Blender's built-in rendering options offer many different possibilities for size, effects, and quality. Different settings may drastically affect rendering times. The goal for this analysis is to discover the most efficient methods for achieving the desired image quality with the minimum rendering time. When rendering for animations it is extremely important to achieve the best results is the shortest time possible, since one second of animation represents 30 rendered images.

The same model was used for rendering comparisons but with the rendering options changed. The default lighting for this model was a buffered-shadow Global Illumination (GI) Dome with the exception of one series of renders which only contained a non-shadow producing directional hemi light. Model materials included raytraced reflections, image textures, procedural textures, displacement mapping, and bump mapping. The model contained 292 objects, 93 lights, 199,049 vertices and 187,247 polygons.

The basic rendering settings used for the analysis are Shadows ON or OFF, Raytracing ON or OFF, Size 1000 x 600 or 2000 x 1200, and OSA NONE / 5 / 8 / 11 / 16 . To compare raytracing settings, three types of directional lamps with raytraced shadows were used in addition to the GI lighting to compare the impact of raytraced lamps on rendering times. The use of a hemispherical or area light and differences between area light settings also affected render length.

Render times used in the comparison are in seconds. The figures will change depending on the speed and configuration of the computer used for rendering, but the overall comparisons between rendering times and efficiency still apply for different machines.

Global Illumination greatly increases realism and overall image quality, but at a cost. Without OSA the GI lighting model represented approximately a 400% increase in rendering time.

Raytraced lights and shadows are easy to use and offer significant quality, but as with GI these lights increase rendering times.

A hemispheric lamp with raytraced shadows will offer basic directional lighting to the GI model. This one raytraced light added to the scene doubles the rendering time.

The shadows cast by the hemispheric lamp are dramatic but missing one key factor in real-world lighting examples: as the shadow falls more distant from an object it becomes more faded and less distinct. Area lights create more realistic shadows by arranging multiple lights (the Samples setting) on a grid (the Size setting). While this lighting method creates impressive results, it also makes rendering times dramatically longer based on the number of samples.

An Area Lamp with settings at Size 3, Samples 5, Clip Circle, Dither, and Jitter will create acceptable results. This setting represents a 60% rendering increase over the hemispheric lamp but gives much more satisfying images.

Even higher quality results can be achieved by increasing the Size and Samples, but render times become higher as well. An Area Lamp with Size 10 Samples 10 (Clip Circle, Dither, and Jitter OFF) doubles the rendering time of the scene with the Size 3 Samples 5 lamp and takes about 350% the time as the same scene with the hemispheric lamp.

OSA is the anti-aliasing used by Blender to remove "jaggies" and artifacts in a rendered image. Using OSA will improve the image quality but with an increase in rendering times.

Anti-aliasing can also be achieved by "over-rendering" an image at twice the desired output (or higher) and using photo software to scale the image down by 50% (or more). This technique is sometimes significantly faster than using Blender's OSA settings.

The quality of an over-rendered image is often comparable to an OSA setting of 8, but OSA also impacts the way materials are rendered. How materials are affected may also determine whether or not using OSA is preferable to over-rendering. Besides anti-aliasing, OSA tends to soften details such as image maps, surface details, and reflections.

Generally an OSA setting of 8 takes less time than over-rendering when using non-raytraced models but over-rendering will be more time efficient if raytracing is used.

When no raytracing is used, OSA is usually more time-efficient than over-rendering. Comparing 267 seconds for over-rendering to 169 seconds for OSA 8 reveals an 58% increase to over-render, but over-rendering is 58% faster than OSA 8 when using raytracing. When rendering models with raytracing, OSA is no longer as efficient and over-rendering is often a better solution.

These rendering comparisons helped to create some general guidelines for getting quality desired results without wasting time and computing power.

For "quick and dirty" renders without shadows, rendering at the desired resolution without OSA provides a fast but pixelated method for testing model geometry and simple texture placement.

For cleaner images without shadows or when using buffered shadows an OSA 8 setting provides decent results faster than with over-rendering.

When raytracing is used, OSA becomes less efficient and over-rendering is recommended for the time savings. Over-rendering is also recommended when crisp texture details are desired from the final image.