Sprite Scale Driven By Image

[triptych79]

Hi,

I have sprites being emitted from a plane. The emission is being controlled with a gray scale image. I was wanting to drive the scale the of emitted sprites with the colour of the image (ie. the lighter the colour, the smaller the sprite). How would I go about doing this?

Thanks,
trip

[mayacner]

You could add the per-particle Attr parentU,parentV,spriteScaleXPP,spriteScaleYPP, first and use the expression to achieve it,
eg.float $u=parentU,float $v=parentV,float $rgb[]=colorAtPoint -o RGB -u $u -v $v yourTexture;float $lum=($rgb[0]+$rgb[1]+$rgb[2])/3;
spriteScaleXPP=spriteScaleYPP=$lum;
In order to prevent from the pop-up at the first frame,maybe you need to add the same expression in the creation expression:)