View Full Version : Object dissolve/Weight maps...Possible???

09-15-2009, 08:59 AM
ok.. i've wasted enough time scratching my head....time to ask for help.

I have some complex geometry (multiple surfaces) and i want to build up with a flyround animation...ie-camera pans around whilst the object builds from the ground up.

Ive split the object into several layers and could easily envelope the object dissolve for each of these over a time sequence. However-im looking to produce something a little slicker than just have the whole layer appear from 0-100% in one go!. Ie-have the object dissolve along certain paths and directions. Question is......is there away of controlling an objects dissolve using a weight map? Again, the object consists of several surfaces so driving the transparancy via the surface editor is a no no.

Any suggestions/pointers greatly appreciated.....oh and fingers crossed I make sense and not babbling too much :tongue:

Edit: Come to think of it maybe im over complicating things. Perhaps a means of creating an animated mask would do the trick but how?

09-15-2009, 09:05 AM
Sadly you can't animate gradients in the basic texture editor. So you may look into using the node system. You can use a weight map as the input value of a gradient. Then you can animated the values and keys of the gradient as you do your reveal of each part. You would have to do it per surface instead of object though, if you go that way.

The good news is.. If you take for example your wheel, and you want it to fade in from one side to the other, you could create your weightmap in modeler, then create your node setup for the rubber surface to just control transparency, nothing else (that way all your texturing still applies if you used the classic surface editor). Then animate a gradient key's position to produce your swipe. Finally just copy those nodes, go to all the other surfaces on the wheel and paste them in. Keep in mind each wheel will get effected unless you have a unique surface applied or they are saved as their own objects.

I don't think there is a way to put a texture into object dissolve. Just an envelope. Clip maps can take textures but they are only on or off, no soft transparency.

Just 1 idea.

09-15-2009, 09:14 AM
Sorry I read your post again and saw you didn't want to do it via surface editor. There may be another way.. I'm not sure. There is always after effects, but doing it in post may not be what you are looking for.

09-15-2009, 09:29 AM
Hey Ben...good to see you again. Im intending on using after effects in post for the majority of the fade ins/wipes etc but you've just confirmed my suspicions regarding object dissolve. Im beginning to think for the more complex dissolves, surface editor might be the way to go. Just means i will have to double up my geometry and do a seperate render pass. Hum nodes.....i try and avoid meddling with them but guess its time to confront my demons hehe.

Again-valuable advice, many thanks

09-15-2009, 09:52 AM
Haha ya, good to talk with you as well. You'll be comforted with the fact that you can drive the transparency with a couple nodes only and not change any of your existing surfacing work.

Weight Map (wheel1dissolve) --input--> Gradient --transparency--> Main Node

Attached is an image of what I was thinking.
Oh ya, I used the alpha to drive transparency, so don't worry about the color values, just make use of the alpha values on the gradients keys.

Also.. you probably know this, but just thought it worth mentioning. When making weights across complex surfaces you can use the 'Weights' tool in modeler, then hit 'n' for Numeric panel, and use a falloff and put in 100 or something, then move the fall off interactive arrow around in modeler until you get it just how you want. Then hit apply.

( I sometimes put a base weight of -100 on the entire object, then apply +200 in the weights tool. That way it goes from -100 to +100. Because the gradient in the regular surface editor only starts at -100.. so dumb)

09-15-2009, 09:58 AM
Ben when it comes to me....never assume i probably know something hehe. As usual thats all very good info. Im gonna give this a wirl tommorrow. I will post something up once it begins to shape up...ta v much

09-15-2009, 10:14 AM
This thread may be relevant to your interests


09-15-2009, 11:35 AM
Just be sure not to lock any of the keys in gradient nodes (RMB) otherwise you'll lose the envelope button when you reload the scene...nice little bug that drove me crazy. You can use the curve node in the same way but you must use the Alpha output rather than colour as each colour channel is treated as a seperate channel.

09-17-2009, 03:30 AM
Well ive been playing around with the technique of driving the transparancy with a weightmap and gradient in the node editor and it seems to be working a treat (well after increasing the Ray Recursion limit...oops 2hrs wasted) However ive hit a brick wall.

Using 4dartist simple node set up-specularity, reflection or fresnal shaders wont fade along with transparency. How do i have these dissolve as well. Ive tried adding a subtracting/inverting node and feeding this from the gradient alpha and plugin it into the specularity, reflection, etc..... but im getting weird results. How do i go about controlling these correctly?

Sorry nodes are freakn awesome in the right hands but sadly not mine.

09-17-2009, 04:28 AM
Heres a couple of test renders just to illustrate my problem....

Transparency is working fine and dandy (image 3) but with spec and reflection on the surface it still remains (image 2).

Any pointers on fixing this with nodes please :thumbsup:......and how to speed up rendertimes when using transparency....eeik!

09-17-2009, 11:31 AM
You're right about the spec and reflection, I forgot those still happen regardless if the object is transparent. Also just plugging an inversion of the gradient into those channels isn't quite what you want. Mainly because you would be saying you want specular to be 100% at one end and 0% at the other. Same with reflection, I'm guessing your object is never really 100% reflective. What you can do is use a 'clamp' node, so you can keep you weights node, your gradient node, your invert node, then toss a 'clamp' in there and clamp the values down to whatever your actual specular/reflection values are. However if you use maps in those channels things get more complicated.

I may be able to come up with a better way to do it w/out nodes, but I can't do it right now.

Your tracks look nice, will be neat to see how you animate the fades. :) Always fun to see your work.

09-18-2009, 05:50 AM
Yeah i spent most of yesterday trawling through the node docs looking for a solution and came across the clamp node...still couldnt get the results i was after. Anyways i resorted to setting up another gradient to drive reflection and spec and set the blending to ADDITIVE and it works. Its just gonna b a ball ache editing all my surfaces. Thank heavens for cut n paste hey.

Im just concentrating on optimizing render times now....i will post some stuff in the WIP once i get it off the ground. Thanks for your input Ben....top man!

09-18-2009, 07:44 AM
Darn it now im applied two different dissolves on two different objects in the same scene im hitting the ray recursion limit of 64 even if i uncheck double sided on the surfaces....argh. Ive read through the archives.....is it true there is no limit on the classic camera? Render times are going through the roof also. My lord im not sure this project will even get off the ground at this rate.