void PerlinNoise_Impl::create_noise2d(PerlinNoise_PixelWriter &writer, float start_x, float end_x, float start_y, float end_y)
{
float size_x = end_x - start_x;
float size_y = end_y - start_y;
float fheight = (float) height;
float fwidth = (float) width;
for (int y = 0; y < height; y++)
{
for (int x = 0; x < width; x++)
{
float result = 0.0f;
float current_amplitude = amplitude;
float value_x = start_x + (((float) x) * size_x) / fwidth;
float value_y = start_y + (((float) y) * size_y) / fheight;
for( int i=0; i<octaves; i++ )
{
result += current_amplitude * noise_2d(value_x, value_y);
value_x *= 2.0f;
value_y *= 2.0f;
current_amplitude *= 0.5f;
}
writer.write_pixel(result);
}
writer.line_end();
}
}
inline float smoothnoise_2d(float fx, float fy)
{
int x, y;
x = fx, y = fy;
float V1=noise_2d(x, y);
float V2=noise_2d(x+1,y);
float V3=noise_2d(x, y+1);
float V4=noise_2d(x+1,y+1);
float I1=interpolate(V1, V2, fx-int(fx));
float I2=interpolate(V3, V4, fx-int(fx));
float I3=interpolate(I1, I2, fy-int(fy));
return I3;
}