Forums > Jitter

Linear control matrix grid in nurbs

Aug 01 2010 | 7:35 pm

I hope my english is comprehensible…

I need to keystone a video on a curved surface. The classic 4 corner pin keystoning isn’t suitable for my needs, since I also need to correct the distortion of the plane on the projection surface.

I thought that a nurb with a video-texture would have been a solution so I downloaded the Jitter Recipes Book n°2 and messed with the Recipe 18: Manipulator, to learn the basics.

The patch is almost perfect, but the control point grid generated by the message exprfill "snorm[0]" is not a linear grid. You could see it by activating the "draw as mesh" toggle. It’s a grid that is somewhat larger on the sides and narrower at centre. In fact, the attached video texture has a slight barrel distortion.

I tried to change the message, but I couldn’t figure out what is the right function to generate a simple equidistant grid of control points. Can someone help me?

My patch is very similar to Recipe 18, but, here it is anyway:

-- Pasted Max Patch, click to expand. --

Aug 01 2010 | 9:52 pm

When you send order 1 1 it looks equidistant, doesn’t it ?

Aug 01 2010 | 9:52 pm

I’m sorry, adding the message ctlshow $1 made me realize that the control matrix is perfectly linear. The problem is in the mesh itself and how the video texture is applied to it.
Some advice?

Aug 01 2010 | 9:53 pm

Yes, when I send order 1 1 it looks equidistant… I have a lot to learn, thanks…

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