//begin main function
int main (void)
{
int xsize = 800, ysize = 800 ;
gfx_open( xsize, ysize, "Test Graph of Function triangle_waveform" ) ;
int stillgoing = 1;
while (stillgoing) {
gfx_clear() ;
gfx_color(255, 255, 255) ; //axis is white
draw_axes( xsize, ysize) ;
gfx_color(150, 0, 255) ;
plot_triangle(xsize, ysize, -10., 10, .1) ;
gfx_flush() ;
char c = gfx_wait() ;
if (c == 'q') stillgoing = 0 ;
}
return 0 ;
} //end main
/* Draw a set of 3D triangles on the canvas. Each point in geometry is
* formatted (vx, vy, vz, nx, ny, nz, s, t). Don't forget to clip the
* triangles against the clipping planes of the projection. You can't
* just not render them because you'll get some weird popping at the
* edge of the view. Also, this is where font/back face culling is implemented.
*/
void canvashdl::draw_triangles(const vector<vec8f> &geometry, const vector<int> &indices)
{
update_normal_matrix();
mat4f transform = matrices[projection_matrix]*matrices[modelview_matrix];
vec4f planes[6];
for (int i = 0; i < 6; i++)
planes[i] = transform.row(3) + (float)pow(-1.0, i)*(vec4f)transform.row(i/2);
vec3f eye = matrices[modelview_matrix].col(3)(0,3);
vector<pair<vec3f, vector<float> > > processed_geometry;
vector<int> processed_indices;
processed_geometry.reserve(geometry.size());
processed_indices.reserve(indices.size());
vector<int> index_map;
index_map.resize(geometry.size(), -1);
for (int i = 0; i < indices.size(); i += 3)
{
vector<pair<vec8f, int> > polygon;
for (int j = 0; j < 3; j++)
polygon.push_back(pair<vec8f, int>(geometry[indices[i+j]], indices[i+j]));
vector<pair<vec8f, int> > clipped;
for (int j = 0; j < 6; j++)
{
pair<vec8f, int> x0 = polygon[polygon.size()-1];
float d0 = dot(homogenize(x0.first), planes[j]);
for (int k = 0; k < polygon.size(); k++)
{
pair<vec8f, int> x1 = polygon[k];
float d1 = dot(homogenize(x1.first), planes[j]);
float del = dot(homogenize(x1.first) - homogenize(x0.first), planes[j]);
float p = -d0/del;
if (d0 >= 0.0 && d1 >= 0.0)
clipped.push_back(x1);
else if (d0 >= 0.0 && d1 < 0.0)
clipped.push_back(pair<vec8f, int>((1-(p+0.001f))*x0.first + (p+0.001f)*x1.first, -1));
else if (d0 < 0.0 && d1 >= 0.0)
{
clipped.push_back(pair<vec8f, int>((1-(p-0.001f))*x0.first + (p-0.001f)*x1.first, -1));
clipped.push_back(x1);
}
x0 = x1;
d0 = d1;
}
polygon = clipped;
clipped.clear();
}
if (polygon.size() > 2)
{
for (int i = 0; i < polygon.size(); i++)
{
vector<float> varying;
vec3f position;
if (polygon[i].second == -1)
{
polygon[i].second = processed_geometry.size();
position = matrices[viewport_matrix]*homogenize(shade_vertex(polygon[i].first, varying));
polygon[i].first = position;
processed_geometry.push_back(pair<vec3f, vector<float> >(position, varying));
}
else if (index_map[polygon[i].second] == -1)
{
index_map[polygon[i].second] = processed_geometry.size();
polygon[i].second = processed_geometry.size();
position = matrices[viewport_matrix]*homogenize(shade_vertex(polygon[i].first, varying));
polygon[i].first = position;
processed_geometry.push_back(pair<vec3f, vector<float> >(position, varying));
}
else
{
polygon[i].second = index_map[polygon[i].second];
polygon[i].first = processed_geometry[polygon[i].second].first;
}
}
for (int i = 2; i < polygon.size(); i++)
{
vec3f normal = cross(norm((vec3f)polygon[0].first - (vec3f)polygon[i-1].first),
norm((vec3f)polygon[i].first - (vec3f)polygon[i-1].first));
if (culling == disable || (normal[2] >= 0.0 && culling == backface) || (normal[2] <= 0.0 && culling == frontface))
{
processed_indices.push_back(polygon[0].second);
processed_indices.push_back(polygon[i-1].second);
processed_indices.push_back(polygon[i].second);
}
}
}
}
for (int i = 2; i < processed_indices.size(); i+=3)
plot_triangle(processed_geometry[processed_indices[i-2]].first, processed_geometry[processed_indices[i-2]].second,
processed_geometry[processed_indices[i-1]].first, processed_geometry[processed_indices[i-1]].second,
processed_geometry[processed_indices[i]].first, processed_geometry[processed_indices[i]].second);
}
