STROB FX Maya tips

November 28, 2007MAYA tips

Je vais faire une nouvelle catégorie dans mon blog pour archiver tous les "tips and tricks" que je découvre dans mon utilisation du logiciel d'animation 3D Autodesk MAYA. Je travaille présentement avec la version 2008 (64 bits) sur une machine à huit cores (un BOXX intel dual quad core) avec 8 gigs de ram.
J'update ce post régulièrement dès que j'y ajoute de nouveaux tips.
J'ajouterai un lien qui permettra de voir tous les tips au fur et à mesure.
1- To create a shader that changes depending on the camera angle:

2-to remove banding in depth map:
Slowly increase Bias from 0.001 to 1.
3- To create a rimlight we can do it in the shader instead of using light.
4- To use sprite: (there are some goos expressions in a Tutorial dvd called Maya Techniques: Particles Effects tutorial)
If we use an animated sequence, we have to remove the extension on the bitmap files and keep a point before the number. Like this: sprite.1 sprite.2 etc
we check
"use image sequence"
and
"use interactive sequence caching" (and we specified the range)
This tells maya not to play the animation on each sprite but to assign a different non animated frame to every sprite. For example frame5 will be assign to sprite depending on the spritenumPP attribute.
5- To change the color of a particle depending on the emitter (for a unique particle shape):
we use this script:
if (emitterId==0)
rgbPP=<<1,1,1>>;
else
rgbPP=<<1,0,0>>;
6- Looping through a ramp over particle life and FMOD mathematical function.
To use a ramp to animate a particle parameter over its life is easy, we just right click on the attribute input box and click on "create ramp" and the new ramp is automatically associated with an new array mapper associated to the particle attribute. But I wanted to loop the ramp over the life of the particle as many times as I wish. Since the maya interface for a ramp is rather is too small to duplicate the ramp manually, we have to use a script that automatically loop. And for everything that loop, there is a very usefull mathematical function in maya called fmod. I got that information from drktding on CGtalk (the most useful forum on earth for CG artist like me). From maya help:

Synopsis
fmod float float
fmod is undoable, queryable, and editable.
This command is implemented using the built-in system function.
Returns the floating-point remainder of the division of it arguments x and y. The result is a number f with the same sign as x such that x = iy + f for some integer i and |f| < |y|. Return value float

So in plain language, fmod give you a result that is the remainder of a division. So if you create a new attribute called ageNomB for example and write this expression in the runtime of your particle:
particleShape1.ageNomB = fmod(particleShape1.ageNormalized*2,1);
fmod will return the remainder of a division by one of particleShape1.ageNormalized*2.
in this case
x = particleShape1.ageNormalized*2
and
y = 1
since you divide by one, the remainder is always zero when x= an integer like 1, 2 our 3 flush. But between 0 and one, the remainder will alway grow and go back to 0 when it reaches exactly 1. For example:
fmod(0.1,1);
// Result: 0.1 //
fmod(0.2,1);
// Result: 0.2 //
fmod(0.3,1);
// Result: 0.3 //
fmod(0.5,1);
// Result: 0.5 //
fmod(0.9,1);
// Result: 0.9 //
fmod(1,1);
// Result: 0 //
And if you multiply x by 2, it will grow, decrease, and grow and decrease again. (Or "it will loop" in more simple terms...). Because it will go back to o when x= 0.5. As you see in these samples of results:
fmod(0.1*2,1);
// Result: 0.2 //
fmod(0.2*2,1);
// Result: 0.4 //
fmod(0.5*2,1);
// Result: 0 //
fmod(0.6*2,1);
// Result: 0.2 //
fmod(0.7*2,1);
// Result: 0.4 //
fmod(0.9*2,1);
// Result: 0.8 //
since fmod will always repeat all you do is take the ageNormalized and multiply it by the amount of times you want to repeat the ramp; in this case it is 2 times. The new ageNormB is what you connect to the ramp. Since it is an output variable to the ramp, the ramp will always return a value.
7- Conversion between Maya and Max (14/05/2008)
Here are my settings for converting from Maya to Max: I use FBX with the default options except I use a scale factor of 0.17143 and when importing in max I leave all at default except I uncheck "Scale Working Units" (that way a box of 12x12x12 cm in maya will gives a 70x70x70 generic max unit in max which correspnd exactly to a quarter of the default grid. And since every part of maya and max or every plugin seems designed in function of the scale of the default grid, it will be useful to use those scales most of the time. but for that to work the scene must have been created with that scale in mind too see the following figures). And I check the "Export Quick Select Set as Geometry Cache File(s)" to export deformations.



Before converting I always make sure all transorms are baked and if the camera is parented I try to remove the parent (I often use the parent constraint to replace any parenting so I can bake it) or I bake the parent too and remove all constraints (sometimes replacing the parent relationship by the parent constraint does not seem to work). We can bake the deformation by two way: by creating a geometry cache or just by selecting the shape node of all deformed objects and using the "Edit/Keys/Bake Simulation" command with "control points" checked. Also to export with FBX we have to create a quick select set with all the deformed objects and make sure to check the "Export Quick Select Set as Geometry Cache File(s)" in the FBX export dialog box.
Tip: when baking you can hide everything by choosing "show/none" in you viewport and it will bake faster if you have memory hungry stuff going on like already baked deformed geometry (if for example you baked deformed object before baking the transform of your camera). Strange but true!
Strange thing to note: if you scrub the timeline back and forth with baked deformation, maya 2008 is unstable and very slow, but, with the exact same scene, 3dsmax is very fast and perfectly stable...
Tip: about the camera: you have to be careful about the setting called "film aspect ratio". I discover this ratio must be the same as the render setting aspect ratio before exporting to max (but I'm not sure. For now I know it must be 1.33 when rendering at 640x480). Because it seems max does not have such a setting. In maya the settings seems to be useful only when using Maya Live to match with the background by taking the aspect ration of the film that was used in a real camera... I never needed this setting to date.
8- Conversion between Maya and RealFlow (14/05/2008)
I use the sd exporter. Baking with geometry cache seems to work but it just doesn't in realFlow. If you try it, the geometry will deform in realFlow but the deformation will not be taken into account by the particle.... DOH! So you have to bake by selecting the transform node and using the "Edit/Keys/Bake Simulation" command with "control points" checked.
I try to keep realflow with a scale of 1 and I scale my scene in Maya to get something not to big nor too small at this scale in realFlow. Because realFlow is very strange when it comes to scaling. If you scale by the same factor in realflow than in Maya, it seems it will give the same scale for the drops of the resulting (identical at both scale) particles...
9- To break the reference of a referenced object in a scene (we often have to do that before baking a scene for export): open the reference editor (file/ referene editor) select the referenced object and choose: file/import objects from reference.
10- To add nCloth dynamics to the cloths of a skinned character. If the cloths are already skinned, just turn your original skinned cloths into nCloth. Make the inputMeshAttract 1.0 and then paint the per vertex input attract values black where you want the clothings to be fully dynamic.
11- To see the graph of an expression in the graph editor, just check "Show Results" in the view menu of the graph editor. This should be on by default but it is not in maya 2008.

by Strob