Polygon mapping not good

[Julien-Robert]

I'm using polygons to select parts of my video and map it to the output in advanced output.
The way Arena transform polygons is not good for me, it king of divide the form in triangles and then the transformation is not straight (see image). It doesn't act like that with slices. The problem is that my input doesn't have straight rectangles to select.
Do you have a trick or a workaround to avoid that?

[elgarf]

It doesn't act like that with slices. The problem is that my input doesn't have straight rectangles to select.
Do you have a trick or a workaround to avoid that?

What about using regular slices with Input Mask?

[Julien-Robert]

Yes with regular slices and input mask I managed to do something, it’s just very longer to do the mapping. And sometime it’s not perfectly right since part of slices (because I put doesn’t match so it’s taking part of the polygon next to it) come in front of others.

[Zoltán]

I guess you're trying to projection map onto irregular shapes.
Try working a bit backwards,
create a polygon that has about the required number of edge points, (don't worry, you can add or remove points later ay time by a double click)
then align it in Edit points mode in the Output transformation to your object.
Now go back to the Input selection, right click on the slice and select Match output shape.
This should get your output distortions flat again, and you can move the Input slice to the position you'd like.

Have a look at this link for a quick explanation why polygons are triangles: https://www.quora.com/Why-do-we-use-tri ... of-squares

[VentMedia]

This seems a bit of a poor workaround. Impossible to prepare the mapping prior to being on site.
Polygon mapping needs to have the facility to have a more complex mesh otherwise they're unusable on irregular shapes

[Zoltán]

Polygons are triangles, because that's the simplest what GPUs understand, and are the fastest to work with processing vise:
https://www.quora.com/Why-does-graphics ... -triangles

If you want to map on irregular shapes, try using rectangle slices with Input masks.

Here you can also find a more detailed explanation about why Resolume uses triangles for polygons https://resolume.com/support/en/input-s ... gon-slices TL;DR because of math.

[francoe]

This seems a bit of a poor workaround. Impossible to prepare the mapping prior to being on site.
Polygon mapping needs to have the facility to have a more complex mesh otherwise they're unusable on irregular shapes

True.
I'm an R fan, but ended using another tool when polygons are mandatory.