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Render Optimization & Renderfarm Optimizing your scene for rendering and Using the renderfarm

Design Informatics

2 12 March 2014

Render Optimization& Renderfarm

• To model or not to model? • Modeling alternatives • Geometry detail • Cleaning your scene • Textures • Lighting strategy • Render Settings • Post-production vs Render-time

• BK Renderfarm

Lecture outline

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To model or not to model?

• Determine camera position(s) • Don’t model what you can’t see

• Don’t forget reflections • Consider simple textures for reflections

• Don’t model details that won’t be distinguished • Distance and size

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Modeling alternatives

• Using Textures • Color map • Bump map • Displacement map *

22 polygons with bump- and color map Total render time: 1 minute 58 seconds

52110 polygons Total render time: 3 minutes 6 seconds

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Geometry detail

• Try to keep the polycount as low as possible

• Relation to distance • Soften edges

Cylinders with 8 subdivisions Cylinders with softened vertical edges

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Instanced Geometry

• Use instances instead of normal copies where possible

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• Remove objects that are not needed • E.g. curves from AutoCAD

• Make sure there are not two or more objects in the same place

• Delete construction history

• Always keep an original version of your scene. Save your (stripped) render version using a different name

Cleaning your scene

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• Optimize Scene Size • Make a backup of your scene!

Cleaning your scene

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Shaders

• Glossy reflections are even more expensive • Especially when you need many ‘Glossy

Samples’

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• Use JPG images • RGB (CMYK won’t work) • Non-progressive

• Resolution

• Keep images as small as possible • Using ‘binary’, square sizes is most efficient

(e.g.: 64x64, 128x128, … 1024x1024 pixels)

• Consider distance. Textures on distant objects can be less detailed

Textures

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Optional for Mental Ray: • Convert large textures to .map files

• Faster to render • Allows Mental Ray to free memory when

needed (prevents out of memory errors)

Textures

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• TOI shelf -> TOI Texture tools

TOI Texture Tools

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• Conform texture locations • Fix problems with texture locations when

you forgot to set your Project once • Clean sourceimages folder

• Removes unused files; can reduce the total size of your project

TOI Texture Tools

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When using Mental Ray: 1. Convert images to .map 2. Update filenodes to use the new .map images

• Don’t forget to update the .map textures when

you change your textures.

TOI Texture Tools

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• Exterior day scene: Final Gather only • Exterior night scene: Global Illumination • Interior: Final Gather or Global Illumination

• When you need secondary diffuse bounces with several levels of extra reflections, Final Gather gets very inefficient: » Use Global Illumination

• When you’re using mainly artificial light or you need accurate artificial light behavior » Use Global Illumination

• Otherwise: » Use Final Gather

Lighting Strategy

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• Use ‘Additional Color’ instead of lights where possible

• It can be found in the ‘Advanced’ section

Lighting Strategy

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• Tuning Raytracing settings Raytracing is used by Global Illumination, Final Gather, Caustics,

reflections, refractions and in most cases to calculate shadows

• There is much to gain (or loose) Too conservative may yield inaccurate results Too aggressive may take too long to render

Render Settings - Raytracing

18 12 March 2014


• Reflections: Maximum number of times a ray will reflect

when calculating reflections


Images courtesy of Mental Images

0 reflections

1 reflections

2 reflections

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• Refractions: Maximum number of times a ray will refract

when calculating refractions Refractions occur when a ray goes through a

(semi-) transparent surface.


Image courtesy of Mental Images

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• Max Trace Depth: Maximum number of times of:

reflections + refractions

for a single ray


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• Shadows: Maximum number of times a ray will reflect

when calculating shadows This setting determines whether a shadow

appears in a reflection (of a reflection of a …)


Shadows 1

Shadows 2

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General • Don’t forget more specific Raytracing settings

for: • Lights • Global Illumination • Final Gather • Etc…


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• Optimizing your Final Gather settings can make a big difference

• Start with low settings and adjust as needed, constantly making test renderings

Render Settings – Final Gather


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Accuracy • Start with 20 • Increase when image is full of spots • Use steps of 10 • Keep ‘in sync’ with Point Interpolation


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Point Density • Start with 0.6 for test renderings • Set to around 1.0 for final renderings • > 1.2 should normally not be needed • Use 0.8 for test rendering when results are very poor with

low Accuracy


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Point Interpolation • Pro: Cheap smoothening • Con: Not very accurate

• Set to about half of the Accuracy • Increase to 1x or 2x the Accuracy as desired

(if more accurate results aren’t required)


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Accuracy: 20 Point Density: 0.6 Point Interpolation: 10 Render time: 0m47


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Secondary Diffuse bounces • ‘expensive’ • Only enable it when it’s really necessary:

make test renderings


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Filter • Set to 1 if you have some very distinctive

bright spots in your image • Caused by reflections (and low accuracy)


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Going to ‘final resolution’: • Remember where the difficult parts of your

image are when rendering low resolution • Set the Render Settings to final resolution • Make a region rendering of the difficult

part(s) and adjust settings as required


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Anti-Aliasing is a process where jagged edges are smoothed to get nice results.

This is done by considering neighboring pixels and/or calculating ‘sub-pixels’ (sampling)

Render Settings – Anti-Aliasing

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• Sampling


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• Samples are at the corner of pixels



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• Sampling



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• Samples for Unified Sampling

• Test render: 0.25 – 0.8 • Final Render: 0.8 – 2.0


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• Samples for Adaptive Sampling

• Test render: -2 0 or -1 1 • Final Render: 0 2 with Contrast 0.05 – 0.01


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Contrast Treshold (Legacy mode Adaptive Sampling)

Mental Ray dynamically increases the sampling accuracy (up to the max value) when the contrast between samples is greater than a set value. This increases the sampling accuracy only when it’s needed.

Test render: default (0.1) Final Render: 0.05


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Multi-Pixel Filtering Samples need to be aggregated and translated

into pixels somehow. The Multi-Pixel Filter determines how this is done.



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Multi-Pixel Filtering Box and triangle: simple but fast Gauss: very smooth Mitchell: sharper version of gauss (more ‘crispy’) Lanczos: even sharper (high contrast, often too sharp) Test render: Box or Triangle Final Render: Gauss, Mitchell or Lanczos


Box Triangle Gauss Mitchell Lanczos

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• Depth of Field (using Z-depth)

• Glow • Motion Blur • Color and level corrections • Finishing touches

Post-production vs Render-time

Color channel Z-depth channel

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• Set Mental Ray verbosity level to “progress messages” to see what MR is doing. This can help you to determine how to optimize your rendertime. » Render > Render Current Frame > Option Box

• Mental Ray diagnostic functions: • Diagnose Final Gather • Photon-map visualizer • BSP diagnostics

Mental Ray messages

46 12 March 2014


New addition to our farm: 2x Intel 10-core Xeon E5-2680v2 2.80 GHz processors Combined: 40 threads, 112 GHz

64 Gigabyte DDR3 memory

Using the Renderfarm

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Workflow: • Prepare your scene • Configure the renderfarm connector • Publish your scene • Submit the job(s) • Wait until your job has been processed • Get the results


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Image slicing: Pro: you can split the rendering of a single images

across multiple comuters: sometimes faster Con: Maya has to do the preprocessing and a part

of the main rendering process (such as calculating

Final Gather) multiple times instead of once: ‘waste’ of resources You can get some artifacts along the borders of the slices. Slicing does not work with post-processing effects such as glow.


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