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RandyGaul avatar RandyGaul commented on May 3, 2024

From header docs

// runs c2Hull and c2Norms, assumes p->verts and p->count are both set to valid values
void c2MakePoly( c2Poly* p );

So we look over at c2MakePoly source

void c2MakePoly( c2Poly* p )
{
    p->count = c2Hull( p->verts, p->count );
    c2Norms( p->verts, p->norms, p->count );
}

Up a couple lines up we see

norms[ i ] = c2Norm( c2CCW90( e ) );

Looks like all of the values of c2Poly are set by c2MakePoly, and initially you must set verts and count to valid values. So what are valid values? We find some more clues from the docs

// Computes 2D convex hull. Will not do anything if less than two verts supplied. If
// more than C2_MAX_POLYGON_VERTS are supplied extras are ignored.
int c2Hull( c2v* verts, int count );

// this can be adjusted as necessary, but is highly recommended to be kept at 8.
// higher numbers will incur quite a bit of memory overhead, and convex shapes
// over 8 verts start to just look like spheres, which can be implicitly rep-
// resented as a point + radius. usually tools that generate polygons should be
// constructed so they do not output polygons with too many verts.
// Note: polygons in tinyc2 are all *convex*.
#define C2_MAX_POLYGON_VERTS 8

Looks like we need more than two verts, and that's it. Set the vertices to floating point values, set the count to however many vertices we have, and use c2MakePoly. It will compute how many vertices are on the convex hull, it resets c2Poly::verts and c2Poly::count, and then sets c2Poly::norms.

Additionally, here's some snippets from examples file
https://github.com/RandyGaul/tinyheaders/blob/master/examples_tinygl_and_tinyc2/main.cpp#L592
https://github.com/RandyGaul/tinyheaders/blob/master/examples_tinygl_and_tinyc2/main.cpp#L773-L793
https://github.com/RandyGaul/tinyheaders/blob/master/examples_tinygl_and_tinyc2/main.cpp#L836

Also we see here an example of manually constructing some AABB polys
https://github.com/RandyGaul/tinyheaders/blob/master/examples_tinygl_and_tinyc2/main.cpp#L797-L816

from cute_headers.

felselva avatar felselva commented on May 3, 2024

Thanks for the detailed info!

from cute_headers.

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