Graph Mapper and bi-rail

Replies to This Discussion

Permalink Reply by Hyungsoo Kim on September 25, 2016 at 9:28am

Hi.

A component displayed orange with warning means you haven't provided sufficient parameters yet.

Try this.

Attachments:

• BezierSpan+Sweep2.gh, 13 KB

Permalink Reply by David Rutten on September 25, 2016 at 9:48am

In addition to Hyungsoo's advice, there seems to be a deep misunderstanding here about how Grasshopper works. Objects to the left of other objects provide inputs and are never changed by whatever you do to the right of them. So if the Bezier Span component did something, it would do it on its own since it does not depend on anything else. Then, once it does its thing, the Graph Mapper gets to do its thing based on the result of the Bezier Span component.

In this case, even though both objects in your file use the word "Bezier", they have nothing in common. The Graph mapper takes in numbers (not curves, or points, or tangents, just single numbers) and projects those numbers onto the graph. Think of it as drawing a vertical line through the supplied number and finding the intersection point of that line and the graph. The output of the Graph mapper is then the y-coordinate of that intersection point.

It doesn't really matter what type of Graph you're using (Bezier, Parabola, Linear, Perlin, ...) only the Graph Mapper object knows and cares about this detail. The graph curve inside the Graph Mapper is not accessible to anything else, you cannot use that geometry in Rhino, and you cannot use that geometry in Grasshopper either.

Sigh, I have a feeling I'm doing a really bad job at explaining this today...

Permalink Reply by Birk Binnard on September 25, 2016 at 11:15am

Actually David your explanation is quite good.  The only thing I would have changed is to add the word "vertically": "... and projects those numbers vertically onto the graph..." And for continuity, "The output of the Graph mapper is then the Y-coordinates of their intersection points."

A good addition to your explanation would be how using the Domain object as an input can control the Graph mapper outputs.

Permalink Reply by Dave Harbour on September 25, 2016 at 8:21pm

Hyunqsoo, David and Birk,

Iam new to Grasshopper.  After looking at other examples of how Graph Mapper works and seeing Hyungsoo example I have a better idea of how to approach this.