markerline Posted August 7, 2005 Share Posted August 7, 2005 Dear Users: I tried to create a 3D spiral using sin(), cos() and $PT as prescribed by the Expression Cookbook in the Help Documents. I came up with something very strange, but not a spiral. Can anyone help me out? I've attached the JPEG's so you can see what's wrong. I enhanced one of the JPEG's in Photoshop to have the expression from the POINT SOP floating over the viewport--it's not any new GUI thing. -penciline Quote Link to comment Share on other sites More sharing options...
markerline Posted August 7, 2005 Author Share Posted August 7, 2005 by the way, I started with a Circle SOP (NURBS) and piped this into a Point SOP to add the expression that would / should alter the geometry. Quote Link to comment Share on other sites More sharing options...
markerline Posted August 7, 2005 Author Share Posted August 7, 2005 by the way, I started with a Circle SOP (NURBS) and piped this into a Point SOP to add the expression that would / should alter the geometry. 20262[/snapback] In the JPEG that I posted the circle was closed, but I changed it to Open Arc and it still didn't resolve the issue. I think something is slightly wrong with my parameters in the expression, but I don't know exactly what. Any help is appreciated. -penciline Quote Link to comment Share on other sites More sharing options...
RickWork Posted August 7, 2005 Share Posted August 7, 2005 Hello penciline, Go to the parameters of your circle sop and increase the divisions to something like 300. You can leave the Arc type as open arc to help visualize the spiral. Cheers, Rick Quote Link to comment Share on other sites More sharing options...
markerline Posted August 7, 2005 Author Share Posted August 7, 2005 Hello penciline,Go to the parameters of your circle sop and increase the divisions to something like 300. You can leave the Arc type as open arc to help visualize the spiral. Cheers, Rick 20265[/snapback] Thanks Rick. That worked. Actually I used 360 for divisions to get a complete revolution (e.g. 360 degrees). I think that's why you have to ramp it up so high. -penciline Quote Link to comment Share on other sites More sharing options...
markerline Posted August 7, 2005 Author Share Posted August 7, 2005 Incidentally, I wonder why the Expression Cookbook uses cos($PT) and sin($PT) instead of cos($PT)^2 and sin($PT)^2 since I thought the equation of a circle is cos^2(x)+sin^2(y)=1. Any hints as to why? -penciline Quote Link to comment Share on other sites More sharing options...
deecue Posted August 7, 2005 Share Posted August 7, 2005 nope, it's right.. i.e. go put down any geometry and put cos($F) and sin($F) in to the x and z translates respectively. it will move in a circle along the xz plane.. Quote Link to comment Share on other sites More sharing options...
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