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[solved] Might be a bug for terrain block info building?
http://horde3d.org/forums/viewtopic.php?f=3&t=284		 Page 1 of 1
Author:  doublue [ 16.04.2008, 05:13 ]
Post subject:  [solved] Might be a bug for terrain block info building?
Sources excerpted from terrain.cpp:

Code:
            Vec3f corner0( minU + u * stepU, 0, minV + v * stepV);
            Vec3f corner1( minU + u * stepU, 0, minV + (v + 1) * stepV);
            Vec3f corner2( minU + (u + 1) * stepU, 0, minV + v * stepV);
            Vec3f corner3( minU + (u + 1) * stepU, 0, minV + (v + 1) * stepV);


            ......
            
            Plane tri0( corner0, corner1, corner2 );
            Plane tri1( corner1, corner2, corner3 );

            for( float vv = 0; vv <= stepV; vv += pixelStep )
            {
               for( float uu = 0; uu <= stepU; uu += pixelStep )
               {
                  Plane &curTri = uu <= vv ? tri0 : tri1;



Assume (0,0) to be the left-top corner (or any), as follows:

V0 -------V2
| Tri0 / |
| / |
| / Tri1|
V1--------V3

IMHO for statement curTri = tri0 iff uu <= vv to be true, the tri0 should be (V0, V1, V3) and tri1 (V0, V2, V3). Otherwise different rule for deciding curTri needed.
Author:  Volker [ 16.04.2008, 11:39 ]
Post subject:  Re: Might be a bug for terrain block info building?
I've not checked it in detail, but it seems to me that it does not make any difference. But I've found another problem in the terrain rendering.
I can't remember why we had the following statement in the drawTerrainBlock method in terrain.cpp

Code:
float newU = (s * scale + minU) * (terrain->_hmapSize - 1) + 0.4f;
float newV = (t * scale + minV) * (terrain->_hmapSize - 1) + 0.4f;


With this code, the rendering seems not to match with the blockInfo used for the frustum culling (You can check this setting the camera position to x = 278.97134, y = 62.080597, and z = 425.14410 and by adding the following line
to drawTerrainBlock method after the glDrawElements call)
Code:
   
Modules::renderer().drawDebugAABB(bb.getMinCoords(), bb.getMaxCoords(), true);


If you change it to...
Code:
float newU = (s * scale + minU) * (terrain->_hmapSize - 1) + 0.5f;
float newV = (t * scale + minV) * (terrain->_hmapSize - 1) + 0.5f;

...everything seems to be fine in the terrain example. Maybe someone else can check this. During a quick check it solves the still existing frustum culling problems also mentioned in this thread

Edit: To use the drawDebugAABB method correctly you should insert the following line after the if( saveStates ) statement:
Code:
glUseProgram( shader );
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