Generating some stuff

geometry.c

#include "math.h"
#include "stdlib.h"
#include "geometry.h"

//Inputs:
//verts: The higher the number the more vertices and the smoother the cylinder, number of verts on each side.
//size: distance of the vertices from the center.
//width: the thickness of the cylinder
//return: pointer to memory on heap, contains points in size verts*2
mesh generateCylinder(int verts, float size, float width)
{
	point *vertData = malloc(sizeof(point)+sizeof(point)*verts*2);
	if(vertData == NULL) exit(0);
				
	float angIncrement = (2*M_PI)/verts;
	int i;
	for(i = 0; i < verts; i++)
	{
		float curang = angIncrement*i;
		point vertPoint = {cos(curang), sin(curang), 0.0f};
		
		vertData[i*2] = vertPoint;
		vertPoint.z += width;
		vertData[i*2+1] = vertPoint;
	}
	vertData[verts*2+1] = vertData[0];
	
	mesh cylinderMesh;
	cylinderMesh.vertCount = verts*2+1;
	cylinderMesh.vertices = vertData;
	return cylinderMesh; //we're good.
}

geometry.h

typedef struct {
	float x;
	float y;
	float z;
} point;

typedef struct {
	int vertCount;
	point* vertices;
} mesh;

mesh generateCylinder(int verts, float size, float width);

main.c

#include "stdio.h"
#include "geometry.h"

int main()
{
	FILE *vertFile = fopen("verts.txt", "w");
	
	if(vertFile == NULL) 
		return 1;
	
	mesh cylinder = generateCylinder(3, 2, 1);
	point* verts = cylinder.vertices;
	int i;
	for(i = 0; i < cylinder.vertCount; i++)
	{
		fprintf(vertFile, "%lf %lf %lf\n", verts[i].x, verts[i].y, verts[i].z);
	}
	
	fclose(vertFile);
	return 0;
}