sprite node in the rendertree is just a way of doing tranparency (its resetting the raycount on each incursion I think) - so you can get through a lot of transparent surfaces without increasing the raydepth. It has nothing helpful to offer to help with uv coordinates on particles.
particles in softimage are points - and you can give them a single UV value easily enough - as discussed here that will just enable you to get the proper color for the texture map. certain shapes have uv coordinates built in - such as the sphere or rectangle - which by default will map a single image on the entire surface. the obvious solution is to combine the single color from the underlying texture with a transparency map on the particle to give them some shape and variation - it can give you the (flawed) appearance of tearing up a surface into pieces - (hint: besides the uv you can also use the normal at the surface which will give you identical shading - very helpful!) - but its not gonna be a proper crop from the texture on the emitting surface. by calculating proper UV remap values you can crop a part of an image - so technically your solution is there. (if you're fine with flat rectangular particles that is) and the link you gave seems to have solved that. With an ordered grid with a rectangular mapping it shouldn’t be too hard to do. 5x5 grid - so each particle will have coords from 0-0.2 with offsets in multiples of 0.2 in U and V - you get the idea. With an arbitrary polymesh surface, having an arbitrary UV set, likely with seams and arbitrarily sized particles, calculating those proper remap values is much more complex, and way above my head for sure. In such a situation I'd rather got the route of fracturing the object, and instancing the individual pieces to particles - but that is quite a different proposition and you will hit performance problems with 100k particles for sure. And there is Guillaume's addon to transform polygons by particles - which is very nice for performance - if the shape of individual polygons is ok for you. -----Original Message----- From: olivier jeannel Sent: Tuesday, October 01, 2013 12:18 PM To: softimage@listproc.autodesk.com Subject: Re: Particle "taking uvs" from it's emitter Damn, that's annoying... What about the Sprite node ? SecondReality did something https://vimeo.com/34463159 But on a grid (my object is 3D with a lot of particles and overlaps) Le 01/10/2013 12:05, pete...@skynet.be a écrit : > you're not missing something, this is totally normal. > at any given position (location) you have a single UV coordinate (one u > and > one v value) - so that will result in a single color for the whole of the > particle. > > in order to get the corresponding crop from the texture, you would need 4 > uv > coordinates for the four corners of a grid assuming your particle is a > rectangle - but a particle is a single point so that’s just not going to > work. (yes - you could save 4 attributes but you can't interpolate between > them in the rendertree) > I guess *in theory* it could be done, by calculating proper values to > drive > the UV remap in a texture node, for each particle based on it's position > in > the UV set and size - and saving those in a number of attributes - - but > this is far from trivial. And you couldn’t account for seams in the map. > > > -----Original Message----- > From: olivier jeannel > Sent: Tuesday, October 01, 2013 11:18 AM > To: softimage@listproc.autodesk.com > Subject: Re: Particle "taking uvs" from it's emitter > > Sorry Grahame, but it's not working. I mean it just gives a a color to > the particle, but not the piece of texture Uvs corresponding to its Emit > Location. > Here's a screengrab, I probably miss something : > > Le 30/09/2013 21:11, Grahame Fuller a écrit : >> Plug Self.EmitLocation into the source port of a Get Data, then get >> cls.Texture_Coordinates_AUTO.Texture_Projection.UVs. >> >> gray > > > > > > > -------------------------- > To unsubscribe: mail softimage-requ...@listproc.autodesk.com with subject > "unsubscribe" and reply to the confirmation email. > > -------------------------- > To unsubscribe: mail softimage-requ...@listproc.autodesk.com with subject > "unsubscribe" and reply to the confirmation email. -------------------------- To unsubscribe: mail softimage-requ...@listproc.autodesk.com with subject "unsubscribe" and reply to the confirmation email. -------------------------- To unsubscribe: mail softimage-requ...@listproc.autodesk.com with subject "unsubscribe" and reply to the confirmation email.
