Optimizing mesh creation

[hach-que]

I've got my terrain loading from Irrlicht into Newton. Problem is that a 256x256 grid results in 345600 faces being added to Newton. This (as you can imagine) takes a considerable amount of time to perform, not to mention the additional time when NewtonTreeCollisionEndBuild is called to actually put it into the collision format.

I want to know if there's anyway to optimize the speed of this (so that terrain loading takes under half a second, rather than 3 minutes). Has anyone done this before, and if so, how did you optimize it?

[Julio Jerez]

newton have a heygh field terrain, int will load in teh blink of an eye. and fopr 256 x 256 map it will be way unt 256k of memory

[hach-que]

The problem is, later on it won't just be a height map. The terrain format will support caves and extrusions not possible with a height map.

EDIT: I can't find the height map functions in the Wiki. Can someone point me to them?

[JernejL]

You can serialize trimeshes and load them so they are created instantly.

[hach-que]

Do I have to create serialize and deserialize callbacks? Or if I provide NULL is there some sort of inbuilt function that will handle it?

[Stucuk]

if you looked at userheightfieldcollision.cpp you would find that the demos used NewtonCreateUserMeshCollision to create the actual collision.

[Julio Jerez]

I think it is easier for him if he uses this instead:
NewtonCreateHeightFieldCollision

it loads in teh blink of and eye, and no code had to be written

[hach-que]

There doesn't seem to be a wiki article on that function Julio, so I have no idea how to use it

This is a line from the examples:

NewtonCreateHeightFieldCollision (nWorld, width, height, 0, elevations, attibutes, CELL_SIZE, ELEVATION_SCALE_INV);

I think I've been able to figure out how elevations is made, but I just wanted to check. Is it just an single array of height values?

I don't understand what CELL_SIZE and ELEVATION_SCALE_INV mean though.

[Julio Jerez]

NewtonCreateHeightFieldCollision (nWorld, width, height, 0, elevations, attibutes, CELL_SIZE, ELEVATION_SCALE_INV);

the elevations is an array of shorts
width and high are bitmap dimetions of the array
atribute is an array of bytes to enconde terrain properties like materials.

the 0, is diagionals 0, or 1 (you enable debig display so tat you see the layout of t eh digonal
CELL_SIZE, is the size in word unit tha convert eacg pixel cell to mesh cell,
ELEVATION_SCALE_INV is the scale the that convert an elvation to convert it to world units.

you use a collision offset matrix, or a body matrix to place it in any orienation you want.

[hach-que]

How do I arrange the array of shorts? I tried arrangement by X and arrangement by Z, but neither are an exact copy of the terrain. The testing spheres hit stuff in midair and go through the visible terrain as well.

Code: Select all

width = abs(terrain->getBoundingBox().MinEdge.X - terrain->getBoundingBox().MaxEdge.X);
            height = abs(terrain->getBoundingBox().MinEdge.Z - terrain->getBoundingBox().MaxEdge.Z);

            scalex = terrain->getScale().X;
            scalez = terrain->getScale().Z;

            elevations = (unsigned short*) malloc (width * height * sizeof (unsigned short));
            attibutes = (char*) malloc (width * width * sizeof (char));
            memset (attibutes, 0, width * height * sizeof (char));

            cout << "Heightmap information: " << endl
               << "  Width: " << width << endl
               << "  Height: " << height << endl
               << "  Cellsize X: " << scalex << endl
               << "  Cellsize Z: " << scalez << endl
               << "  Cells X: " << width / scalex << endl
               << "  Cells Z: " << height / scalez << endl;

            a = 0;
            for (int x = 0; x < height / scalez; x++ )
            {
               for (int z = 0; z < width / scalex; z++ )
               {
                  elevations[a] = terrain->getHeight(x * scalex,z * scalez);
                  a++;
               }
            }

            cout << "Heightmap is: " << endl;
            for (int b = 0; b < a; b++)
            {
               cout << elevations[b] << ",";
            }
            cout << endl;

            collision = NewtonCreateHeightFieldCollision (physworld, width / scalex, height / scalez, 0, elevations, attibutes, scalex, 1);

[Julio Jerez]

Code: Select all

width = abs(terrain->getBoundingBox().MinEdge.X - terrain->getBoundingBox().MaxEdge.X);
height = abs(terrain->getBoundingBox().MinEdge.Z - terrain->getBoundingBox().MaxEdge.Z);

// grid must be regule size scalez == scalex
scalez = terrain->getScale().Z;

elevations = (unsigned short*) malloc (width * height * sizeof (unsigned short));
attibutes = (char*) malloc (width * width * sizeof (char));
memset (attibutes, 0, width * height * sizeof (char));

a = 0;
for (int x = 0; x < height; x++ )
{
   for (int z = 0; z < width; z++ )
   {
      elevations[a] = terrain->getHeight(x, z);
      a++;
   }
}

// you need teh hight scale that is
// how many meter a unit is
// elevation goes frem -37766 tp 37637
// say scaleY  1 / 1000
//that mean thet higest mountant is 37 meters
collision = NewtonCreateHeightFieldCollision (physworld, width, height, 0, elevations, attibutes, scalez, scaleY);

then you need to position it with a the body matrix, therefore the x, or z is irrelevant because you can rotate the terrain to match the anything you want.

[hach-que]

I'm a little confused as to what 1 meter is in Newton. Is it 1 pixel? I know that 1 Irrlicht unit = 1 Newton unit. So how many Newton units is 1 meter?
a meter is that a meter.

You accidentally edited my post.

I do no undertand whey you find thos so hard, there is a demo that create a collision just like that. It is quiet simple

[Julio Jerez]

upps, sorry abopu that

[hach-que]

I'm still getting the scale wrong (hey, it's 32 degrees Celsius here ). The maximum value from getHeight is 256, so I put (256 / 37637) as the scale value, however all the balls drop onto a flat place.

[agi_shi]

Your units depend on your terrain/etc. size. If you terrain is supposed to be 1x1 kilometers, but it goes 1000 units in each directions, then that means that it's using meters. Therefore, you will want both Irrlicht and Newton to use meters (there is no "setting," just properly place your camera in Irrlicht and use the correct data in Newton).

Seriously, though, observe and play with the demo height field. See what changes what, etc.