4. Modeling grass

great work now we've got all the math we needed for a computer program to draw as many lines as we need to create a good approximation to a parabola let's return to some of the artistic aspects of grass starting with the width in this interactive I can move the points around and I haven't drawn the legs of the control polygon just to make it look a little bit simpler and let's see that kind of shape for the spine looks pretty good so let me move on to the next step which is to define the width and I'm going to do that using something we'll call a skeleton the skeleton is a set of lines like these that cut across the blade of grass at 90 degree angles so here's a skeleton line here's a skeleton line and so on and if I connect all the the left sides of the skeleton lines and the right side of the skeleton lines I create a region let me fill that in and that region looks a lot more like a blade of grass and I can control the width using this slider here so that's just adjusting the length of those skeleton lines and that with there looks pretty good and finally I can control the color I can go from a deep green to a lighter green to a really light green our artists control parameters like this to create the kind of convincing grass that you see in brave use this interactive to see what kinds of blades of grass you can create and then in the next video we'll talk about how to animate