. ## Hermite patch

Unfortunately, the control points are altimetric data. In this case, surface must connect the control points. In the case of Bezier, control points are not on the surface.
7. ## Hermite patch

Hey guys! I am developping a landscape where I would like to generate a Hermite patch or a patch closed to its behaviour. What I need is a patch defined by positions and normals and with a surface going through control points. The problem is that I find a lot of documentation about 2D curve but not for 3D surface. Do you know where I can find it? Thansks a lot! Arno. [Edited by - ArnoAtWork on June 8, 2006 7:46:03 AM]
8. ## window selection

Thanks for your answer. The problem is that I must select only objects with at least 1 pixel visible in the selection window. To make the list of potential visible objects, I already have a portal engine. The problem is how to quickly find real visible objects.
9. ## window selection

Hey guys, I try to do a rectangle selection of visible elements in 3D application. And after several tests, I need help. Obviously, I begin by finding possible elements in the rectangle using a frustrum culling. I tried using ray - elements. But obviously, if you have a 1024x768 window, you have 1024 x 768 rays to test...to much for real time. I tried using OGL render mode (GL_SELECT). But if you make a window selection you just have the list of culled element, not the list of visibles. And I try using a selection zone of 1x1 for each pixel of the window selection. But too much element to render to have real time result. When I want to do a window selection I already have a OGL render(and so, Z buffer filled). So good think can be to do a ZEQUAL rendering and test if I re-write element. If so, i select it. For the moment I do not have occlusing query in my system. It seems to be good but probably a simpler approach can work. Thanks. Arno.
10. ## portal engine question

Thank you for you answer. It's clear. How to you manage complex wall(like arc wall,...) ?
11. ## portal engine question

Hey. I am developing an application allowing user walk trough architectural environment(home, ...). For this reason, I would like to cut world by room using doors and windows as portals. I read several papers of "normal" portal engine and I have several questions. * Cut environment in convex parts using BSP is it still interesting? Nowadays, I think not using ZBuffer test is not really interesting. But bsp allows quickly to find where an moving object is(with convex test). Without bsp, it's probably a pick to the ground which allows to find where a element is. In the case of complex rooms(a cavern, ...) with thousands of polygons, how BSP can do something correctly? In this case, it's impossible to find convex zones.. * How to manage big object crossing portals and being in several rooms at time? * Finally, occlusion query is a good technique to test if a portal is visible (after frustrum culling of course...). But I read that it's not really quick. In nvidia paper, it seems that occlusion query becomes quicker with new card. But is it quick? too slow? ok for less than N objects? Thanks you. Arno.
12. ## strange callbacks approach

Great !!! I use boost and then, my callbacks are as I wanted ! Thanks very much for your help. Arno.
13. ## strange callbacks approach

Hello, I am looking for a way to customised callbacks. I explain, Callbacks are used in a way that a base interface class exist with prototypes of methods. After that, several childs are implemented with method implementations. So, callbacks allows to register object pointer + function pointer. In my case, rather than writing prototypes methods, I just would like to register objects pointers + functions pointers but without knowing function name. I only knows parameter types and returned type of these functions. So object pointer can be of any type. Is it possible to cast function pointers?
14. ## GLSL & VBO

Huuuu, something strange When I test your function : LogGLInfoLog(...), nBytes is equal to 1, and so the log is null. Morever, glValidateProgramARB do not do anything? When I call after this function: glGetObjectParameterivARB(_id_sh, GL_OBJECT_VALIDATE_STATUS_ARB, &i_res), i_res is not changed. [Edited by - ArnoAtWork on July 13, 2005 11:47:59 AM]
15. ## GLSL & VBO

Ok, I am going to try and give you answer. Thanks for help.