Hi this is a samll tutorial for creating a flag using nCloth in maya

Interview With PIXAR TD Kim White

Check out this cool interview with the Technical Director of Pixar Animation Studios "Kim White".

http://www.swcp.com/animate/pdf/winter98.pdf

Tips for Lighting for a Chroma Shot

• Keep your character at least 6 feets away from the screen do that you can avoid the spills happening in the edges.
• Always try and use a kicker so that its easy to extract the character
• Make sure the bg is lit evenly, try and use a vetroscope so that you can make out what is the chroma and luma levels normal lightmeters won't give this values
• Don't use the sharpen mode which is available in most HD Cams it will compress the fottage and give bit mats in the edges

CHROMAKEYING

What is Chroma Keying ?
“Chroma” is the word used to describe color that a camera can record in technical terms. (As opposed to “Luma”, which is the word used to describe the light that a camera can record.) Keying is an old production term that refers to removing an object from a picture using a form of matte.
The processes of Chroma.
The principal subject is filmed or photographed against a background consisting of a single color or a relatively narrow range of colors, usually blue or green because these colors are considered to be the furthest away from skin tone. The portions of the video which match the preselected color are replaced by the alternate background video. This process is commonly known as "Keying", "keying out" or simply a "key".
In analog color TV, color is represented by the phase of the chroma subcarrier relative to a reference oscillator. Chroma key is achieved by comparing the phase of the video to the phase corresponding to the preselected color. In-phase portions of the video are replaced by the alternate background video.
In digital color TV, color is represented by a triple of numbers (red, green, blue). Chroma key is achieved by a simple numerical comparison between the video and the preselected color. If the color at a particular point on the screen matches (either exactly, or in a range), then the video at that point is replaced by the alternate background video

Animating an Eye Blink

1. An eye blink always sells the emotion.
2. An un-animated eye looks like dolls eyes.
3. Give time for the eye to follow the objects it means eye never moves same with object it always has a delay of some frames.
4. Never do a random eye blink.
5. It conveys the shift in thought so plan when to blink the eyes.

Flickering R & D

Hi recently i did a research on flickering while rendering here are some note that i made during the research.

SSS FLickering

• FG problem
  

• Not 100% sure, but I think it could have something to do with the resolution of the lightmap. Try upping that some (I recall reading or hearing that a low resolution will cause similiar problems. The recommended size was the width being the width of your render and the height being twice that of your render).

Painteffects Flicker

• convert it to poly

• This is most likely a anti-aliasing issue. There is no need to convert to polygons however as
  the maya software rendering options at the bottom in the Paint Effects rendering section there are 2 boxes, Oversample and Oversample Post Filter.

Oversample will improve the anti-aliasing of your paint effects, most likely removing flickering and rendering problems.

Oversample Post Filter will add a further smoothing effect to the paint effects in post.

Of course you take a rendering time increase but this is better than flickering!

More info is available in the mayahelp document section for paint effects rendering options.

Hope this has helped, it fixed my grass problems.

Software Render :

• Is it a nurbs surface? if so make sure you check on 'smooth edge' under Common Tesselation Options
  
  
• adjusting near and far clip planes. bring the 2 values as close together as possible. (high near and low far value
  
  
• depth map shadows, you can fix the problem by increasing the resolution of your dmap shadows.
  
  
• adjusting your filter size, and\or bias size
  
  
• To fix the problem of maya software dmap shadows going through walls at the edge I would make another plane inside the wall.

avoiding flikering without increasing fg rays

• try increasing fgrays density. btw, use the new multiframe fg mode if you're animating with mray3.5.
  
  
• using an AO pass, rather than FG ..then you contorl the blur in post
  
  
• increasing the FG filther value to 1 or 2.
  
  
• increasing point density (point density takes crazy amount of memory.)

Shave and haircut or FUR Flickering

• if You have polysmooth node in DAG chain, get rid of it.
  
  
• If u open ur UV editor window and change ur current frame u will notice ur UV's getting animated. It is b'cos of while smoothing the surface the smooth UV's option would have been on by default. Pls try switching them off and render. it worked for me it may well work for u too. (note- Check the image attached)
  
  
• Render the FUR in seperate pass

Render with GI and Final Gather

• Try using an ambient occlusion shader instead of final gather and then multiplying it over the blinn shader.
  
  
• reduce your contrast even further,0.03. Try Mitchell or gaussian filter. View radius in pixels. Jitter:On. Keep min radius to 1 max to 100 (experiment with this, you can go down to 1,20). Use around 500 rays. Hope that helps.

Structure of RIB

Most RIB files begin with the declaration of some options and attributes that are specific to certain renderers, We will look into these a little bit latter, but for know lets go over some calls that every RIB file must have, either by declaration or by using the renderers default value.

Image Declaration

Before anything can be created or rendered at all the renderer needs to know several things. Where will it send the output of the image (the pixels)? What name will this image have? What file format will this image be? What resolution will be the image? All of these questions are answered on a block that will usually read like this:

Display “./myImage.tif” “file” “rgba”

Format 640 480 1

These calls tells the renderer to generate an image named myImage.tif on the same folder where we are reading the RIB from (./.), to save the scene with the default image format specified by the current renderer “File” and to save the red, green, blue and alpha channel on that image “rgba”. For most renderers the default image format used when “file” is passed is “tif” (make sure to check though). To send the rendered pixels into a screen window you can replace the "file" parameter for "framebuffer". These calls are usually followed (or preceded, the order isnt really important) by the quality settings of the scene:

ShadingRate 1

PixelSamples 3 3

PixelFilter “catmull-rom” 3 3

ShadingRate specifies how small each mycropolygon should be. A shading rate of 1 means that each mycropolygon will be the size of a pixel. Since RenderMan renderers usually shader the corners of a mycropolygon, this means you are getting an average of 4 samples per pixel. If the ShadingRate is set to 0.5 then the renderer will make mycropolys that are un quarter the size of a pixel, so it will be shaded 9 times per pixel, which will result in more detailed textures. A shading rate of 2 will generate mycropolys with a sieze of two pixels (less detail). Smaller shading rates will result in higher rendering times, as you would assume,everything that adds more detail or quality to your image will result on higher rendering times.

PixelSamples is somewhat similar to ShadingRate but it affects the anti-aliasing of the edges of your objects. It determines how manytimes the final pixel will be sampled. Higher values will give you smoother edges. Higher values are also necessary when rendering with depth of field or with motion blur. PixelFilter allows you to select what kind of filtering you want to use on your final images.

Camera Declaration

After the image settings are declared a camera needs to be created. This is usually done by calling

Projection “perspective” "fov" 45

This call tells your renderer what kind of camera to use, it can be perspective or orthographic, the number after the fov parameter indicates the Field of View (FOV), 45 degrees on this case.

A special note must be added here. Remember that RenderMan has a hierarchical graphic state and it keeps track of the current coordinate system. This means that when you apply a translation or a rotation, it is the whole coordinate system that is affected. When you call the projection command you have just created a camera and the camera has its own local coordinate system. Since everything in our digital world is created AFTER the camera then we can say that the world is positioned in relation to the camera or is a children of the camera. This is a concept that is a little hard to grasp at first since in most 3D apps we tend to think of the camera as one more object in our world. For this reason you will usually see a bunch of transformation calls before the camera is declared. This moves the camera (and its coordinate) to where it needs to be.

World Declaration

After the camera we can finally begin to create our world. Calling WorldBegin creates a new coordinate system where all of our objects will be added to. The first thing to be created are usually the lights. This is done because RenderMan uses things as they are declared. You cant declare a model and then a light that is supposed to affect it, because the object will have already been passed to the renderer, so the light cant affect it. Lights are declared with the following call

LightSource “lightShaderName” lighthandle parameters

Here is an example of how a point light is usually called

LightSource “pointlight” 1 “float intensity” 10 “color lightcolor” [1 0.5 1]

After the lights are declared the objects can finally be created. Objects are usually created inside what is known as attribute blocks. You can change anything on the graphic state in an attribute block without affecting the rest of the scene because the graphic state is “popped” back to its previous state when you exit the attribute block. Lets look at a simple example of how the whole graphic state and attribute blocks work:

WorlBegin #Begin declaring the world
Surface "plastic" #Declare the current surface shader
Color [1 0 1] #Define the current color - all objects from now on
#will receive this shader and color
AttributeBegin #Now we start a new attribute block,
#we can override the previous shader and color
Attribute "identifier" "name" ["nurbsSphere1"] #Name the sphere
ConcatTransform [2.1367 0 0 0 0 2.1367 0 0 0 0 2.1367 0 0 0 0 1] #Apply a transform to the sphere's coordinate system
Surface "rudycplasmaball" "float additive" 0.75 #Change the current shader
Color [0.5 0.7 0.8] #Change the current color
Sphere 1 -1 1 360 #Declare a sphere
AttributeEnd #The end of the attribute block, we go back to the
#original Surface and Color
Sphere 1 -1 1 360 #This sphere will use plastic and the color [1 0 1]
WorldEnd #End of our world