During the first term, I did a lot of research in to lighting and rendering for: The Deep, Unhatched and Patience. Some of it I scanned and uploaded earlier on, but here are the rest of my notes.
Simulate a direct light source on the shader itself.
You would use the mia architectural material and attach the mia_light_surface node under the advanced tab to the light contribution called additional colour.
Ensure Final Gather is enabled.
Increase FG on light surface node [Final Gather contribution].
Refl contrib- this attribute calculates reflections.
This node is good to use conjunction with a direct and illuminating light source, not just by itself.
Under the mental ray tab in the attribute editor you can enable the light shape option, such as: cylinder, sphere etc.
Detailed Overview of Depth-Map Shadows.
Increasing resolution will make depth map shadows less jaggard, however this will increase render time. Do it in K’s; so 1024 (1K), 2048 (2K) etc.
Mid Dist point- averages distance to determine where a shadow should be.
When mid-point dist is turned off, noise in the shadow increases.
Filter size- controls the degree of softness in the shadows
Filter size- blurs reflection.
Tip- low res map with large filter size.
Bias- offsets whether the shadow is close or further away from the light source.
Shadow colour- increases lightness of shadows to soften them. You can also change the colour as well.
The down side about depth map shadows is that it does not work well with transparent objects or textures with an alpha.
More accurate than depth map shadows.
However it increases render time.
Light radius- controls how soft and blurry the shadow gets the further away it gets from the light source.
Shadow rays- increases the amount of shadow rays calculated, this reduces how noisy the shadows are.
Ray depth limit- determines how many surfaces it calculates.
You can also go in to the render globals and change the quantity of shadows- this increases the realism and quality of the raytrace shadows.
General principle for most of these attributes is that if they are increased then the render time will be increased as well.
Multiplier: in effect the intensity. You can over drive this.
RGB conversion– controlling the luminance values that are returned to the camera. Once these options are set higher then the luminance values are increased when returned to the camera.
Haze– controls the overall amount of medium that is in the environment. This can help scatter the light to shift things more to the red side of the spectrum.
Red/blue shift- counteracts haze. This can be done by increasing or decreasing the amount of red/blue shift. This is the kind of attribute where a little bit of change can make a dramatic difference in the render.
Saturation– controls the overall strength or coloration of the environment.
Horizon height– controls the cut off point where the sky meets the horizon of the physical sun and sky.
Horizon height- this will have an effect on the overall colour of the image.
I would expect the horizon height to be quite low for unhatched so that the tree(s) can be in focus.
Horizon blur- controls the blur line that will happen between the sky and horizon.
Ground colour- controls the colour of the horizon below the sky. Application- can emulate grass for unhatched.
Sun disk intensity- controls visibility of the inner disk of the sun.
Sun glow intensity- controls out glow of the sun. Tip: you can reduce glow intensity in order to see what you’re doing when controlling the sun disk intensity.
Sun disk scale- control the size of the inner disk.
Use background: allows the use of a custom background (i.e. texture or movie)
This option is good for compositing purposes.
To use this option you have to:
connect an mib_lookup node to brighten the texture use a muliply and divide node, connect texture to input 2 of M/D node and connect M/D node in to texture area of mib_lookup.
Application of use background- this could be used to plug in a blue sky with white clouds background, this could avoid the process of tracking in after effects when adding a background in on a moving camera.
Good for realistic outdoor scenes.
Found inside mental ray lights.
Can be connected to any maya light.
Be easier and quicker to create physical sun and sky in render globals.
Rotating the main directional light can give us a decent representation of the time of day.
There are only a few controls for the physical sun because most of the control is in the physical sky options.
The options for the mia_physical sun node are:
Shadow softness- softens shadows can give an impression pf the scale of the environment.
Softer= bigger environment.
Samples- reduces noise but increases render time.
Shadow softness, a good application of this could be for Unhatched to give the impression that this environment is bigger than actually modelled, this way giving a false impression of the scale of the environment.
Ensure Mental Ray is turned on.
Under mental ray tab enable Final Gather (FG).
With FG- use raytrace shadows.
The ambient light attribute on the Lambert can trick the renderer in to thinking it’s giving off light.
Irradiance (under mental ray tab)- controls quantity of Final Gather contribution.
Irradiance- similar to ambiant color. This attribute works better when an image is attached (like a ramp). These FG points will then display some illumination from the color on its surroundings.
Irradiance color- controls the amount of environment colour that is brought back on to the object. White= full colour. Black= None.
Final Gather Accuracy.
Tip: diagnose final gather displays the FG points.
FG accuracy controls how many rays the FG points it will emit with more complex scenes. FG accuracy of 400-500 is not out of the question.
Density attribute is the quantity of points assigned to the scene.
Point interpolation- controls the number of points that are going to be calculated before indirect illumination is displayed.
Final Gather Intensity.
Can use a planar as a light source with final gather. Increase ambiant color.
Scale- increase or decrease the light calculation. This can give the scene a tint.
Save and re-use FG point data.
Two options for this: rebuild and final gather file.
This will allow you to save and re-use FG point data.
Rebuild “on” means that point data is re-calculated every frame or every time I render.
Rebuild “off” means if the camera moves then new FG points will be recalculated and added to the existing map.
Rebuild “freeze” will not do any kind of calculation and will rely entirely on the stored information.
Render pass utilises something in Mental Ray called frame buffers.
Frame buffers work by independently calculating components in the scene. So it will do a calculation phase for the direct light, calculation for indirect, shadows, reflections, refractions etc. All of those aspects are calculated independently of each other and then compressed in to one image, however with render passes all of this information is generated anyway but rendered out in to individual files.
Where as render layers its doing a separate render for each layer. So when rendering out The Deep, and we were using render layers we could easily be doubling and/or tripling render time.
So the benefit of Render Passes is that you don’t really add any additional render time when comparing render time of a standard colour render.
Application- have to mindful of what materials we would be using in the scene:
Maya materials work fine with render passes (completely compatible).
Mental Ray materials can be an issue: Render passes are only compatible with materials that have “_passes” at the end of the name. Due to the limitations of mental ray materials with render passes, the mia_material_x_passes can only have the render passes:
Mental Ray Physical light node.
Can be attached to any Maya light.
Go to light attributes, under mental ray.
Attach through the light shader attribute of the light.
Physical light is based on real light physics.
Intensity of physical light node is derived from the colour.
Cone- this is the cone angle if node is attached to a spot light.
Thresh hold- cut off point that you can define for the overall intensity of the light.
If you tick the option “use light shape” you can dictate what angle you want the area light when rotating the area light.
Using the physical light node can create hotspots or points of burn. To fix these you can use lens shaders such as simple_exposure or photographic_exposure.
Film Gate- would be used if you were to send this back out to be put on film, match up with film footage so you want things to be aligned correctly and then matchmoved. This film gate would be very important.
Resolution gate is the most appropriate because all the films that I’m going to be working on are 100% computer animation, no live action will be incorporated in the films and so this will be the camera attribute that I will be using.
Caustic light patterns.
Caustic photons- which create light patterns which you see through glass and water.
Global illumination- responsible for secondary illumination and colour bouncing.
Photon intensity determines the amount of energy of the photons leaving the light.
Exponent is the dropoff energy rate of the photons (1.000 is pretty much constant) at it increases the more quickly the photons will lose their energy.
Caustic photons determines the look of your caustic pattern.
Portal light- this attribute is good for lighting indirect lighting scenes. This has to be used with an area light.
You attach this to normal light, through the light shader (under custom shader).
Turn on the “use light shape” forces mental ray to be used and tick “visible”
Portal light: used in conjunction with final gather.
The “visible” attribute blocks final gather rays coming from an external source and uses indirect illumination.
The standard area light options such as colour, colour and intensity are overridden when portal light is applied.
The portal light has to be adjusted to adjust these kind settings.
Ensure global illumination is on.
The quantity of photons is dependant on the size of your scene.
Caustic photons- create light patterns (see through glass and water)
Global illumination- responsible for secondary illumination and colour bouncing.
Before I researched this I thought there would be applicable to The Deep, but after I researched photons I came to the conclusion that this will be useful information to have and apply later on when the opportunity presents it self, but at present I cannot see an application for this in either The Deep or Unhatched.
Depth of Field Lens Shader.
This will work on a per camera bases.
scroll down to mental ray
select lens shader checker
scroll down to lenses- select physical lens_dof
Two simple options
plane is the attribute to determine what is in focus. This is the distance from the camera, anything out of this range will be out of focus.
To determine the distance from the camera you need to turn on “object details” under the “Heads Up Display” menu.
When entering numbers in to the plane option, make sure they’re negative.
Radius controls strength of blur.
To reduce noise, go in to render globals, under anti-aliasing and in raytrace/scanline quality, increase max sample level.
Could be applicable for patience- film noir and The Deep- bedroom and living room scene.
Simulates a direct light source on the shader itself.
You would use the mia architectural material and attach the mia_ light_surface node under the advanced tab to the light contribution called additional colour.
Ensure final gather is enabled.
Increase FG on light surface node [FG contrib]
Refl contrib- calculates reflections.
Good to use in conjunction with a direct and illuminating light source, not just by itself.
Under the mental ray tab you can enable the light shape option and you can also change shape. You can have: cylinder, sphere, cuboid etc