DAZ to get quick human rigs

I've found DAZ Studio (4.6) to be an awesome resource for quick human models and rigs, its FREE and can export to Maya well. highly recommend it.

Noise in Mental Ray Render

I've been learning Vray for Maya recently but I want to stay fresh in Mental Ray so I did a quick study of noise in renders and how to solve different types of noise.

here is a simple test scene which shows four different sources of noise:

• noise in the reflection of the MIA Material
• noise in the shadows of objects
• noise in the general diffuse (when using mental ray's "use light shape" option)
• stepping and pixelation edges of object or in high contrast areas

to fix these issues you have to increase samples on each of these setting, knowing which samples to increase can help you resolve you issue faster.

for noise in the reflection you need to up the glossy samples in the reflection tab of the mental ray material, the less glossy it is the more samples you need to blur the reflection. 32 is often a good setting but if the reflections are very blurred you may need to go much higher than this. Going up exponentially is helpful (eg. 16, 32, 64, 128, 256)

noise in the shadows is normally due to ray trace shadows being on and the shadow rays not being increased. area lights need to have more than 1 ray to be smooth, upping that to 12 seems to smooth them out nicely.

the general diffuse noise is caused by the area lights high sample settings, increasing this to something like 16 can help smooth things out. The low sample setting is not often used, I believe it is called upon when the lights rays pass though an object or the reflection is seen in a reflection. If you notice grain in the shadows reflection you can try playing with that and seeing if it fixes it.

lastly edge noise can be due to the render sampling of the image, in the quality tab of mental ray's render options you'll find the raytrace/scanline quality, changing the max sample level to 2 and the contrast to .08 does the trick for me. Turning the max sample past 2 drastically increases render time so be careful.

hope this was helpful. This (along with most of this blog) is kind of a note to myself in case I leave mental ray for a while and come back to it later.

Fabric Shader effect



I recently had to create a fabric bag and I used a gamma correct with a facing ratio fall off that added a nice velvet style effect. in my render it's subtle but the effect is still there. There are many tutorials for this but not many for maya.

 

 

 

All I did was use the fabric texture twice, one brightened with a gamma of 1.6 and another with a gamma of 0.7. The texture with the darker gamma is used for the facing side and the lighter one is used on the edges applied though the facing ratio from a sampler info node. It helps convey a softer  fabric that's hard to get. 

 

Mentalray IBL sphere transform Issue



Mentalray IBL sphere transform Issue

 

I ran into an issue using mentalray's  IBL sphere. I would move or rotate the display sphere but in the render it changed nothing. The solution is to turn off the "infinite" check box. turning off that setting in the spheres attribute editor allows you to move it around and that transform will be reflected in the render.

 

mia_roundcorners to fake beveled edges

I've recently been using mia_roundcorners a lot especially with text to fake beveled edges. what it does is modifies the polygons normals so that where there's a sharp edge it adds a roundness to it come render time, it does not change the geometry so for close-ups it's not the best but looks good from afar, a good example is below. I used mia_roundcorners on the ends with the Rolodex logo to catch some highlights without having to go in and add little bevels to the text.

 

 

the mia_roundcorners gets plugged into any textures bump map input and you can set the radius of the bevel in the node itself, if you want to map another bump map, that can get fed into the mia_roundcorners nod or if you're using mia_materialX put the mia_roundcorners into the over all bump and your normal bump into the "standard" input. this is using mental ray for maya

nParticle Instance Geometry and random rotation

Instance different geometry to random particles and give particles random rotation and rotation speed.

nparticles are a pain, here is a fairly simple way to get the nparticles to grab random geometry from the instancer, all you need is an instancer that contains your geometry that's connected to your nParticles. next you'll want to "create a dynamic attribute" in the nparicle shape node, you'll need 4 new attributes:
* all are per particle because we want each particle to be different.
1) randomPeicePP - FLOAT and will be the random geometry from the insatncer
2) randInit - this is a VECTOR and will contain the random starting rotation of the instanced geo
3) rotateSpeed - FLOAT this will be the ransom speed of the rotation
4) rotationFinal -FLOAT this is where our final particle rotation values are sent to for the nparticle to look at and apply to particles

go to the expression editor for your nparticleshape node and create the following expressions.

//creation//
nParticleShape1.randomPeicePP = rand(0,7);
this is generating a random number between 0 and 7, go one higher than the number in the instancer.

nParticleShape1.randInit = <<rand(-180,180), rand(-180,180), rand(-180,180)>>;

this gives a random vector rotation (X,Y,Z)

nParticleShape1.rotateSpeed = rand(-1,1);

 this is the speed of rotation, it will be spinning between 100% forward and 100% backwards

 

//runtime//

vector $rotInit = nParticleShape1.randInit;

this just stores the random start rotation in a variable for reference  below

float $spin = $rotInit.z + (frame * 80.0 * nParticleShape1.rotateSpeed);

this creates the final rotation variable, it takes the random start rotation of the particle and adds rotation to it based off time and speed, "80" is just multiplying the grand total because it was too slow, if you wanted to you could change "rotate speed to "rand(80,-80) " and get rid of this but this allows me to easily change the max speed in one number.

nParticleShape1.rotationFinal = <<$rotInit.x, $rotInit.y, $spin>>;

this just assigns the final rotation to an axis of the particles, this is what is assigned to the particles come runtime. only the Z axis is used because if you assign rotations to more then one axis you get weird rotations, like a Frisbee or axe being through thing normally only rotate around one axis.

 

the final step is going to the instance options and in "object index" and find your "randomPeicePP" attribute you created and in the rotation section set it to your "rotationFinal" attribute.

3d modeling reference

I made this quick reference/cheat sheet for modeling, especially organic modeling like faces or hands or feet.

The top steps are for simplifying, for example the hand is pretty dense in edge loops but when it comes up to the arm you don't need that much topology so you need to simplify and this is what I use to do that.
the middle is simply two different flows being mixed, I kept having trouble getting that right and once I drew this out I found it much easier to model. the last is for re routing a line and adding more topology while avoiding triangles and 5 sided faces.

I've found triangles don't matter much on geometry that doesn't deform but on deforming surfaces triangles seem to deform oddly so sticking to 4 sided polygons is the way to go.