import { BufferGeometry } from '../core/BufferGeometry';

import { Float32Attribute, Uint16Attribute, Uint32Attribute } from '../core/BufferAttribute';

/**

* @author Mugen87 / https://github.com/Mugen87

*

* Parametric Surfaces Geometry

* based on the brilliant article by @prideout http://prideout.net/blog/?p=44

*/

function ParametricBufferGeometry( func, slices, stacks ) {

BufferGeometry.call( this );

this.type = 'ParametricBufferGeometry';

this.parameters = {

func: func,

slices: slices,

stacks: stacks

};

// generate vertices and uvs

var vertices = [];

var uvs = [];

var i, j, p;

var u, v;

var sliceCount = slices + 1;

for ( i = 0; i <= stacks; i ++ ) {

v = i / stacks;

for ( j = 0; j <= slices; j ++ ) {

u = j / slices;

p = func( u, v );

vertices.push( p.x, p.y, p.z );

uvs.push( u, v );

}

}

// generate indices

var indices = [];

var a, b, c, d;

for ( i = 0; i < stacks; i ++ ) {

for ( j = 0; j < slices; j ++ ) {

a = i * sliceCount + j;

b = i * sliceCount + j + 1;

c = ( i + 1 ) * sliceCount + j + 1;

d = ( i + 1 ) * sliceCount + j;

// faces one and two

indices.push( a, b, d );

indices.push( b, c, d );

}

}

// build geometry

this.setIndex( ( indices.length > 65535 ? Uint32Attribute : Uint16Attribute )( indices, 1 ) );

this.addAttribute( 'position', Float32Attribute( vertices, 3 ) );

this.addAttribute( 'uv', Float32Attribute( uvs, 2 ) );

// generate normals

this.computeVertexNormals();

}

ParametricBufferGeometry.prototype = Object.create( BufferGeometry.prototype );

ParametricBufferGeometry.prototype.constructor = ParametricBufferGeometry;

export { ParametricBufferGeometry };