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Sorting face indices...

Started by ogracian Mar 7, 2003 at 11:15 PM 1 replies 250+ views

Original Post

Mar 7, 2003 at 11:15 PM

Hello I am coding a KDT for my visibility test, and in general it works fine, but after read some docs about the odered vertex I noticed that my indices are all but ordered, for example. My faces indices (using indexed triangle list) has the following indices: 167 178 165 177 166 176 165 176 166 55 56 44 45 44 56 ..... And as far as I know this could hurt the performance, so I was wondering if someone could help me with a good algorithm to remap my faces indices in a more optimal way like for example: 0 1 2 3 2 1 3 4 5 ..... I really appreciate any help about this. Regards, Oscar Gracian

Osc

Mar 10, 2003 at 7:09 AM

Here's an easy one...

      
void RemapIndices (unsigned int* const indices, const unsigned int numIndices, Vertex* const verts, const unsigned int numVerts)
{
    assert(indices != 0);
    assert(numIndices > 0);
    assert(numVerts > 0);

    unsigned int i; // loop counter


    // allocate temporary storage

    unsigned int* const remap = new unsigned int [numVerts];
    assert(remap != 0);

    Vertex* const newVerts = new Vertex [numVerts];
    assert(newVerts != 0);

    // initialise

    const unsigned int NULL_INDEX = 0xffffffff;
    for (i = 0; i < numVerts; ++i)
    {
        remap[i] = NULL_INDEX;
    }

    // build new indices

    unsigned int next = 0;
    for (i = 0; i < numIndices; ++i)
    {
        if (remap[indices[i]] == NULL_INDEX)
        {
            remap[indices[i]] = next++;
        }

        indices[i] = remap[indices[i]];
    }
    assert(next == numVerts);

    // build new vertices

    for (i = 0; i < numVerts; ++i)
    {
        assert(remap[i] != NULL_INDEX);
        newVerts[remap[i]] = verts[i];
    }

    memcpy(verts, newVerts, numVerts * sizeof(Vertex));

    // free temporary storage

    delete [] newVerts;
    delete [] remap;
}

[edited by - Osc on March 10, 2003 8:49:35 AM]

[edited by - Osc on March 10, 2003 8:50:22 AM]

ogracian

Mar 11, 2003 at 1:31 AM

Hi Osc

Thanks for your replay!, it is exactly what i was looking for!

Best Regards,
Oscar

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