cspears2002 Posted October 27, 2008 Share Posted October 27, 2008 I'm working on the 3d Buzz sprite rendering tutorial. I'm rendering out particles as sprites with the VEX Polka Dot shader attached to them. I want the Frequency and the Dot Color for the sprites to change on a per particle and a per frame basis. However, when I put the expression "rand($FF+$PT)*25" into the shader's Frequency parameter, I gott an error message: Unable to evaluate expression. Undefined variable. I played around with the expression. I think the shader parameters don't like the $PT variable. How can I get around this? sprites_v06.hipnc Quote Link to comment Share on other sites More sharing options...
rdg Posted October 27, 2008 Share Posted October 27, 2008 I think the shader parameters don't like the $PT variable. $PT is a local variable of some SOPs. You need to create an attribute and read this in the shader using a parameterVOP. Just like in this example: http://forums.odforce.net/index.php?showto...p;hl=$LIFE Instead of $LIFE you need to write $PT or you expression into the attribute. Quote Link to comment Share on other sites More sharing options...
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